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CONTI-INES C? 30A=Sl ANlD _1?HYSICPJJ TESTING

P~,DJWTN'2 PrTXTLLON OF' P2SntTS

Prepared for

Tjt- FO1U$Pfl473 1CoAFT INSTITUTE

(Project noB)

lby

TheIntituto of Pnnor chonicotry

PartL t

lPpjctO-jh Wjgconrifif

Jiuno 2, 1945 . .11 I., , . , , P I . -. : . k - ...... 1, .

Copyright, 19 4+5, by

The Institute of ChemistrY : : '' *'..'* *"^--..rJ. 4

152

FOLDING ETDURANCE

422. American Instrument Company, Inc. Calibrator for folding tqsterso (chopper and others). Bulletin 500:3-4(Sept., 1934).

A brief description of the calibrator which is described by Carson and-Snyder in National Bureau Standards, Tech. Paper No. 357.

425. .American Society for Testing Materials. Standard method of test for of paper. A.S.T.M. Designation D 643 - 43. A.S.T.M. Standards 1944,-part III:336-340; A.S.T.M. Standards on paper and paper products, Nov., 1943:82-86.

This method corresponds to TAPPI Standard T 423.

424. American Society for Tooting Materials. Paper and -- characteristics, nomenclature, and significance of tests. Philadelphia, The Society, 1944.

Folding Endurance. The folding endurance test has much significance, ranking along with bursting and tearing strength among the physical strength properties most to be desired in many types of . Folding endurance is of particular importance in such papers as box lining, bag, bond, ledger, currency, cover, index, and in numerous other applications where paper is subJected to harsh or repeated folding. The marked difference in folding endurance with the grain and across the grain is evidence that sheet structure has an important bearing on this quality. However, results are influenced in varying degrees by surface treatment, such as sizing and calendoring. Some types of surface coatings affect the values, particularly when the coatings arc absorbed into the fibers to the oxtont that they may be stiffened, softened, or otherwise altered. The effect produced by changes of fiber characteristics io illustrated by the fact that the moisture content of the paper has a Lmch more pronounced influence on the folding endurance than on any other of thu common physical tests. Because of the marked influence of atmos- phuric conditions, it is most important that tests bo conducted in the prescribed manner under standard relative humidity and. temperature conditions. Since spocimnon arc folded while under tension, the tensile strength of the papor may also have come offoct on its folding properties. While folding endurance is an empirical property, it also defines one of the elements of utility, as well as of manufacture. The values obtained are absolute.

42_. .'-thor oasting Instrument Co., Inc. Anthor folding endurance tester. CitLialar .15. v. id.

The spucimIen is heldc andor standard teorcion Ly two Jaws of the floating typc which movr in the same horizontal plane without rotation. They are k-ept in ouri'cct alignment by frictionleas supports. A recipro- catinc blado doubLeh fulAd the specimen between the quadrant rollers until i-t breaks at the crease. The number of double folds is registered on a 4-figure counter. At the -point of rupture the counter is instantly dis- oeraged and the motor stopped. Folding Endurance 155

426. Bailey; A. J. Fold failure in !craft paper. Paper Ind. 21, no. 2:156-160(May, 1939); B. I. P. C. 9:462; C. A. 33:5182; B. C. P. A. 1939B:925.

It appcars that a strong fibor-to-fibor bond and a good shoot for- - nmtiorn provcnting soparation of individual fibers ore highly important for obtaining a high folding utrongth. The following factors contribute t) higher f olding endurance: Cooking and bleaching procoosco favoring high individu'J. f:bor strength and retention of gel-forming material in th fibc-ro, a beating operation forming this go with a ninirin of fiber destruction, a ccmcnting size, nooans of osecuring a random fiber orienrttion in thu shoot, and proper calondcring proccduroo with regard to to:nperature, noicturc and pressure.

427. btuoeUon, M. D. Uniform conditions for' papor testing. Paper Trado J. 92, no. 24:7 8 (Juno 11, 1931); 54, no. 23:18, 50 (Juno 6, 1931); Paper Mag. Canada 31, no. 27:790, 810(July 2, 1931); C. A. 25:5024; T. S. 93:195.

This article is primarily a plea for standard conditions of tempera- turc and humidity. It is pointed out that a sample folded at 65% rcla- tive humidity and 70° F. will show a test averaging approximately double that shown by the same shoot conditioned and tested at 50% and if the temperature be raised to 90 degrees and the relative humidity to 70 or 75%, the tear may be tripled or even more. The fold test is the most susceptible to small changes in temperature and relative humidity but tear oan Millon and other tcets arc affected to an appreciable degree. Tho fact that folding endurance is being recognized as one of the most significant physical tests for hig,,h graCo papers is demanding uniform testing condltions.

.42c. Bo iding and tonsileo trongth tootor for popeor board, etc. Popior-Febr. 22:65 8-659(0ct. 19, 1924); T. S. 81:70.

The raw Schoppor bending and tensile strength tostor for paper- board in pictured and briefly described.

429. 7c3)dinc tcotor for paper board. Paper Trade J. 82, no. 3:47 (Jan. 21, 1260).

An abstract from a pamphlet distributed by Foroign Papor Mills, Inc., describing the Naumarn-Schoppor bending tester. Examples of practical applicato-.i are pointed out. Similar to the article by Naumann in Wochbl. FP-iorfabr.

430. Bcrcovitz, D. Apparatus for the measurement of the deflection or bending of paper under various moisture conditions. Zcllotoff u. Papior 10, ro. 1:C0(Tan., 1930); T. S. 92:4.

Description of Lponrotus and methods.

----I· ---- - I -- -- u--- -- . -1 -- , . .- : -. ; .

Folding Endurance 154

. _ ... 431. Borndt, Kurt. Latest laboratory instruments for the . Zollstoff u. Papier -17, no.- -:09--314; no. 8: 349-352(July, August, 1937); B. I. P. C. 8:74; C. A. 31:8188; B. C. A. - -- 1957B:1321; T. S. 106:95.

The review includes a discussion of the Schopper endurance bending tester.

452. Carrier, N. H., and Young,' J. H. An application of statistical methods to the dotcrnination of the folding ndurance of paper. World's Paper Trade Rev. 105, no. 20:159Q3-1594, 1596, 1598, l600, 1602(May 15, 1935); B. I. P. C. 13 T. S..103:380; B. A. 1936B:636.

An analysis is given of the results of folding tests made on several consignment of mold-made paper. The methods of analysis arc not given but the article is of interest in that it gives examples of the value of statistical analysis in drawing deductions as to the significance of individual factors influencing the property being measured. From the data presented, conclusions are drawn concerning the effect upon folding strength of such factors as selection of the sample shoots, the particular instrument employed in making the test, .the direction of the shoot, the humidity to which the paper was subjected in seasoning and the consign- ment from which the samples were selected.

4_ 5. Carson, F. T., and Snyder, L. W. Calibration and adjustment of the Schopper folding tester. National Bur. Standards, Tech. Paper No. 357. Oct. 15, 1922. [Vol. 2:125-140].

The Schopper folding tester, which is designed to test the bending endurance of paper and its resistance to such types of wear as involve creasing and folding, ir so constructed that a number of variables are introduced by reason of the several rollers and. other working parts which are dr-iven by the specimen bci:g tested. Those mechanical variables affect the folding results in mcc!: the same anner as do errors in ad- justing the tension applied to the specimen during the tost and apparently can in general be expressed as equivalent effective tension. The tension on, the specicnl is very critical, the effect on the folding results being inversely proportional to something like the tenth power of the tension (according to available data). The variables listed are: fold- ing blade nnl li.n1._ago, quadrantai rollers, supporting rollers, and tonsion on the clnmp sprirs. Under the adjustment of the clamp spring there is a discusnioj: of the; vcrticni susnpcnsion method and calibra- tior in pinc:, inc.ud-ing¥tlc rric'ion: ess pulley and a now method in- volvi!: a balanced b2:.l-crronk ie.co. annll errors in adjustment are, for th, rt.Cst part, inconuoquential but errors in adjustment amounting to more then about '5 grains i.r t-enion become serious. The friction in the rollers, particularly in the vertical ar.ndrontol rollers, may be considerable. Stati,: friction in the quL'cd.rLntl 'iOllors equivalent to 50 to 100 grams tori .o:icnpcra to be unlvoidablo. A method is Ouggostod for =manurii: roller friction. I Folding Enduranco 155

44. Clark, Frederic C. Paper testing methods. New York, TAPPI Publishing Corpn., 1920. 24 p.

Folding endurance is discussed on p. 14-15. The calibration of the Schoppor folding-machino is described-. -- - -

~ - 435. Clark, Jamcs d'A. Method and apparatus for testing the -folding endurance of paper and like materials. U. S. patent 2,179,1-16- (Nov. 7, 1959); C. A. 34:1486; Papormaking Abstr. 1941:70.

This covers the Thwing multiple fold tester.

43b. Drying upon the . Papicr-Ztg. 61, no. 60: 1134-1135(July 25, 1936); B. I. P. C. 7:71.

The importance of uniform moisture conditions in testing rooms is stressed. An example is given, in which variations of 1% above or below the standard moisture content resulted in variations of 200 or more double folds.

4_7. Evans, A. II. M. I. T. folding tester. World's Paper Trade Rev. 101, no. 17:1325(April 27, 1934); B. I. P. C. 4:245; T. S. 100:78.

A very brief description, with illustration, of the M. I. T. folding tester.

48. Fournier, Raymond. Folding resistance of paper. Papeterie 55, no. 3:146, 149-150(Feb. 10, 1931); T. S. 92:345; C. A. 25:2286; B. I. P. C. 1, no. 7:14.

A description is given of a new type of folding resistance teeter, based on the same principle as the Schoppor-Rieglor tester but quito difforcrt in construction. The test strip is 15 by 180 rm. and both ends are climped in a two-kg. weight, so that the tension is exactly one kg. The fold is effected by passing the test strip through a slot in a blade which iE reciprocated vertically between 2 pairs of 14-mm. stool rolls mountecid on ball bearings. When the strip breaks, the fall of the weight stops tho motor and applies a powerful brake to the flywheel. An automatic revolution counter indicates the number of double folds.

439. CGreen's improved standard folding tester. Paper Mill 47, no. 13:10, 32, 34(March 31, 1923); T. S. 77:1.

It is pointed out that this tester (developed about 1917) produces an abrupt flexuro in a standard way and imposes the pressure alonG the line of fold and to a fixed and predetcrmined dcgrec,4 entirely free from friction. The operation of the tester is described. A chart shows the relation of folding endurance and other properties to the tiin of boating.

440. Harrison, V. G. W. Paper testing. XIII. The folding on- durance of paper. Patra J. 2, no. 4:171-174(Jai)., 1939); B. I. P. C. 9:312.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Folding Endurance

A description Is given of the Schopper folding endurance tester and of the conditions for carrying out the test eas employed in the 7A'TPxmA labo.ratories.

Hau±'y, Fritz. "Paper strength in theory and practice. Wochb3.. Papierfaor. 66, no'. 27:512 515; no. 29:54f5-5kSQ(-,ulj 6,-2o, -15535);-… Panlicr-Fobr. 33, no. 28:233-235(Jul~y x4, 1955); C. A. 29:85217; 13. r.-_1. c. 6:184;-T.-s..o3:27.

The control methods for paper strength t6sting at the Papyrus plan,,t cf the Waldhof Pulp Mills include tenuile strength (breaking lenEgth), number of folds, and bursting strength. However, only the two former are considered in this study, in which the mean values wore obtained~from the control tooting laboratory's protocols with daota ex~tending,- over a ten-month period. -An attempt was made to measure the ef~cctc of varying conditions existing at different stages of the man- uffactu'inG process on the strength of the finished shieet. in preparing his rgraphn, floury used the arithmetical m6on. (14) of st~rength tests carried out with strips cut inP the machine direction, (1) and in the Crass direction C(9. The strength ratio of l/_j is termed Z, and, wheon I = 1, 1M =a(Z + 1)/a. Two different types of slow 'stock T7o-753 3.--It) aInd three classes of free stock (35-40e S.-R.) were used. Whecn the number of' folds were plotted against grams per square meter,,the imaxinfuin streng:,th lay within the range 55-70'r grams per square meter. According to practical tests, the weight/volume of the finished sheet does riot increase l~inearly with the ariount of stock that flows on the wire in a Civen time., Here, too, the curves follow a course and show Maxima childler to the folding ecidUrance-weight/voluneo graphs. However, similar relationships did not obtain between M for breaking leng-th and, grams per square meter of the finished. sheet. Thec tecring length is a measure of tWhe feltin- of thefie throughout the length of the strip, where~as th fodin;s- ondiinrance is limited t:- an exceed~iigly narrow area, 'and thus ccer%-s 1, record the behavior of tndifividual fibers. in. machnine-made t~mrthis toot is cspoelolly valualeni in shjowin- the relaction between fiber 0r2nato r4 strength. These anti other instainces serve to Show! that the folding enldurance test, is of mriterkd practical -value. Do- termin~nionn of the perczntange moistureo of t~he sheect as it enters the dlry e~nd of the paper machine strengthens the hypothesniis that shripnkage, irhih is at its maximan with those papers that, retain nest water, is e('vrrlatcd with the folding3 endurance dlata. 'With a moisture content irecrcasing item 0 to 1~5%, the number of folds incre.-ase and the tearing le~nt-th decreases. The effect of tension during-, manufacture was noted an.O. the results wore supplemecnted by the use of a new laboratory instruL ent Lye measuring the percentage of stretch in ltest sheets mand® in sheet zanichinUS. Thlis instrument is fully describe. and furnishes a quantita- ti1vu neasure rjf the effects of the deg~ree of boat-iing a d of water coo- tenDt ol the stock on the eloongation of theo slheet under tension,.

44I2. Hodin Ltd. Hodin paper folding tester. Circular, n. d.

One of the two jaws, similar to 'the one desi(gned by 14I. I. T., as- CHilton through an ang;le of' 270 degrees- and is at its center provided Folding Endurance 115'(

with two edges between which the paper is clamped and. aver v:hich the paper itt bc-nt altern-atoly. The folding therefore always occurs alont& ------nonand the same line. The jaw, with the oxcentiork Of' the edges, is riado at' a >6ry 3.iht motal and-when. changing thic-iroction. of folcl~in-!

tespeed Is reduced; the effect of inrertsa, which would introduce stray - Lt!rknowr frTces, A-"s there by uliml~nated. The other jaw holds the paper under ten-sion whichr ma-y be~at~justu~4 frofai 0,25 to 1.0 pounds. The jawt3u On' uot rnevio sco na to cause, the tenuion to fluctuate; of -the points of contract a-Ir, Triccinn njar tho fold. are simple, there nrjvary little viear aedJ2t7nt trfe with the r~ccalts. ' ThO usol.1 Sm'e0d is 32(0 oIs~1jxl minut.U"0

lit-KhertCeg,. C. c.,2hte, E. R., and Corpanter, L. A. t11ucsurcma,~,nt of' strnenth. aid stiff'ness of' fiber boards bj recrs of uta tic' ben6ing. Pa Te'rude J. 89, no. I7:50(-53(0nt. 24, 1929); Tuh) Fiiper Mweg. Unnadan 23, flo. I8:U6)7-(71-(Oct. 3, 1929); Pop'~r 14111 52, no. fi4:l0, 12, 55-35(N1ov. 2, 1929,); TI.8. 91.:91; C. A. 2)4:959. A rzrthod heni boon. developed for the evaluation of the atrength and rtiallfncss of fiber boards by a static bond.inU test from which the noduli of trnsvsrss strength, rupture, aMd cloaticity ore obtained. Theoo values- aroc expressed In terms thut evaluated the utrltoturnl. properties of the material, and not simply the properties of the piece under -test. 'The values can be regarded with little or none af the qualifying data nu'cessary in the empirical methods applied in mills at the present tine. The method. is otriple and Inexpensive and has been shown to be sufficienbly accurate for the pur~pose. It may be applied to boards of a wideL ;,-aricty and,1 is particularly usefhl in deten'idinin the strength of roulot-irr- anti, well boards. A further applica-tion is in the testin.- of" nulne, -for stren,7t'h, where it has boon found, to hove a jparticular volue, In the ev~aluati~on of QrouhiriwDotl r~uin,.

4:04_ iwizbor., W. ½~cperl'iox obtained i'r..r worlhirn wi7th three Sehorppr frldnrs. Mitt. klc~.noeh.-teeh. Verouchs 19, no. 14:161-i83 (1903.); Wr~chbl.- Papieirfdbi'. 3-5, no). 14:873-876; no. 16:l003-1C05; no. 18:115). 1153; no. 20:l268-3J270 n.29l(3-1; no. 37:240oi-2b108(AprII 5, 19, 1aY 3, 17, July 19, SeptA. 13, 1902).

The results of this xtnsv study ore pruesnted in a scrl-C's oDf 17 table.!_,L It d!C, not cove-(r paro:Irs of hiCgh. fodn c nduranco. The0 wide~di'foru;ncs obtainn~ ix indiviffun) touts ore duec to nonuniformilty tftt r)lar oran rob, to my;-, fault 'ifthe*, Machines. Ave~rnges of tests lnbt ircin for 9'pnape~rs wrhIch hadifror~i 2 tbe212; aDzyblo folds inwica';e tht thu foiling, nusbor incroasocd 126% when the teonsiont was rfuuo..iY:t 1000 tn 900 -gratis, _-38%~ f-an 1-000 t, 800 (;ran, andc 71h%31 *ro X100 to '(00 r-cj. In, the vi cinit~v ot 1000 ,rami',tht'lig nuriber IC affected, approximately i% ."Dit each Jt hange in, tension. The folding enduranLce is affected 1.5% far every 0.03 m.changc in distac between the slotted plate, which creases~- herc paper, nd the; rollers between which, ~thc parper poseses. When, the ro] lets wer at at 0.53 end.r 0.54 rmt. fromn the plate, the averarge_ tc'cnacTcreosu in the folding3 nuriber Ler the creater dist!onc, was 1352%1. Ho ~eoa nrfta distance of' 0.33 rmzi In a study of t1he~operatin~ speed~ It Folding Endurance15

was feoind that the average percentage differences of the folding numbers, using, Ur55 revolutions per miruto. as a basis, were: 45, 99%; 6o, 96%; 20, .114%; 100, 105%, 109, 88%,; 130, 96%. He recommends a speed of~ - 100 to 120 revolutions por minute.

41jf'r. UFrzborg, W1. Folding resistance of normal papters. I. Wochbl. Panicrfabr.-415, no. 2l:1854t-1856(Hnay ?3, 1914).

Data ore given for '35 papers.

10s6. Horzbeorc, W. lFurther oxpcrimcrts with the Sohopper tester. Mitt. k-l. m-ch. -tech. Versuchs. 26:1BJ.(1902); Papior-Ztr. 33, no. 56: * ~~2179-2180(JuLy 12, 19-08); C. A. 3:246.

Variations of results obtained with the Sehopper tester are clue to fruity Ymnipulation anOd lack of uniformity of papers tasted. The. machine, works snirub4y witch vropev handling, cnM the 'results chock vor oscly.: The following cuercstions are given for obtaining best results: keap as free as poseible front d~ust, clean) weekly w,.ith soft brus~h, overhaul thoroug-hly every month, use for papers up to 150 grams per squcre motor only.

447. Horzborg, W1. Further results with Schopper's folder. Mitt. I4. Mcttorial. 25, no. 1:28-40(1907); Papiocr-Ztg. 32, no. 27:118 (April 4; 1907);' Wochbl., Papierfabr. 38j, no. 20:1546-1547(MoaY 18, 1907); Papier-Fobr. 5:931(1907); C. A. 1:2490O.

The experience of the Materialprcfungsantr up to Octolber, 1905, * x4Lih the Schopper machine for testiDg the resistance of paper to folding was ao follows: Complaints reoCrn1dinj -its resul,.ts were faound toteo due either to lack of' care of the machine or to nonngoossamples. Tests of different parts of the same papeor argq-eed well. Ton tests on ~sehofall th clse etdaroci Conpletcly-, and 93% of the control tests prat the paper in the caom class ao the firs,,t tent-. The results of S other control tess froy: Octbobr, 1905 to October, 1906, are given ir! tnblos. Of' thece, 93% agreec. with the first ciccsificctior, cni all the others were just on the border between two classes.

)!43. Ilerzberitg, W. Handc cad, machine folDUing. IMitt. k~l Mnterial. 22, Do. 4:200-201(1904); Wo~chbl. ?apicrfabr. 36, no. 14:1006-1007I(Aprll 8, 1905); Papierfobr. 3:838(1905).

Hond. foldingr, g,-ives higher results than nnichino tol-aing; a. c., a paper which showed. So double folds by herd. 3ave 37 on the riachine.

Th'clirzberg,, W1. Rcsistminee of )papr tofolding.. M-itt. k,1l. Materiel. 25, Do. 3:1L06-109)(1907); Pcjierx-ZtG. 32, no. 68:2982-2985 (Aug,. 25, 1907); W-achbl. Papierfobr. 538, no. 355:2860--28j62(Png.- 31, 1907); 0. A. 1:2943..

It has bean. eustonryr, at the n U~tran~ugo make a tesft for re;s!stan)ce be fo 3i'n 20 st-Ins fr-anr each sampler (ifpaPer, IC in I , -- 1, . .

- Th,~irz Endvuranco 159

each direction. The results obtained, during 'the past years on 925 samples have been examined. comparatively, to See whether testing 5 stripes - frm)each -directiortn would1 not nyce e ually satisfactory results. To make. the cozper2 sOn, 'thd bavcrage of' the first ton toots on each camplie was compared, with that of' the last ton. 'Oat of the 925 papers, of all

-, ~cJaccoon, 794 or 86% wereo-plccod in the same folding class by the f irst tnas by 'the lust ton tests. It is conudd ha to:tssacaf-. ficiort1 unless the paper gives results very close to the lower limit for i-tx class, in which case 20 should be token.-

4I~O. florzber-, W1. Resistance to crumpling. Mltt. kgl1. moch.- tbosh. Vorsuchas. 17, no.~ 1:57-60(1899); Papier-Ztg. 24:2463(1899); Wothbl. Pzpiorfabr. 50, no. 491:4503-4504(ncc. 9, 1899).

Tests on stri ps 50 rm., 15 mi. and. 5 mm. wide gave voluos (averages of machine dnd cross drciootiens ) of 95. 75, 5700 anid 5475 in.; results are alse given for six Samples Using strips 15 and 50 M. wide.

III!. ~dcrzbo-rli, W. Resistance~ to folding in the longitudinal and tansveroe directions of' taper. Mitt. k1l. Material. 33:226-228(193.5); Pcp~icr--Ztg. IL1, no. 9:137(Jan. 30, 1916); C. A. l0:1268; i4:2262.

Tents of 93.8 papers Showed that the foldin g Strength Is greeter in the Liach-ine direction In about 66%1' of' the papers anid greater in the cross direction, in the rermindur. Variations botween individual speci- mens of a given cloes-of normal tapers ore !rnch greater in the case of the fo3.dirg test than. ini the tensile or Stretch tosts.

:)V5L2. Hcrzbe,)rr, W. Vario~tic~n in, the fold-number in trial strips freu th snnr, hohet. Mi'tt.k. Mtotrial. 30:1718-180; Wochbl. Papier- f-obr. s;o. 5:4b1V(Sp.21, 1912); PaPier-'Ztg. 37, n~o. 55:1C986)

0vdbar;writ>ng-; nw)ers show a maxiwma variation of over 200% in th, :,nchiren -ctir and. JOOo In. theo cross direction. mch influence *f Uri-nID'-ro papein theo ioldirg- number was found to be: 50%P relative hauidit0- y, fdip- -.unbor of' 50; at 65% 68; at 80%,, 67. ~How, Luwe. Bndimg Strength tester. U. S. patent 2,151,805

The instrnpsent comprises oirotory disk havin[z a suitable scale sroxtr:t oaportIon :4 ito nor iphory, and.0 a ring- shaped. piece around. the 0iisk-, . sultabjon.e prtion, of the ring also being Gradunted. A weighted L nrpOLUT1atwith (a pointer at the top is0 pivoted at the center of the Us!, so as to be r~ntatblo independently of the disk. rhiih latter cnrrier; two nino on;ninst which the test saniple is laid and is held, in -)acc by means o~a third pin connected by a small arm to the pondauliun avrc. flispl1aCOMort Of tlhe disk causes the pendulumi to exert s bendin,7 atr~-4 s on thep cardb.Uoard, the r-i-unt, oi bending being measured or) one of the scntic-,~and the ztrernGtl' of the ample on the other. Folding Endurance 161

b-twoon the anvils under pressure due to the weight of the upper jaw assembly. While the lower assembly is on the way up, the specimens are forced into the correct position for creasing by moann of pins (7)

----- which-move alternately to the right and to tho loft, just touching the ~puciclnan approximately at the point where the - rease wilrt-e -for-med-. The pins are operated by a lever actuated. by a earn which is driven by the sarm -chaft that moves the lower jow-assemibly. By the ti-MI the lower cssr.emly comes into contact with 'the upper assembly, the pins hae-i boon movedl out of the way. The reciprocating motion of the lower jaw as-- sembly is impartedl by moanc of' a moving bar operated by cans at either end. An the lower jaws myov avay from the upper jaws, the paper specimens are straightened, and as the supporting bar continues to drop, the entire weight of each lower jawo assembly is supported by the corresponding test strip. This tension Is maintained until the supporting bar starts its unvard motion. Ac the bar passes thes zero peint---thint is, that point in tiW! cycle atu vh~lh t'he speciaens are slways inerte"d- -ali tension is r-eracved,.. As the second cycle bopInsi, thu folding, pins Conec into action againl, this tii&: touching! the test strips from the opposite sidec so that they fold in the opposite directionr. The pins ore moved out of the way, the; jaws cone togo-thor, api4 -the strip is crecased. This action, is con- tinued until the test'u Specimen breaks. At this point the lower ossombly Is no longer supported by the specimen as It formerly was durIng one port of the cycle. Instead, thle lower assembly rides oil the way down. on the supporting bar, and. the armL which operates the counter for that particular specimen or head is disengaged. The instrument was studied from the standpoint of' accuracy of' construction, the effect of' tension, ena the affects resultinCg from the moss of the assembly. An.. approximately line~ar relationship existed between -the lo-, of' the folding enduraince aned ttlu, tension for ropers of relatively hig.,h enduraince, whereas for weolcor papers the curves departed from linearity and. develo.ped a re-hhl.' charactecristIc- curvature with the co)nvex side toward the origin. Irvrastigeiion indicatedti that the units dlo net act indepkindently and that comn- p.-rable results cannot be obtained unlens the saere nwnber of Heads were us-cl tit the saout tine. The s~a:rralo havin, 'Ghe poorer formation would, I-n general, give the lower results on thi~s Linstrunelnt, since- the breaking rjf tbhe: w.-akir strips would~ subject the stronger spocimeons to undue. stress. Certain ouggesctioin arc made for ipvngtheli instruxxn-1t.

hL. Jaco~bsen, P. M4.Hi. Investigation of the folding zmnber. Panicr-Fabr. 25, no. l-7--9; no. 11:178; no. 36:573-574(Jon. -i-, March 15, Sept. 6, 125); T. S. 81:24i5; 82:263.

A nmathematical dizrnvssic~n is g-i-ven of results obtained for the folding, endurance by unans of the Schoppor apparatus. Twe variables are considered: (1) uniform te~nsion and different striui widths and (2) variable tens tm)i with co~nstent strip widtth.

t 7-Kicly, Hlolen UI. Bonort on Schoriper tc idim, machine aer That(I' J. 76, nor 9h5-KMa 0 12) Tech. Aessoc. Papers 6:97-100 (Jano, 195); T. S. 77:76.- Folding TEdurance 162

In, the Schopper' folding machine, it is very important that the spring tension be 1000 grams. By reducing the tension 500 grams, the fold was increased over 1000%.. It is recommended that the rollers be 0.015 inch from the folding plate end firmly set in this position. A variation of between 0.015 and 0.013 inch did not show a very wide -.--.-. - c'd-iscrepancy in results. When the clearance was more than this, great .iscrcpancies were observed. - Dsits are given for five laboratories, from which the following conclusions arc drawn. The relative humidity at which the paper is run is the source of greatest error; a difference of 5 to 5', in relative humidity shows a marked variation in results. The error caused by paper, machine, and. method of operation is less in testing the paper cut against the machine direction. It is rocommcntlud. that paper be tested only in the cross direction. A given machine checks itself within about 10% as the maximUm except in an occasional. instance; ally wider variation mast bo attributed to the paper or motho'd of operation. It appears that the error caused by relative humidity is more marked between 55 and 70 tlidn between 45 and 55'; therefore, it may be advisable to rtnm tests at a lower humidity. A tolerance of approximately 30% in the cross direction must be allowed, in consideration of the results from various labora- tories; therefore, the value of the folding number in purchasing paper on specification is questioned. It does not seem that a minimum value can be stated, because there is no ultimate standard machine to which the paper can bo referred and a machine will not check itself within 10%. If a folding Dumber is to be specified, it is recommended that a tolerance above and below the number determined upon as being sati-cL.nctory bo allowed. The following tolerances, recommended by F. P. Ve-itch, seem to cover the field:

Number of Folds Tolerances

10-40 10 40-100 25 100-200 50 200-5n0 100 500-1500 250 1500-3000 500 3000(- Up 1000

Wor' should be carried out on paper before it is tub sized. Data in- disatc ohatthe ongineo-sized paper is sometimes increased as much as 1000l by a 4 0 Bd. glue tub size. It in also recommended that work.be -'one on the folding machine after removing one of the plates, which should g3ivc a single rather than aQdouble fold. Some workl of this kind indicates that thero is a definite ratio between the single ard o nuble Cold on different types of paper. At present the author foolo that the folding nuibeor nay or may not express the quality of the paper. However, by running folding tests on the engine-sized paper, the trcat!eont of the raw material con be very carefully supervised and improperly prepared stock can be corrected.

t

· aab·daalBBb8k2e,. I Folding Endluranco o

Lj5t. Kiely, Helen U. TAPPI Corrmittee report on folaing; tester. Paper Žrnde J. 75, no. 23:45Z46(bjc. 7, 1922); Parer In&. 4, no. 6: 1129, I151(Nov., 1922); T2. S. 75:306.

In a c0o-per tuie stadlyof--the-foldling-teeater, resu~lts-were obtained- - aim1 nachinesU. In geIneral the machines were adIjusted by the me thod a? Vc;Itelh, Saxrn.Ejt>' and Roeed and -ails could not be the cause, of the *mr~iatlor in results. 1I1h1an the hur_4dity was not nontrollocl or-voricd- O rinz-g te tuos'L, there wao a noticeable Variation in the tes ts. Wi th bhj, oXp% ;r'f hiumiCity, no reason, could be-, given ror- the, dIscrepancy rn rsu~c Thec 12 aets of results varied from a I to a 7(2% deviation -1-A th-e avnrage numnbcr of folas. The nunber of fo~lds in the Crass 1~'t~t~nran ~,ory muach more uniform than those in the ianchine direction. On the whole, any given machine seemed to run consistently above or tbcmjrj. the average. Hovever, there wore not sufficient Ldata to draw any :s1el'crel conclusion.

i~.Kienzl, Hubert. Foldinc- iaumber. Papior-Fabr. 25, no.- 38t 59S-5197(Sent. 1S, '1927().

46P. Kirchner, Ern-st. BoarO. testinG apparatus. W'ochbl. Pnpior- flh.50, no. 1S:l051-1055(MaY 3, 1.919).

Sun apparatus ic decscribed and illustrated for etetrrtiniG 'the mexirmuat' bontlin- atrcng,,th coefficient. flReoults are) given for six typos

]+.Kirchner, Ernst. Tester for bending anti breakinrg juallitiez DIcanburi crn ptn 36298; Papicr-Fabr. 1(:03iA; PuLOp Paper I-lag. Canada. 109:1308; Papor Trade J. 75,1 no. 26:52.

WCho: to be tooted is clanpod. in a hinge anid the awl through which it may be bent without breakinig, is measurer. and the tonzion. required, for breakiing in reginturod by neann of a spring,,.

!1&2. Kirchncrt s new ttesting apparatus f'or cardboard and0 pape-r Woshbi . Piorfnbr. 50, roo 23:1365-1354(JUnc' 7, 1919).

'5csu~lts ore; u,,Ive-n for t, hoadnada_ boards.

Uc. 2 KOn, Rt Irm-ectigations, of the now Sihopper boP''ning, cn- Lirnlc Ustter in comparisons with the folcArtng enlu11ronc to-oter. Panio--2 PuLbr. 7'5, no. 5:53-37(Jan. 29, 2.937); Voroi-r ellstOff- u. Papier- Cl'uri~~~~ce1 . ngoPSnicure Jahrcsbericlit 1936:104-10D; lB. I, P,. C. 'T:2-77; C. A. 51~:4117; 1it C. A. 1957B:332; T. S. 105:372.

The rangeso anrl telativc rzerits of' the ieuw bendling- tester and the old, told tester arc discussed. Wo simple, coxrrelation between the resultsc of the two inatruments is obtained. For paper, the noaii to- Via~tioris of 50 ifeterninations, the probable errors JrP ite- ovotragos OnLthe ranges in, th naxi-ritin and ninirun values ware troticolly thu E3Qec Lo~r the new ands the old instrument, rTe errors aC th- nsoa-ure- itsto crthin cellulosic foils or filnn were greecter for the oild WnldinS Endurance 3.64

than. for the newu tester. -The-ratio of folding to bending numbers varies froim one for writing paper tLo 100 for tissue. Representative date&are- given which show the variations of folding and bending numbers as a function oI' tension. With few exceptions, the curves of' the logarithm of the bonding niunbers versus tension for different directions for a

- - Ptvon parer and. f or dif ferent basis weiCghts of the same stock extrapolate iincary to a common valu5 of ending, numtor -for- zero tension. -The son~o cno be oaid'of tho locarithmL. ef the. faihing number versus tension curves. It is_- etumosxd that thC eXt6rapolated, bending~ number for zero

Uters&non may be irbeornrete)d to a 'material constant-" of the stock. -

4(4. M1-eliitz; Wi11i11am 13. Apparatus for testing sheect material. U. S. patent l,2~31,812(Oct. 11, 1932).

An apparatus; designed, particularly for artificial leather, measures the force nececcry to produce- a g~iven lateral displacement of the control portion of the campleI and. also the force req~uirod. to rush the opposite edges of a sample toward each other through a given distance. The onppratus consists of a platform, a pair of vertical rails rising; thorefrom, a carries slidable up and. down between, the rails, tho plat- form and carria~o.c having a pair of opposing grooves, one over the other, to receive, the o'PTosito edges) of a place of sheet noatrial to be tested, and an, unstarding- feeler horizontally slidable on the platform toward and from the planes of the grooves.

4:65. Moglitz, William D3. Apparatus for bending sheet material. U. S. poteont l8183Ot 11, 193)

U ~~~~Ainapparatus for tenting- artificial, leather and the like consists of a base, a standard, a vertical guide supported by the standard above the base, a pniunger vertically movable in the guide, tin elongated roll. horizontally supported on the lover Lend of' the plungeor, a platform. to receive weights carried by thle plunger, a work- supporting anvil mounted on the base and adjustable towardl and from the path of the pluriger, means for clompi~ng the work on the anvil with a portion, pro- jecti,,n into the vertical ;Uth Cf the pluncer, and noons for indicating the on!-le of bond of the projections portion of the work.

4156. Mloss.-er, H. Pr..orW sing inochines. t roc. Tech. Section, PaT'nr !Makers' Assoc. ('-. Tritcl: Ireland Pi, pamrt 1:77-87(Oct., 1927); WrdsFa,_Žr Thatto Rev. .2y, r-. 15:1164, 1166, 1168; no. 16:1252, 1254t, 12,56; discussion, no:. 17762 36'4-_1365(April 15, 22, 29, 1927); Papr-Mker75, no. i8-2. LC-9(Mey, 1927); PnPer Makers' Mo- J. 65,

Thr Schorpper folding ese is the recognized standard machine for Ueter~mining~the resistance offered by a paper to repeated. folding; thep n,.,ner of folds is a reliable ~:ieasurc of its cohesive properties. The folding, effect is produced. by a slotted steel plate wThich, by its reciprocating nor'tion, folds a (tensib~joned) oLrip of peapor backwards and Pofrward~s until it breaks. The arced of this machine should be 120 r-p-n. Tuvarious itonor inv.ro1ved. in the calibration ore listed. It is a very CCDE~iive:-paratus and. demrands iore atten~tion to maintain. than any other

I Folding Endurance 165

tester. 'he head piece and the tension springs are the most important parts. If the rollers or the slotted plate get out of alignment, the ....-- otest strip is subjected alternately to oblique stresses and will break too early. aIck of lubrication-on-the roller bearings will cause uneven wear in the bearing pin holes; under this condition, the results are excessively-high.- - .

467. Mu'rzinger, Walter M. Determining the-bending strength of artificial leather. Nitrocellulose 5, no. 10:179-181(Oct., 1934); B. I. P. C. 5:88; C. A. 29:1533.

An illustrated description of a motor-driven apparatus.

438. Multiple folding endurance tester (Thwing). Instruments 9, no. 3:59(March, 1936).

''en folding tests can bo made simultaneously in this new iO-spindle LdeviL'c. Specimens (15 cm. wide) are held in cam-action locking grips aiJd cr alternately folded under compression and straightened out under tonrzoln. A definite sharp fold is made under the compression load. Tho compression load is 0.5 1i. Depending upon the grade of paper the tuonrioi lead may b; variedfrom 0.5 to 3 kg. A tripper folding device alternately folds the'papcr in two directions. A counter registers ' tnthe numltbr of folds made to the breaking point. If doeired, toots can bc made on fdver thor ton spindles. A clutch is provided to disengage i: tthe driving mechanism while test pieces are being inserted in gripc. . ko465a~.Naoumof, K. 'Dtermination of the resistance of paper to crumpling by the Schopper folder. Papier-Ztg. 30, no. 78:2954-2958; no. C0:3030(Sopt. 28, Oct. 5, 1905).

4l.0. Neaoumof, P. Use of logarithmic coordinatos in paper testing. iletlod of plotting results from Schoppor folding machine. Papior-Ztg. 30, no. 74:2802(Sopt. 14, 1905); J. Soc. Chen. Inrl. 24:1028.

n cxpressing the results obtained for the rcsistanco of paper tc 'oliLing, by means of the Schoppor folding machine, the tensions 'botwocn the springs holding the paper are plotted as abscissas, and the number of double folds which the paper resists is plotted on the ordinate axis. Tie resulting curves have the form of hyperbolas. !r' TnThoso may be reduced to straight lines by plotting the numbers propor- tionallyr to their logarithms, which may be done on paper ruled for that purpose. The inclinations of the straight lines so obtained. inidicatc the law according to which the resistance of the particular paper varies with the tension, whereas any point outside the main line ray be rccoinizecd as an experimental error and corrected as such.

1471. National Association of Purchasing agent, Inc. Corrugated fibrobaordi chilppi'e containers. No. 19, 1934.- p.

.ondinE Tcst. 'ho official technical test for bcndirf---four snmplos .1 s.mch, inh t.h; running 'oh long wroainway and the short way, shall 1^ Folding Endurance 166

carefully cut from the liner cir container to be tested. The samples shall be 15 mm. (0.59 inch) wide and, of sufficient length to i nsure a firm smnooth grii in the jaws of the tester, and shall be cut from unwrinkled, unscored, and urbTernished. stock. The teat sample shall -bthe chmncpd in--the tester (H1. -I. T-.) without-mo .certra. I~ortion (to wib~listand. the bendingl) boing touched by the hands, thle tension adjusted tekuozrnand the spre-imen folded through a combined angle of 270 dc;raeo luitilI it breaks. Each of thfe two) sate. ½f four samples --- (ts' be folde-d with and tpentthe grain, respectively) 'shall be slut- Jlariy tested enid 'the average number-~ of fields each way shell1 determine c')uiipliarce with the npocificotio-o. Not more than one of eoac of the sets of four tests may fall short of' the required. number. However, if' either or both of the two sets of tests in below the soecification, a series o)f 12 re-tests of that test or -tests, shall, be tan'do:, of which n-et more than three nay fail to comply, with the avernage of all 12 meeting~the specification, for acceptance. A simple substitute test, ind~icative in a crude, but reansonably re-liable way of bending qualities to be desired, coit be nvdo by hand- Linnipulotien of' sonplo boxes and sections of double-faced board cut from- then. The flaps of 'the box shall' be doubled comipletely back upon the sides, first inwardly and enenoutardl, u.on the horizontal scores, each bend boing tightly prronscd down by the hand. This bending shall be repeated until a total *-jf 'three bends have been mjde inwardly and three outwardly, and the aboard inspected both 'inside aind outside, f'or cracking or failure of'

the board. Further, twom pieces, appro:ximately 5 inches square, shall be cut frome an unscored. and. unprinted. section of a boxy and. each shall be hand scoredl by moons of a ruler or other fairly sharp straight-edge,

to break down thle corrugations but not brook or cut the ourfhce of tmc facingE. Two scores shall be rodeo at right angles to each other bisecting the board with and against the gri.OenCpcsalb folded naganst thoe grain or with the cornigations (the~(rain runo at right angles to the corrug~ations), that. doubled back upon itself' with the grnin, and. rhall, choir no sirgn of failure when thle second fold is * ressed down tightly by thes hand. The other narie~l shall be folded with the grain, then) doubledl back, upon itself ngainst the Groin, and shall show only slight tearingP at the cor:'or represenrting the junction If' the two folds whean nrrssed do-wn tig-,htly by the hand. The interpreta- tion or' the bcn~izig qualities )f' the boar,'. from this last test is n1-osstLriiy at better a- xnoxmŽC-ienco in nnkcinr; the toot anJ shiould be ccrsinudered as erecrly irndiecti~ve rf [general. strengIth or weakneMss.

W72. Na-tional Ri~ronu -:f' St~ariferri. Caor end adjustment of' fold< in"teuters of, the Suhn)ppjr typo~. Circular e.379. Nov. 19, 1~929 7 P-

This is a surpleit-otary rernoz't to the nturly of' Carson and Snyder [IDe 433], which (Liscuseed. -the relation of' niozn if thle mechanical -Tariables to 'the., teat results in1 the liGht -of danta then available and described a newly developed delvice, for fadjuetir<- thle, tenion on the snOcincll. This device., which isq a i:)cd-wcAight, tester iolngthe use of a balanced boil-crank lever, has been il-pr~oved an d odnted to the noasurement of' the friction of the. r-llers; th1in iietiiod is described in detail. 'The, rol-ler frictioni hoe, bonobservoe to %vry from 25 to 220 g-rayas equivalent torsiorn anmi usuaIWLLy. from1 50 tuo 30 g-rams for

I1 Folding Endurance 167

rollers in good condition. A variation from 25 to 100 Crams is objec- tionmabie but i's about the boot that can be done, considering the Itiltat'inon of the tester. A test is doocribed. for detecting poor a_ jrflfnpnon of the rollers. A number of' sueggetions are g7iven conrcerninu hocare and. ndjustnont- of the foling tester.; a procedure is outlined .rrperiodic inornoction. this is essential for the bent results.

L7% National Bureau jf Smndlaidb. -The testing of paper.--Oircu- - lor L'on.107. Feb. 1-2, 1921.

A brief description of folding endurance is given on p. 17-18. V3~,NumanH. Board testing. Zdls~toff u. Panier 5, no. 11: 43719l~v.,192);T. 8. 82:301.

The construction and application of the Naunonn-Schopper paper board bending- tester arc Iescribed. Constructional skeotches of the rneilinc are Given.

£7_25 ?Naunaun, M. A rbw apparatus for testinCg the bending, strenGth anik', hf bondingr anlet of- board, etc. Wechibl. Phpierfabr. 55, no. 33; 20753Cb20s' ncr-.35:2202-2205; no. 36:2263-2268(Akig. 16, 30, Sept. 6, 1924B; T2. S. C0:247.

The ncw 1:bursnnn-Schopper bending tester for heavy poperso, cardboard, ctc., is describedt at considerable length. The results of actual tests Ore re'onroducod in order to demonstrate what may be expected o:f the in-i suL-urn.nt. The followInC advantagesa are claimed for the tester: constant crn~tol -ff product; influence of thickness and pressuro Onr the bendinC pronortics cnn be ascertained; manufacturing variables can be studied.; the.r arSle of b!reak Is easily deternincd; and the uniformity of the ca-rO,- bo~ard. nay bea Thllnwed.. The abvov hac beer translated. into Er.glish Ond. -oul-iobcc ns Booklet No. 507 of' Louis Schopper. £7.Naumann. 14. Schopper bending tester. Poapir 29, no. 8:985- QK'(Sept., 126); T. S. 84:278.

A, toot ijeco 50 mm. wide is held In jaws, the inner woile of urP>cK cor at an)an.-le of 180 degrees. By turnirvg a hand.0 whool the A t I':ja is Civer a rotary motion, and. the upper Jaw, hinch corrnea a wcighL pordulun, offers a resistance cgqual to the banendin strength 1~ iV of the test piece. It therefore only partially follows the 0.isplace- non~t of' the lower jawr and the angle between the two prad~ually rleerconocs -% Th~Fietest is continued until t~he test piece brooks, and the scale reaftinG Cives the bendinCg resistance in. kios and. the bending; angle in degrees, the latter being the rnaxinan- angle to) which the product con be bent. The curve betireen the resistone andL the bending angle1 io automatically recorded.. This is covered by U. S. patent 1, 559,4I66 (Ot27, 1(925).

)I77. Tiew folding,, endurancb tester (Anthor Testingr, Inztrrncnt Coryo.nny). Panor tfAdel J. 101, no. 2:27(JulY 11, 1935). Folding Endurance 168

4738. Paper Makers' Association of Great Britain & Ireland. Techni- cal Section, Paper Testing Committee. First report. London, The Associa- tion, 1937. 85 p. Also issued, with discussion, as Vol. 18, part 1A, of the Proceedings of the Technical Section. See also World's Paper - Trade-Rev., Tech. Convention-No., -March, 1957:4-72; B. I. P. C. 7:348.

- Specifications are given for the folding tost using the Schoppor folding tester. The test specimen is 15 + 0.25 =m. in width and 70-nm. in length; the apparatus is driven at such a speed that 90-120 double folds per minute are offectod. The test gives information about certain properties of paper, such as the durability, which cannot be obtained by other instruments. In the Schoppor tastor, a test strip of theopaper is hold by two clamps attached to helical springs, and the folding is carried out by the reciprocating action of a vertical blade. The tension of the springs on the paper is such that, when the paper is extended to its full length, each spring exerts a pull of 770 grums; when the folding blade is at the limit of its travel, however, and the paper is bent to the maximum, the pull exerted by each of the springs is 1000 grams. Dioad- vantages of the folding test are that strong papers (those that resist upwards of 1000 double-folds) require a long time for the completion of the toot and the results on a narrow strip nay show such variations as to cast doubt on the accuracy of the -figures. There arc inherent difficul- :' ties in. the nature of thu test. Thus, a thin paper has less stress upon j; the fibers of the outer arc of the fold and loss crush upon the fibers of the inner arc, than is oxerted in the case of a thicker paper. The folding test is particularly susceptible to atmospheric influencec. . Li It is impossible to correct the folding test oven approximately for variation in substance. Therc is no definite ratio between the width of *i, the strip and the folding figure and it is necessary to standardize on one width. Sompl.es of a paper ]4, 15, and 16 mm. .vidc gave values of 245, 301, and 366 double folds. A lodger paper tasouted at 55, 64, and 7250 relative hun.idity, gavo values of 675, 997, and 1587 folds, respectively. Details are -ivcni of the calibration of the spring. ,! !** tS7. Rood, E. 0. Efi'cct of tomnpraturo and rclativo humidity on tho folding endurance of' paper. Paper Traieo J. 79, no. 25:55-57(Doc. 18, 1924); Paper 35, no. 7:209-272(Dcc. 4, 1924); Papor Makcrs' Mo. J. 63, no. .1-:17, 29; no. 2:50-52(Jan., Fob., 1925); World's Paper Trade Rev. 83, no. J4:290(Jan. 23, 1925); T. S. 31:70.

Tests were made at 60°, 70° , and g5 ° F. at a relative humidity of 65'yj. A rise in temperature causes a decrease in folding endurance, 4| the effect being more marked with tests made in the machine direction than thoso made in the across machine direction. Theo results show the .f need of controlling the temperature within limits of approximately 10° F. The effect of the relative humidity was studied by making tests at 25, 30, 40, 45, 55, and 65% at a temporaturc of 70° F. (oxccpt 65%, which mws at 65° P). The results show very markcrC incroascs in the folding endurance in the rmachi:ne direction as the humidity incrcasccs. There is a much loss but more uniform increase in foldin endurance in the across direction with the inurcsaing relative humidity. The increase in results in the machine direction is very mnrkcd, being from 155 to

I I 4_ -rI -.. 1-:1

Folding Endurance 169

1409% at 65 rather than at 25% relative humidity; the results in thb cross- direction arc 17 to 299% through the same range. The increase between 45 and 65% varied from 40 to 2553 in the machine and 0 to 104% in the across machine direction. Interesting results owre obtained for different ..typcs of papers. Thus, in changing from 45 to 65% relative humidity, the rosulfts i'o thd-nachine direction showed-incroases_of 276% for kraft, 354'; for rope, and 749%ofor unbleached sulfitc; in the across machine -direction, 0G%for rope, 135% for kraft, and 330% for unbleached sulfitc. Tub-sized bend and lodgers showed considoroble increase in the machine direction but dififrent samppljs do not show the saBm percentage increase. These results indicate that it is impossible to secure any factor for cnJca.lotins folding endurance results at one condition to equivalents at I another or to a standard condition. Because of the wide difference in tlho effect of atmospheric conditions on folding endurance, the comparative tent values of papers cannot be the sane at different humiditics and tcnpcraturso. Therefore, it is paramount that, in the selection and adoption of a standard testing condition, this condition must be in harmony with the use and service demanded of the paper. mT folding cn- duranc in the machine direction of all papers tested is higher at 65% relative humidity than that of the across machine direction. The difference between the folding endurance results in the machine and the across nachino directions is ruch greater with all papers at 700 F. and 65% relative humidity than it is at 70 ° F. and 45 to 50% relative humidity. The folding endurance results in the across machine direction at 70 ° F. and 45 to 50% relative humidity are greater with some. papers than those in the nachine direction. The advantages of using 50% relative humidity for testing arc pointed out.

480. Red, E. 0., and Larson, Frank E. A. Foldiug endurance test value. Pulp Paper Mag. Canada 25, no. 4:97(Jan. 22, 1925); C. A. 19:1948; T. S. *1:70.

In connection with work being carried out by the Bureau of Standards for the United Typothotao of America, tests have been nado on 94 connorcial bond papers and 59 ledger papers. From the results it appears that the folding endurance results arc the most indicative of serviceability, durability, and quality, and show the most striking variation in the papers toctci. Therefore, the folding endurance test, properly i-tcrpretcd and in combination with the bursting or tonsile strength, nay be found suff'i- clct to classify thcse papers.

481. nibioro-Raverlat, J. Results with the Nauiann-Schopper flexo- molbet as compared with those with the Mullen tester. Ponior 35, no. 10: 1055-ln05(Oct., 1932); T. S. 97:72; C. A. 27:1750; B. I. P. C. 3:144.' Z;, From a comparison of the results obtained on tWo different boards, Ut is concluded that there ic a relationship between the results obtuined 1.o with the two instruments but -that its determination would require further

t tests on a more extended range of samples. Though the .ulion tester ''t does not permit distinguishing between machine and cross directions, it gives a good discrimination between the two sides of the test piece, ard for a given set of sanplcs, it gives characteristic results which are in all points comparable with those of the bending testcr. It prosunts the same drawback of slippage between the jaws, but it is much simpler and quicker to operate.

. . in,, ^n--p -., piirI ii_ .L,

Folding Enduronco 170

4C2. Ribiere-Raverlat, J. Use of the Naumann-Schopper flexometcr in board manufacture. Papier 35, no. 2:177-178, 181-182, 185-186, 189-10,, 193-194, 197-198(Feb., 1932); T. S. 95:75.

Irom a detailed analysis of the mechanism of-the action of the. Naumann-Schoppor flexomotcr and of the information which it gives, - illustrated-by means of an example of the results obtained with a given sample and of the curves which can be calculated 'and plotted from thom, the author concludes that the instrument permits of distinguishing between the two faces of a sample of board and of revealing tho internal defects which may exist in the shoot. The operation of obtaining the results and information, however, is long and tedious and they should be coordinated with a view to subsequent comparisons.

LF83. Schnablo, George L., and Abbott, Frank F. Method of and apparatus for testing fibrous materials. U. S. patentl1,436,323(Nov. 21, 1922); C. A. 17:635; Pulp Paper Mag. Canada 22:657.

Paper is subjected to friction by drawing it over stationary plates and simultaneously subjected to repeated folding until separation of the matcrisl occurs.

i;' io4(:.Schoppor, Alfrod. Apparatus for testing the bonding strength : of p)asteboord, cardboard, etc. U. S. patent 1.559,466(Oct. 27, 1925); .g T. S. *3:204.

The test piece io attached to two plates, which are rotatable about a common. axis, so that, by moving thom in an angular relation with each [ir ~ other, the test piece is bent end broken. The rotation of one of the (i' plates from a position of rest is opposed by a progroesivoly incrcosing force produced by a weighted pendulum or equivalent device; moans arc provided for measuring the anglo through which each plato is moved.

4C5. Schoppor, Alfred. Endurance tentin3 of paper, , and board. Wochbl. Papierfobr. 68, no. 6:97-100; no. 7:119-124(Fob. 6, 15, 1937); World's Paper Trade Rev. 109, no. 14:Toch. Supply.:45-60(April 8, 195();. B. I. P. C. 7:277; C. A. 31:4116; T. S. 105:372.

R feronceo is mado to a now type of folding endurance tester, suitable for tooting paper and board, called the endurance foldirg t-stor. A osaplc strip 15 nm. wide is bent under constant tension until failure occurs. The upper sample holder bends the paper through 90 dogrcoo to the left and to the right of the equilibrium position. The lower clamp applies tension to the strip by means of adjustable weight. The radii of curvature of the edges of the upper claop are 0.01 mn. The instrument operates at a speed of 110 bonds por- minute. Physico-rnthorLmtical con- aiderations and a large number of tabuladted st data and Craphs arc given.

486. Scribner, B. W., a:)d Snyder, L. W. Stury of physical Droportion of binders board. Paper Trade J. 95, no. 1:29-33(0ct. 20, 1932); C. A. 27:1752; T. S. 96:135

______.- . - *Folding Endurance 171

Th_ Naumnnn-Sohoppor bonding tester was used. The test specimens wore 2 x `c irches. The inner faces of the two clamp Jaws arc in the sarn:e lance with funds touching when the instrument is in zero position. The outbi surfaces arc-adjustable to-pornit the insertion. of boards of different thicknesocs. The board is bent by turning a hand wheel, which -*- - causes'.one of the clarps to revolve about a center. The resistance of the board to the applied stress causes the "other clamp, which is fastened' -. to a weighted pcnduliun, to revolve about the same counter. The total movoinnt of tho second clamp is dependent upon the resistance the board offers to the Increasing load applied through the movement of the first clrap. WVhon the board is broken, a raxiran indicating pointer, which follows the novomeont of the second clamp, indicates the bonding strength on a scale. Data arc given for five samples of boards. The results aro ccrlpared with flexural strcrngth tests carried out on a modified tonsile strength tester. In general the Naunann-Schopper tests are '. higher because of the use of a wider tooest specinon and a shorter test span. Flexural strength tects arc commonly made by supporting the test specimen on two separated parallel knife dges and applying a load to tho specimen at rnidspan. through a third knife edge parallel to the dther two. In testing board, however, rods have boon found noro satisfactory than knife oedes, the rods used for binder boards being 1/8 inch in -'~ dianctcr. 'The rods wcrc used in the form of stirrups clamped in a stan- dard type of paper tensile breaking strength tester. The details of ,. the stirrup device are shown.. The size of the specimen was 1 x 5 inches. c2 Data ore given for the breaking load and the deflection at rupture for the lergt!hwius and crosswise directions. In addition the bursting strength ~ cand the tensile properties are given.

. LQ487. Sirnords, F. A., and Doughty, B. H. Application of elementary statistical nctlhols in the testing o01' pulp and paper. Paper Trade J. 97, no. 2;:32-35(Duc. 21, 1935); correction, 98, no. 13:34(March 29, 1934); 'Tch. Assoc. Papers 17, -7. l:473-478(June, 1934); B. C. A. 1934B:139; C. A. 2c:2527; T. S. ,.:9..B. I. P. C. 4:117.

Thc rccults' ' f'-.llin' endurance tests nmade on several tarn.arack kraft g -i.pr' -G cI'" >fc ..r, i_n rcanl. eight and. in degree of calendering arc given. ~$ Thn cofi Icl .' ....-reariation var;- over a relatively snall range without S any regular trend. 'ljs su-,;cets that, for this particular series at . uas., the varicblity of the folding test is not influenced either by the reoan weight, the degree of calendering of the paper, or by the direction of the tost strip and that the factor of greatest influence is tho formation of the sheet. Thc values of the probable error of the mcan permits certain conclusions as to the significance of the varin- ttims observed in the several runs. It is also possible to calculate tho nuLber ,'-, tests roquircd. to produce an average, the raxirmn error 'ft' which will fall within a prcdotcrrnined limit.

48C. Snydler, L. W., and Carson, F. T. A study of th_ M. I. T. paper * :lding tcstcr. Paper Th'adc J. 96, no. 22:40-44(Juno 1, 1933); Zcllctoff '1.PaDier 13, no. 9:441(Sopt., 1933); C. A. 27:40'75; T. S. 98:14; B. I. P. J. 3:270. -- --...... Folding Endurance 172

In the M. I. T. folding tester, a strip of paper is fastened at one end in a tension clamp, which is actuated by a spring. The other end of the strip is fastened in an oscillating clamp, the jaws of which - terminate -in rounded edges. near the center of oscillation. This clamp oscillates through an angle of 135 degrees each way~from the -verticlio- -.-- and in so doing bends the paper, first one way and then the other, around the curved edg6esof-the Jaws.- The tension on the specimen is determined by the displacement of the tension clamp at the time the strip is fastened in the two clamps. Some of the features of this design are: No align- meont rollers arc required and there are few working parts which are Oriven by the specimen. Tho tension is practically constant throughout the folding cycle. The tension may be adjusted easily to any desired value within the capacity of the spring, thus permitting reasonably rapid testing o. a wide range of papors. Manipulation of the plunger under lead so as to allow it to come to rest first on the downward stroke and then. on the upward stroke indicated that the possible error in applying a given tension to the specimen is of the order of about 25 grams, which is in conformity with results of the determination. of the average frictional resistance for a tension of 0.5, 1.0, and. 1.5 kg. In addition to this friction in the plunger bearing, another source of uncertainty in the applied tension results from small vertical displace- morts oi' the specimen itself, necessitated by the fact that a small ;portion of the specimen must be wrapped around the odges of the jaws of the oscillating clamp. The choice of a folding clamp such that the ~'. speocimoen to be tested nearly fills in -the distance separating Jaws will j. rn~minimiz2 the tension changes. Tloi change in effective tension resulting ff from the curvature and position. of the folding odges is in most cases small. An. error of 50 grams in the tension applied to the specinon might result in an error of 15 to 20% in tho folding results, depending upon. the absolute value of the tension; actually, this is probably high. The curvature of the folding surfaces in discussed but, because of the difficulty in obtaining, data on this question, it was not studied. Variation: in the folding rate between 130 and 200 double folds per '..inuto did not appear to affect the results appreciably. Data obtained b with si. M. I. sT. testers showed that if the folding surfaces were a lways un.do of the correct contour, if tho variation. in. applied tension wore rlinimizod, and if a sufficiently largo number of tests woro made and averaged, the tester would yield consicte:nt results. There is no semblance of correlation. botweon the results obtained with the M. I. T. and the Schoppor tostcrs. The M. I. T. results are always lower, probably because the tension in. tho case of the M. I. T. tester is nearly constant at 1 kg., whu-roas the tension in the case of the Schoppor tOtoer varies from i to about 0.3 kg. during the folding cycle and because, in the former case, tho sample i: boing continuously bentt. whereas in -th latter It is bont only whilc it is bcins pushed between the folding rollers oan while it is under tension of about O.c kg. It is evident that the specimen is not treated in. the some way ir the two types of toestre. A proposed method is given for making, 1'. I. T. folding tests.

4h9. TAPPI. Folding endurance of paper. TAPPI Standard T 423 n-41. Approved Standerd--Sopt., 1927; corrccted--Sopt., 1936; reviscd--rFb. 1941. 2 shoots. Various versions have appeared in Paper Trade J. 85, .1* no. 19:60-6l(Nov. 10, 1927); 86, no. 8:211, 213('0ob. 23, 1928); 111, no. 7' 34-36(Aug. 15, 1940). '· "y;~~~~~~~~~~~~. C~~~~~~~~~~_f~"'r'~ - :lf

Folding Endurance 175

.-_ -- The standard covers the Schopper folding endurance for papers hav- in. a th:!cknoss of not more than 0.01- inch and the M-.- I.- T. folding.. enditranco which can be adjusted for papers of any thickness. There is 'no constoat relation- between the test values obtained with the two types of testers.

4ii0. TAPPI. Operating factors affecting folding endurance. Special Report No. 214. Juno 21, 1934. 14 p. Mimeographed.

Replies arc given from a number of nills regarding the influence of such factors as cookinti cookingoki temperature, bleaching, beat- ing, sizing, fillers, jordaning, drying, machine speed, etc., on the folding endurance of paper.

i491. TAPPT. Committoo on Papor To ntig. Folding endurance. In l ~ Paper testing methods, 12:58-64.

:j,! A cneral dicvres ion is given of the method of using the Schopper .^. ffolding taster (-Lhis Oisow covered by TAPPI Standard 423 m). A brief discussion is given of the M. I. T. folding tester.

4.2 TAPPI. CPoamitte, on wapsr Tcstinf;. Paper testing methods. ;. Folding endurance. Paper Trade J. 75, no. 4::43-44(July 27, 1922).

~ ~iThe Schopper tester is used; the calibration and accuracy are dis- *- ~cusscd. Mlon.ion is made also of the Green folding tester, designed for use with hand shots; it is applicable to any shoot irrespective of bulk or tcncile strength. A brief description is given of this tester.

p - i4r4.3-Taylor, Casper E.. Paper-testing machine. U. S. potent 1,'i,549(iMarch 6, 1928); T. S. 90:31.

iV' ~ To ensure that the clamps holding the ends of tho test strip shall mve in a true horizontal plano without any lateral yielding or oscilla- tion bout a horizontal axis, horizontal rollers of substantial width are iprovxidod on which the clamps are made to rest. Vertical adjusting ncans for the supporting rollers are provided.

494. Tinius Olsen Testing Machine Co. M. I. T. folding endurance pacper tester. Circular. n. d.

Tn this machine strips of paper 1.5 cm. wide are held between two jaws, the lower of which rotates through a given angle and the paper is thus folded forward and backward around a certain radius. Tle upper head is attached to a weighing system so that a definite tensile load may be applied to the sample during the foldinG operation.

99 .. Veitch, F. P., Saumnct, i'anh, and Peed, E. 0. Folding endurance ')f paper. Paper 20, P.o. 12:13-19(May 30, 1917); C. A. 11:2275...... ~I._~ ~-fi-~a -:,. .- . -..

Folding Endursinco 174

- c-Schopbor folding endurancetester (German patent 94,901) has proviou.ly been studied only by Herzberg. This test is designed to imitate, in a general way, the practical conditions involved in the handling, foldit7, ond' brnmpling-of paper. The numerical exprcssion--the. number of double folds resisted--is an indication of the quality and, probably, of the durability of the paper. Six machines were used in this study; they were standardized with the rollers set at 0.015 inch (Horzborg used 0.015 inch); results obtaircd with machines in which the rollers were set at 0.015, 0.017, and 0.019 inch were closely concordant. A mi-thod. of sBondardizing the machine is given. Foldirg tests should be madc-i at approximately 120 revolutions or double folds per minute. The tost samples wore conditioned at 65 ° and 65% relative humidity. Bond, book, andc lodger papers were examined. The averages of ten tests on the same or on different machines, using a paper of low or high folding endurance, are not widely different, when the machines have been care- fully nd.justcd and the tests made under uniform temperature and humidity conditions. A closer agreement is obtained by making 20 tests. The great irregularity in paper is shown by the maximum and minimum results ob- tainJd or each paper with each machine; 21 to 42' of the individual results vary loss than 10% from the true mean; 47 to 735 vary less than 20-;, and 69 to 89% vary less than 30%. At this time, 16.1% may be rc- gar!. Cd as the maxirnu allowable variation from the moan of averages of two cericn of 10 tests on. the sam machine. The data indicate that the dilcoi'-nco between individual results is causedby variations in the paper and not to irregularities in the machine. In routine testing, the folding cndurcncc is determined only in the weaker direction, which is usually the cross machine direction. The avcragc of five tests will generally indicate the range of folding endurance of a paper, but for closer and roro reliable averages, it is advisable to make 10 or even 20 tosts. The ve-races of two sets of 10 tests should not vary more than l6 and those of 20 tests not more than 11' from their mean. Distinct differences in quality nay be observed in papers, the folding endurance numbers of which differ by 10 when the folding endurance is from 10 to 40 folds, by 25 between 40 and 100, by 50 betwcon 100 and 200, and by 100 between 200 andl 500. It is believed that the instrument is valuable for indicating thc probable durability of paper and its suitability for specific purposes.

:-- 175

HYGROEXPAMSIVITY

40.6. Abel, J. G. The interpretation of'tdsts-)n paper; Proc.- --- - Tcch. Section, Paper Makers' Assoc. CG. lritain Ireland 14, part 1: 171-18'.; iiscusSion, -18 1-- 0(Oct., 1933-); World's. Paper Trade Rev. 99, o. 12:867-868, , -870,90- 913-914, 916(March 24, 1933); Paper- iMa3or 86, no. 2:TS157-l60; no. 3:TS167(ug., SSpt., . 9335) Zellstoff u. Papier 15, no. 5:216 -217(loay, 1933); C. A. 27:5973.; T. S. 98:147.

The Schoppnr wet-stretch tester is an admirable instrument. By fixing a time'limit of 5 minutes far a test, very reliable comparative tests have been obtained. Papers giving a big stretch under the con- ditions of the test gave a greater expansion in a humid atmosphere than those which gave a low stretch. One strong objection to the test is the tension which is applied; however, it is difficult to suggest a remedy.

4±31. Bercovitz, D. Extension meter for testing papers Under difJ;'Crent humidity conditions. Zollstoff u. Papior 10, no. 1:40 (Jan., 1930); T. S: 92:4.

2; An apparatus is described by which it is possible to measure the extension of ten strips at one time. The samples are placed in the i apparatus and dry air is passed through until the samples are completely dry. After the length has been measured by means of a micrometer, rmoist air of the desired humidity is passed through (time not stated) and the length again measured. A microscope is used for reading the i-icr onctr.

498. Bialkowsky, Harold W., and Probat, T. Richard. Dimensional chances in paper. Paper Trade J. 111, no. 2:34-38(July 11, 1940); Tech. Assoc. Paners 23:246-250(Juni, 1940); Paper Ind. 22, no. 7:718, 720, 722(0ct., 1940); B. I. P. C. 10:465; B. C. P. A. 1940B:738; C. A. :''i 34:8275.

In a study of the of ect of' relative humidity on the dimensional chnecao of paper, the papnr was humidified at 50p relative humidity and 76 i'., placed in samnpi holders to accornodate strips about 25 cm. longC; (held taut by weights with a mass of 32 grams) and then in glass tubes, through which air was passed at a definite humidity (15 and 95%), ~ tthe rate being about 5 liters per minute; the elongation was measured by means of a microscope (the accuracy was about 0.1%). Samples were X' also immersed in water at 23° C. for 1 minute and the elongation measured. Noernal bond papers change in dimensions about 0.6% in the machine direc- tion and 1.6% in the cross direction, when the relative humidity varies from 95 to 15%. The basio weight and. furnish seem to have little effect on these changes. The machine and cross directions change about the same amount when the relative humidity is lowered from 50 to 15%; if the relative humidity is changed from'50 to 95%, the cross direction expands about 7 times as much as the machine direction. There is no geood correlation between dimensional changes caused. by varying the relative humidity and the expansion produced by actual wetting of the sheet.

I flyzroexpa"Bivity - 176

'3 Davis, Harold S. New methods for measuring the effects of tenpcratu'e and humidity on the dimensions of paper. Paper 51, no. 12: 7-2~, ).0(JYan. 10, 1923); World's Paper Trade Rev. 79, no. 10:804, 806

(lvufii -CI4) I%53)yT. S:- 76:186;-c;. A;. 17:0~78.… --

- - --- Ar.- illuctra~tior and. a-briof description are c~iven of a conditioAnin aet~arntus corsi-sLtrg of a glass tube 0.7,5 inch in diimeter~and 3N'eet long, th-ruugh which conditioned, air wad passed; the conditioning tube was surrounded by a gJlass jacket through which water at any, desired teupracrture couJld be passed. Paper strips 20 inches long were suspended from adjustable supports at the top of the conflitioning~, tube and were attached, at the bottom to aluminuni pointecrs. The pointers vere ar- rne!so that each inch the pointer mo-ied corresponded to a change of o.i% in. the lenQ~,th of the ropers. With constant relative humidity, the dinmolxjaions of the papers are substantially constant over a tempera- ture rapngeI of 70-lOW0 F. Vlhcni the absolute blimid-ity is decreased atb a constant ttemnorature, thec dimensions decrea se and vice versa. The rato ct which the parer changeso its dimensions is denend~ent upon thle rate of' flow of the air over, it". The rate at which the raper increases itfs dimensions vith ii s~ing relative humiility is somewhat greater than. the rate at ithich it Pecreases with falling relative humidity, but the diIS'erencc betwe-en the twoe is not very great. Tho rates at which the paper charges its dimensions in a moderate current of air are fairly rapid, being nearly complete in 5-10 minutes. The rtes are increased with rise in tempera Lure.

>00.- Davis, Raymond, and Stovall, htery, J., Jr. Dimensional changes in aerial photographic films and papers. J. Be0scarch Natl. BLor. Stondnrde 19, no. G-:613-637(Doc., 1957) (PP 1051); B. T. P. C. 8:209.

A machanical.ge or extoneometer was developedi for measuriing fiL11 ohrikngcand, on- optical. extensomoter, suitable for both paper and- f i 22. Ihe latter employs to C52-mon. M~icro-Tesriar objectives, one movable and, one f! ied. These lenues are- in fixed. focus or. thle u:pper surface of the pia:~-glsstop of the instrument. Dy moans of Trrisms the beams from the lonnacs are brought to focus on a tu~nrfk-Irodhum photometric cube, which, brings the separate irxinges into juxtaposition. A brass tube fitted wi Lh a lens and hard-r-ubber cop with a smoll hole constitutes the eye- Piece of the instrument; this is focused on the photomeitric cube. At the, riglht of thle boxc a micrometer is fitted to move the lens anid measure B ~ ~itsdisOplace-ment. At the other enC, of the box is a dial rage, whic also indicates the position of the lenis. Either miAc:oronctc5. or dial Cngo may be read.; the letter is preferable because of eave' of raig The distance, between lenseGs is i$ inches.

CI.~ Deternination of the influence of moisture on, the dimens-ions of paper. PapiCer-F&br. 22o:659(Oct. 190, 1924); 1'. S. 81:70.

The Sehopper test-Dr fo7' Jloterminrti, the influencecof moistutre on P,'ni)r is sketched cr4 dOcscrlhect.

j~L2. Griffin, Rotger 0. £'Zcflaruiofl of papor- wi th vrr-ryine humiditly. Pape- Trade J. 8,o55-hM.4, 1.927); Tech. Assoc. PThmors ll:8o-U5 (June1, 1928); C. A.- 211:4067; T. S. 86:193. R fly~ro0xpnnsivity -77

This in an extension bf the work Of H. S. Davis. An expanniometer has bee-n designed, which cqnnists of a conditioning chamTber (a glass tr 1.5 inches inside diameter and 2 feet long) which is cappedto and bottlom with brass collars, through holes in each of which aru&placed - ---- two slid Irz. brass rode, adjustable. vertically by set screws end. ter- nhilrat.trnt2 at the( top anid bottom in clumps to hold strips of paper. The two Jlowe:' ronds a~re connected to two pointers, so counterpoiseDd as te -puu-oract'icnaly; no strain on the paper strips.' Thle 1'unfl-ity of the ailr in1 the chamber is controlled by thle use of the oroper crrt su-14uric acid. solution. The pointers areo so designed that, with a 1-0-inch strip of paper, cacli 'anall division en the scale correeporde to a change of o.oi% in the length of thle paper strip. If the paper is completely dehydrated and, then tested under increasing humidity con- ditions, more concordant results may be obtained and the paper coeis to equilibrium In. a imtch quicker time than wjhen the tests are started at a h11gighr humidity and, tile humidity conditions are ciu'oequently lowered. Thc results from teats on 12 different types of' paper showed that the percentage elong~ation between 20 und 80% relative humidity is approxi~mntoea a straight line. The elongaltion is considerably greeter in the cross than in. the machine direction. In most eases, the incronso in diongatuion between So and. 10oo hutaidity is considerably greater than thiat between 60 anid 8o%.

50. Hamburgor, T. A flow arrangement for testing expansion and. contraction of paper. Parier.-Fabr. 229,. no. 44:693-696(Nov. 1, 1931); T. S. 05:152; B. I. P'. C. 2:11614.

Teapparat'us (designed by Riesenfel~d) consists of an airtight glass contanenr, which has a hair hyGrometer, a thermomecter,: ind a sample of paner. 'The expansion and. cortrocti.on of the parer are rieasured at diffrenthLani.LiticE.

H0.iurLton, Paul L., Carsun, ?roffer.ok T., and Kirkweood, P-1. S. Effect of atmospheric hvinlid-ity in the physical testinG; of 'paper. Paper Tracle J. 76, no, 15:257j, 239), 2hl1 245,, 215, 2147, 249, 251Ari 2 195;Tech. Pasoc. Papers 6:614-71(Junc, 1-923); T. 3. 77:1; C. A. 1-7: 2501.

Data are Given for the cxpansion and. con~traction.m of paper with huŽ.~liditio-s of' 15 to 835e for 1.1 ropers. rfll readings were: made by mnean * - ~of a microscope amounted. over a steel scale g~raduated in fifths of a mijl-imcter. The effect is greate~,r in the- cr-oss thIan in,. the trnchine director. !Par the moat tart, thle culrves arec similar to thie moisture (Otcntor curvos. In some cases, there I~s a tendency for the rate of change to decrease with the higherhu dii.

2. Institute ofC Paper 0wnismtry. I-lstru:= ntationstde.X. Effect Of relative humidity on physical proneN'les with respect to ULh hysteresis effect in change's from cor' huniffcity to another. Paper 1957:657J.1, no. l5:1;5-kQ(Apri1 15,,1937); B. I. P. 0. 7:314; B. C. A. 193B:67;C. A. 31:4815. Data are gi1ven showing the change in exponflion (in and. across), using 65% relative humidity as the base line, when the samples oare hUnlidified at 140, 50, 65, and 755S relative huml:~ity (ascendirg series) * and at 75, 65, 50, anid 4'0% relatIve, humidity (descending series). llygr~oexpnsivity - - 178

296. LTairocque, Gl. L. The extension of' paper by adsorbed water vancuvr. Pulp Paper Mac. Canada 37, no 84199-209(Miarch,). 1936); Proc. TPech.- (lciou'a.Tlp Paper__Aaoc. 1936:83-94; C. A. 30:3641;

B. C. A ;K*6E:_44q;--. B. i. P. c. 6:342; T. S. lb:3-_270t -- -

2':` zt ccors~.hted of.' strips of paberr 5e-m. wide and hocm- long k~.u L~ony the erosu direction of 'the paper), which were :coiled to givc cyll inders 4o cm. long and 1. on. in diameter. A piece ci rl r:kel.- stool wire, 0.01 eni. thick, was fastened at the top and anoti,0r- pi~ce of wire at;~the bottoml,. or' the cylinder by means of sealing~wax; thel lower extr-emirties Of the two w~ire2 were in close, proximity to eachel other, and; their, dilstarco, apartU could bu measuared by El cothotomotetr. lrthe measuroinorjt Of' the, rate of' expansion of paper by water vapor 4n the absence of air, the sampnle tLas hung vertically inside a glass cylinder inmmersoa in a water bath at 250 C. and connected. with a source of' water vanor and a vacuum pump. A method is also described for the k ~~menauroment of -the rate Of expansion in the presence cif air, the moisture being supplied by a stream of compressed air. A second apparatus; was co:jstructed for the measurement of~the adsorption Of water vapor by paper an-d the mn~nitude of the resulting extension at various humidities. 'The equilibrium extension and. moisture ad- sorption took place, at the end. of about 30 hours, and no further change NK ~was observed ait tho end, of 100 hours. Thcprimento were also carrIed. out withi the wet extension test of' TAPPI, in which the sample on a shoot of' clean plate g)lass was covered with a film of' water for 10 minutes, after which the change in length was determined. Values arc reportoDd. for the equilibrium moisture content of 20 typical papers, as wlrl~l as- their expansion in both machine and croos directions, in an

1 rji~ 1'rOV OUorpincycle from 5 to 95% relative hurdldty and beck.

rvi'sThin lastrgel iscrevie of the woprko nlcodl rinffin, ans Witsor

Mnrinlaiofa M.emcExp otifot ondCa~ntada JT. procedure fnor takiong

phays "cal tests of fibrem buildir,,; board. iqfC-19g-1940 (tentative). Jan. 51, 194g. 2 p.

Liner 7hnasir Th,: -laxirz*Im -inear empannion is determined front o Specimen ~, x 12 inch.,L that heni been cult parallel with the long direction of the board aid. fro~n a like specitisot cut at right orgles thereto. The expansion is maoenurod between two points approximately 1.0 inches apart on the center line of' each specimen. Mhe specimens are COnditioned for 24 hours at 505S2 relative, humjidity and measuremunts Ore' made Of the distance between the two rreferencc Points. The OpoCiflcro are; then conditioned for 24 hours at 97%1 relative humidity, after which! ...... - -

Hygroexpanaivity . .179 .

the distance between the two reference points is again measured. The ox------_ _ _- pension may be mnaoured by any convenient method, provided that the re- salts are accurat6twithin 0.005 inch; - -Tho-nasuromonts oro ando in air, conditioned as specified in each case, or as quickly as possible after each specimen is removed therefrom. The linear expansion is reported as Lth increase in length between the reference marks, expressed as-a - prcounthgoc of the length at 50% relative humidity. Sodium dichrornto nny bo used for an atnosphore of 50% and potassium sulfate for 97% relative hurlir .ty.

092. Ocl'eont, C., Wheeler, S. H., and Croncy, R. G. W. A ricthod for -.icsuring the oxpannion and contraction of paper, etc., duo to changes in r.oi:turc content. The Printing and Allied Trades Research Assoc., London, Tech. Paper No. 3. 1938. 32 p.

, 10. Reed, Robert F. The charactertistics of paper and their rola- tionto lithography. Lithographic Technical Foundation, Bull. No. 1 r (Resoearch Series No. 1). 1925. 11 p. Paper 'lTadc J. 3l, no. 27:45-46 ,*l (Dec. 31, 1925); T. S. 85:84.

Data are given for the average change in linear dimensions between 35 and 65% relative humidity for 5 papers (the method used is not stated). Between 0 and 80% relative humidity, tho dimensions of a sheet of paper vary in almost direct proportion to the humidity, according to oarlicr vinostigaotors. The present results chock the percentage change across the Ugrin, brlt parallel to the grain thero in a distinct difference. The chanrg in oflfst paper across the rrain is front 4 to ;',tinms that in thu ruichinc direction.

',11. Roberts, D. The curling and waving of papers. Pulp Paper Canada' i:, no. 8:461-465(July, 1933); T. S. 98:158; C. A. 27:4923.

The percentage expansion was obtained by measuring the length of trips of papers, cut in the machine and croas direction, at equilibrium with air at 45% relative humidity at 75° F. and then by a second measure- .on' of the length of the strips after equilibrium at 95% relative i'.lniidty at 75° F. The method employed a box in which the samples were C.ri-ionred clams for the strips, and means for measuring the length o. she strips with no tension beyond that which was necessary to counter- ince each movable clamp and keep the strip taut for the measurement. T.e results for 14 papers show that the greater expansion is always in !hs cross direction of the fibers.

.1 2 Scribner, B. W., and Carson, F. T. Study of fiber wall boards :"-'developing specification standards. Paper Tradc J. 89, no. 13:61-63 (Snt. 26, 1929); C. A. 23:5592; T. S. 91:84.

,Anextensomeotr consists of a motal framework, at one end of which I - p:votcd a lever, the shorter end of which bears against one end of 0 the pecimon and the longer end serves as a pointer as it moves along the ccnic. The scale is graduated directly ir percentage of a definite length o,; WLich the specimen is originally cut. The indicating luvcr is countcr- ';'' wVeigihtced to insure that it will always be in contact with the board.

I 'I"~g~~~~~PS"~"""lp------··~~~~~~~~~~~PLYIWI . --- . -t

Hygrocxpansivity - 180

At the opposite end of the framework there is pivoted on the framework a second luver, one end of which bears against the end of the specimen. -- This-Lcvcr.ie.adjustable to provide a means of adjusting the position of the specimen until the pointer registors zero. -A-specimen so-ad- Juoted 1D an extensomctor and exposed to a relative humidity higher than that corresponding to'tho moisture- content of the specimen will expand and push the pointer along the scale which indicates directly in per- centago the expansion of the board at any time. The expansion in the long direction of all boards-studied was less than that in the short direction, the ratio'in the case of laminated boards being from 1/5 to 1/6. Data are given (for the short direction) for boards exposed to an atmos- phere containing saturated water vapor, after which the specimens were immersed in water for an hour.

513. TAPPI. Moisture expansivity of paper. TAPPI Standard T 447 m-42. 1 sheet. Paper Trade J. 110, no. 13:28-29(March 28, 1940).

,;. Expansivity is the capacity to change dimensions. Moisture expan- sivity is indicated by expansion or contraction with increase or decrease of moisture content, respectively. Practically the same value will be obtained by measuring either contraction or expansion, if conditions are properly controlled. For convenience, the expansivity.is determined by measuring contraction. The TAPPI Standard is based on the method of Weber and Goib.

54. Van den Akkcr, J. A. The Neenah oxpansimeter. A method for measuring the expansion or contraction of papers caused by change in relative humidity. Paper Trade J. 109, no. 22:105-106(Nov. 30, 1939); B. I. P. C. 10:128.

*.: ^ A sensitive spirit level vial is suspended from the lower end of the tost specimen, which is cut in the form of along strip. One end of the vial is supported by the paper specimen and the other end is supported by a pair of sharply pointed wire feet. The test specimen is supported at its upper end by a simple micrometer arrangement. Tho lower end of the strip is naintainod at constant elevation by means of the spirit lovcl vial, and changes in length are measured at the upper end by means of the micrometer. The pitch of the micrometer screw and the length of specimen are so chosen that the percentage change in length may bc read directly from the micrometer dial. The construction of the instrunont is described. A double system is used, so that hygrocxpanoivity for tlh machine and cross-machine direction may be measured -simultaneously.

515. Van don Akkor, J. A., Root, Carleton, and Wink;, Willncr A. ·* Iltiplc-specimen Nocnah cxpansinoetr. Tech. Ancoc. Papers 25:351-354 (Juno, 1942); Paper Trade J. 115, no. 24:33536(Dec. 10, 1942); B. I. P. C. 13:153; C. A. 36:7314.

The original Nocnah cxpansinetor was designed to accommodate two test specincno; the determination of hygroexpanolvity is intrinsically rygrooxpansivity 181

slow and therefore an apparatus has boon designed which will accommodate 20 specimens at one tine. Detailed drawings are given for the now instrument. Each of the 20 spocirmns is suspended from a rod which '· bears up against a micrometer screw. The specimen supports, in turn, ------.- -one end of--a small spirit level vial. The other end of the vial is supported by a short length of .003--inch-otool Fibbon, so-that a - - - vertical notion of the lowol' cnd of a specimen causes the level vial to'tilt. -With the lower-end of the specimen hold at constant elevation - - by means of the level viol, change in length is measured at the top (to the nearest 0.0001. inch) with the micrormter. The metal supporting imnborc clanmpd at each t:nd of a vial have weights chosen in such a manner that very little force is required to lift the end of the vial supported by the specimen. If it is desired to place the specimen under an appreciable tension, the required force is obtained by placing a suitable weight on the connecting link between the lower end of the spccimrcn and the level vial. The length of specimen between the lines of clamping is nominally 10 inches. A method of maintaining constant relative humidity within the apparatus in discussed. Constancy of tcmporature is important.

2.6. Weber, Charles G., and Cobb, R. M. K. Register studies in offset lithography. Bur. Standards J. Research 9, no. 3:427-440(Sopt., 1932)(RP 480); B. I: P. C. 3:38.

Changes in paper dinonsions were determined by means of a rule designed for measuring the displacement of reference marks on large sheets of paper. It is equipped with two magnifying glasses, each with a snail glass reticule having a vertical cross hair mounted directly underneath. One magnifier may be placed at any point within the range of the scale (24 to 64 inches) and readily set so that its cross hair -will coincide with any division on the scale. The other magnifier is set over the second reference mark by means of its micrometer adjustment. The distance between the reference points ray be read to 0.001 inch.- Eleven papers were conditioned and tested in atmospheres of 30, 45, 65, and 75% relative humidity. Tensions of from 9 to 455' gram were applied to specimens 15 inches wide and the elongation for each increment of tension was observed. The results did net indicate any significant d.ifferencos in elongation between the various samples tested. The greatest differences in the elongation of the different papers occurred at 75% relative hwurdity; the wiicot difference was loss than 0.1% for the cross direction; differences for the machine direction were much smaller. The minLrimu variation between the expansions of the different papers occurred at %"5,rolactvc humidity and changes in expansion for changes in relative humidity were of smaller magnitude in the vicinity of 45%,' than at other humilitics used.

517. Wober, Charles G., an.d GCib, Martin N. V. Now test for dimeonsioral changes in offset aDccro. J. Renoarch Natl. Bur. Standards 19, no. 6:665.673(Doc., 1957)(sP 1054); T. S. 108:145; B. I. P. C. 8:214.

The apparatus consists essentially of a wooden cabinet approximately 40 inches high, 16 inches lido, and 12 inches deep (inside dimensions). The specimen is hold in clamps, the lower one being fixed and the upper one being suspended from a light flexible cable which lend over a pulley. I*r' >*

--- -- I..I L:Z ·:,· I · · -I II:.. i. I . '

Hygroexpansivity 1l2

Tension is applied to the specimen by a dead-weight load on the other end of the cable, the tension being equal to the difference between the total load and that required to move the upper jaw. The pulley shaft extends .th ough the back of the cabinet and a mirror is mounted on the end outside the cabinet. Movement of the mirror, through rotation of the shaft, changes the position of a spot of light reflected by the mirror to a graduated scale near the baoe of the. cabinet.. Expansion or contraction of the specimen turns the shaft through travel of the cable over the pulley. Using the ratio of the radius of the pulley to the'distance of the mirror from the scale, the change in length of the specimen can be calculated from the travel of the liht bean on the scale. The same paper was tested under dead-weight tensions ranging from 50 to 1000 grams for the specimen two inches in width. Although increased tension il. resulted in stretch of the specimen as indicated by the separation of the curves, for the range of tensions used, nearly all the stretch humidities :4 occurred at above 70%. Varying the tension from 25 to 500 fi grans per inch of width did not change appreciably the slope of the curve in the region belolr 70, humidity. Hence, if the expansivity is taken from this part of the curve, precise control of tension is not I important. There is a possible error in the o:pans:inn and contraction of the cabinet crd. large variations in temperature during a test should be avoided. A suggested method of test in appended.

218. Weber, Charles G., and Snyder. L. W. Reactions of lithographic papers to variations in humidity and- temperature. Bur. Standards J. Research 12, no-. l:53-65(Jan., 1934)(RP 633); Vorld's Paper Trade Rev. 101, no. 19:1502(May 11, 1934); Paper-IMaker 88, no. 4:311-312 (Oct., 1934); B. C. A. 1934B:358; B. I. P. C. 4:161;.

.i^Fp i-1 The studies were made in a room of approximately 10o0 cu. ft.. in which humidity and temperature were controlled by means of a humidifying- dchiutnidifying unit capable of conditioning air at the rate of 2500 cu. ft. per minute, thus providing a change of air evory 3n seconds. Dimensional moasurcnonts were mado accurately to 0.002 of on inch on specimens te1 24 x 24 irchos by moano of a micrometer rule. Within the range oi' about 30 -to'72.5T relative humidity, at 8300 F., the dimensions vary directly with theo moisture content irresnoctivc of the causo of the moisture change. The data obtained for different huiditieos with constant tempera- ture are. for different temperatures with constant humidity result in a single regular curve. The paper having tho geateot number of fibers parallel to the machine di.rction will have the lowest dir.onsional change in that direction, because this direction is parallel to tlhe diameter of the largest mnumbor of fibers. Coated papers hod the largest dimensional change per unit of moisture content variation and nachine-finished offset papers had the lowest. Surface sizing with starch increased the di- monsionIl changoc slightly.

PTssJ--- ___ 153

IMPACT TEST - -- -

5t.1. Association of American Railroads. FreiRht Container 'Bureau. The inclined impact testing device. F.C.B. 673. Sopt. 15, 1938.

520. Dahill, Edward. Methods of making rough-handling test of containers. _Fibre Containero 24, no. 4:38-39(April, 1939); abstract in no. 3:22, 38(March, 1939); Chem. Industries 49, no. 6:642-643 (Nov., 1941); B. I. P. C. 9:473.

The principal faults of the revolving drum test are that it is difficult to repeat an identical test and that a container is subjected to chocks, falls, impacts, and stresses not encountered in normal handling and in transportation. The test gives quite accurate results over a long series of tests but this situation does not work out satisfactorily wihenlonly one or two aamplus are available for study. -Tho need for :another typo of device lead to the development of the inclined impact tester. Some of the ideas considered in its deovlopment are outlined. The angle of the incline was selected as 10 degrooo; reasons are given. | hThe max:imnm fall obtainable is 4 foct 2 inches and from this height, disregarding friction, which is present, the speed at the instant of impact is 11.2 miles per hour. The friction is so small in comparison with the force of the frcc-running loaded dolly that it need not be considered.

?1. Teow incline impact testing device. Fibre Containers 23, no. 12:40, 74(Dec., 1938); Converter 13, no. 4:22(April, 1939); B. I. P. C. 9:265.

A brief description is Givcn of thc tester.

522. Plaosanco, A.'V; Now fibro container dcvolopoionts. Fibru Cotaini.crs 24, no. 6:28-29, 63(June, 1539); Paper Dox and Bag Maker 88, no. 3:92-93, 89dl(Sopt., 1939); Sh'ars 57, no. 559:42-43(July, 1939); B. T.-. P. 9:577

The inclined impact testing device consists of a track inclined 10 degrees to the horizontal. At the foot of the track :ts a strongly braced bumper whooo face is 10 degrees from vertical, forming a right angle with the plane of the track. The nackagos to bo tested are placed, on a dolly with roller-bearing casters which run on the track. The loaded dolly is rolled up the track to a predetermined point and, when released rolls down the track at increasing speed until the pockago strikes the face of the bumper. The force of the impact is determined by the speed of the truck at the moment of impact, which is practically constant for any given length of ran, and increases with the length of the run; it is proportionate to the aggregate weight of dolly and package. The package is placed exactly flush With the front end of the dolly so that the impact will not be affected by the package sliding on the dolly. The impact may be applied to anir facc or any odge of the package by positioning it on

BfLC-----·I Tnnaet Test l~b

the dollar. A movable hanrt( In the iform of a 4 x h-Inch-timber may be - - attached to any part of the face of' -the bumper. This may be used to concentrate the impact across the top or bottom edge or center of the packageo or at any desired corner. The speed of impact may be correlated

- -- - -with Loirroaci; force o.C a freight; car in switching by the use of' a

Barees fin~ds that it is -x'ossbico to detcorrdno by this :aeene the ldntth of- rui c'ropodn to frediht car Impact at a given switching speed

- niltu dcAlolcrnncwhcthior robthe corntain-r--wilj. give- protection- uncior- pc-o uwt *h r-o usually encountered. The weigh-b of t'iL co':mntent causes. the anckange to bond and twist, and the measure of this distortion cdetermiDncs t'he amount o' clearance or cushiioning L marcccanary to ~)r:otct the, contents, or the extent to which the container rizot bie s~trengthe1Lned. The dev-,ice oiccupies, a floor space ci' about 2:; x 41feet an Ti nter-ials for its construction cost about "'5C.

2% Quinn., Don. Conbur irrpact tarter. Fibre Containrcr 26, no. 3:53(Morch, 2941); B. I- P. C. 11:331. L ~~~The~Conbur. tu~pact testnr isv essentially a dolly, running ein a 10- deg~ree inclined tracks, impacting a rigidly bunaper. t value, in addition, to, thu n iumle formi, Mooc in the npossibilityy of posritioining hazards of various kinds oin the bairqier and also on the dolly. By' the use of these attachments, there can be deve~,loped almost every sort of 'impact which co-ntainers encounter in handling and, shipping. Its use is illustrated by the testing of containers containin g2 conned foods, in which it was shown that the cones impacted sidewise tyithsteod about twice the forces they could withstand leng-thwise with appreciably loss denting-~ of the cans. Studies, hove indicated that far nore accurate measurements can be obtained or the tear resistance of boards along horizontal edges * than. is possible. with the revolving drum. By positioning a specified. load behind the coas, and by using; a standard -imp~act recorder en the doily, 'the crush resistance of the cases under im:pacts can. be determinedt endI correlated' with the results of the Olsen crush tester.

52L. Quinn., Don. corbur ineline impact tester. Fibre Containers 2,nc. :5(c.,194KV

'Pie besct useO of heri,incline Impanct touiter is to simulate th-e stresses :)-I' strains; Wh-ct crntciners enlcountejr whenstl e as a carl' cicil ii. freight CCDSWhe a ierh car to impactedj, thercis. a distinct vertical as w~i as! a h or i zo~ntal I pact.a' -To cimxloat this condition, holes havoc b>Žn;r drilled in, the i-clined- track about 12 inches apart and round headed carriageo bolts width washers inserted, in these holes. When the deity tfIr dwni the track, there i~s a series of vertical impacts, followed by-~ tro dfinit horizontal impact. TIt is probable that there should ber a) h-don top and on cbhind, the box beingiC tested.

).Quimi, Don L. Wo(,w container testinG deovices. Pacricar !'Ianagert~ntL Association, Iteduction 2x.ri cs No. 115 :36-4o(1959).

4 . ~~This article is concerned princinailly with the inrcline impact tester. * - The test sirmlates the destructive Threesc of' freight car irtpacts, 95% of WhIch Occur in yards anti 5%;o in trains. This test should be used if the * 4~W' ContLainer mo.ve--s in carload iota, whereas the drum test should be used. i-f the ·L-YCglldferi*Unrrrrul-**I1IL·

Impact Test _ 185

container is to move by parcel post, express, or local freight. Certain modifications of the test are possible. As an example, a plank positioned on the face of the bumper so that it contacts the extreme top edge or - th- extreme bottom edge of the container at-impact will. simulate the . forces of a direct drop on the edge and sot up an edgewise diagonal stress in the container; a small block positioned so that it contacts , ilthe container at impact adjacent to the corner will establish a strain similar to a corncnriso diagonal compression test.

;?> >26. Rcod, E. 0., and. Veitch, F. P. Impact tester for fiber board. Paper 24-, no. 21:24-27(July 30, 1919); Fibre Containers 4, no. 9:8-9 (Sept., 1919); C. A. 13:5010.

Because the determination of the bursting strength does not give sufficient information concerning the strength of fiber board under . ';-'ico conditions, an impact tester has been designed for the purpose of establishing minimrum impact requirements for the different weight or thicknloes of boards. The tester consists of a two-kg. hammer, which is -uidodby two vertical rods. The upper end of the harnmr is so constructed that it con be held in position and roleasod from a crosshead which can bo -o.cd up and down the'guide rods and locked in position by set screws. The right-hand guide rod is graduated to 0.5 cm. and is adjustable to allow for variations in the thickness of thd boards tested. By raising or lowering the crosshead the hammer may be adjusted to any desired height above the plunger. The plunger weighs one kg. and has a spherical lower end, the diameter of which is 2 cm. The plunger rests in the center of the fiberboard to be tested, which is clamped under the clamping plate operated by a lever, in the center of which is a circular hole 6 cm. in diameter. A hole in the base of the tester of the same diameter corresponds exactly to the hole in the clamping plate. 'Th!is p3 te is 5 x 7 inches and, because of the large clamping area, the booad may be firmly clamped with but little pressure and without crushing the board. The test strips are 5 inches in width. The burst- igi; height is the distance at which the hammer Just drives the plunger throul'!i to the shoulder of the bovel. There is practically no parallel- io-n b-twcon the results with the impact tester and those with the llullen te tor.

527. Swocnoy, 0. R., Hartford, Charles E., Richardson, Roger W., and Whittemoro, Edward R. Experimental studios on the production of insulating board from cornstalks. Iowa State College, Iowa Eg. Expt. Sta., a1ll. 102. June 10, 1931. 64 p.

Impact Test. The tester consisted of a vertical steol rod support- ;'- inr two horizontal steel arns. The lower arm was sat with the under cido at zero. The upper arm was set at the desired height for the test. -: leThcover on the test cup at the bottom was replaced by the board to : * sf;. bc tested. This cup was adjusted so that the zero setting on the peeon

,'* ',;, , rod resting on the board was zero. A weight attached to the upner rm · i '..:. wat. cllowvd to drop to the top of the peen rod. Tho ii.dortnat;ion ir. the .- board under the force of the falling weight was read from the gradua-- %::;^~ .tiJnn on tho peon that project below the lower face of the fixed arm. Impact Test - .

528. TAPPI. Impact resistance of fiberboard shipping containers. TAPPI Standard T C01 sm-44. 2 sheets.

''hc..imnact resistance of fiberboard containers or boxes is an '' arbi'trcry measurement of the energy required to ruptue-e the box by impact when successive blown of increasing--'crce are applied- in the prescribed manner. The result is expressed as the fina L distance, in feet, travelled by a dolly, carrying the loaded box, along an inclined plane to a bumper before rupture of the box occurs. The device consists of the incline impact testing device developed by the Freight Container Bureau.

5'2°. Werner, A. W. Manufacture of fibre shipping containers. Chicago. Board Products iubl. Co., 1941. 70 p.

inclined LmLpact Tester. Since impact is the aoulcc of most failures to containers in transit, a device was recently developed which is in- expcnsivo and simple in operation. With it the intensity of impact can be controlled and repeated ao often as desired. Full sized containers ;: arc subjected to test with the intention of recording the effects of jt shock on the container itself as well as on the contents amd cusiioning !~ materials used on the interior. The dcvico consists of a long inclined runway having stool tracks and a rise of 4 ft. 2 inches. A ball bearing equipped wheel truck or dolly capable of carrying the largest container, runs on this track. A bumper block is located at the base of the runway, having sufficient strength to resist repeated shocks. The angle of ,K? the runway is 10 degrees and the truck wlhcn started at the top attains a speed at instant of impact, disregarding friction, of 11.2 miles per hour. Toats are seldom if over conducted, starting at the top because destruction of the contairor wonlid be aosured. Thcreforer markings j-, along th-_ track arc desirable so that tests can be rcpcstcd from a ·;'" definite point. Srlow ot'o7n mo-ing pictures record cprmiinoetly the exact co-nditionj Cxisting3 at the moment of impact which can be studied anytime later and in absolute detail. Further than this, these picture rccordc arc of considcrablc valuc when comparing conditions on similar conta'iers, tests on, which arc run at various times. When. rigged with nroncrly located scales, within focus of the camera, the distance in which the shock is absorbed can be recorded and the efficiency of the inner packing determined. The container to bc tested is placed on the truck or dol.v and by mcons of a small winch or rope block the truck :i pmtllud up the :t,'Uete to t;ic desired starting point where it is ro- leased. Being acted upon by the force of gravity only it attain a speed connensurate with the starting position and each successive test, weights b',ing equal, will produce identical irmpnct-.

I 187

PUNCTURE TEST

529A. American Society for Testing Materials. Tentative method _ .. of test for puncture and stiffness of paperboard, corrugated and solid fiberboard. A.S.T.M; Designation D-781 --44- T A;S.T.M. Standards-- . 1944, Part III:1342-1345.

This is the same as TAPPI Standard T o05 m-44.

530. Beach, R. L. Evaluation of fiberboard box quality by labora- tory testing. Unpublished mss.

The three vital factors in fiber shipping container quality are resistance to crushing, puncture, and tearing at score lines. The author i ~ indicates that these three properties can be measured by the Beach punc- ture tester. The comparative stiffness of combined board or solid C: fiberboard can be measured by the puncture tester and, when made on different grades of board, should parallel results obtained on tube tests or compression t9sts on boxes with uniform fabrication from the same grade of material. The puncture tester, constructed with different weights to give varying amounts of energy and having an acceleration and deceleration produced by gravity alone (except 'or the comparatively mall percentage of the total energy absorbed in puncturing the material being tested), would seem to be the simplest mechanical apparatus for measuring the resistance to puncture of all grades of boxboard material. Actually, it has been found that the results are comparable for all grades of material from 9-point corrugating material to 600-lb. MT doublo-wall corrugated board and are independent of the fiber forma- tion, depending solely on the basic fiber strength of the material being tested, weight per 1000 sq. ft., and the stiffness of the material. The puncture test results will parallel the Mullen test results on boards having the same fiber formation and rf.rnish. The puncture tester makes three tears, approximately 1.5 inches in length and at angles of 1200, proceeding from a central point, irrespective of the grain direction of the liners or the corrugations. The numerical results are a sum of the tear resistance and stiffness of the material but either factor can be eliminated to determine the other; consequently, the puncture tester is a definite measure of tear resistance of score line strength of all grades of box board and has the additional ad- vantage of tearing the corrugating laedium simultaneously with the liners.

>31. Beach, R. L. Puncture testing of box board. Tech. Assoc. Papers 22:240-245; discussion, 40-41(Juno, 1939); Paper Trade J. 108, no. 5:30-35(Feb. 2, 1939); Fibre Containers 24, no. 3:42-44((March, 1939); Papicr-Ztf:, 64, no. 56:1219(July 18, 1939); B. I. P. C. 9:287; C. A. 33: 4027.

The desired features of the instrument wore: (1) rapture a consider- able amount of material to avoid small variations; (2) rupture all con- ponents of combined materials equally and, as far as possible, nimultan- ';-S eously; (3) rupture along defined lines so that the rupture would be }[. independent of such factors as grain direction and direction of corrugations; Puncture Test 188

(4) rupture in a sufficient number of different directions so that the results would be an average strength in all directions; (5) itself have relatively few inherent variations because of friction, gages, and springs; (6) be calibrated in definite units of energy, and which could be duplicated and checked without elaborate apparatus or difficulty. The final apparatus involves the use of a pendulum, on the end of which -- is fixed a rod bent-in the form of an arc of-90 degrees. To the end of the rod is affixed a metal point having the shape of a triangular pyramid, one inch in height. Advantages of the pendulum principle are listed. The test specimen (corrugated board or similar material) is held between two clamping plates which are approximately at the level of the axis of the pendulum. The upper plate is fixed and the lower plate is held by spring pressure against the material. The pendulum is held up by a trigger and stop in a horizontal position. If there is no material between the clamping plates and the trigger is released, the pendulum will swing through an arc of 180 degrees to the horizontal position, except for a small retardation from friction; this friction is compensated for by an adjustable stop against the pointer. If material is between the clumping plates, some of the energy of the owing will be used up by the puncturing point punching through the material and, consequently, the pendulum will not swing as far as 2.80 degrees by the amount of energy that has been used. The pointer remains at its maximum reading position by a simple friction bearing. There are no variables in the apparatus except the friction of the bearings and the pointer sleeve. With the use of high-grade ball bearings this friction is constant and very small. In the model described, the bare pendulum weighs 9 pounds and the center of gravity is 5.43 inches from its axis, so that its potential energy when in the horizontal position is 48.87 inch-pounds; additional loads are provided to give total potential energies of approximately 87.9, 183.25, and 357.5 inch-pounds. The apparatus will test materials ranging from 0.016-inch liner board to combined solid fiber or corrugated board of the heaviest grades manufactured. In order that the apparatus give cominparblo results when used with different weights, it is only necessary to keep the velocity of the puncturing point practically uniform, other factors being constant. Much of the energy of the pendulum is used in bending the specimen so that it is also a measure, to a certain degree, of the stiffness of the material. By cutting a '"Y in the material before making the test, with each leg of the Y slightly longer than the tear which will be made by the point in its usual rupture, the stiffness of the material alone can be measured. The chief reason for choosing the triangular pyramid form of point was that it duplicates the corner of a box, the angle formed by the edges being 90 degrees. licsults of tests arc given. An appendix by E. H. Hull gives the theory of the compound pendulum as used in this type tester.

52. Beach, R. L., and Coloby, L. Study of variations found in testing of corrugated boards. General Electric data folder 3528. Nov. 1, 1939. 9 p. Charts.

The tests were carried out on three types of boards: one with a 42-lb., dry-finish Fourdripier on both sides and 0.009 kraft corrugations; one with 90-1b. 0.030-inch Fourdrinior kraft liners; and one with 95-lb.

. H Puncture Test 189

cylinder kraft liners and 0.009 kraft corrugating sheet. The material was conditioned at 65% relative humidity and the tests were made con- tinuously within the space of a few hours by an experienced operator. Five hundred tests were made. Puncture tests were made half with one leg of the puncturing point parallel to the corrugations and the other ": half with the leg perpendicular to the corrugations.' The curves for-'. l, ~the 42-lb. Fourdrinier and the 95-lb. cylinder kraft boards lie quite I'- - close together; there--are exactly the same number of tests having zero . ~deviation from the average for both materials and the spreads (including 100%' of the tests) are so close together that the points cannot be dis- ~ ~tinguished on the curve. The values arc 10.8% for the 42-lb. board and 11% for the 95-lb. board. The number of tests necessary for 99% probability are:

$t &Possible error, 42-lb. 90-lb. 95 lb. % Fourdrinier Fourdrinier Cylinder

7 ' 6 5 4 5 9 8 6 3 19 18 11 2 37 32 20

555. Eckhardt, Henry C., and Snyder, Lco W. Study of the Thwing impact tester. Paper Trade J. 86, no. 15:64-66(April 12, 1928); Tech. Assoc. Papers ll:91-93(June, 1928); T. S. 88:199; C. A. 22:3297.

In the Thwing impact tester, a heavy plunger, falling in vertical guides, punctures the specimen by its impact. The work done in piercing the specimen is determined from the initial energy of the plunger and the compression of the nDrings placed at the bottom of the guides, which absorb the remainder of the energy left in the falling plunger after the specimen is pierced. A description ani, illustration of the tester are giver. Tho formula for the calibration of the inEtrument is developed. With the oxcuption of papers which' stretch irordinotely, the strongest material which actually can be tested is one requiring about 77 inch-pounds of energy in being punctured. The tester was designed to test heavy boxboards which, through service conditions, are often subjected to direct impact such as this tester is intcndcd to simulate. Because of the manner in which the data arc e::prossed, the results are not directly comparable with those obtained with any other -per-tcstingPa device. However, results obtained with the Mullon bursting strength tester are included, because it was thought that the two instruments might grade a series of papers in the sami order. Tests with kraft wrapping paper showed that the order in which the samples are graded is different for the two testers. One reason for "K-.. this is the nature of the test. In the Mullon tester, the specimen i^'1. is ubjectcdl to a uniformly increasing pressure until it bursts; in the Thwing tester, the specimen is subjected to a direct impact suffi- p>. cient to cause its rupture. Another reason for the differences is '* . that the capacity of the impact tester is too high for this type of P,aper. In. tests on heavy boxboardo, the moan porcontage deviation ': '-. of the individual test values from the average values obtained with .', the impact tester is lower than that obtained ,wth the iullcn tester.

-_ -_ . Puncture Test 190

This is an indication that the impact tester is capable of producing consistent results. Forreadings on the Mullon tester from 100 to 300 points, the approximate relatior--Thwing impact value = 0.156 Mullen --' bursting- points--holds- withi-n-about 15%- of the-observed. values. The Thwing tester is not suitable for testing single plies of light weight p.pr, . because the resistance of such paper is insufficient to give an adequate scale reading. 'iThsignificance' of the results in terms of ------secrviceability of the board can be determined only through extensive experience.

534.' G. E. announces now box board tester. Paper Trade J. 117, no. 12:33(Sopt. 16, 1943); Paper Mill News 66, no. 38:25(Sept. 13, 1943); Paper & Paper P'oducts 85, no. 1:12(Sopt. 20, 1943); Fibre Containers 23, ro. 9:26(Sopt., 1943); Instrumental6, no. 10:651-652(Oct., 1943); Paper Ind. 25, no. 7:808, 810(0ct., 1943): D. I. P. C. 14:43. Cf. also Paper Tradc J. 119, no. 1l:16(Nov. 2, ].944); Papor Mill. News 67, no. 45: 60(.Nov. 4, 1944); ibrc Containers 29, no. 10:78(0ct., 1944).

This relates to the Beach puncture tester. The tester will doter- mine the strength of boxboard from 0.014-inch liner to 0.140-inch solid kraft, as well ac waterproof boxing material. It will also measure the strength, without deformirg. or flattening the corrugations, of corrugated board of various grades. The tester consists of a pendulum on the end of which is a rod bent to form an arc of 90 degrees; the , point is shaped like the corner of a box to simulate actual shipping conditions. The unit holds the material to be tested firmly between I two clamping plates which are level with the axis of the pendulum. The pendulum is operated by a trigger and, as this is tripped and the released pendulum savings through its arc, the number of dereeoos loss than 180 degrees through which it swings is a measure of the energy dissipated in puncturing and bonding the test sample.

535. generall Electric Company. Punctu-re tester (Cat. No. 8257564G1). GEI-20213. Juno, 1944. 7 p.

A brief description is given of the puncture tester, formerly known as the Beach ?urctvu-e tester and also known as the G. E. boxboard tester. It La desigL'ned for the measurement of the stiffness or the resistance to puncturc of fiberboard and similar material. The energy possessed by the bare pon;lulum is not sufficient to enable it to puncture strong materials, and auxiliary weights are supplied which increases the ca-ac'ty of' the instrument 2; 4, and 8 times. The test procedure is --.>'. outtlioed. The samples should be placed in the clamping plates in such "a mannel that o.n nns-. ha]' of' the tests the leading edge of the puncture point makes a t.sr in one direction of the material and, on the other -1 ,:; halfhe of the ' estn, in a direction perpendicular to those tears. The puncture point should hit on the outside liner of corrugated board and .', on the smooth side of the uncombined board. If low readings are ob-

-t^: ' tainod, they are not necessarily the result of poor fiber strength but ay bo caused by any one of the following conditions: poor liner ad- hesion; crushed corrugations; poorly shaped corrugations; poor quality

.ft.

- ~ Puncture Test 191

of corrugation. Instrumental maladjustments, such as an unstable founda- tion, too much pointer friction or tightness of pendulum collar cause high readings. Making tests too close to the edge of the material or too close to each other on the surface of the material also may be the -- reason for high readings. General-ly, however, high-readings are the_ results of tests made on an unusually sound area of the sample.

56. Hull, E. H. Theory of compound pendulum as used in pendulum- type puncture tester. Appendix to article by Beach (No. 531).

| -.7 Institute of Paper Chemistry. Beach puncture tester. Report No. 53to American Paper and Pulp Association, Aug. 24, 1943. 15 p.

The Beach puncture tester, an instrument for measuring the work C : required to pierce a paperboard with a pyramidal point, has been investi- gated as regards principles of method and design. Fundamental measure- ments made upon the instrumental constants and scales showed the latter to be accurate. Fictional losses were found to be small and of such nature as to be allowed for, with one exception: an appreciable loss occurred from the method of mounting the auxiliary weights. A signifi- cant error was found in the displacement of the release mechanism when the auxiliary weights were added to the pendulum system. Strain- energy set up in the puncture arm was found to result in appreciable error. The effect of sharpness of the edges and point of the puncture head -'~.'9was investigated for a number of boards, and a consistent relationship .';--' between test r-oults and sharpness was not found; this led to the con- clusion that, whatever the ultimate significance of the instrumental B^' : reading, a difference between a pair of readings on different boards tjs'. is not significant. The influence on test results of thin films of !Ff':, tacky and lubricating materials was measured; it was found that the if^ nature cf the surface of a specimen could, under certain conditions, i:11;". affect the puncture work quite natorially; doubt is oxprossod that differences of this origin reflect the relative abilities of two ihtte- boards to withstand puncturing forces. The effect of varying the size ~Ko' and angular orientation of the triangular sample aperture was observed :X^^.~ 1 with the view of establishing manufacturing tolerances on these variables. .~K^i,!. Results are virtually independent of the angle between sample aperture -ItR^'- and puncture hcad for angles up to about 7 degrees. Specific sugges- $ K.$ tioeo are made for improving the instrument.

2~8. Plcasanceo A. V. New fibre container developments. Fibre E . Containers 24, no. 6:28-29, 63(June, 1939); Paper Box and Bag Maker 88, no- 3:92-93, 89d(Sept., 1939); Shears 57, no. 559:42-43(July, 1939); '); B. I. P. C. 9:577.

..v4i4 The Boech puncture tester is a very simple mechanism, essentially g ;Wtfi'.' pair of claepirE plates which hold the board with crushing while a fE i;pointod pendulum swings against an exposed section of the board. The ~'~ tPtndClum1 has a point in the form of a three-sided pyramid with rounded E O'?80, si,smulating the impact of the corner of a wooden box or similar 'i ^- ,c~tengeulaar object. The amount of energy required to force the point E l^!tt1 O'gh the board is read directly on a scale. For testing different A Pdes of board, various weights arc attached to the pendulum ard there ~ e a .~, S different scale on the dial for each weight.

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v Puncture Test 193

i the container under consideration. It is acknowledged, however, that two series of tests (such as are herein discussed), extensive and time- consuming as they may be, are obviously inadequate for the establishment of i - fundar-ental principles or rigid.rules for procedure, and that the studies

I'.i should be extended to include every type and make of flat stock, ad- hesive, design, fabrication, and combination encountered in the industry.

i 541. Werner, -A W.. Manufacture of fibre shipping containers. Chicago. Board Products Publ. Co., 1941. 70 p.

',I Punctilre Resistance. The resistance to puncturing is usually tested by cropping a pointed object from a predetermined height on the face of the box and observing the extent of the failure. The amount of punctur- inc will depend upon the size of the box face and the quality of the bonrd as well as upon the nature and weight of the point. Comparisons obtained through testing boards of a standard size are more accurate than those obtained through testing the faces of completed boxes.

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194~19t

SCORE TESTS

542. Carlson, Thorwald A. Apparatus for testing fiber board. U. S. patent 1,612,415(Dec. 28, 1926); Paper Trade J. 86, no. 2:59-60 -(Jan. .2, 1928); T. S.-85:241;-87-:72..-

The apparatus comprises moans for applying a combined action of tension, tearing and repented bending to a specimen while it is bent- over and drawn firmly against a sloping edge. In-the case of scored boards representing material from an edge of a fiber box, the speci- men may be bent initially at an angle of approximately 90 degrees, the bend being parallel to and at the score, so the score may be in contact with the sloping edge during the test. The number of times that the test piece is bent through a predetermined angle, together with the maximum tension applied before it is torn apart, is taken as an indi- cation of the amount of rough handling which the finished box will withstand. The stationary clamp of the instrument consists of an adjustable jaw mounted on a fixed jaw having an extension in the form of a plate with a transversely sloping edge over which the test speci- men is bent. The other clamp is carried by an oscillating arm which is equipped with mechanism tending to stretch the test specimen by drawing the clnam away from the axis of oscillation of the oscillating arm. The letter is mDved back and forth through the desired angle. The two clamps are so placed that when the oscillating arm is in its central position the planes o tLhe clamping surfaces are at right angles to each other, intersecting, if extended, in a line approximately at the axis about which the oscillating arm oscillates. In making the test the specinmn is bent over the sloping edge, which is approximately on a line through the axis of rotation of the oscillating arm, and the ends of th., test piece are held by the two clamps, so that the position ChC: i simulatciL th.-c iIn which tIe material is placed in a sot-up and loaded box. The tost piece is bor-t back and forth at the sloping edge and the tension caused by the force applied to the movable clamp causes the specimen to tear along the sloping odgc. Ty using, for the ex- tension of the fixed jaw of tlhe tationary clamp, plates terminating In edges having different slopes, the severity of the test can be varied. Suitable means arc provided for determniing the number of bonds and the {I maximum tenrioTr which the test piece sustains before failing. 54j. l'laskott, C. A. Principles of box and crate construction. U.. S. Dpt. As-. Tech. Bll].. No. 1.71. April, 1930. 151 p.

Fiberboar-d Score Te--t. A snccilon containing a scored edge is cut

i· . from the bo:. and tostcd in. combined bending, tearing, and tension. by V, means of tl. score tester. On the machine aro two clamps, one mounted on a Gtatioimrr inclined lodgo at the top and the other on an oscillat- ing ar. Tilis rm is connected with a driving mechanism by moans of Vlich it can be .madc to swing through various angles and at different Bpoeds. The movable clanp is conrccted through a calibrated compression spring to a screw and ratchet !olel which causes a downward movement

3Hss:

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Score Tests 195

of the movable clamp when the oscillatfing arm moves back and forth. ' zi The test specimen, which is 1 inch wide and'about 4.5 inches long, has the score midway between its ends and at right angles to its K1I?. length. It is first bent through an angle of 90° at the score and is then clamped in the machine with the score resting at the sloping edge at-the end of-the cxtcnsion oif tho lower jaw of the stationary _ clamp. Thus, when the machine is in motion, the specimen is bent back and forth at the sloping edge, and the tension caused by the force applied to the movabb cldamp-causes the specimen to tear-along-tthe sloping edge. This action simulates the conditions which are on- countered by the edgos or scores of a loaded fiber box when it is subjected to rough handling or to the skewing and racking caused by the swaying of a moving freight car. The test is continued until the specimen fails, and the maximum pull and the total number of bends which the specimen withstood are taken as measures of the ability of the box to withstand rough handling. The degree or intensity of the tearing can be changed to simulate different conditions by modification of the sloping edge, together with the possible variations in speed, angle of swing of the oscillating arm, and rate at which the tensionL.is increased. A combined boeding and tension action without tearing can be obtained by using an cdge having a horizontal ledge over which the tension and bonding is applied to the specimen instead of a ledge having a slope or inclination.

_44. Quino,'Don. Simple strength property tests. Fibre Containers 25, no. 6:41(Juno, 1940).

A description is given of the "Eullen strip test." It is similar to the toot described in the following abstract. Test results and, for comparison, drun tests are given for four boards.

Lot Strip Test, Drum Tests lb. Falls

1 83 31 2 120 56 3 125 65 4 148 97

245. Quinn, Don. Strength of corrugated containers along creased odges. Fibre Containers 26, no. l:41(Jan., 1941); B. I. P. C. 11:216.

If one box has cylinder-foracd liners and the other has Fourdrinier- ili .. I, fornod liners, the bursting strength is not a very dependable criterion of their retention of contents strength properties (this is defined as ' that property of a container i :"^ which enables it to hold the contents -^ B' intact as a unit during its life of service). The operation of creasing depreciaten the strength of a board. Thus, the standard bursting test, which is made over uncroasod sections, is not a criterion of "W! the strength along the edges. The following method is suggested. Use 4 the the standard Mullen or Cody machine. Cut the strips 1-1/8 inches W5^i> Wide. This width of trip can be positioned over the orifice of the w',

-- m.r --"I.·'I.. * I--en- : * - - * :~ - ~ .r *w*-

I r Score Tents 196

tester without danger of either edge contacting the edge of the orifice. One sot of strips has the corrugations perpendicular to the length of the strip, the other has the corrugations parallel to the length. In each instance, the creased edge lies across the width of the strip. Position-the creased-edge exactly over the center of-tho-rubber _ diaphragm of the bursting tester. The clamp pressure must be tight, otherwise slippage will occur. The outer facing should be up in this test. If the specimens are cut from bbxes with vertical corruga---- tions, the strips with corrugations perpendicular to the length represent the vertical edges and those with corrugations parallel to the length give the record for the horizontal (flap) creases.

546. Werner, A. W. Manufacture of fibre shipping containers. Chicago. Board Products Publ. Co., 1941. 70 p.

Score Tester. Investigations have clearly demonstrated the need for a test on the scores of fiber boxes, since the strength of the score appears to depend more upon the condition of the board at the time of scoring and upon the scoring process than upon the quality of the board. A fiberboa:d ccore tester has been designed by the U. S. Forest Products Laboratory to test the score of a fiber box. A speci- men 1 inch wide and about 4-1/2 inches long, containing the scored ridge midway between the ends, is cut from the box and by means of the testing machine, the sample is tested in combined bending, tearing, and tension; the action of the machine is quite similar to the forces 1i causing failure at the scores in actual service. Tests on the scored edges of the box are especially valuable for determining the efficiency of the scoring process.

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.a~ . ;I" - , ,, 197

SERVICE TESTS

i47 Jiggle tester.- Fibre-Containers 25, no. 3:56(April, 1940);- B. I. P. C. 10:398.

.i.TheP Jiggle tester (illustrated) simulates the jogging and bumping motion which shipping containers receive riding in freight cars and motor L trucks. One or more loaded containers are placed on a suspended platform to which motion is imparted by means of a series of rotating cams care- fully timed so as to produce various combinations of vertical and lateral movements in a definite sequence. The speed can be regulated so as to obtain a slow jogging motion or a rapid vibratory action. Containers are subjected to this treatment for a definite period of time and then examined and tested to determine the effect on case rigidity, bond adhesion, etc. It is believed the test will be particularly valuable in detcrmining the effect of prolonged vibratory motion on the adhesive structure of corrugated boxes.

548. Plaskett, C. A. Principles of box and Crate construction. U. S. Dept. .gr., Tech. Bull. No. 171. April, 1930. 131 p.

The weaving test is designed to simulate the side swaying or rolling of a moving freight car, or the repeated starting and stopping of a car. The swaying action of a train is reproduced on the testing machine by an oscillating table or car, which can be made to move horizontally for- ward and backward at different speeds through any distance up to a maxi- mum of 8 inches. The box to be tested is fastened rigidly to the table by clamps along two of its bottom edges and a weight equal to the average load carried by a container in the bottom tier of a loaded car is fastened on the top. When the machine is put into operation, the con- tainer is carried back and forth with the movement of the table. This test affords a means of comparing boxes with respect to their rigidity, which is indicated by their resistance to weaving or skewing. The test maf be continued until complete failure occurs but usually the box or crate is tested on the machine until the joints are loosened and then it is taken to a drum-testing machine.

Impact-Shcar Test. The oscillating table is used also to simulate the starting and stopping action of a freight car, which produces an impact shear in the container. For this test, the box is suspended freely and above the table by two metal straps. The supporting straps form a parallelogram suspension and horizontal guides, fitted with rollers to reduce the friction, allow the box to swing only in the direction of its length, which is parallel to the motion of the table. Two stops are fastened Oscurely to the table and the ends of the box strike against them as the table moves forward and backward. Any M- jLM desired weight may be placed on top of the box during the test. The number of complete oscillations of the table before failure of the box is indicated by an automatic counter. ItI

190

SMOOiTNESS

--- -549r- Advancos- in the surface testing of paper. -Popier-Fabr.--32, no. 41:428-429(0ct. 14, 3934); B. I. P. C. 5:95.

Reference is made to the comparison microscope of E. Stach, - which has been modified for testing surfaces of paper, etc. Illustra- tions of two kinds of paper.are given.

522. Barnhart, John W., Baumruckor, William, and. Dodge, William G. Apparatus for determining the surface texture end finish of various materials. U. S. patent 2,056,315(April 7, 1936); T. S. 103:380.

The apparatus is constructed to measure the contact pressure re- quired to cause slippage botwven two contacting surfaces of the material under test with a predetermined torque, the smoothness of the sample being measured as a function of the pressure exerted to prevent slippage.

5_1. Beazley, Warren. The measurability of printing quality. Pulp Paper Mag. Canada 41, no. 2:117-122(Feb., 1940); Proc. Tech. Section, Can; Pulp Paper Assoc., 26th Annual ?teting, 1940:98-103; B. C. P. A. 1940B:351; B. I. P. C. 10:254; C. A. 34:3087.

The Bokk, Williams, and Gurley testers are modifications of the air- leak method of measuring smoothness. From the standpoint of testing 'the printability of paper, these testers arc open to the following objections. In the Williams tester, th3 pressure of 14 pounds per square inch is in no way comparable with printing pressures which are of the order of hundreds of pounds per square inch; because the paper is clamped between two herd surfaces, the paper is not subjected to the same forces Ea these which arc produced on a printing press. The Gurlcy tester is open to the same objections. The Bckk tester is subject to the first of the above objections but is Yfrc of the second, because the rubber is the counterpart of the backing or blanket which is used on the cylinder of a printing press. These instruments measure a smoothness but not the right kind. The author discusses general objections to the air-flow mnthod of measuring ormoothnees, and points out that the real requirement is some measure of the number and size of spots which lie below a plane, the position of which,relative to the paper, is fixed by the pressure conditions specified.

_25. Bekic, Julius. Apparatus for measuring smoothness of paper surfaces. Paner Trade J. 94, no. 26:41-412(June 30, 1.932); Paper Mill 55, no. 358:4, 6(Sept. 17, 1932); T. S. 95:222; C. A. 26:5206.

The Bekol smoothness tester is illustrated, and its method of . operation is outlined. Data arc given showing the reproducibility of the - results and values for nine types of paper. The apparatus may also be 5,'; used for the determination of the porosity of paper (results are given i.i- !for13 types of papers). I I C) 4' 'C PI) 0 'd Pi ) P4 A1 0 03 03 4-' Pd o. 0 k-,d 0 03 ' I N P- C) a) 44- r-. I C C a Ci H m a) o -% -:I o l. COa 000 P. 1400 P4 -=t0-l C) $ - - - ' -to OC O tc- t 74 C 4.4 si C- 0 C) 4-40 CHo 4 O 44 0 si , t d j -aLr NP 044 4CC m- -p Pd34 4 O 0 444 'd C) .AQf .. P. C) C C) ) CC 00 -P -c -i A Pt . KcIC , N I CO 4- 003ID - 0C Lr H1 '.' 0$ 4 ' " c I I CD, C) 40 0 Q 4- 44C 544CHI'd '-I H1 44 0 P4 - t 0 tO 0 P, 0 Ci $4 4 00 O-PC): A C3 0d co In $4 to 0 In-H SiP C 'iN KN -H I-) C)4 m C) 03 4) OH 0 -PI to -: -N C C) P,03co a a~ 574 \ ofICC U C Cs) C) 4H 0 4.' C) t C) -~~~C C H $4 tI-P. O -c- 4' P o ~otL', coJ' H A -.0444-p C)P, C o 44 C) Id 0a O~N WN0 ci a r L \o ci - 03- 'ti C D H C N f -CP CC)+ -C) c- 0 a. 440 0a a P-t C) 00 C) a 4.HCO.s si 0 Q '4- t-c C) -PC 4)0 H04'.O ,- C) o5 0 H 0C)Ia C) -p p O 4O $ 4'W~ tc'c C O C -I4 $ 0 -Pd C P 4P, 7 C-P, r, ON C) -H -P coI C) to'U l44 0 PC>- i qC3 0n0 0203 C - C a P , u c t - o coC)CC C) SiONON''--I -4-4 4-) o 4.' 430 CO V1.-4tWN C'-,MG~ - $4 004 -I 40 04'- C) ( P -d a C IC 0 -I'~ tr\~ 4- Z ) : 0 0 0 -at CC) 04 C,~. C)4 PI CC) _zrO'- 0 U2 t4 0 440 4-i 4E, C) flz- $4. 0 3 4C P ID 4) 04 -p0 o Ca C 'H ,- 0 P.C ;Si P t I N r C U-NCQ 0n'zt rd 0 -4 044 C A OP -P-- - Ci 04C C4~ 4 4 - a4-- C) C Pc- m Ho C)JI•\ r- Ri oat $40 H orC\* -$. o 4-14 a)E-4 r-4o0 0 to - 4).0 *-4 C) Q $4 4~ o4)0 H C CI -N e- rc -P 4i a) -- 4.' C)-i'] C) -4 ; .clOX0Z 43 0 Id a a C t $4 4-l 0 0 k-~ 0) C( 2, I - I -- - -4~4

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55. Brecht, Walter. Methods and instruments for testing the smoothness of papers. Papier-Fabr. 30, no. 29:457-463(July 7, 1932); Wochbl. Papierfabr. 63, no. 22:419(May 28, 1,32); Zellstoff u. Papier 12, no. 6:265-266(June, 1932); Boll. staz. sper. ind. carts 12, no. 1: 4-6(Jan., 1933); C. A. 26:6129; T. S. 97:131.

Various published methods of measuring the smoothness of surfaces are described. Good visual characterization can be obtained by observa- tion.at a magnification of 3 diameters in light coming from one side at an angle of about 4 degrees to the surface. '

556. Brecht, Walter, and Staedel, Wilhelm. Investigation of the suitability of Belck's smoothness tester for paper. Zellstoff u. Papier 11, no. 12:679-686(Doc., 1931); T. S. 94:257.

Data are given to support the following conclusions: A single de- termination with machine-finished paper requires 1 to 2 minutes. The limits of error are at the most 2.5%. For reliable results, 10 indivi- dual measurements should be taken at various places on the sample. The test should be carried out at a constant moisture content. By means of this test, it is possible to distinguish between the wire and felt side of a. paper sheet.

557. Brush Development Company. Surface analyzer. Rev. Sci. Instruments 12, no. 1:40-41(Jan., 1941). Sec also Brush Tech. Bull. No. 552.

The instrument is designed for making instantaneous and permanent chart records of irregularities in finished surfaces such as metals, paper, etc. It consists of an analyzer head, a calibrating amplifier, and a direct inking oscillograph. The analyzer head consists of the pickup arm and its drive unit; the arm contains a piezoelectric crystal actuated by a sapphire tracer point. The crystal element of the pickup arm has the property of generating a voltage proportional to the vertical notion of the tracer point as it moves over the surface under test.

558. Clar:, James d'A. Roughness. Proc. Tech. Section, Paper Makers Assoc. Gt. Britain Ireland 8, part l:64(0ct., 1927).

In a discussion of gloss and its relation to roughness, Clark ncn- tions a roughness tester used in Scotland, consisting of an inclined plane on which the paper was stretched and a wooden block around which of the same paper was wrapped. The angle of the plane was I another piece inclined until the block began to slide down, that anglo giving a measure of the roughness of the paper.

59. Davis, Myrl N., and Malstrom, Homer E. Apparatus for testing ; the smoothness of paper. U. S. patent 2,050,486(Aug. 11, 1936); T. S. 1041:88.

3^^ ' The apparatus consists of a glass block having a light reflecting base surface on whicl a paper sheet to be tested is laid, and oppositely Wiy^'

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Sroothnoes 201

1 beveled edges, each at an angle of 45 degrees to the base surface, means 11'; for pressing the sheet on the base surface, means for projecting a light beam normal to one of the beveled edges through the block onto the paper- 1I glass interface, and means for measuring the intensity of the reflected beam emerging from the other of the beveled edges. It is possible by this apparatus to determine the percentage-of the paper surface which is actually in good optical contact rith the glass, and this fraction V - .should serve as a measure of the smoothness of the paper surface at the pressure in question. The apparatus described in the patent provides for pressures from 0 to 11,000 pounds per square inch.

560. Dodge, W. G., and Tarvin, E. C. The testing of for smoothness, ink penetration, and opacity. Paner Trado J. 100, no. 5: 38-40(Jan. 51, 1935); Tech. Assoc. Papers 1:348-350; discussion 60-62 Juno, 1935); C. A. 29:3834; B. C. A. 1935B:400; B. I. P. C. 5 :1i6.

In-testing smoothness, two pieces of the same sample are placed upon stool plates which have boon ground to a perfect fit. A mechanism is described whereby a rubbing action is act up between those sheets. If the sheets are smooth, they will slip over each other easily; if they are rough, this slippage will not occur and a weight is changed (position and magnitude) until an end point is reached. Tho device is calibrated to give rcoadings in units of torque (kg.-cm.) exerted around the axis to which the weighted bar is pivoted. Newsprint gavc readings in the range of 12 to 37 fnits. Tlis instrument gives a good correlation with the Bold: tooter, but the readings arc samcwhat more reproducible. This is probably because of the larger samples used. In a series of readings, the maximamn deviation is about 5%. readingss of about 30 indicate that the popor has sufficient. smoothness to take on oven in- presci on in printing, and yoet is not so smooth that difficulties would be encountorod in folding and conveying nochanisms.

561. Fleraing, Herbert. Detormiaing tho smoothness of papor. Wochbl. Papiorfabr. 64, no. 21A:38-41l(iLy 27, 19355); C. A. 27:5971.

A sa!.plc of paper is rotated under a 1-rn. ball fooeeler, the vertical motion of which actuates a light lever arm. A rider on the arm stands ft on a smooth plate in suchl a way that it "walks" with the motion of the arm. The distance traveled is a measure of the vertical motion of the feeler J-' ;. and is reported as rmillimeters per meter length of paper. A second . S reading with a 10-mm. ball corrects for the gross inequalities in the - 2 AA not casac An rouAgnhs1sB....,;a n u; _ W . r suruEtCC not clansed. an roug-noes. ±eaurings con DC UpllaLXuU^u wliilll ,P, :& , . and inequalities of 0.0003 mm. can be detected.

~ _ 65_02.2FuCes, R., Inc. The Be;k smoothness and porosity testing apparatus. Instruments 6, no. l:22(Jan., 1933).

...- An illustration and brief description of the apparatus and its operation are given.

563. Gurley, W. & L. E. Gurlcy-Hill S-P-S tester. Bulletin No. -' 1490. Fob. 15, 1938. 4 p. Paper Trade J. 106, no. 14:31(April 7, ';i. 1938); B. I. P. C. 8:349. ZR:. -

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Air, at a low,--uniform pressure, is supplied by an -inverted. cylinder, floating frccly in an outside cylinder portly filled with oil. The atr is forced downward, through an open tube, to the upper orifice plato against which the sample is clamped. Each 50 cc. is marked by rings on the inner cylinder. Thc test consists in timing the rings as they dLop past the upper edge of the outer cylinder. In the smoothness tost, the papor is hold botireaonthe upper crifico plato - -- and e lowor platc having a plane annular ring, polished opticsally flat. - The contact area -is 1 square inch. Light- pressure (3 pounds per square inch) is provided by an urtweighted lover arm. Eight thicknesses of paper are tocsted at one time, which gives an ovcr-all, top-bottom average of 16 surfacc areas in one reading. The smoothness value is the time in second to leak 50 cc. of air (for more rapid work, thc actual reading may be on 25 cc. of air leal;). The paper pad is perforated by a punch before testing, in order to eliminate the porosity factor. The test may also be carried out with an 8-ply folded sample.

564. Gurloy R. D. smoothness tester. World's Paper Trade Rov. 102, no. 6:4O7-408(Aug. 10, 1934); Paper Trade J. 99, no. 5:20(Aug. 2, 1934); Paper Ind. 16, no. 5:343, 345(Aug., 1934); Instruments 7, no. 8:170 (Aug., 1934); Paper-Maker 88, no. 3:194(Sept., 1934); Papior-Ztg. 59, no. 71:1243(Scpt. 5, 1934); B. I. P. C. 5:18.

A description is given of the Gurley No. 4160 R. D. smloothness tester. It measures the surface porosity or the rate at which air -,j .flows through the inequalities in the surface' of the paper. A measure- 4:W? mont of the time in seconds for a 5-cc. air flow is taken as a rmasure . ~ " of the inequalities of thc sample and indicates the finish."

.56. Helladay, J. F. Printing usc requirements of boxboards. Paper 'ismdc J. 106, no. 25:35-44(Julio 23, 1938); Tech. Aasoc. Papers 21:215-224; discussion, 49(Junc, 1938); B. I. P. C. 8:444; C. A. 32:8142. i . An appacLratus was constructed for measuring smoothness at increased pressures. It conistbod of a block of gray iron which was bored and threaded It rccive the optical flat of tho Bckc tester, drilled with air pasc" 5 s, and connected by copper tubing through a 'rnas adaptor : . ~to the rorcur;, c-liurm of thc Be!ld tester. Thc block of gray iron | 'g carrying the optical flat is nloced on the platform of the hoovy Poctory scal, ond centered beneath the screw of an arbor pruss, the ,:-. sid_ tension ncnbers of which arc bolted to the main frame of the ~. . scale. By the use of this apparatus, it becanome possible to deternine the approximate smoothnces of samples according to the Bokk prrinciplc but under pressures up to 400 pounds per square inch. The data covcr- ; inig boards of higher caliper and lower snoothnloss are, for all practical Plurposes, linear rolationslipsa between smoothness and pressure. One BSnplc chowed a tendency toward curvilinear trend witlh constantly do- '[ .croasing slopc. This type of trend is apparent alco on other snmiplos having a comparativoly high Bckk smoothness. This particular phenomenon L ~1 was attributable to the increasing affect of lateral porosity. Thesc '

i. - r: - W - 566; Harrison, V. C. W. -~ The flokk sri:othn6sa -and -porosity tester. Patra J. 1, no. 5:186-192(March, 1953); B. I. P. 6. 8:4437.

Thec Bokk smoothness tes-ter is briefly described, and. its r2Dthod. of operation is outlined. The following3 liultetions of thu ins9ti-ment are tainted out:-() It is assumed, that the spaces I ormod betw-ee-n paper and. glass ope-n into each other so as -todttf continloit -air channel.L;- Although microscopic exaiilnntion shows that this is true in neost causes, it- is possible -to-hove a rouGh surface with, a honeycomb or closed -- cellular structure Axiiehohiii have a very- high Bek'k smoothiness fi~ure, because the surface provides few opnenpsae from the circunferencoe to the center, cf the rlass ring. (2) -Because of the compressibilitY of Paper, the snoothnoes changeso rapidly 6ur ingL the first few minutes of the application of pressure.- (5) The rate ofIflo)w si air Uhrough a tube, other things bo-ing equal, depeInfts upon the four-th power of 'uhe radius of the tube. This nears that- the effect' of theo largeOr air channels is Jct.rweighted, at the. expe,,nse of the simller, and. a surface whicli p-rovides a few large and mnany er-a11 cIlornels may appear

to be rougher thrmn actnIal2.y -is the cane. Thus - U'' instrument foils to rtiffc-rcnrtiatu beo.ween. a svrfL'aee on. which tho ia'glrtc rc large but comparatively, few, and. one on which thoey Qgo small but numerous.

567. Heingo, M4., and. Baiid., P. K..- A method for evaluating -the surface roughness of paper. Pa-per Trade J. 113 no.- 15:31'-56(oct. 9, .II I 1941); Tech. Assoc. Papeors 25:619-624(June.,, 1942); Paper LInd. 23, no. I m 8:83o-832(Nov., 1,941); B. T. P. C.- 12:81; C. A. 35:8292.

i

7 The roughness tester is based upon t~he prircin~le of direct deter"- .I nination, by chnnical neane of the deviations Cram1. a fixed plane of i.. the paper surface~at a series of" points. K1.though it emaploys the tracer principle, it diifei'-s in. thant the detector needle rvekos contact by means of an ixiterti-ttiont vortical. intl-an which elirminates the objection- ab)lo side stresses oantplowing- offset of c"ontinnous tracinG. The paper to be tested is held by a damnx consisting of anfixed. upper contact niece and n Ymovablec lower ca ta t iec e. Me uppr),pic e fins a 0.254- nixl. Eianetor hrle th-rouh w~hcich the detector eed~le imaes contact vith the paper surface. This neodl.e consists _f' alstea-l stylus, the point of which is jreunE to a-truncated cone havi-ng a fis~t end. 0.053~ Lm. (0.0015 inch) in dliameiter; an lo ofi approx-trntel::, 0.05 gram is en- ployed on the eele About 500 rcandLtyrs are tak':,, onl one sampqle. tione the factors investigated, were the'arspei conditions and.

.- mechanical disturban)ces, ciraning p)ressure, diameter of the r!etector- needle h-.haleprosscure of the deotector needles, diame10ter of the needle ~7{'point, and r? -Thor of rcadings;F p)-r sample. Values are given, for a

--- number of typi:cal -papers. Thec stand.-ard deviatilon of 'the readings is )--Glesinfluenced by th; Cer-r-r oif:ensuror.'.en' Lhan the0 arithmeotic aver- age. A curve. i½ vhich Inrgecrsoli glecs is n~td against roughness, Chohws the. inadequacy of tho ls esrmn to) evaluate roughness.

2GImatli§~. -Instituite of Parecr Chemistry. ITnsatrm. xntatin studiesu. IX. The Bflek anti Gurley soriuthnesu te-sters. Popur Trade.c J. _104, n-a.12: 62-66(March 25,. 1957); 13. I. P. 0. '(:279; F. C. Al.1{95713:657; C. A. 31: 4813; T. 3. 106:50. Smoothness 204 ',

A description is given of the two testers, and a discussion is ;' presented of the theory of the Bckk tester. From the data for a large "i number of papers, it is concluded that the two testers do not measure the same properties of a paper shoot. The results lead. to the suspicion that the Bokk readings are influenced by transverse porosity and to greater extent than .in the case of the GurIcy instrument. The-Bckk readings, which are high in comparison with the Gurlcy readings on the ----- same-samples, roe-taken on papers having a relatively high porosity. . If a correlation exists between the two instruments, the difference in the effect of transverse porosity could logically be accounted for by the design of the instrument, because the air pressure at a given rate of air flow is higher in the Beld than in the Gurley tester.

569. Institute of Paper Chemistry. Instrumentation studies. VIII. An analysis of smoothness. Paper Trade J. 104, no. 11:43-46 (March 18, 1937); B. I. P. C. 7:279; B. C. A. 1937B:427; C. A. 31:4813; Tech. Bull. 14, no. 5:57-58; T. S. 106:50.

This article is devoted principally to a discussion of the smoothness characteristics of printing paper under the hoadit:ga: typical surface defects of uncoated papers; surface defects due to tho coating process; surface defects due to both the uncoated sheet and the coating. Mention is made of a device for making a single measurement on a large area of paper. For this purpose, a separate panel and attachment were built to be used on a brightness tester. The sample could be rotated through 180 degrees about on axis at 22.5 degrees to the fixed direction of the incident Jight bean. The possibilities of the method were not thoroughly :[I *investigated.

570. Institute of Paper Chemistry. Instrumentation studies. X. A discussion of methods for measuring smoothness of paper, with special reference to a new electrical capacitance method. Paper Trade J. 104, no. 13:30-33(April 1, 1937); correction, 105, no. l:127(July 1, 1937); B. I. . C. 7:314; B. . A. 1937B:657; C. A. 31:4813.

Under methods for measuring the smoothness of a free surface, there are considered the following methods: direct measurement of the surface contour by means of a microscope with micrometer focusing adjustment; direct measurement by means of a small "rider" under which the paper surface is caused to move; electrical "pick-up" method; friction methods; "|: methods utilizing oblique illumination; and electrical capacitance method. The second section considers methods for measuring the smooth- ~; - ness of a compressed surface, which include the method of air resistance * -- (the basic principle of the Beldc, Gurley, and Williams testers)' and . : the Davis smoothness tester. The promise and limitations of each method are considorod briefly. Details are given of preliminary work on the electrical capacitance method, in which the electrical capacitance is " ~i measured of a system consisting of two brass plates separated by a sheet 0'..of paper and of a system in which one of the brass plates is replaced '^' by a liquid mercry.. surface. The results were compared with Bckk ' .a..and Gurley tests; no correlation existed between any one of the three g- Rsets of instrumental data and visual grading. The investigation of the Davis tester showed that the instrument does not grade coated papers in

1 Smoothness 205 I;.

agreement with the visual grading and that, taicing formation into account, the irstrumrnt seems to give a reasonably good nmasuro of printing smooth- ness on finished coated paperc. A variation in tho tester is suggested, in which tho face of the glass prison is covered with a thin, uniform film ..|. .. of clear oil; lwithithis modificat'.on, thc area of optical contact, with increasing pressure, would incrcaco at a rate depending on smoothinoas and corprcssi'ility and the thiclc;ess of the oil filn. It is apparent that the prcsauro-requirod for-noarly the whole of the available surface to cone into optical contact would bo reasonably low.

571. Institute of Paper Chemistry. Instrumentation studies. XXV. The Williams srioothnoss tester. Paper Trade J. 106, no. 4:38-42(Jan. 27, 1938); T. S. 106:325; B. C. A. 1938B:499; B. I. P. C. 8:252; C. A. 32: 2745. The Williams smoothness taster provides for measuring a constant volumo of air, which is compressed and applied to the conter of a cloap holding a folded-ovor sample of paper under definite pressure, in such - way that the air can pass bctwoon the .two urfaces of the paper. The results nay be corrected for the transvorso passage of air through the sheet structure (transverse or plane porosity); provisions arc made for this neasuroment. The various units of the instrument were studied, including the air measuring cylinder, the timing mechanism, the clamping device, the calibration standard, the measurement of the transverse porosity, anrd the reprodcucibility of the results. A comparison is also given of thc results from the Williams and the Bock smoothness testers. It is concluded that transverse porosity accounts for all or practically all of the air escape when smoothness readings are mado on coated !.'^' samples of hi,,h smoothness. As a corollary to this, it rust be con- eluded that, in the case of very soooth papers, smoothness readings made on this typc of inatruncnt are principally a measure of transverso porosity rather than a nmosiaro cf smootihnloss. Also, it is doubtful if the fornmlle used for calculotirg the ocrroctcd :.aootlmrosc is applicable - under those conditions. Fro these results it would seemon that all in- strur.onto based on this princinlo are influenced to an appreciable "^*t'- Oxtont by transverse porosity. Thec results given here cast some doubt upon the valuo of those instru^cnts for uce with very smooth coated papers and. indicate the necessity of applying the transverse porosity A'.. correction to all. tests. When factors affecting transverse. porosity, ;.' such as thiclmoss, apparent density, and furnish are considered, it is K-; °:'apparent that transvcrse porosity can vary widelyy without a necessary 4',i,,. '[ variation in smoothness and if the uncorrocted smoothness reading, ¶ '&.:Kf."' which is a measure of both smoothness and porosity, wcre used, erroneous conclusions might be drawn. The W'i'lians tester rnasurcs i ~ ,^^ij! ' a similar quality to that measured by the Beld: inostrlnint but differences '"g~ . do exist and the two testers do not omasuro exactly the same quality. i·. i.. It should be said at this point that whatovor lack of correlation is y:..,shown in thus results is not a criticism of either instrument. As t pointed out before nonc of the instruments basuod on this typo of test con nmasurc a single fund:aicntal property. Rather, the results O6are affoctcd by several conditions; therefore, the value of any in- -strumentO lies in its ability to ovaluato a paper for a specific use ;. requirement.

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Smoothness 206

572. Institute of Paper Chemistry. Instrumentation studies. CXXXVI. The Gurley-Hill S-P-S tester. Paper Trade J. 110, no. 23:27-33 (June 6, 1940); B. I. P. C. 10:429; C. A. 34:6067; B. C. P. A. 1940B:662.

The Gurley-Hill S-P-S tester was designed to measure the softness _.(or compressibility)/-,dr6osity, and smoothness of -paper. In each case, the measurement consists of observing the rate of air leakage over or -- through the paper specimen.. Uniform air pressure is supplied by means of an inverted hollow piston floating freely in a cylinder partly filled with oil. 'The air is forced downward, through an open central tube, to the upper orifice plate against which the sample is clamped. Interchangeable lower test plates provide for measuring softness, porosity, or smoothness. Uniform clamping pressure is provided by means of a lever; one end supports the lower plate and other end supports weights calibrated to give the desired pressure on the paper. The rate of air leakage over or through the specimen, depending upon the property being measured, is determined by timing the movement of the graduations on the piston oas they pass the upper edge of the outer cylinder. Except for the inter- changeable lower plates and the lever arm, the instrument is similar to the Gurloy Improved Densometor. In the Gurloy-Hill S-P-S rapid smoothness test, eight thicknesses of paper are perforated and hold be- tween the upper orifice plate and a solid lower plate having a plane annular ring, stated to be optically flat. The test does not differen- tiate between felt and wire side smoothness but gives an average value for sixteen surfaces. By means of the lever arm, unweighted, a pressure of 3 pounds per square inch is provided over a contact area of 1 square inch. The smoothness value is defined as the time in seconds for 50 cc. of air to pass. For rapid routine control testing of smoothness, a single sheet may be folded 8-ply. The pad thus formed is perforated and tested without unfolding. For more accurate work, eight separate plies should be tested. The following aspects of the smoothness procedure were investigated: (1) Proportionality of observed time to volume of air flow; (2) proportionality of observed time to number of plies used in each obsorvation;'(3) effect of orientation of wire and felt sides of adjacent plies; and (4) effect of grain orientation in adjacent plies. The observed tine in this test was directly proportional to the volume of air flow and inversely proportional to the number of plies tested at one time. The results correlate fairly well with Bekk readings but very poorly with Gurley R. D. smoothness values. For papers within the 'ordinary range of smoothness, the testing of 8 plies simultaneously yields an average and reproducible instrumental reading. For very smooth papers, the nuzmber of specimens tested at one tine may be increased to 4 t- twelve or purhnps oven sixteen and the volume of air flow reduced to 25 cc. The results thus obtained can be refeorroed with small error to standard .'"' conditions. However, for accurate work, conversion factors should be dc- ,] t'. termincd for each closs of pcpor. Orientation of both the sides and /4 ,' direction of grain of adjacont specimens tooted simultaneously apparently had no affect on the smoothness values obtained. In grouping a number jj ~ . of± specimens to be tested simultaneously, precaution should be taken to :, \iY arrange concentrically the punched porforatlorn in the sheets. The Gurley-Hill S-P-S tcostr nooasured in a reproducible manner certain proper- 4 ? V,, ties of napor si-ilar to those measured by the Bokk omoothnces tester and the Gurley densonoter. However, poor correlation was found between Smoothness 207

S-P-S softness and Federal compressibility and between S-P-S smoothness and Gurloy-R. D. smoothness.

57'I. Jones, Charles H. LoP. Paper-finish tester. U. S. patent 1,668,593(maY 8, 1928); Paper Tlede J. 88, no. 4-:50(Jan. 24, 1929); Zollstoff Tu.-Pnicor 9,- no. 5:294(4May, -1929.).

With this apparatus, a numerical indication can be obtained of the relative smoothness of any numteCr of snIpplos and compared with the Indication obtained from a satisfactory sample adopted ns standard; the operator can. detorrrino with great accuracy whether the finish of the sample is above or below standard and to what degree. The principle of the instrument consists in placing a shooeet of the paper on a smooth plano surface, causing a smooth-faced drag to be moved over the surface of the paper by the action of a predetecrr.inod force (such ns gravity), and obtaining; an indication of the mcan rate of movement. Preferably, the drag is always moved th-rou3h a fixed distance, and the indication is of the tine occupied by the drug in traveling that distance. In practice, it has been found that best results are obtained if the table is sot at an crgie of boat 27 degrocs to the horizontal and if the weight overbalances the draes in the ratio of about 10:9.

574. Kantrowitz, M. S., and Sinmons, R: H. Evalunting the printing qualifications of paper. Paper 'Trnalo J. 105, no. l:97-102(July 1, 1937); Paper Mill 60, no. 27:13, 15, 18-21(July 3, 1937); B. I. P. C. 7:434; B. C. A. 1937B:894.

Smoothness is one of the most important properties of paper from the standpoint .of printing. Brief reference is made to the Bclck, Gurlcy, and Williams testers, and a proposed TAPPI standard is out- lined for the BckXk test of the rclotive printing smoothness of paper.

575. Kott, Hermann. Surfaco smoothross tostcr. U. S. patent 2,251,613(Aug. 5, 1941); Austr. 1:195; C. A. 35:7194.

Tro beams of substantially identical intensity are directed from a constant source of light upon the opposite faces of the sample to be tested, and the li3ht reflected from the surfaces is then directed to a photoelectric call. The twon light besrn originating from the source are alternately interrupted in such a fashion that the rays falling on the photoelectric cell from each bcan vary sinusoidally with time and arc 180 dCegees out of phase, so that equal areas of the photocell are illuiinatod nltornatcly. One side of the surface to be tested is sErndgcd wit-h ink so that it appears darker thlmn the clean surface, the degree of dsar:cning dcoending directly upon its smoothnesss. The light now reflected from the sznudgcd surface is con- siderably less than. that reflected from the clean surface, thus pro- ducing an alternating current in the circuit of the photocell. The alternating current is amplified in. a specially balanced amplifier until it is of sufficient magnitudc to operate an indicating metor. The bean of light which .is directed on the clean side of the test surface is now reduced in area by reano; of an -iris diaphrau- until the reading of th indic tin, t rought -to zero, at which point

1& I

Snoothness 208;

the beams of light reflected from'tho smudged surface -and the clean - surface are equal. The relative smoothness of the surface may then be read directly from the iris diaphragm, which may be suitably calibrated to read percentage smoothness.

- ____ ...... - 576. ILnrocque, G. L. The control of printing quality in the paper and board mill. Paper Trade J. 106, no. 26:86-90(June 30,1938); -'' Paper Mill 61, no. 29:17-18, 20, 22, 24(July 16, 1938); Paper Ind. 20, ro;.4:46o(-July; 1938); Am.-Pulp Paper-Mill Supts. Assoc.,--Year-Book and Prograr 1938:236-240; discussion, 240-242; B. I. P. C. 8:490; C. A. 32:8141; B. C. A. 1938B:1026.

This article contains a brief review of the measurement of printing omoothnecs, with reference to the work of The Institute of Paper Chemistry, Halladay, and that of the author.

577. Mastcn, Ralph A. Smoothness tester. U. S. patent 2,019,541 (Nov. 5, 1935); T. S. 103:191.

The invention provides an instrument for measuring the smoothness of paper by determining the time required for a known quantity of air under known pressure to escape between a smooth true plane of standard dimensions and a sample piece. It permits the determination of this property for each side of the a same separately and simultaneously.

578. Paper testing device. Ind. della carte, Jan. 31, 1924; T. S. 79:147.

tAn apparatus for measuring the surface smoothness of paper is based on thi resistance it offers to the movement of a point--that is, on the basis of the attrition which develops when a point traverses the sheet under constant conditions. The device consists of a pendulum carrying a pen which touches the sheet as in writing. The sheet is placed upon a horizontal plane with a to-and-fro motion. The oscilla- tions of the pendulum are proportional to the smoothness of the paper.

579. Prior, Philip H. Experiments in printing. World's Paper Trade Rev. 102, no. 25:1874, 1876, 1879-1880, 1882, 1913; no. 26:1944, 1947-1948, 1950, 1952, 1954(Dec. 21, 28, 1934); 103, no. 1:60, 62 (Jan. 4, 1955); discussion, Tech. Convention No.: 68, 70, 73-74, 76-78 (March, 1935); Papor-Maker 90, no. 4:TS155-160; no. 5:TS1l4-166(Oct., Nov., .935); Pnper Trade J. 101, no. 15:39-44(0ct. 10, 1935); Proc. Tech. Section, Paper Makers' Assoc. Gt. Britain Ireland 15, part 2: 335-354; discussion, 355-364(March, 1935); B. I. P. C. 5:159. An appendix (page 354 of the Proceedings) describes an apparatus for viewing the surface of paper which is under pressure. A glass plate is held by Jaws, which arc shaped to allow a microscope objective to approach, while giving the maximiu possible support to the glass. The sample is pressed againat.the-glass by a plunger, spring, and screw. The pressure can be determined from the compression of the spring; thus far it has booen possible to attain a pressure of 100 pounds per square .inch. If an intense and narrow boea of light is projected on the end of the glass I 1

I".ras C=~l·~ -anraar, ( I . - 'Atrtr A'~- --. "" r" ,

Smoothness 209

in. a direction normal to the plane of the diagram, the points Of contact between thep paper and. glass appear bright against a dark backg'otuied.

580. flondall, A. G. Paper testing. Proc.. Tech. Section, Paper-

nker . U4so-Bti~tcin Iroland5", part 2:l36(Ma1reh, -1925). -- -.

-- The. method suggesoted for ~the slip pi' paper is the same as that rQtTofl by Clark, (Nol.558").

58~1. 1Rouglhr.os tlester. Patra J. 3, no. 2:76-77(So-Pt., 1939).

This instrument (developed in theo Scarutinovian lhboratorIos) is a modification of thea Iokk- smoothness toter. 'Bic principle is the sane, in tha t -the speed. at which air ~s nade to fl'Iow across the paper surface is a measure of the roughness of the surface but, instead of causing the air' to flow between the, rough paper~surface and. a smooth glass rina: of considerable area, the now instrument uses a narrow ring~, the breadth of which is less than, the cavities which are likely to be present -in. the surface of the papor. In. order to minimize the errors resulting from the porosity of the paper, the pressure used to drive the air across the1 paper i's reduced to a constant value of about :t5 cm. of water end thre rate at which it £lows is measured by means of a rotameter. Thle roughness of the paper. surface is measured, by 'placing the r,)per to be tested en a smooth Class plate as a support. rThe tester is placed on top, and the nosition of the cone in the rotameter column gives an nnnodliate reaffinj of th's roughness. By increosirj, the pressure on) the tester, the eff.-ct of the compressibility of the paper can be studied. A-n additional appliance also enables the tnntrur~ont to be used for roronity::, rnasvremriotp.

p8.Simzons, R. H. Paper quality in. relatiror to printing., Paper Thande J. 109, no. 19:37-4i0(Nov. 9, 1939); Tech. Aosse. Porror 22, t-o. 1: 469-473; discussion, .119-121(Juno, 1939); B. I. P. C. 10:129.

The sirgnificnrco of nnoothncsc in printing~papers is discus,-rce. Pzogthe wzntlxofs listed are the Bekk smloothness testtr, the WiJliansi smoo0thness and. r~nen. norocity tester and the CvrJley sueothness tester; the last has,, been eiie to nyrecuce the Gurcy-Y-Hill softnesis tester, rhichis nce adcmted.c to make smoothUness tests; mcntlon is maode also if he TLevijs ro thod. These methods all give relative readings f or speoliocbiTht because, of variations in the nressures and, methodsG of merasuring, the n7iznerical read~rnGs oI' one are. not directly con~vertible i-nto any other.

58.Underhay, G. F. The BcIr,:400ot1Lmess and p~oros:tty tes~ter. World's pajnur rrnaoeBoy. 101, no. i1-3:11d4$,lFFOia, 1954); Ppr Mnker 87, no. 5: 1428-429(M4ay, i1954).

A brief description Is given of the apparatus, and! comoroarativo figures are reported for the Deirk s1moiothnessj and the) Thg-crsoil gloss for three types 01 newsprint. I

Smoothness 210

584. Wehmhoff, B. L., Simmons, R. H., and Boyce, D. H. The Bekk smoothness tester as an aid in studying the printing quality of paper. Paper Trade J. 96, no. 4 :36-40i(Jan. 26, 1933); Tech. Assoc. Papers 16: '.264-268(June;-1933);--C;-A--27-:2808; T. S. 97:222;-B. C. A. 1933B:263; B. I. PC. 3:145.

A brief description of the tester is'given; From a series of-tests, the experimental error was assumed to be 9.5. FvnPrt-ltFn+ it+h m+nt-ri- als other than ruJbbor (vinylite resin in acetone, tinfoil and acetone, lacquer and cellophane) showed that the use of any adhesive or means of insulation other than soft gum rubber entails useless labor and detracts from, rather than adds to, the accuracy of the tests. The results at 65% relative humidity are approximately 10% lower than those at 50p relative humidity. Tests on some 300 samBplo of commrcial newsprint gave average smoothness values of 43 seconds on the felt side and 51 seconds on the wire side. Smoothnosc increases regularly with the amount of calondering. A comparison of newsprin)t from 5 mills showed a varia- tion from 47 to 92 seconds for the wire side and 41 to 108 seconds for the felt side; similar variations in smoothness were found for samples from the sane mill. rNo definite relationship could be established be- tween the anoothncss and rate of oil absorption of newsprint and mimeo- graph papers.

585. Williams, 'Frank M. A new electric finish, formation, and planoradial porosity tester. Paper Trade J. 98, no. 15:41-43(April 12, 1934); Tech. Assoc. Papers 17:286-288; discussion, 70-72(June, 1934); Paper Ind. 16, no. l:46-47(April, 1934); C. A. 28:3898; B. C. A. 1954B: 474; T. S. 99:94; B. I. P. C. 4:218.

A uniform air supply is provided by neans of a definitely weighted cylinder, closed at the upper end but open at the bottom, which is al- lowed to fall a definite distance into a mercury reservoir that acts as a seal to the lower end of the compression column. Tho end point of the test is accurately and automatically determined by means of a plunger rod attached to the falling cylinder which makes an electrical contact, closing the circuit of an eloctromagnet which is connected through a spring and pull rod to a stop watch. Uniform clamping pressure is so- cured by c screw clonp rith a diaphragm hydraulic press foot, and the exact pressure is accurately indicated upon a gage. Holes or perfora- tions in the center of the folded sample or of the sheets allow free access of air to the space between the two surfaces which are under test. Tho nothod of operation is described. The accuracy of the test is doubled by having two surfaces of paper in contact. Plano-radial porosity io tih tine required to force a definite quantity of air, under standard prcscureo conditions, a fixed distance through the actual pores or tc:-:ture io the sample in the sane plane as that of the sample. After the firil!ch of both sides of a'paper has been determined, a per- forated pieco of rubber is inserted between the folded surfaces of the sample anrd the clampingopressure brought to standard conditions. A reacurcd quantity-of air at a definite pressure is forced out through the presc or fleo' in the anme plane as the sample to a distance equal to 0.5 inch. c::~~~..·x·.··r.t·~'- ~ :\Bi~;~-.I? ~~w~ J~, ;··i.~s

Smoothness 211

586. Williams, Frank M. The relation of smoothness and plane porosity to printing qualities of paper. Paper Trade J. 100, no. 23:37-39 (Juno 6, 1935); Tech. Assoc. Papers 18:437-439(Juno, 1935); C. A. 29:5268; B. C. A. 1935B:719; B. I. P. C. 5:308.

The snoothncos of a sample of paper is dotoriiied by measuring the time (in seconds) required for a definite amount of air at a definite pressure to bo-forced between-two surfaces of-tho sample folded upon.it- self, perforated in the center, and clamped between rubber-faced plates which seal the two outside surfaces of the folded sample against any escape of air. The compressed air supply is obtained by a weighted cylinder, open at the bottom end, and descending into a reservoir of rmrcury. The sample under test is clarpod at a definite pressure, as indicated upon an accurate pressure gage. To make a test, it is only necessary to raise the central colunn to a given height and latch it. The soaple is inserted and clamped to the desired pressure; a lover un- latches the falling column, and the tino is indicated by a stop watch or Telochron clock. Various experimental data are given.

587. Williams, Frank M. Studios upon smoothness, porosity, and printability of paper rith new methods for determination. Tech. Assoc. Papers 20:305-309(Juno, 1937); Paper Trado J. 105, no. 8:43-47(Aug. 19, 1937); B. I. P. C. 8:34; T. S. 106:92; C. A. 31:8188; B. C. A. 1937B:1189.

The Willianm tester consists of a base in which a vertical outside cylinder is inscrtod. Inside and concentric with this is a 1/0-inch pipe reaching practically to the top of the outside cylinder, which is connected with the sanple claom and furnishes a rnans of conducting the compressed air to the sapnlo. Tlo annular space boteeon the 1/8-inch pipe and the largo outside cylinder forms a rmrcury reservoir. A thin, movable cylinder, open at thu'bottom, is inserted in this annular space. The operation cf the instrument is described, as well as the method of making a test. BaroLmtric pressure, as well as the temperature and humidity conditions, is an important function of all smoothness testers of the air-flow type. Standard permanent test plates should be available for chocking any smoothness testing instrunent. In specifying a definite comprcsuion area, both the inside and outside diameters of the limit- ing circles should be given. By using square. clamping plates, omothness and plane porosity tests nay be made upon a sample with an air flow of equal velocity over the entire surface of the sample tested. It is possible, by moans of square test plates, to make smoothness and plano porosity tests both in the machine direction and across the sample. The reading upon the Williams instrument may be correlated with those of the Bcldc instrument when those are taken under carefully controlled condi- tions.

588. Williams Appcratus Co. Paper smoothness and formation tester. Inotrumont;7, no. 10:218(0ct., 1954).

A brief description is given of the Williams electric smoothness and for:n.tion tester. Ar illustration is included.

589. Zipkin, G. S. Bckk's apparatus for the determination of the smoothness and porosity of paper. Bumazhnaya Prom. 15, no. 3;49-52(March, I. 1936). I a I I ______ ..M I T

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Stiffness, Softness, Rigidity 213

The apparatus is similar to that used for measuring compressibility by a dynamic load (see Compressibility). The height of the rebound is road on a scalo fitted attlio side and thoolostici-y of tihe paper is expressed as the percentage which this value represents compared with the.hoeighit of rebound obtained .from the- uncovered steel- support. An apparatus is also shown for measuring the resistance of paper to bend- in; stresses within the elastic limit. The sample piece is arranged so that it forms a semicircular arc of 10 cm. diameter, provided no flattening is produced under the influence of its own weight. The whole arrangement is placed upon the pan of a balance which is adjusted to the equilibrium position; a plate of glass is placed above the arrangement in such a way that its lower surface, when the balance is adJusted, is exactly it cm. above the baseplate holding the paper. The weights necessary to be added to the balance to produce equilibrium in this position ropro- sent the force necessary to press down the semicircular strip by a dis- tance of 1 cm.; when the value is calculated for a strip cmn. wide, it represents the resistance to bending or the stiffness of the paper.

~~. lBorrdt, Kurt. Recent laboratory instruments for the pulp and paper industry;. Zollstoff u. Papier 17, no. 7:309-312, 314; no. 8:349- 352(July, Aug., 1937); B. I. P.- C. 8:74; C. A. 31:8188; B. C. A. 1937B:1321.

A description of the Zander stiffness tester is included.

24k. Berndt, Kurt. Stiffness testing of papers and boards. Papler- Fabr. 33, no. 48:393-393(Dec. 1, 1935); B. I. P. c. 6:245.

An apRaratus is described and illustrated for measuring the stiffness of paper and boards. The force necessary to bend a strip of definite width and length through a measurable arc is determined.

29. Bragg, A. O. Stiffness tester for boards. Paper Makers' Mo. J. 63, no. 2:49(Feb. 15, 1925); Paper 35, no. 5:177-182(Nov. 20, 1924).

96. Brecht, W., and Blikotndt, F. A new instrument for testing the stiffness of papers and boards. Papier-Fabr. 38, no. 4:17-22(Jan. 26, 1940); Ind. carts 7, no. l:15(Jan., 1940); B. I. P. C. 10:300.

A new instrument has been devoloneod for measuring the bending stiff- 'neas of paper and board. One end of the sample strip to be tested is fixed to a cylinder so that it follows the curve of the cylinder for a certain distance, a weight being attached to the other end of the strip. The force required to revolve the cylinder is taken as a basis of the measurement. Strictly, for each paper thickness a certain cylinder diameter should bc used; because this is not practical, a scrics of cylinders are used, the diameters of which form a Coometrical sequence. The best relation of the weight in grams to the cylinder radius in mm. was found to bo 4.5. The theory of the measurement is discussed. The oppllcation m, the bonding test method to thc d.tcermination o'f ulauticity is described.

-'-.1.iL ~~~~I~~~~~~~~~~; .~ . . .i.;; - - ...

Stiffness, Softness, Rigidity 214

597. Brecht, W., and Blikstadt, F. Testing the stiffness of paper and boards. Papier-Fabr. 36, no. 4 9:532-538(Dec.- 2, 1938); B. I. P. C. 10:21.

After a theoretical discussion of the resistance to bending and elasticity in general, bending formulas for paper, cardboard and similar - - - terials are derived.--17 references.--- -

98. Brown, T. M. A method for determining softness of soft papers. Paper Mill 52, no. 23:19-21(June 10, 1939); B. I. P. C. 9:515; B. C. P. A. 1939B:1029; C. A. 33:c635; Tech. Bull. 16:115-116.

A description is given of the Brown Company paper softness tester, which measure the force necessary to crumple a wad of the specimen into a definite volume; hence, it is different in principle front the usual commercial stiffness testers. It has the great advantage of being very inexpensive and can be built from ordinary laboratory equipment at a coat of less than $5.00. It is sufficiently reliable on the types of paper where softness is an important factor, such as napkin stock, facial tissue, lightweight toweling and similar stocks. I 599. Carson, Frederick T., and Worthington, Vernon. Evaluating i the wearing quality of currency paper. J. Research Natl. Bur. Standards 26, no. 6:467-480(June, 1941)(R. P. 1390); B. I. P. C. 11:417; C. A. 35:6108.

A stiffness tester is described for use with crumpled paper. Be- cause the results did not give the necessary information for the problem in hand, the apparatus was not completely developed, although there were indications that a very sensitive and significant asooure of plane shoots night be obtained by further dcvclop:ont of the instrument.

6O0. Carter, E. .The Carter paper stiff ncs tester. Paper Trade J. 93, no. 15:54(0ct. 8, 1931); C. A. 25:5987; T. S. 93:276; B. I. P. C. 2:135.

An apparatus is illustrated and briefly described. The stiffness is taken as the load in granm required to bond a sample through an angle of 90 degrees.

601. Clark, James d'A. Determining the rigidity, stiffness and softness of paper. Paper Trade J. 100, no. 13:41-44(March 28, 1935); Tech. Assoc. Papers .8,no. 1:234-237; discussion, 62-65(Jurn, 1935); C. A. 29:3832; B. C. A. 1935B:490; T. S. 101:510; B. I. P. C. 5:249.

A review is given of the types of stiffness testers under the headings: cantilever, bean, column, folding, modified cantilever and pendulum. A new method is proposed, which is now the basis of the TAPPI method.

602. Dantzig, Tobias, and Peterson, Esther C. Apparatus for measur- ing the stiffness of flexible materials. U. S. patent 1,824,395(Sept. 22, 1931); T. S. 94:280. ~~l 11 11 111111 I 11I.-Miii

uuaIYIII,_._I, I Stiffness, Softness, Rigidity 215

Two flexible rolls are mounted near the upper edge of and vertically to a vertical board, which supports an inclined straight guide, the longitudibnal' xi s- o f - wh ich passes thrbough-the liTnoeof-contact of the rolls. Thu end of a test strip of convenient length and width is engaged be- tween the rolls.and the latter are slowly turned until-the free end- of the test strip barely touches the guide. The stiffness number of the material (defined as a number proportional to the cube root of the elastic moduli) is read off directly on a scale marked on the guide.

603. Davis, D. S. Nomographs for rigidity, stiffness and softness of paper. Paper Ind. 17, no. 6:409(Sept., 1935); T. S. 103:85; B. I. P. C. 6:146.

Two charts are given, one which permits the computation of rigidity, stiffness, and softness, and the other of the rigidity factor.

604. Elald, W. New stiffness tester for paper. Papicr-Fabr. 25, no. 20:301-502(May 15, 1927); Zcllstoff u. Papicr 7, no. 3:112-115 (March, 1927).

Illustrations are given of the stiffness tester used by Schulz and I Ewald [No. 626]. Data are given for strips from 5 to 13 cm. in length. The effect of length is not as great as previously assumed.

605. Fuocs, R., Inc. Paper testing instruments make possible new tests. [Smoothness, fuzz and stiffness testers]. Instruments 6, no. 1: 22(Jan., 1935).

Diagracs and description of the stiffness tester.

506. Gurlcy, R. D. Stiffness tester. Paper Trade J. 99, no. 25: 43(Dcc. 20, 1934); Paper Ind. 16, no. 8:573(April, 1935); Instruments 8, no. l:22(Jan., 19355); soo also Gurley Bulletin No. 1420(Feb. 1, 1935); B. I. P. C. 5:129.

The [tiffncss of the paper is measured by clamping a prepared sample in a movable arm and drawing the paper over the top of a weighted pointer until the bending of the paper releases the pointer. The amount of deflection of the pointer, road on a scale at the bottom, is the measure of stiffness. The clamp holding the sample can be raised or lowered on the am, permitting the use of samples from 1 to 4.5 inches in length. The pointer can be loaded with weights of 5, 25, or 50 grams, placed at any one o' three distances below the pointer. The clamp arm is rotated by n wire bolt running from a capstan handle, which is turned in order to move the papcr. The operation of the instrument is described.

607. Institute of Paper Chemistry. Instrumentation studies XIV. A comparison of the Smith-Tabor and the Gurloy stiffness testers. Paper Trade J. 104, no. 21:43-47(Mny 27, 1957); B. I. P. C. 7:390; B. C. A. 1937B:770; C. A. 31:6877; T. S. 1056:93. .,

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w Stiffness, Softness, Rigidity 217

The reading of the Gurley instrument is highly dependent upon the nature of the cdge of the paper sample and the smoothness of the surface. An apparent increase in stiffness is produced by any friction between vane and paper. The effect of the edge and surface of the sample is clininatEd in the Cartcr' although the-length and width should be ac- - curatoly established. The Gurley is very sensitive to length of sample. The angle of bond. being larger in-.th Carter tester, thc force required is correspondingly larger and thus more accurately measurable. However, the disadvantage duo to the deformation of the paper is objectionable. It would be instructive to build a Carter tester using an anglo of bond comparable to that of the Gurloy. If an accuracy in the determina- tion of this bend comparable to that obtained by the nethod employed in the Gurley tester could be secured, the advantage of the static reading of the Carter would be obtained without the disadvantages of either in- struront. The zero of the Carter instruwont is not as dependable as de- sired. Any friction in the bearings is objectionable in establishing the zero. As the curves indicate, however, stiffness as measured by the Carter tester is closely comparable to that as measured by the Gurley. The'curves arc very nearly straight lines, and the experimental points fit the curves very closely. The Gurley tester is useful over a widow range of papors, but for light papers the Carter is very convenient, readings bcin:; obtained in a shorter time than with the Gurley. The weight of the paper would tend to lower the value of stiffness as measured on the Carter while increasing the value as measured by the Gurley. This is a possible explanation of the fact that the curves do not tend to pass through the origin. For papers whose stiffness is very high, the Carter instrument is unsuited, because of the uncertainty in the force to produce 90-degrec bonding, this force varying with time. For such papers the Gurley tester is to be preferred. All papers were ranked in the sane order by both instruments, and any departure from the curves arc within the experimental error.

609. Institute of Paper Chemistry. Instrumentation studies XXXV. The Clark paper softness tester, with an important note on the Gurley stiffneos tester. Paper Trade J. 110, no. 7:29-37(Feb. 15, 1940); B. C. P. A. 1940B:351; B. I. P. C. 10:249; C. A. 34:5085.

The operating technique for tho Clark paper softness tester has been studied in rsoe detail. The overhanging length of the paper strip inserted in the roller mechanism of the instrument has been found to bear a straight-line relationship to the angle of rotation necessary to cause the strip to fall over. The correlation between Clark rigidity and Gurley stiffness was poor for limp paper but somewhat better for .-' ^ stiff paper. One of the principal reasons for this poor correlation wasoo found in the large source of error in the Gurley method, wherein errors range up to about 90% of the apparent Gurloy stiffness. Clark rigidity was found to correlate well with flexural rigidity as determined by a research method involving a torsion pendulum.. Subjective tests for softness of facial tissue, towel tissue, waxing glossine and broad wrappers correlate with th neoan of the machine direction and the cross direction Clark softness values. The accuracy of determinations carried out on the Clark paper softness tester depends largely on the nature of the paper tested. For heavy, uniform papers, five' determinations in ' ,- each direction ore sufficient, but at least ten representative strips in !: ^.,' each direction are necessary for lightweight papers.

I I_· (I·

... -Stiffness, Softness, Rigidity 218

610. Isnard, Raymond. The testing of cardboard. Elasticity or rigidity and folding. Papeterie 43, no. 11:578-586(July 10, 1921); Paper Trade J. 73, no. 16:40, 42, 44(0ct. 20, 1921).

The general principles of the tasting of the ctrcngth of beams .may be applied .to the tooting of the rigidity (or clastLcity) of -- cardboard. If a strip of cardboard is placed-on two supports at a distance 1 apart and subjected to a load P at its center, the deflection f is (iP37/4E I, where E is the modulus o' elasticity and I the moment of inortia of the section. In the apparatus used, a strip 1 x 10 cm. is supported on knife edgeo exactly 50 mm. apart, so that 25 mm. project I at either end. A graduated lever, pivoted at one end, carries a third knife edge, by moans of which the load is applied to the middle of the test strip. The weight of the lever and knife edge is counterbalanced by moans of an adjustable counterpoise and the load :is carried by means of a rider on thi lover arm. The deflection on applying the load is road by moans of a mirror fixed to the lover and a scale graduated in mm. If d and D are the distances of the deflecting cnife edge and of the scale from the mirror, P the equivalent load at the center of the test strip, n the reading on the scale and c the thickness of the board, E = 6250PD/no3 d. The limit of accuracy is not greater than 6%. If the toot abip is folded completely over (presumably without creasing), weightod in this position for 15 minutes, released, and allowed to stand for several hours, it will finally attain a definite "fold angle" which varies from 20 to 25 degrees for very rigid cardboard to 60 dogroos for roofing felts. Comparative tests on various samples can be obtained only by applying the test in exactly the sane nannor in each case. If properly carried out, this test will class boards in the sane *ordcras the detcrmination of the elasticity.

611. Jacobsen, P. M. Hoffoann. Evaluation of pulp and the properties of paper. Svonsk Popporstidn. 35, no. 8:267-268, 273-274, 277-27, (Aril 30, 1932); Papior-Fabr. 30, no. 39:577-579(Scpt. 25, 1952); T. S. 97:131; B. I. P. C. 2:289.

A simple stiffness tester is described, in which the paper strip (30 rm. wide) is supported on a concave surface by moans of a cylinder; shot is dropped onto the paper until it bonds; the weight of shot is a measure of the stiffness.

612. Kottc, --. New stiffness tester (Taber) for paper and pulp. Zcllstoff u. Papior 19, no. 3:142-143(March, 1939).

This is apparently a translation of the nanufacturcr's announcncnt of the V-5 stiffness gagc.

.J . Martin, R. I., and Bray, G. R. R. Flexibility or stiffness tests, using the flexoncter. World's Panor Trade Rev. 100, no. 26:2008, 2010, 2012, 2014, 2016, 203.8, 2020, 2068(Doc. 29, 1933); Paper-Maker 87, :*: no. 1:4, 11-13(Jon., 1934)'; B. C. A. 19534B:90; T. S. 99:106; C. A. 28:2897; B. I. P. C. 4:138. .n ,. I -- .. ,. -.1.''. I--.--

Stiffness, Softness, Rigidity 219

Determination of the relative flexibility or stiffness of thin sheet electrical insulating materials by means of the flexometer (Pierce, J. Textile Inst. 21:T477(1930)) promises to have applica- tion to papers (both untreated and varnishqd) and other materials. With many materials the plain rectangular strip specimen curls and kinks, sometimes to such an extent as to make any reading impossible; -insuch cases, by using a-pear-shaped-loop specimen much more-con- sistent roadings were obtained. The method of making the test and of calculating the results is explained.

614. Maston, Ralph A. Stiffness tester. U. S. patent 2,092,809 (Sopt. 14, 1937); T. S. 106:95.

The'test sheet, of definite length, is clamped on a rotatably mounted arm. A freely movable pointer, pivoted coaxially with the arm, has one end positioned so as to contact the free end of the test strip. The arm is rotated so that the test strip causes a de- flection of the pointer until the deflection of bending of the strip end of the pointer arm. The stiffness of V4 causes it to slip off the the test strip is obtained from the maximum deflection of the pointer. 'ft,I21: ; . ..615. Micoud, . Rigidity of cardboard]. Papier 34, no. 2: 251-252, 255-258(March, 1931). I· The cardboard is cut into strips and each strip is fastened in a clamp in,such a manner that the length of the strip extending out of the clamp is exactly 20 cm. The weight of the strip causes it to bend and form a parabolic.curve. The curve is more or less flat, de- I. ! W.:· pending on the stiffness and the weight of the board. When the paper has no stiffness at all, it will fall down. almost vertically; and when it possesses absolute rigidity, it will remain perfectly horizontal. The distance through which the board bonds is characteristic of the stiffness. Stiffness increases with the weight per sq. n. The de- flection of the strip diminished more rith increase in weight per sq. m. with samplcr cut in the machine than in the cross machine I3 direction.. Moisture diminishes the stiffness of the board. The com- position of the pulp, the nature of the sizing, the method of boating and the calcrC.cring all have on effect on stiffness.

616. Miror, Charles A., and Minor, Jessie E. A study of stiffness testing of pa-ers. Paper Ind. 17, no. 1:35-37(April, 1935); C. A. 29: i , i" 4578; B. C. A. 1935B:623; T S.. Cl:300; B. I. P. C. 5:250.

A study of the stiffness of tag, index, bond, and ledger papers, C carried out mostly on a Curlcy stiffness tester (with a few tests on the Suvant instrument), gave the following indications as to the value of stiffness testing for paper quality. Stiffness is largely a matter of manufacturing manipulation and is, therefore, not a factor of fiber quality except in so far as different kinds of fibers are subjected to differences in manipulation, as in beating, in the sizing added, and in any other sources of fiber cementation. For the heavier papers, stiffness is much more sensitive to beater hydration than is tearing resistance;

..LI

Fiiiilesri·au;PwrI------Stiffness, Softness, Rigidity 220

it is also probably less sensitive to fiber weakness and to the shorten- ing of fiber length than is tear. For thinner papers which are beaten to noximran strength, as aro bonds and ledgers, stiffness has no partiou- lar advantage in sensitivity ovor tear; for such papers stiffness brings less distinction between rag and wood papers than does tear. Stiffness for some grades of paper should be a valuable test as a noasure of boater hydration. - - -

617. M:lhonen, E. J. Strength and stiffness of white wood fiber- board. Firnish Paper and Tinber J. 17, no. 12:592,'594-596(Junc 30, 1935); T. S. 103:82; B. I. P. C. 6:132.

A conpletc description is given of the use of the Smith-Tabor stiff- ness tester, and a comparison is made of the Mullen strength, freeness, and Sith-Taber readings for a sannpl of fiber board.

6l1. Paper softness testers. Instrunmnts 7:78(April, 1934).

Two new paper softness testers are announced (by the Thwing In- stiuaCent Co.), one for routine testing and the other for research work.

619. Paper stiffness tester. Paper Ind. 14, no. 2:141(May, 1932).

This tester is manufactured by the Toledo Precision Devices, Inc. but was originally developed by Rcnington-Rand,. Inc. (cf. Stuart, W. H.). It is mounted on a Toledo paper rean autogage and consists of a special bracket supporting on adjustable loading nouber which contacts one end of a sample to be tested. The other end of the test strip rests on an aluminum plate on the scale am. In testing, each strip is inserted in the gap between the aluminum plate and the end of the plunger. The handle is turned slowly and steadily to bend the paper. The pressure is indicated on a chart. The naxinmu point regiEtored represents the stiffness.

620. Papcr tests for special properties. 4. Rigidity. Paper- Maker 87, no. 2:TS51(Fcb., 1954); B. I. P. C. 4:162.

The importance of rigidity has increased since the advent of auto- matic focders which speed up the flat-bed printing machines. Beating is an important factor in producing rigidity; good fiber length and addition of starch and silicate of soda nay also increase the degree of rigidity. Records of tests for rigidity should be kept when it is ascertained that the tests have been conducted under standard and normal conditions.

621. Pcirco, F. T. The inandlc" of cloth as a measurable quantity. J. Textile Inst. 21:T377-416(1930).

i'.- L An instru-cnt is described on which it is possible to measure the ; - anGlo through wilich a specimen of cloth droops when a definite length

,;SI, - is held out ovcr an cdge. By neans of a natlheratical forrula, this angle .; - is converted into a trln called the bending length of the material

4 1.L t9BW!mmmm- - Stiffness,- Softncss, Rigidity 221

(i.e., the length of fabric that will bend'under its own weight to a definite extent); the stiffer the material, the longer the bending .. _... length. The standard procedure for determining the bending length nay be varied with regard to the shape -and dinonsions of the-test-- - _ specimen for very stiff or very limp materials. Although developed - - -- for textiles,-the principle night be applied to the testing of paper.

622. Ricsenfold, E. H., and Hamburger, T. New stiffness tester for paper. Papier-Fabr. 27, no. 46:709-710(Nov. 17, 1929); Zollstoff u. Papier 9, no. 12:841-842(Dec., 1929); World's Paper Trade Rev. 92, no. 25:2262(Dec. 20, 1929); Papior 33, no. 2:187-188, 191(Fob., 1930); C. A. 24:3366; T. S. 91:205; Paper Ind. 12:585.

The paper is held in a horizontal direction and supported at each aen, or it sags in the center of its own weight. The angle of this bend is measured. The paper strips are 15 x 120 in., and 100 Mn. project beyond the clamp. After being in place for 15 minutes, the angle between the vertical through the point of clanping and a line through this point and the free end of the strip is taken as the measure of the stiffness. The weight of the paper and moisture content are influencing factors.

I- .- :623.. Saxl, Erwin J. Physical testing of rayon yarns and staple fiber. In Rayon and Staple Fiber Handbook, 3rd ed., 1939:554-565.

- A discussion of the Saxl tester and the Schiofor flexonctcr. 22 references arc given, all pertinent ones being contained in this bibliography.

624. Saxl, Ervin J. The quantitative measurement of stiffness and resiliency. An. Dycstuff Rcptr. 27:P65-69(Feb. 7, 1938); Rayon Textile Monthly 19, no. 1:57-58; no. 2:77-78(Joa., Fob., 1953); C. A. 32:2363.

A stiffness tester is described, which was designed for cloth or yarn, but which night be applied to paper. It consists of a clamp in which the test spccinon is inserted and a balance (with sliding weights) with a scnsitivity of 0.02 gram.

625. Schooller, F. Method of dctcrmnininG the bending elasticity of pliable materials, especially carton papers. German patent 646,253 -:i: (May 16, 1954).

626. Schulz, H., and Ewald, W. The stiffness of paper and its .] nmeasurenent. Papier-Febr. 23, no. 48:768-770(Nov. 25, 1925); T. S. 83:52.

!i2.;' "A strip of paper, 20 nil. wide and 80 rr.. long, is fastened hori- zontally and a weight io added until the strip bends. The distance Ai"& ., of the weight from the fixed end of the paper indicates the stiffness o''o the sanple.

N2i Stiffness, Softness, Rigidity 222

627. Shamaan, C. F. The stiffness of paper. Proc. Tech. Section, Paper Makers' Association Gt. Britain Ireland 23:251-241(Dec., 1942); B.--I.-P.-C.-14:20; B. C-.-P.-A-. 1943B, II:346.

Because of the difficulty of measuring-the stiffness of paper-by the usual static method, a dynamical method is proposed in which an - elastic restoring force derived from the stiffness of the paper controls the vibration of an inertia system of long period. The paper strip is cut in the required direction, accurately parallel, and of the standard width (2 inches); It is then formed into a ring tightly round a nandrel and its t)o ends are clamped together by a screw clip, which fits into o groove nilled out of the mandrel parallel to its axis. The clip carrying the paper ring is screwed in position on the bob of a pendulum. The free period .of the pendulum is measured after it has been adjusted by cans of a leveling screw to a value of about 8 seconds. The next stop is to fix the side of the ring remote from the pendulun, which is done by means of a largo rectangular block which slides on the base plate and carries a linear clanmp which can be slipped over the ring and screwed up tight without disturbing the pendulum. The coupled period of the pendulum is now measured by tiring several sets of ten complete oscillations. The oscillations are conveniently initiated by means of on air jet from a rubber bulb directed against the bob. The linear relation between the displacement and the force applied to the paper ring was confirmed by a static noethod for displacements up to 3 cm. on a ring 22.25 rn. radius. The close correlation which exists between the substance and stiffness allows the individual stiffness values to be corrected to the nominal substance if the actual substance of each sample is neasurod and the result can be expressed as the average stiffness in dyne-cn. at the nominal substance. A linear relation exists between relative humidity and stiffness; adequate accuracy of stiffness measurement is obtained if the relative humidity is controlled within + 16. The nathenatical theory of the paper ring is developed.

628. Srlith,. George H., and Taber, Ralph F. Apparatus for menasur- ing the stiffness of flexible materials. U. S. patent 2,113,389 (April 5, 1938); T. S. 109:149.

The test strip is mounted vertically in a suitable yieldable holder. The top of the strip is deflected by means of a pivoted pointer which is moved annually over a suitable graduated scale to the position whore the test strip disengages front the pointer and springs back. The scale is gr aduatedd on either side of' the vertical, so that readings can be taken by bending the sane strip in both directions. Means are provided for increasing the ronge of the instrument according to the type of material to be tested. t. >629. Smith, S. F. The rigidity of box board. A nethod- of measurement and some results. World's Paper Trade Rev. 99, no. 6:403-404, 406, 4o8, 442, 444, 446; no. 7:4853, 486, 520, 522, 525-526(Fcb. 10, 17, 1933); Proc. Tech. Section, Paper Makers' Assoc. Gt. Britain Ireland 135, part 2:429-448; discussion, 448-450(March, 1933); Zcllstoff u. Papier 13, no. 4:158-159 (April, 1933); Wochbl. Papicrfatr. 64, no. 20:342-3544(May 20, 193355); C. A. -. g 27:5818; T. S. 98:15. Stiffness, Softness, Rigidity 223

The tern rigidity is used in the special sense of stiffness--i.e., .resistance to bonding through a snall anglo. The,present ncthod of testing depends upon the estimation of the force required to deflect the center of a strip of board through a definite distancewhen.the end s..-- - of -th trip are froo and rest on two rollers. The measurement is Made below the point at which the board takes on a sot--i.e., below the elastic linit. A strip of board 3 cm. -wide and a convenient length, usually 12 cn., rests on shoulders at the base of the supporting rollers, which are 10 cn. part. Pressure is applied to the center of the strip through a roller on the bottom end of a pointer, whose upper end travels over a scal- showing the horizontal travel of the roller in rn. The sanplo is held in place before pressure is applied by the pointer, which is exactly balanced at the pivot except for a horizontal projection giving rise to a sarll sustaining force sufficient to hold the sanple against the roller. Tlc pressure is applied by a weight arrm pivoted independently on the sane spindle as the pointer, and having a stop which maintains it at right angles to the pointer while the weight is being applied. There are two positions for the weights on the weighing arm one being exactly twice the distance of the other fron the fulcrun. Four weights nay be used, 3.33, 12.5, 50 and 100 grams. Details are given of the ncthod of conducting the test and calculating the results. Certain precautions are outlined. The pressure on the sample is indc- pendent of the readinC of the pointer. The construction of the appara- tus is such that the pressure is applied only on the center line of the test strip when the scale reading is zero. At any other reading, it takes affect at sonm point above the center line and at the highot reading coinonly obtained, (at 6 nr. ) tho point of contact has risen 0.48 rml. At least four sannple are used for an average result. The rigidity of a board is proportional to the cube of its thickness, the density being constant. It is also proportional to the square of the thickness, the substance being constant; at a given thicmknss, the ri-idity is proportional to its density; nathcrmtical proof is offered. Fron these orlations nay bc derived the equation: Rigidity = K x (thickness) x density, in which K is tcmed the rigidity constant. Values for K have been dotcrmined for a variety of boards; it has a characteristic value for each distinct class of board. Fron the op- proximntcly constant value of K for each type, it follows that rigidity of a board can be calculated with fair accuracy if its type, caliper, and substance are known. Practical mnthods of controlling rigidity are discussed. A theoretical discussion of the nature of rigidity is included.

630. Srmith-Tabcr. Duo-rar:o snap tester. Advcrtising leaflet, -; - n. d 1 p.

An apparatus for ctrmininC the initial stiffness of paper front substance 2°- to 15-point bristol. Toot speciEons 1.5 x 3.5 inches arc clanpcd in the pepdului: and the pointer is ilovcd slowly across the scale tc the position whore the string slides front beneath the finger ,ago anc srnps back to vertical. The overage of the right rd. left scale rcadirgs represents the initial stiffness.

'.';. ~ 631. Snith-Tabcr. The Snith-Tabor pliability corpnrator. Smith- i-. Tabor Dull. 535. n. . * . * 4-'~;- ' a: -- -'

Stiffness, Softness, Rigidity 224

The apparatus is illustrated. The sanple to be tested is placed in the clamp and the dial rotated. The reading is taken when the sample touches the gage. Tho operation is repeated against the opposite gage. The averages show the .pliability in. one direction. -To dcterminc - --- the pliability the opposite way of the grain, the clanp is loosened and samples turned 90 degrees. To doterdine the resiliency or elasticity, the pliability test is-carried-out; thoesanplo being allowed to remain bent from 5 to 30 minutes or until the plastic flow has ceased.. Rotate the dial until material tends to leave the gage, take readings, subtract the average pliability and average resilience readings front 100, divide the basic result by the pliability results and multiply by 100; this gives the resilience in per cent.

632. Stiffness of paper. Zellstoff u. Pepier 6, no. 2:77-78(Feb., 1926); T. S. 83:112A.

-:'; ,-The stiffness test for paper and its interpretation are briefly discussed. The article is a review of a paper by Crolard in Mon. papeterie Frangaisc.

633. Stuart, W. H. Paper stiffness tester. Paper Trade J. 93, no. 21:39(Nov. 19, 1931); C. A. 26:842; T. S. 94:191.

~S ^ The equipment consists of a Toledo scales and a Black and Decker , '.: drill stand with special vertical shaft, coil spring, collar, and test strip holding plate. The test strips are placed between the end of the scale beam and the plunger of the stand. Pulling the hand lover on ' the stand forces the plunger down and bends the test strip (1 x 3 inches).

':; 634. Tabor, Ralph F. Apparatus for measuring the stiffness of i^' flexible materials. U. S. patent 2,063,275(Dcc. 8, 1936); T. S. 105:104.

The invention provides a pair of relatively movable members for " ' bending the test strip with suitable means for limiting the movement of the members in each direction relative to each other. A separate [t .' handle or lever, that may be operated either manually or mechanically, is provided for operating one of the members. The motor used for e chanical operation is controlled so that it will stop automatically ' when the strip has been flexed the desired amount, and signalling moans

. .tf,' are provided to indicate when this stage has been reached. Means are ': Wprovided for measuring both the initial and basic stiffness of the ,'"i ' material so that the amount of plastic flow can be determined and the . elastic properties of the material calculated therefrom. Cf. Smith and ' Taber, U. S. patent 2,113,389.(No. 628).

b' "' 6535. Taber Instrument Co. Stiffness tester. Instrumcntn11:164 (1938); J. Textile Inst. 29:A554.

A very brief announcement of the V-5 stiffncss gage and triple- /- !cut shear for mcasuremont of stiffness and resilient qualities of paper, etc.

Xw

os-in-··;sa;la?8U· II*---- I Stiffness, Softness, Rigidity 225

636. Taber Instrument Co. Taber V-5 stiffness gauge. Leaflet, 1938, 6 p. Bull. 3802, Rev. 1.

The weighing system is of'the pendulum type. The face of the specinmn clamp is mountedexactly on.the center of rotation, -insuring- --.- constant length of the moment arm. When the load is applied to the free end of the test specimen, a torque is imposed on the holding means -that--is-accurately weighed by-the deviation of the pendulum from the vertical. Indication is made by the simple alignment of the pendulum insot with the 15-dogrec angle graduation on the loaning disk. Under sustained loading the test specimen, especially, if it is one of the softer materials, exhibits considerable elastic fatigue in the form of a drift to a lower stiffness. The first registration of the lines indicates initial stiffness which should be recorded; additional readings are taken until no further change occurs over a period of one minute. The last reading represents the normal stiffness. After the first reading there will be noticed a residual deflection or temporary set that slowly decreases and may eventually disappear. The normal oscillation of the pendulum between tests tends to neutralize'. this residual force and should be prompted, if necessary, by manually oscillating the pendulum weight back and forth a few times.

637. TAPPI. Rigidity, stiffness and softness of paper and paper- board. TAPPI Tentative Standard T 451 m-44. Paper Trade J. 111, no. 22:125-124(rlov. 28, 1940).

Rigidity is defined as the property of a paper or paperboard of resisting an applied bonding force, its fl.oxurcl resistance, and is proportional to El, where E is Young's modulus and I the moment of inertia. Stiffness of paper or paperboard is its ability to support its own weight, the inverse of flabbiness or limpness. It is propor- tional to EI/W, where W is the basis weight. The softness of a paper is the feeling of softness when a shoot is crumpled in the hand. This deopnds upon the case of crumpling,together with the absence of sharp edges in the crumpled sheet. It is inversely proportional to the rigidity ElI modified by a function of the thickness of the shoot. The method is a nodlification. of that of Clark.

656. Technical description of Smith Taber Model 'E" precision stiffness tester. Smith Taber Bulletin E-10133. n. d. Paper Trade J. 97, no. 22:22(Nov. 30, 19553).

A general description of the apparatus and its applications.

639. Thwing-Albcrt Instrument Company. The physical testing of paper--tonsilc strength of paper. Thwing'c Papor Tester 1, no. 2 (1936). 4 p.

A general discussion, including definitions, significance and I interpretation of results, application of tensile strength, test methods, cutting the test strips, home-madc apparatus and corzeorcial instruments.

; E. iGIB?RIL1I)*r·rrrmll-" Stiffness, Softness, Rigidity 226

640. Vaughan, Leonce, Jr. Device for measuring stiffness of sheet material. U. S. patent 2,044,411(June 16, 1956); T. S. 103:580.

The apparatus provides for means to lead the free margin of a -. _ --- shcet,-which is secured along -it oppdsitoo parallel margin, by means of a weighting chain, one end of the chain being provided with an element by means of which it may be.readily attached -to or- detached from the - - shcot, and mechanism being associated with the chain for rapidly adding to or subtracting from,' under the close control of the operator, that portion or part of the chain which is actually supported by the free cdge of the sheet. The weight necessary to bring the free margin of the sheet undergoing toot into a predetermined position may be added to the free margin thereof. 'he chain weight is suspended in space and offers no resistance to horizontal movement of the free margin of the shc-t. The apparatus consists of a base, sheet margin retaining or holding mcans, and weight-applying mechanism.

641. Withanm Goorce S., Jr. Papcr-Tostor. U. S. patent 15,35,l64(July 19, 1922); Canadian patent 214,457(Nov. 29, 1921); Pulp Paper Mag. Canada 20:885; Paper Trade J. 74, no. 19:58.

An instrunmnt for testing the flexibility of paper comprising a support in which a sample of paper to be tested is loosely mounted, .''S:t'1 a bending device for bonding the paper both longthwice and crosswise of thc grain and. for moving the paper flatwisc through the support, a liquid receptacle connected with the bending device and a calibrated ;.. tube for delivering liquid to the receptacle.

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STRETCH

642. Apparatus for determining the effect of moisture on the stretch and shrinkage of paper. Paper Makers' Mo. J. 65, no. 1:19, 21(Jan., 1927).

- - A British instrument for measuring the stretch of paper when moistened and its shrinkage when dried.

643. Carlson, T. A. Study of and its com- ponent parts as engineering materials. Fibre Containers 24, no. 7:22, 24, 26, 28-51, 34-35(July, 1959); B. I. P. C. 10:31.

In a test designed to show a stress-strain relationship, a Tuckcrnan optical strain gage was used aomoans of measuring the stretch. The specimens of board, 1 x 6 inches in size, are clamped in a horizontal position, each clamp overlapping the specimen by one inch. The optical strain gage, which measures the cxtention in an initial length of one inch, is placed at the middle of the 4-inch portion of the specimen between the clamps. The rear clamp is attached to the dial scale by means of a flexible chain passing around a ball-bearing pulley mounted behind the box. The dial scale is hung from the movable head of a box- testing machine and tension is applied to the specimen through the scale by operating the movable head upward at the desired speed. Si-iiltaneous readings of stretch and load arc made until a currently plotted stress- strain diagram shows that the proportional limit has been passed. The gage is then removed and the application of load is continued until the specimen breaks. With the 1-inch gage used for the tests, redings? to 0.000,004 inch can be obtained. The gage has a capacity of about 0.005 inch but it c'p Je reset during the test and the stretch to naxinurc load determined. A scale of 150-pound capacity is used for test liners. Another scale of 50-pound capacity and graduated in 0.1 pound is used in testing corrugating papers.

- 644. Clark, James d'A. Some observations on burst, tensile, ana stretch tests. Paper Trade J. 102, no. 2:40-42(Jan. 9, 1953); Tech. Assoc. Papers 19:264-266; discussion, 90-94(Junc, 1936); 0. A. 50:2578; 3. C. A. 1936B:186; B. I. P. C. 6:275; T. S. 103:193.

Data are given to show the effect of rate of loading or the stretch of a sulfite ledger paper and also the variation in results for stretch obtained by a :iunbor of cop rating lab.jrat-oris.

645. Fcnchol, K. Manipulation of the apparatus for testing the elongation of paper in water. Papicr-Fabr. 24, Fcst-u. Auslandhcft 1926:98-105; T. S. 84:279.

A description is given of the new Schopper water-elongation tester for paper. The stretch properties of paper, either after inmorsion in water or exposure to moist air, can be ascertained with this oppara- tus. Actual tests of samples immrsed in water for one minute and then allowed to stretch for three minutes are reported. I . - - _ -

Stretch 228

646. Harrison, R. Paper stretch recorder. lorld's Paper Trade Rev. 101, no. 21:1698,-1701(May 2 5, 1934); B. I. P. C.-4:277; T.-S.- 100:78.

A brief description and illustration is given of the Nogrotti and Zanbro stretch recorder. The sample strip of paper up to 6 inches long anti about 0.25 inch wide is held by a r.anll spring clip at each end and is suspondcd-from a loo6klaft the top 6f the supporting fraoe, the bottom .clip being attached to a lint connected with a crank of variable -.... -longth on thn open-orn spindle. A small countorbalanc-c weight kccps--- tho paper in tension;. Aftcr counting the sample, the recording pen is sot to a suitablec position on the chart by mnans of a screw at the top of the supporting frano. This novos the top suspension hook vertically over a small rangb. The tubular cover is then placed over the paper- supporting franc and conditioned air is passed over the sample by connecting the top of the tube to suitable humidifying or drying appara- tus. The chart is arranged so that coach division represents an altera- tion in the length of the sonple of 0.002 inch and the full pen travel an alteration of 0.1 inch. If the sample is 6 inches long, this represents a 1.6% alteration in length.

647. Henning, Hans-Joachim. Device for measuring the elastic properties of materials. U. S. patent 2,070,731(Fcb. 16, 19537).

A swinging pondulun acts through the modiunm of controlling neans upon the test piece by a piston. The controlling nmans connect the pendulum and the piston at an adjustable Doint and sever this connection at another adjustable point, so that the amount of work done on the test piece during the swings of the pendulum--i.c., the work done between the beginning and the end of engagement of the pcndultun and piston--is always the sCae. The power by which the nmatcrial opposes dcfornmation acts against the attacking force, whereby the total work of the pendulum is reduced, resulting in a lose in omplitudc, so that the pendulun approaches a position of rest noro quickly than if it swings freely. Thic decrease in caplitudc furnishes a basis for cal- culating the elasticity of the material.

648. Institute of Paper Choneistry. Mecauromnot of the stretch of paper. Paocr Trado J. ll8, no. 26:12-16; 119, no. 1:24, 26, 28, 30; no. 2:24, 26, 28, 30(Juno 29, July 6, 13, 1944); B. I. P. C. 14:414.

The signlilcanco of stretch and the load-olongation curve are dis- cussed briefly. Theo nosuronent of stretch by moans of the A-r.thor uni- versal tondsile strength tester, the Clark stretch tester, the Schopper electrically driven strength totter, a:nd the Scott Scrigraph is exanined in sonc detail. The principle of the Scott ScriJgraph is satisfactory. T'he particular r-odel used in this study was of rather low sorsitLvity. The stretch indicating nochanicn of the Schoplper instrniment is dynamically unbalanced to such a degree that the indicator jumps to higher readings when the instrunont is jarred by the failure of the cpccimcn. This fault was temporarily minimized by counterbalancing. The Pnthor and the counterbalanced Schoppor instruoents agrc fairly well but indicate strobchcs which arc seriously high, as compared with values obtained with the Scott instrument. The reason for the discrepancy rests in the fact that both Anther and Schopper instruoento are so designed as I I '.. -.- pM';s -or

Stretch 229

to include in the indicated stretch or elongation reading some of the elongation which occurs after start of the specimen failure. Stretch values obtained with the Clark instrument tend to be less than those obtained with the Amthor or Schopper instruments. The elongations measured with this instrument also include part of the failure elonga- tion mentioned above, although a smaller part than those measured with the Amthor and Schoppor testers. The Clark tester was not compared with the Scott instrument. Corroborating published results-of other workers, it was found that stretch decreases as the length of the specimen increases. Contrary to suggestions in the literature, tests with two papers showed no change in stretch with change in rate of loading, and showed that stretch tends to increase with increase in specimen width.

649. Koester, Homnan. Paper stretch tester. U. S. patent 1,885,209(Nov. 1, 1932); T. S. 97:222.

A series of paper strips of uniform length and width are rigidly secured at one end within a closed chamber through which suitably condi- tioned air is circulated. The free and of each strip is placed under uniform tension, which is the same for all strips, and each strip is connected to a suitable indicating number whereby any change in length due to stretching of the paper will be registered in such a way that comparison may be mode among the various samples under test.

6_0. Mandl, K. Testing cigarette paper for elasticity. Oesterr. Zontr. PFpicrind. 40:115-117(1931); Zollstoff u. Papier 11, no. 6: 354(Juno, 1931); Boll. stoz. sper. ind. carton 10, no. 6:77-78(Junc, 1931); Paper Ind. 15:911; T. S. 93:276.

Strips of paper of a definite length are wound around a pin which is rotated. The strips are held fast to the end which is rot wound around the pin. The incomplete return revolution of the pin when it is released is a measure of the elasticity of the paper. The appara- tus consists o' a tube which is rotatable and which is clotted for in- troducin,, the paper strip, of a stopping device for the frc end of the strip, and an indicating device for shoving the angular rotation of the tube. In ordor to secure more certain fastening of the paper strip, a second tubc is inserted with the outer tube. The second tubc is carried along by the outer tube by friction and carries the indicator which travels over the scale. The indicator is loaded with a weight which brakes the back rotation and is so dimonsionod that the graduations on the scale correspond to about gram weights. The crank of the instrument is turned.'. so that the indicator passes through an anglo of 360 degrees; the crank is then released and the shaft is allowed to be rotated backwards by the elasticity of. the paper. The cxtent of this back rotation is a measure of the claDticity of the paper.

651. Sindall and Bacon. Stretch and expansion of panors. Paper i" Mnkors' Mo. J. 50, no. 5:159-160(May, 1912); Paper 7, no. 153:23-24 (June 12, 1912). -A 3 'A1i1 t.-

BC3iig I Stretch 230.

Preliminary experiments on the stretch of esparto printing papers were carried out by placing papers (having two lines exactly ten inches apart, the weight of the papers being known) between damp .shoots of- blotting-paper for-12-hours, after-which-the distance-between - the two lines was measured and the weight of the wet strips determined. No conclusion could be reached as to the relation of the csparto content and the amount of expansion.

652.. Stretch and shrinkage in paper. A new Schoppor apparatus. World s Paper Trade Rev. 86, no. 16:1244(0ct. 15, 1926).

A brief description is given of the Schopper apparatus which is designed to measure the stretch of paper when moistened and its shrinkage when dried.

653. TAPPI. Stretch of paper and paperboard. TAPPI Standard 457 m-42. 2 sheets. Paper Trade J. 102, no. 8:132-133(Fcb. 20, 1936); 115, no. 7: 39-40(Aug. 13, 1942); Tech. Assoc. Papers 19:270-271(Junc,- 1936).

The test result includes not only both the elastic and the inelastic .-i stretch of the paper up to failure but also the small distance through which the broken strip will elongate during the test while being hold Ip.I, together by protruding fibers, as this factor prevents the indicating mechanism from being released at the reading when the break starts. For this reason, the test may be termed more correctly 'the percentage clonga- tion of a strip of paper up to, and partly including, rupture under tension." Details are given of the apparatus, calibration, and procedure for making the tent. 231

TAPING AND JOIN~T TEST

654. National Association of Purohasinc Aqgents, Inc. CorruGated fibreboarO shipping, containers. No- 19, 19341. 8r -)

Tnaphy and Joint Test. There is no established procedure for testinc7 manufaobuzoivris-jointc- If a taped joint, the quality-and appli-- cation Ct fl tape uhoulif bo determined by a careful. inspection. If. a:iy doubt ar'-sc-s as to the quality of tape used, separate samples- of in'uuad tone shctJld be secured, identified as the soae as that of the rdcnuft-ctu~rcrs'joint, and tooted for tea:?rin otrongth asheinfr nrvdod

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TEARING STRENGTH

655. Ainslie, R. A. Uses and limitations of some paper-testing instruments. Proc. Tech. Section, Paper Makers' Assoc. Gt. Britain Irclandl17, part 2i473-8RPi;-d.iscussibn, 468-492(1March, 1937); Wcrld's Paper Tr-o.e Rev. 107, no. 13:TS8-12; no. 21:TS28-32(April 30, May 21, 1937);. Paser.-Mkor 93, no. 2:TS26l31(Feb., 1937); B. I. P. C. 7:276; B. C. A. 1937B:228; C. A. 31:6876; T. S. 106:93.

When assessing the quality,of a paper for general strength, it is usually Just as important to know the tearing strength as the burst- ing and tensile strengths. The main uses of the tearing resistance test are: (1) For controlling the quality of the product on a machine. Since a single operation on a sample tears several inches of paper, a reliable result can be obtained with fewer tests than is the case with bursting and tensile testers. (2) For investigating the effect of beating and furnish on the average fiber length of paper. (3) For specifying the'quality of a paper, particularly where toughness rather than a hard craclkle is required. .The limitations are: (1) The moisture content of the paper may affect the test results more than in the case with tensile and bursting tests. (2) The number of sheets torn together in a'test may affect the calculated result for a single sheet. This may be caused by the friction of torn edges over each other, altcredcconditions of stress, or variations in the rate of tearing. With readings of 20 to 60, the variations are not appreciable. (3) Instruments of the Elmondorf type do not measure the initial force required to start a tear but only that required to continue a tear. Resistance of the starting of a tear appears to involve a combination of tensile strength and stretch. (4) The necessity of checking the zero setting of the instrument regularly, preferably before each test. (5) The stiffness of the material affects the results; this is a serious limitation when dealing with material such as boxboard. The Thwing- Elmcndorf tester is mach easier for cutting and inserting specimens but the Marx-Elmcndorf'appoars to be more likely to give accurate and reproducible results over a long period. The factor given by the makers of the Marx-Elmendorf for calculating the gram-weight per single tear from the actual reading is twice what it should be. It is suggested that the unit should be orgs and not grams-weight. The ratio of the Marx/ Thwing readings (in the range between 15 and 70) varied from 0.99 to 1.09 for the machine direction and from 0.94 to 1.11 for the cross direction.

656. American Society for Testing Materials. T-ctative method of test for internal tearing resistance of paper. A.S.T.M. Designation D 689 - 42 T. A.S.T.M. Standards 1944, part III:358-361; A.S.T.M. Standards On arper and paper products, Nov., 1943:108-111.

This is similar to TAPPI Standard T 414. :.

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Tearing Strength 233

657. American Society for Testing Materials. Paper and paporboard-- characteristics, nonenclature, and significance of tests. Philadelphia, Th6 Society, 1944.

Tearing strength. Tearing sttrgngth is a property of the inncr structure of the sheet, but surface treatment sometimes affects the values to a marked degree. Moisture content of paper has a large effect on its -toring-strength.--Tearing strength is an-empirical property, and is also in the class defining manufacture of paper. This is in part due to the fact that the test is of long standing and widely used; hence it serves a useful purpose as a nill control test. The tear test can sometimes be interpreted to reflect the general nature of the fiber present in the paper as well as the beater treatment to which it has been subjected. For example, the test will usually provide some indica- tion of fiber length and coemnting action. Ordinarily, a dense sheet gives a lower tear than a bulky one of the sane material and sane basis weight; and long fibers offer greater resistance to tear than short ones. The test has great significance in the requirements of paper which is to be subjected to tearing strain in conversion or in actual use. This would include paper used for'bogs, boxes, building papers, wrapping, tissue (except creped), and nany specialized industrial fields. As a rule, converters bf paper in these industries rely nore heavily on tearing strength than on any other single property. Anong users of paper in sheets ordered to specifications in the converting trades, the tear test will be used more often than most other standard tests, with the exception of the all-important basis weight and the venerable bursting strength test.

658. Anderson, B. Tearing test for paper. Svensk Papperstidn. 25, no. 22:t05-406(Nov. 30, 1922); C. A. 17:2783; T. S. 77:161.

An original apparatus used at Vastcras is described, with a cut. It'is graduated in kg.-cm. The specific tearing work, R, is calculated from the equation R = Ru/lnd, where Ru is the tearing work read front the scale, 1 is the length of the strip of paper tested, n is the number of parallel strips, and d is the thickness of the paper, all ex- pressed in cn. R/10 tines the specific gravity gives the tearing surfaco-- the area of free hanging paper whose weight will cause the paper to tear. A table shows the variable effect of temperature.

659. Borgoao, Eric. The calibration of Elonndorf's tearing tester. Svensk Papporstidn. 45, no. 4:71-73(Fob. 23, 1942); B. I. P. C. 12:290.

After briefly discussing the general principles according to which dynamic tearing testers (such as the Thwing-Elonndorf and the Poller- Elncndorf instrunonts) work, brief reference is nade to the calibration method of J. d'A.Clark CNo. 668] which enables a correction factor (determined from a table or graph) to be applied to each observed value. A simpler procedure of sufficient accuracy for most practical purposes is outlined, which is based upon the adjustment of the tearing distance of the sample sheets, so- that the instrument will yield approximately correct values for an ordinary working rang. A graph is prepared for _~ jt %alBd/ W b ma ---·-- _I 1

Tearing Strength 234

each tester in which the readings on the scale are plotted against the calculated tearing distance for the range 3.9 to 4.9 cm. of the specimens. This yields a rather flat curve for the higher readings. From this graph it is then possible to select the proper tearing distance to use so as--to give- approximately- correct -results-over the -chosen working. - --- range. According to the TAPPI Standard, enough sheets must be torn at one time that all readings on the scale lic within the limited range of 20 to 40 groms, whicl ifs advantageous in this method of calibration. The author suggests that, rather than use the standard tearing distance for testers of this type, each instrument should be calibrated and the correct tearing distance calculated for each individual tostcr.

660. Booth, H. C. Apparatus for measuring the mechanical conditions of paper. J. Sci. Instruments 4, no. 1:5-8(0ct., 1926); World's Paper Trade Rev. 86, no. 24:1842, 1844, 1846(Doc. 10, 1926); T. S. 85:102.

It scomo reasonable to suppose that a method of estimating the mochani- cal condition of paper depending upon the measurement of the energy re- quired to tear a given length, rather than the force required to rupture a given width, is.likely to bo more consistent. It will be loes in- fluoncod by local variations, since it essentially consists in the measurement of an integrated effect. The apparatus consists of a double pair of flat clamps which hold the sample; it is passed through a wire

::,~- loop or stirrun which is free to move in the spaco between the clamps. The loop io connected by means of a flexible cord to the lower end of a *^-'S pondulurm, which is raised to a horizontal .position and which, on being released, drows the wire loop through the paper. The pendulum swings with negligible friction on a horizontal axis. The connecting cord is so attached that, after the loop has torn through the paper, it becomes dctachod from the pendulum and the latter is free to continue its swing; it rises to a height which will vary according to the amount of energy which has beer uxpondeod in tearing the paper. The amount of energy oxpcnded will blso depend upcn the breadth and thickloss of the strip. Tosts show that this energy is closely proportional'to the width

it is advisable to use paper which is originally of the same thickness. The values arc expressed in millions of orgs. The apparatus has been used for tho estimation of the extent of deterioration that takes place in the paper dielectric of an electric cable.

661. Brccht, W., and Irnot, 0. A new apparatus for mnnsurlig- the tearing strength of naper. Wochbl. Papiorfabr. 64, no. 43:848-853 (Dec. 2, 1933); T. S. 98:296; C. A. 28:6306; B. I. P. C. 4:113.

.:'-i : A now inctremtont is described in which the sheet is torn by a plunger operated by a lever. It permits tearing the sample in and across 'th machine directions simultaneously and records the initial

';: -. tear and the tcar-through. It is claimed that the now device corrects ': CGZone of the faults of- tho Elmcndorf tester. In geonral the results obtainod, with the two machines are the sane. The time for ten tests i'':z with the EJ]cndorf was 7.5 minutes, for the now tester 3.25 ninutos ':iB.,;' (with practice as little as 1.5 minutes). .

Saao;rsllll------ Tearing Strength 235

662. Brecht, W., and Imset, 0. The initial tear and the through- tear resistance of papers. Zellstoff u. Papier 13, no. 12:564-567 (Dec., 1933); 14, no. l:14-16(jan., 1934); C. A. 28:2529; T. S. 101:132.

The manual initial tear and the through-tear (ripping) tests are two fundameiitally different testing procedures. The' results are not identical and they cannot be substituted for each other. The mathe- matical treatment of the tests is given and-the mechanics of the tearing-- -- -resistances obtained is illustrated by several diagrams.

665. Brecht, W., and Imset, 0. Testing the Elmcndorf tearing tester, its method of operation and its importance. Papicr-Fabr. 31, no. 27A:46-60(July, 1933); C. A. 28:1530; B. I. P. C. 3:291.

A method of calibration of the Pollor-Elmondorf tester, based on the operating characteristics and estimation of friction losses, is described; the results agree closely with those of the Clark method , (Paper Trade J. 94, no. 1:33(1932)). Ihen a number of sheets are torn together, the starting cut is not the same in all, because of poor .:! design of the knife; there is a marked tendency for the outer shoots to split, an abnormally high tearing force being required; the friction between tile torn edges increases the tearing resistance abnormally. , ~. The errors from those sourcoo are separately evaluated, and shown to 'i .ji reach 15% or more. Also, the relation of tearing resistance to weight of sheet is not linear. To obtain reasonably concordant and useful results, the instnaent should be calibrated often and enough shoots torn to give a scale reading of at least 20 grams; the weight of the shoots should be quite constant; and the weight and number of shots 2 .i, torn should be reported. Not enough is Inown. as yet about the mechanism 7: ,.' of this conpl.x test to permit its use as a measure of fiber shortening r '., in the manufacturing process.

Pap'e664. Carson, F. T. Strength with reference to machine direction. ,. ' Paper Tradc J. 91, no. 14:64(0ct. 2, 1930); Pulp Paper Mag. Canada 30, no. 23:639(Dec. 4, 1930). ::T4 A machiner direction tearing t-st involves the tearing of paper so '/M that the tear proceeds across tlie fibers which lie in the machine direction-- ;. ~ that is, so as to rupture the machine direction fibers. It would seem ; ,~illogical to Epe6k of the machine-direction tearing strength when tearing paper so as to rupture the cross-dircction fibers. Most people designate the direction as tilnt ir which the tear proceeds, a practice which is in

,-' confornity with engineeriing practice as applied to the shearing strength of wood. To make the analogy complete, one should speak of the "resis- tance of tcaring long the machine direction. " The proposition of designat- ,ing direction in connection with the tearing strength of paper is open to question.

ii 665. Carson, Frederick T., and Snyder, L. W. Increasing the capacity i of the ELtecndorf tcoring tester. Paper Trade J. 86, no. 13:57-60(March 29, 1928); C. A. 22:3296; TS. . 88:199.

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'!f~ .~ Tearing Strength 236

In--tho Elmordorf tearing tester, a sector-shaped pendulum carries a clamp which is in fixed alignment with a fixed clamp when the pendulum is in its initial position of mnaxinum potential energy during a tent. A specimen of paper is fastened in the two clamps, a slit is made in the paper between the clamps as a starting point for the tear, the pendulum

_ - -' - . ris-rcloased, and thespecimen is-torn in two -as-the moving clamp-moves-- -- away from the fixed one. As the paper is torn, work is done upon it,

-_ which is ncacured by the difference in potential energy at the beginning and the end of the swing. Dividing the work done on the paper by the distance the paper is torn (which is constant for all tests) gives the- result as a force--the average tearing force. Since the initial dis- placement angle of the pendulum is fixcd, the work done is a function of the final displacement angle--or the angle between the vertical and the line from the center of gravity perpendicular to the axis of rotation. The calibration of the instrument is accomplished by means of a formula derived from the behavior of the pendulum. friction in the instrument, most of which is in those friction sleeve of the pointer, somewhat com- plicates the calibration. The derivation of the formula is given. The determination of the instrumental constants is illustrated. A simple procedure for the periodic adjustment of the instrument is described. The precision of tho tester is probably not better than 1%, because of- irregular variations in the instrument friction. A method is given by which the capacity of the tester was doubled. This was accomplished by means of a brass insert which was made to fit snugly in the open sector, ;.' and was fastened in place by means of lugs placed symmetrically with respect to the center line. The weight of the insert was 2501 grams. The use of the calibration equation in designing the modified tester is discussed. The tester has boon used in studying roofing felts. Some suggested improvements in the tter.atorar given.

666. Case, H. N. Strength teats for paper. Description of a paper tearing resistance tester. J. Ind. Eng. Chom. 11, no. 1: 1F9-51 (Jan., 1919); Paper 23, no. 19:13-15(Jan. 15, 1919); J. Soc. Chem. Ind. 38:169A.

Twelve strips, 1 by 2.5 inches, are cut from the sample to be tested, six with the long dimension parallel to the grain of the paper and 6 across the grain. A quarter-inch slit is made in one end of the paper. The apparatus consists of a nothod of clamping the strip and water is allowed to flow into a bucket attached to one end of the strip until the paper breaks; the weight of the water in the bucket in grams is .---: taken as the tearing resistance. If a tearing distance of more than th As. .. 'i 0.25 inch is used, the poling effect will have nore influence upon the ^..~ ! results. Satisfactory results cannot be obtained by clamping the A, .. F -':strip in a Schoppor tensile machine and measuring the load required to :' ;," separate the two pieces. The exact rate of flow of the water is not

.^ -:' . important. The following ndvantagos are cited: The comparative length ;,? ?j;/, "of the fiber and the peeling qualities of the stock arc shown, i the l;Y^. result. Sizing idocs not increase the tearing resistance to suchan -r · '';: o.extent as it does other tests. The apparatus is siniple and is applicable ."- S^_, to both li.ht end heavy papers. The amount of grain in the paper is 4S 4•- shown. Tlhe load is applied with on unchanging rate of increaseoo. How- ·'*yv, - over, the testing is tedious and there is a wide variation in the results l*~A on a givon sample. In this it rosemblec the Schoppcr folding machine. Tearing Strongth 237

667. Clerk, TFederic C. Paper testing methods: microscopical, chemical and physical processes described, with an account of the apparatus employed. New York, TAPPI Publ. Corp., 1920. 24 p.

A photograph of the Thwing tearing tester is given, with a very brief description of-its method-of operation.; - . -.

668.- Clark, James d'A. Calibration of Elmendorftearing tester. Paper Trade J. 94, no. l:33-34(Jan. 7, 1932); Tech. Assoc. Papers 15, no. 1:262;-discussion, 77-80(June, 1932); T. S. 94:191; B. I. P. C. 2:203.

The instrument is leveled and adjusted on a level sheet of plate glass and a known weight (W grams), the center of gravity of which is marked with a punched dot, is clamped to the radial edge of the sector beneath the Jaws. The sector is raised and set as for proceeding with a tearing test and by means of a surface gage or other convenient means the height of the center of gravity of the weight above the glass plato is measured (h cm.). The sector is then released, allowed to swing, and the pointer reading noted. Without touching the pointer, the sector is raised until the edge of the pointer just moots with its stop, in which position the height of the center of gravity of the weight above the glass plate is again determined (H cm.). The work done is W(H - h) g.-cm. If f is the average force in grams to tear .asingle sheet of paper through 4.3 cm. (d) in the case of the Thwing instrument or 4.4 cm. in the case of the Marx instrument, then the work dbne is 2fd. Thus W(H - h) = 2fd, or f = W(H -h)/2d grams. If the instrument is designed to tear a single sheet, f should equal the pointer reading r. However, the Thwing instrument is calibrated so as to road the force required to tear 16 sheets at one time through a distance of 4.3 cm. or a total tearing distance of 68.8 cm.; thus, r should equal W(H - h)/137.6 grams. With the Marx instrument it is W(H - -s)/52.8 grams. The difforoncc3 in results given by the. two instruments arc discussed; the Marx instrument at prosont is not calibrated so as to give grams force to tear a single sheet when 6 double tears or made, as roconmondcd by the makers, but half that nunmer; thus, six single tears should be made to obtain a direct reading.

669. Cottrall, Leslie G. Tearirn resistance of paper. Papor-Maker 83, no. 3:TS127-132(March, 1932); C. A. 26:6130; T. S. 96:136; B. I. P. C. 2:246.

Bursting and tensile tests may be carried out in what may be termed either a static or ballistic manner. Previously the question of static vs. ballistic conditions of testing has not been important in the case of tensile tests because static condition can be approximated and are invariably used. Hovover, with tearing testers of the type of the Elmondorf, in which the test is completed. in about 0.1 second and, therefore, these instruments test the tearing strength under conditions approximating to ballistic conditions ard may be termed 'ballistic tcaririg testers." The ballistic condition of testing gives higher results than the static condition; this has been investigated by Carson [No. 56] and an explanation has boun offered. The applar-tus for determining the tensile test of paper can be adapted to cnrry out a i I 0$4 4co co O,4 4-' Q, tD 0$. Z 4- CC) 41 I co 0) t~nC) ci $4. 0~4- 44 $4, o4a+ccc 'IO oo -C)P '34L,' -I-,- 002 *' 0 '0r 4-H El 0~ --I C)4 441 C I4 n H X:it, . C) la g a -' 0 ZP, v-I k0$0t>.4- 4-vIt0r ml~~~, 0' P4e,4 '4: -H 4Ž4 0 0) o 'd in.% C~ OH' 4 P mt oo ml 4 "C3 $4- I P.AC O0,f -41 C)Q I- 40 0 5V0C '00 F4) a) E-It- F- '34. 34 ) A00 ~'ci F- 0- wY+ 04 I2 4 $40 ci 0 $4 - 4- sin 014' 4-i I MrI ~ 4 'S 0C r 4a03 'd o '4- C) C -S.- 4-i ,~0 -4~ COCH 0 C 0' .I '102 C) $410 co IC)I C H 04-' 0~~~4 .3 r- C) 4i 4 co)C 4fr r. C)0)4 4C) C -1 - 04, D - 0CC 4- 00 2C '0 IC joG 4) r-4-C)') i-C 4-' c''d $4 002 Hs 0 4 $4~~~~~~; 3: O~~~~-- 4, 0 C CC)M0 Pr4r '0 vA :'5 m0 O 4to 302 P, C30 C) >0 ccs SrI0C)CI rrfl 4- '$4 'C 2,0 S C3 C)0'd 043' 41 4, D 40 C) S to O 'dC) 4-.C a-40 a0Al *C) ai4~ 00 4~',4~-j $4oa '41 ci 4) 10 C) 4,0 0+)~0 * ci4) 4)4C ~~~~P C)' 00 41 CcU '4- 43 *C] v-H $4 -CO C41~'- C) Ic C -4 CP3 O'd0 4:0 04- Xri 'd 51,- 4CO -I ZiF $41C))I 4) O'd 'C) '4-I P,$40oc - C~ 0r ci o zi Cr444-0-r- 0z 0C)q co O.-aWW P. -P00C 4) ''$4 4 wl 0 04- o 'C) vi~ do1 '44 £acog' 0 CD )QL r-PI tr4- '0S' i - 00 piQ$ Lc C) L,) w o - .1 0- -v-t C) P,>' $4 C O0iC- t 0 C) ) ,-C4) o $4 ~4 LO- C) v- $ , 041 +2 4a 0 0 '0) 0C) -$0 0 0 4' Si o~ > n 441 $ ola, Iodoo HC) $4 C '-I 4.C ~Iw - 4) v 4)0jI

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674. Elmendorf, Armin. Tearing tester. U. S. patents 1,423,841 and 1,423,842(July 25, 1922); Paper 34, no. ll:484(July 3, 1924); Pulp Paper Mag. Canada 22:667.

. -- A-pendulum with a pointer attached is swung to its extreme left position. While it is in this'position, the paper to be tested is placed in the jaws-of the instrument, one of which is fixed to the framo and the other to the pendulum. On releasing the pendulum, the paper is torn for a length of exactly two inches and the work done decreases the distance to which the pendulum swings to the right, which is auto- matically measured by tho pointer. If the dial is graduated in degrees, the work can be calculated from the weight of the pondulum, the die- tanco of the axis of rotation to the center of gravity, and the initial and final angles which the pendulum makes with the vertical; or the dial mny be graduated to read the work done directly. The difference in the two patents resides essentially in the design of the pendulum and jaws. In the first patent the pendulum consists of a weighted arm attached to a wheel and in the second it consists of a sector of a 4. -circle which is suitably graduated. 675. Elunndorf tester. Wochbl. Papiorfabr. 63, no. 15:286-287 0 .. (April 9, 1932).. A brief description is given of the Elmondorf tearing toster and sone of its advantage. In Germany it is handled by Firma F. R. Poller, ' ,.-- ". Leipzig and is known as the Pollor-Elnondorf tooter.

::;- ~ 676. Finch; J. M. Simplified tear test. Boll Labs. Record 21, :,A- no. 2:58-59(0ct., 1942); B. I. P. C. 13:111. ".P- ~ The Firch cdge-tear stirrup consists of a motal plate, roughly Y-shapod and abcut 6 inches long. This serves as the suspension bar and sidos of the stirrup. The transverse rmmber is a metal plato 0.025 Jl: inch thick cnd cut in a shallow V at tho-top. The upper edges of this V are recessed and short lengths of 25-nil rod are inserted to give the .,- s.ides of the V a smooth cylindrical surface that will not cut the material under test. A 1-inch strip of paper is passed through the stirrup and its ends bent down and fastened to the lower jaw of any i"t convenient forn of tension testing nachino. The suspension bar of the stirrup is fastohcdo to the upper Jaw of the testing machine and force is applied. Because of the V across which the test strip lies, the force is applied to the strip at its two edges. As the force is in- creased, the strip ultimately tears from the edges toward the center , -, and this force is used as a measure of the tear resistance.

i(%" 677~. Griuncwnld, --. The Elnondorf tearing tester. Zellstoff u. . SK Papicr 1, no. 8:232-233(Nov. 1,. 1921). I-7tU- This is a Gcrman translation of a part of the article by Elnmndorf (No. 672).

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onn narplo in torn four or noro tinrs. The text is given, without the data, in Pulp Paper Mag. Canada 20, no. 16:320(April 20, 1922).

681. Houston, Paul L. A preliminary study of tearing instruments and tearing test methods for paper testing ..Natl..Bur. Standards,--- - . Toch. Papor o.' 194. July 27, 1921. 18 p.

.- - The first part-of-this-paper gives results showing that it is necessary to cut test samples the same size in order to compare the tearing strength of papers. Three sizes were used: 1 x 8 inches, I 2-3/4 x 1-1/8 inches, and 4 x 10 inches. If the test samples are cut the same size, very good check results arc obtained. From a study of the action of the paper as it was torn, it was evident that each fiber in the path of the tear receives assistance from all the adjoining fibers as far as the edges of the test samples. The larger the test sample, the greater the amount of this assistance, provided that the beginning of the tear was always the same distance from the end of the test sample and just halfway across the width of the test sample. This is used as an explanation of the fact that the larger the test samples the grcoter the values of the tearing strength. Three instruments were used in this study; one was a tensile strength instrument; the second was tho'Thwlng tearing tester (termed a recording instrument); the third was a nonrecording instrument. The Thwing instrument is concluded to be neither delicate, sensitive, nor accurate, since the amount of friction in the pin-slot bearing and the friction between the pen point and the paper chart do not allow careful accurate cali- bration. Because the test results obtained by using different factors will not check, there appears to be a defect in the mechanism of the instrument. The paper sample is cut by means of a die in such a way as to give five initial tears and a curve showing the maximum and minimum tear. There is greot doubt whether the five peaks in the curve actually represent five initial tears. The fibers very near the edge of an angular slit in the test sample (or perhaps halfway between two angular slits between which the paper is torn) may be stronger than those fibers at the very edge. In such a case the result would be a rising curve and the peak would not represent the initial tear but the tearing strength of the fibers near the edge, or halfway be- tween two slits of the paper. The nonrecording type consists of a beam balancing on a knife edge (the two arms of the beam being equal). One end of the beam holds a 300-cc. glass into which water as the load may be poured from a 500-cc. burette until the paper tears. At the other end of the beam one half of one slitted end of the test sample is clamped; the other half and the other end of the test sample are clamped against a vertical plate opposite. A special die is used for cutting a slit and eyelct hole at each end of the middle of the test sample. The force at the tearing end of the beam is equal to the weight of water in the glass. This instrument gives merely the mnxirma tearing strength of the paper. The error caused by the bean position and that resulting front the impact of the water are discussed. It is believed that the second instrument will give results within a 5% error on those -mority of papers. Because butter comparative results arc obtained by tearing paper in the machine direction, it would socn that all tearing tests should be nade in this direction. 3Further, because

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Tearing Strength 243

most papers are nuch stronger in the cross direction, the direction of tear as o'rule turns to the machine direction soon after the beginning of-the -tear.-- - -

682. Houston, Paul L. A supplementary study of-oormercial in- - -struirits for determining the tcoring strength of paper. Paper Trade J. 74, no. 10:43-46(March 9, 1922); C. A. 16:4059.

-Supplementing the work reported in Technologic Paper rNo. 194 of the Bureau of Standards, a study has been nade of the Elr-ndorf tearing strength tester. A brief description is given of the instrument' and a formula is developed for the calculation of the tearing strength, and also for the calibration of the instrument. Tho particular instrument studied was found to be graduated correctly. Tests indicated that thore was a slight variation in friction in the ball bearing which might result front imperfect balls. However, any error that night be caused by slight variations in friction in ball bearing or indicator sleeve would be too small to be considered in cn instrument of this type, which is not a precision instrunont. Tests with writing and bag papers indicated that check readings could not be obtained by using different plies; 1 to 32 plies wero studied. It would seem necessary to reconmond the number of plies to be used for certain grades and weights of papor. The manufacturer has rocomncnded that readings be taken between 10 and '20 on the scale; this ranie is small enough to allow the use of not noro than two different numbers of plies. In the case of some papers (ledger in this study) both one and two plies gave readings between 10 and 20. The tests with the majority of the papers showed that one ply gavo higher results than the other plies. Therefore, it night be well to eliminate the use of one ply where it is possible, oven though it should give an initial reading between 10 and 20. It is concluded that the instrument is built on sound principles of mechanics, is cali- brated correctly, and will perform satisfactorily provided certain rccornondation- are made mandatory.

683. Improved Elnondorl' paper tester, with a sinplo moisture content indicator. Paper 28, no. 10:16-17(l(oy 11, 1921); Pulp Papor Mag. Canada 20, no. !6:326(April 20, 1922).

Thc inprDvermnt appears to be the addition of a knife for cutting thl slit which starts the tear after the specimen is in place. A simple moisture content indicator has boon devised front which the percentage of contained moisture nay be read. This consists of a balance, graduated to read from 0 to 20; comparison of the sample is made with a shoot of known moisture content . Data are given showing thatat noisturc contents of 0, o.06; 0.10, 0.13, and 0.16%, tihe tec-?ing strength of a was 60, 76, 88, 96, and 105 grams, respectively. With a of moisture content of 0, 0.066, 0.09, and 0.15, the values were 300, 400, 416, and 500 grams. - Tearing Strength

684. Institute of Paper Chemistry. Tearing strength of paper Paper Trade J. 118, no. 5:13-16, 18-19(Feb. 3, 1944); B. I. P. C. 14:214.

- - Elmendorf's method f-testing- paper for tearing strength satisfled a long-felt need in a very simple and effective manner. However, since the advent of this satisfactory method for-measuring tearing strong5th; many data on this property have been obtained which ore not well unIder- stood. Many practical facts regarding the behavior of tearing stre ngth are known, such as: the negative correlation between tear and tensi le or burst; the usefulness of tear in controlling beating and other rofining, as regards cutting,'when considered in conjunction with tensile or bursting strength; similarly, the usefulness of tear in comparing d.ifforont types of beating actions. Very little work appears in the litcraturo on the theory of tearing strength. If a theory is to be useful and com_- prchensive, it must account for such facts as: tho'variation of tea ring strength with degree of beating (slight initial rise to a narrow macximum followed by a decline); the dependence of tearing strength on fiber length (positive correlation); the increase in tearing strength acccompany- ing a decrease in bonding strength brought about through the use offmaterial added to the furnish, and the inverse effect. A new theory is pros oented, by means of which a careful analysis is made of the manner in whichh the energy expended in tearing a sheet is dissipated in the paper. Whocn a shoot is torn, _m fibers are ruptured in tensile failure and n fiber'sare pulled intact from the mesh of contiguous fibers. The average work: ro- quired to break a fiber is ordinarily insignificant in comparison Vrth the work required to pull a fiber intact from the mosh, the force i -n- volved .in the latter case being somewhat loss. Since the average te;aring force is equal to the sun of these two works divided by twice the 1.ongth of line of tear, discussion of tearing phenomena with theory reduce's to consideration of the effects of various treatments and pulp prop)ertics on (a) the relative numbers of fibers ruptured in tension and pulle;d intact from the fiber amesh, and (b) the average work required to pu.11 a fiber from the mush. The initial rise in the tearing strongth-boot ;ing time curve is due to the fact that, in the initial stages of beooti ng, the "frictional drag work" increases by virtue of tighter onmnshmor it caused by clightly"incrcased bonding, during which timo only 6 ncgl.igiblo number of-fibers fail in tensile rupture. As"thc boating continues1, however, more fibers fail in tensile rupture and, therefore, fewer fibers arc pulled intact from the ncah. Since the frictional drag work pccr fiber is very nuch greater than the rupture work, this decrease in.the number of fibers pulled intact from the mnosh causes the tearing atrlength to decrease. Similarly, the addition of a matcriol which reduces I ending strength will increase the tearing strength by increasing the nunbc.r of fibers pullcd intact from the sheet, and it is frequently observed that the addition of a bonding agent will ccuse a decrease in tearing st;rcngth. , ,. The positive correlation between tearing strength and fiber length is duo to the fact that the frictional drag work depends directly on t~ho average fiber length, boing theoretically proportional to this leng;th. Thc Elmondorf-Thwing inotrunent is based on a uniquely simple, atrtaight- forward, and intrinsicolly accurate method. Excepting certain obvJLOUs mnladjuotnonta which could be noted by any observant operator, this3 in- 4i ',: strunent, should reannin in accurate calibration after having been ccarefully

^BRisWnri~iiiiw · IIIl- 1 Tearing Strength 245 checked and calibrated. A theoretical error arising in the manner of allowing for friction in the pointer mechanism and bearing has been - - studied,- and-lt is shown that this is-of io-real significance, provided, of course, that the pointer stop adjustment is properly made. An error due to multiplicity of specimens simultaneously tested is briefly described.

685. Institute of Paper Chemistry. The Thwing initial tear tester. Paper Trado J. 113, no. 4:21-26(July 24, 19111l); B. I. P. C. 11:457.

The Thwing initial tear tester was designed to measure the force required to start a toar on the edge of a specimen, which approximates a failure frequently appearing under use conditions. From a considera- tion of the mechanics involved, a tear should be caused by a force which is pure shear. In other words, the forces acting on the specimen at the point of rupture should be perpendicular to the surface, resulting in a compression on one side of the sample and an opposed compression on the other side. In testing a specimen, such as heavy paper or light board, the stiffness of the specimen is not sufficient to result in pure shear, so that some tension will be set up in the sample. The farther apart the jows holding the specimen, the greater will be the tensile resultant of the force applied. Under such conditions, the test becomes moro of an edge tensile than an initial tear. The Thwing initial tear tcstor has two jaws, each with a surface 3/4 by 2 1/2 inches, mounted one inch apart on horizontal shafts hold in a rigid supporting framework. The jaws are so mounted that their surfaces are horizontal and one edge lies along the center line of the shafts. The back of each jaw is three fourths of an inch from this center line, allowing spcciricns to be inserted accurately before applying pressure by moans of the tightening nute. A ratchet is attached to tile shaft supporting the rear jaw, and a crank and paDwl mechanism is provided to act upon this ratchet. In tho starting position, a nctal pin on the ratchet rests on the framework. Tho shaft carrying the other jaw supports a weighted pendulum and is connected by mcans of goars to a noodlo mounted on a dial at the front of the instrunont. Those gears amplify the notion of the pondulun so that the noodle travels through a greater arc than that through which the pondulur- passes. Riding on a small shaft of the gcar assembly behind the dial is a strip of spring nctal which, through friction, holds the needle in any given position. A stop engages the pendulum in n vcrbiccl position before each test, allowing the noodle to be returned to the zero reading. The specinmn to be tested is clamped firmly in the joaws. The pendulum stop is released, and tho crank is turned at a uniform speed, causing the roar jaw to rotate. Through the co-nroctjng test strip, the front clamp and the pendulum rco also caused to rotate. The indicating noodle moves until at the instant of fi:Lure, the pendulum recedes toward the vertical position, the ncodlo rencining at the position of naximn-n displacement. A reading is taken, the ratchet returned to the starting position, the stop' insortod in tho pendulum, and the needle moved back to tho zero mark. Thc following conclusions aro drawn front a study of this I[nstumcnt: Tearing Strength 246

The Thving initial tear tester gives reproducible results. The nagnitud - - - of the results, in general, is incroased'by increasing the width of the specitridn. Within reasonable linito, the rate of loading does not appear to hare -a significant effect on the results. Inconsistent results 'are obtained by testing several strips sirnltancously. Initial tearing strength correlates in a general way with Elnondorf tearing strength and with tensile strength. Initial tearing strength ns determined by the subject ncthod is largcly dependent upon tensile strength and stretch, the nature of the depcndcncc being such that an increase in tensile strength and/or stretch causes an increase in initial tearing strength. The following channgs arc recommended. (1) The adoption of a means of loading at a more uniform rate. (2) The calibration of the dial in terns of actual pounds of force exerted on the specimen. (3) The installation of a wing-tipped pointer on the dial to reduce error in reading the scale. (4) The provision of variable pendulum weights with corresponding dial calibrations to zepand the ronge of the instrument to cover lirhtor and heavier materials than those covered by the present range. (5) The design of supporting rmebero so rigid as to ensure constancy of separa- tion of the two pairs of jaws.

686. Jacobsen, P. M. H. Paper texture. Wochbl. Papierfabr. 56, no. 46:1398(3,ov. 14, 1925); T. S. 82:501.

The ratios of the breaking length of paper samples with and across machine direction are given for strips-of length 0, 1, 2, 5,'and 180 mm.; the values for a kraft wrapping paper are 0.55, 0.57, 0.57, 0.56, and 0.53. The percentage adhesion is defined as the breaking length with 180 cc. free length divided by that at 0 m. times 100.

687. Jacobsen, P. M. B. Strength tests on paper. Papier-Fabr. 23, no. 45:717-718(iTov. 8, 1925); Wochbbl. Papicrfabr. 56, no. 48:!54'- 1456(Nov. 28, 1925); T. S. 82:301; 83:52.

The so-called zero breaking length (at 0 mm. free length) of paper rapidly increases at the beginning of the beating process and then slowly decreases. Possible reasons for this are discussed.

688. Johnnsson, David. Testing methods for chemical and mechani- cal pulps. Svensk Papperstidn. 40, no. 9:210-21 8 (.May 15, 1937); Zellstoff u. Papicr 17, no. 7:286-289; no. 9:389-392; no. 10:436-458 (July, Sent., Oct., 1937); B. I. P. C. 7:359; C. A. 31:4812; B. C. A. 1937B:1321; T. S. 106:91, 94.

A comparison between the values of the Thwing-Elmondorf, the -Iarx-Elmendorfand the Brecht-Inoct instruments for determining the tear-through strengths of papers has been carried out at Ocstrand. For beaten papers, the instruments are of equal value; for unbeaten sanplos, the Thwing-Flmondorf values ore considerably higher. The Brocht-Imact apparatus permits accurate testing with a single paper .hcet.

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.-...... Tearing Strength 247

6S9 . Mallett, E., and Marx, R. The calibration of the Eimendorf tearing tustor. Proc. Tcch. Section, Papernakors' Assoc. Gt. Britain Ireland 4,_part 2:212-222(March, 1924);C.. A. 18:1907; T.-S.-79:219.

The initial step is to determine the first moment of the pendulum or sector about-its axis; the next -stopis to determine tho dffoct of friction in the instrument and the low which it follows. The -difference in the angle at the conclusion of various half swings was found to be due to energy becoming stored in the pointer. The method of graduating the sector is outlined. The operation of the instrument depends primarily on the tine period of the sector when swinging freely and the friction of the pointer. It is therefore possible to formulate the following two conclusive tests for its correct operation which are sufficiently accurate for all practical purposes: (1) The sector when allowed to swing freely from its initial position should nake not less than 180 complete swings before coning to rest. (2) The sector when allowed to swing fron its initial position but with the pointer held securely against the stop should nake not loss than 12 conplote swings before coning to rest.

690. Marx, R. J. A new tearing tester. Paper Makers' Mo. J. 59, no. 4:151-154(April 15, 1921); World's Papor Trade Rev. 75, no. 2:172, 174(Jan. 14, 1921); Zollstoff u. Papier 2, no. 2:35(Feb., 1922); C. A. 15:2185.

A brief description is given of the principle of the Elnendorf tester as modified by Marx.

691. Nagl, Hans. A study of the nochanisn of the rfllnondorf tearing tcet. Pnpior-Fobr. 27, no. 27:421-424(July 7, 1929); C. A. 23:5589.

Th_ tearing test is especially valuable in showing the oxtunt to which the fibers have bococr shortened in processing. The sanm pulp boaton t- S0 dogreos Schopper slowness in bcaters- with store and with iron tacklo gave, respectively, 190 and 111 grams tear. In sgncral t$c1ic strength and tear vary inversely. Calondering docreascs the tear, whereas normal moisture variations have no definite effects. iThbasis weight and the number and width of the strips torn affect the results. Data are given to substantiate those conclusions.

692. National Association of Purchasing Agonts, Inc. Corrugated fibreboard shipping containers. No. 19, 1934. 8 p.

Tcarin, Strength (Elnondorf) Toot. This test is only applicable to individual shots of lincrboord and corrugating nediun and to pieces of unused tape. Tost specineon should be cut from unwrinklod, uncrcased, and unblemished stock, four each with the grain running the long art short way of the specimens (in the case of cloth tape, the long or the cross throads-). The spocimons shall be not less than 6.3 cn. (2.5 inchcs) in length (on sanplos cut along the cross tircoads of two-incl -. E: tape such lornth is acceptable) and of such width that the distance from the apex of the starting cut to the top edge of the specimen in position in the tester shall be exactly 4.3 cn. (1.69 inches). The '^^- ?-'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. IC 1 iadsB

Tearing Strength '248

specimen shall-be placed in the Jaws of the tester with the bott-o cdge rooting upon the bottom plates and so that not loss than 2.5 cn. (1.0 inch) of the specimen extends into the novable jaws, the initial slit nade, and the pendulum arc released tearing the specimen. Tests in which the tear deviates noro than 6.3 rn. (0.25 inch) from the line of the initial cut shall be disregardd. -The tcaring-strongth-shall be calculated in grams by multiplying the readings on the inotrunent by 16. Not more than one of the four tests in each direction nay fall below the specification, with- the-average of the four teots meeting the requirement, for conpliancc. Howovcr, if the initial tests'in either or both direc- tions fall to comply, a series of 12 re-tests of either or both (accord- ing to tho'failurc) shall'be node, of which not more than three tests nay fall below, with the average of all 12 tests complying with the speci- fication, for acceptance.

693. New tearing machine measures strength of paper. Paper 26, no. 26:11(Sopt. 1, 1920); C. A. 14:3319.

The samples of paper to be tested are about 5 inches square and two parallel cuts, about 1.5 inches deep and about 2.5 inches apart,. are node on one edge. The resulting center tongue is then turned up at right angles and the paper is clamped to, the base of the machine with the tongue projecting vertically along the side of the flat metal clamp. The tongue is then gripped by means of the '"vor Handy" letter clip, front which a wire rnus up over the wheel. The counter weight on the other end of the wire balances the weight of the clip. The wheel, which is graduated in dogrcos, is mounted upon a ball-bearing bicycle wheel hub and a lever is connected to the near side of the shaft. This lever, which is much in the nature of a pendulum, is provided with an adjustable weight. When the pendulum is released, it swings downward, carrying with T it the wheel and the wire, thus pulling the letter clip upward and tearing the sheets of paper. This is an early forn of the Elnondorf teeter.

694. Ncw tearing tester. Paper Trade J. 83, no. 26:40(Doc. 23, 1926); T. S. 05:162.

The Thwing tearing tester consists of a support front which is suspended a pondulun that swings on a ball bearing. On the rilit arm is a clamping joer. On the supporting frame is a similar jaw, at the sane level as the one on the pendulum armt, when the latter is in C raised position. 'The paper to be torn is inserted into these jaws and, to start the tear, a slit is node in the paper by raising a knifo edge which is attached to the franc. The ponduluw, when released front its raised'position by lifting a simple catch, tears the paper until the resistance offered by the tearing paper bring the pendulum to rest. This resistance is designated in grarn on a large dial, by a needle pointer which is actuated by a pinion in ncah with a larger gear whecl which rotates with the swing of the pendulum. The needle pointer travels almost completely around an 8-inch dial, for the full swing of the pendulum, making the scale reading very accurate. The most valuable characteristic that the machine has is its oscsi- tivoncso in tearing one sheet of paper at a tiio, whether tissue or ledger, thus allowing the paper to tear as naturally as when torn L between the fingers, in which case nore than one sheet is never torn to ; detorninc tearing quality. I: , .. II.-- -

'earing Strength 249

695, Nichols, Lorrel Bi. Apparatus for determining tearing strength. U. S. patent 1,989,625 (Jan. 29, 1935); T. S. 101:238. A test strip of paperi o secured at two areas,- whch are spaced .. apart along its straight fre e edge and which are preferably semi-circular in shape with their centers at the free edge of the paper;-progressively increasing tensile stress is applied along the marginal edge of the paper between the centers of the secured areas until initial tearing takes place; the centers and /or torn edge arc then separated by causing or permitting the secured or oes to rotate about their centers at a oubotantially uniform rate. Moans are provided for measuring and recording the tensile stressas applied throughout the operation.

696. Oliver, Cyril V. Variability in results- rt with in paper strength testing. World's Paper Trado Rev. 93, no. 8:660, 662, 714; no. 9:754, 756, 758, 796, 798; discussion, no. 11:938, 940, 942, 994, 996, 998 (Feb. 21, 28, March 14, 1930); Paper Makers' Mo. J. 68, no. 3:103-109 (March, 1930); Paper-Maker 79, no. 6:595, 597, 599-605(Juno, 1930); Proc. Tech. Section, Papor Makers' Assoc. Gt. Britain Ireland 11, port 1:53-74; diocuosion, 74-84(0ct., 1930); B. C. A. 1931B:582; C. A. 24:3366, 5484; T. S. 92:157.

The Morx-Elmondorf tearing tester was studied. One disadvantage of the tearing test is the fact that some papers "skin" during th' test; this is especially true of thick papers. Another point about the tearing tester is the fairly frequent alteration of the zero; in two sets of 50 tears, the zero altered four times in one set and three times in the other and the maximum alteration was two points on the actual graduations, or an error of about 7% on one of the sats of results. In those tests the average toar was 57.8 and 30.3; maximum deviation 5.2 and 7.25%, average deviation 1.6 and 3.4%; maximum zero alteration 2 in each case; tooar which okiuicd 24 and 15%. The result of tearing two shots of a paper together is not always double the single sheet tear. Results prove that the tearing tester is more accurate when the reading registers above 20 or o-er than -hen it is 10 or under. If four or more shoots are torn together, very consistent results are obtained (data for 1 to 10 shotss. Readings above 70 arc not very reliable. The one large variable in the tearing tester is the pointer.

697. Paper Makers' Association of Great Britain & Ireland. Technical Section. PoarE Testing Committee. First report; London, The Associa- tion, 1937. 85 p. Also issued, with discussion, as Vol. 18, part 1A, of the Proceedings of the Technical Section. Soo also World's Paper Trade Rev., Tech. Convontion No., March, 1937:4-72; B. I. P. C. 7:350. Specifications are given for the tearing test, using the Marx- II )f, Elmondorf tester. Those include the preparation and dimensions of the I test oamplo, the checkinn and adjustment of apparatus, and the- operation of the instrument. The tearing test is most significant for those papers AT which, in actual use, are subjected normally to folding and twisting and in which the rupturing forces involved are relatively small and arc not L, vcry variable; these include cigarette papers, waxed tissues, envelope k- I.I 11 ,all. . I

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Tearing Strength 251

699. Poultor, A. C. An initial tear tester. Patra J. 8, no. 1:. 14-22(Aug., 19,4); B. I. P. C. 15:103.

--A-clothod is deocribed-for-adopting the Schoppor tensile tester to anouiro the initial tearing resistance of paper, boards, and film. The Marx-Elmordorf and the Thving-Elmcndorf testers measuro the forcc- rcluired to continue a tear which has already been started in the material *under test; this is usually termed the tearing resistance but should properly be called the internal tearing resistance. These instruments do not reproduce the condition when the break or tear starts from the edge of tile shct. The ratio of the initial to the internal tearing resistance is not constant for different materials but varies with the extenaibility and structure. The Schoppor tester (selected be- cause the pendulum system can be used to record the tearing resistance) has boon modified by the addition of a clamping unit to act as an initial tear tester. aro clamps are used; the left-hand clanp is fixed to the base of the unit, whereas the other is mounted on ball races and is free to rotate about an axis along the front edge of the clamps. Details are given of the method of operation of the instrument and of carrying out the test. The fixed clamp can be adjusted to give distances of 1/iO, 1/4, 1/2 and 1 inch between tho clamps. The depth of the paper held in. the clamp can be adjusted to 1/4, 1/2, or 3/4 inch by positioning pins. Friction in the clamp bearing is compensated by setting the pendulum zero for each range. The force measured is not simply rlatoed to a fundamental property of the nmatcrial but depends upon its tensile strength, extensibility, and rigidity, and also upon the distance between the clamps and depth of material clamped. Although increase in the distance between the clamps has the sane general effect on all natoriola tested, the magnitude varies so that tests made witl a i/10-inch spacing nay grade the materials in a different order from those rmado with a l-inch spacing. The sacm is true of the depth of rmtcericl in the clamp. Over the practical range of the in- struniont, the tcorirp resistance is independent of the rate of tearing. This test is empirical and the results depend upon the test conditions. Data are given Cfor cotton fabric, vegetable parchmenont, filter paper, and several plastic films.

700. 'Rcnniclcs, Norbert G. Mbnufacturc'of paperboard. Chicago, Fibre Containars, 1939. 47 p. Chapter on paperboard tooting in Fibre Containers 24, no. 9:20, 22, 24, 26, 28, 30(Sopt., 1939).

Tearing streonth. The Elnendorf tester is used. This test io appli- cable to individual heots of paperboard. Samples nust not be loss than 2.5 inches in length. The width of the sample nay be explained by saying that an initial or starting cut is nade in the sample, and the width nust be such that the apcx of the starting cut is exactly 1.69 inches from the opposite sido of the sample. The spocincn is placed in the jaws of the toestcr with the bottom cto resting upon. the bottom plates, so that not less than 1 inch of the specimen extends into the movable .I jaws. The initial slit is then made and the pondulun arc released which toars the sanmlo. Testo are ignored in which the tear deviates moro than 1/4 inch front the line of the initial cut.

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I -nl I- _ iearling obrengtf 252

701. Rieth, I. Strength determination. Papier-Fabr. 27, no. 45: 693-6941Nov. 10, 1929); T. S. 91:205. .

_.--_ -_- Thc-rclativo-huidifty, -upon vhich the noisturc content of the .-- . -- . papor is dependent, is of groat importance in papor tosting. -- In passing - fron 5.8 to 9.?1%oisturo content therc-i-a-diffoernco of 25% in - ..--. - -- -- the tearini strength.. -

702. Sanmot, Charles F. New tearing tester.. Paper Trade J. 83, .| ' -no. 2T:40(Doc. 23, 1926); T. S. 85:162.

A brief illustrated description is given of the instrument built by the Thwing Instruncnt Co., consisting of a support fron which is suspended a pcndulun that swings on a boll bearing. On the right arm of the pendulum is a clamping jaw and on the supporting franc is a similar jaw at the sane level as the one on the pendulum arm when the latter is in a, raised position. The paper to be torn is inocrtod into those jaws and then to start the tear, a slit is rado in the paper by raising the knife edge which is attached to the froac. The ncchanisr. is oxtrcmcly siriple and sensitive to slight differences in the tearing strength of the paper. It con bo used equally well for testing tissues or ledgers and a single shcct can be.used for the test in either case.

703. SaOmlot, Charles. Testing tearing resistance of paper. Paper 25, no. 22:17-l8(Fob. 4, 1920); J. Sec. Chcn. Ind. 39:330A; C. A. 14:1217.

The instruiont used was a Trodificd Schoppcr tensilt strength tester. The toot as a-ppliod is to allow the lover arm to owing from a definite raised position after there is clamped betwoon the jaws a piocc of paper, so slit that one end fastens to the upper and the adjacent ord in the lower' jaw, and the strip is brought to a tout condition by the hand whcel, tearinG it slightly--n distance of about 1/8 inch. The lover arm is then released front its fixed position and the resistnnc in tearing offcrcd by the paper prevents the arm from falling its total: distance, nakiDn it cono to rest at that point on the scale wherc the tcering resistance balances the force of the. falling arm. A wooden arm was substituted for the mntal arm of the machine and waa so weighted that, when it is allowed to fall from the 30 nark, it will swing to rest at zero on the scale. The method of calibration is indicated. Results ore given for 100% rag bond, artificial parchncnt, M. F. printinG, Manila wrapper, Icraft wrapper, and newsprint. An avcrage of 5 tests will g'ivo a practical working value and, for more accuracy, 10 or more tests nay be averaged.

704. Satact, Charles F. Tcaring tester. U. S. patent 1,447,185 (March 6, 1923); Pulp Paper Mag. Canada 22:62°.

The invention consists of two jaws for grippinG tho papor, one being fixed to the frano and the other to a movable clement (preferably in the forLi of a weighted swinging lover) which moves under the action of g-ravity until the resistance offered by the paper to tearing, balances

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Toorin& StrcI1gth 255

the pull of 6-rovity. Throe forms of instrument embodying the principle are doscribcO.. In each one the two portions of the paper remain in the cane plone during toorina, thus ensuring equal tensiontltbacuhoutt --- tho- operation. - T126 thlcory of the Instrument is outlined. The scale can be Graduated to give the tearingj resistance directly in grams- - The range of the instrunolnt can be mado to embraco papers having eithlcr hic~ or low tearingI resistance by chalL~inCr the weight or by adjuatin3: its position on the lower era.

7- Ctt HCrfry L. New toorina strength tooter. Paper 29, no.99" -412ott'2 1921). .

The wall-Imowun theory of the slidinC or rallied-, weigt upon. an inclined plane is the basis of thle Invention and by this novel design~ all difficulties encountered through machine design and construction in other models have boon overcomIe. An Iron base nupportitiU two side franca contains the entire mchanism. Twro bearings mounted upon the top of the side frames carry a walking boom or inclineablo plans upon which root two round voichto connected together by a ball-boarinc carrinac. Fastened to a cross bar in this carringne is a chain which paseo over n screw and Is adjustoble for different lon~ths of the specimen. The inclined plane is operated by slidine across hands on A either aide which In turn arc lowered by maons of'o vertical screw : upon which a worn Goarp acting as a nut, revolves. The worn drivine3 this gear is operated by a train. of change ,-csrs driven from the nochanion below. 'ihe machine is fitted with a chart, the vertical lines &cnotinc, strength and the horizontal lines Otretch., The chart Troves horizontally from right to loft and the pon, supported from the rider on the scale, moves upward as the specimen clon~atco. Ad-vnn- togas of this typo of tooter arc pointed out.

706. SolIus, N., and 1,audonbak, W. Mechanical stron~th of paper in relation to- the composition quality and degree of boatine of the p -~ Tsonlu~ol Nauch.-Ioalcdovatcl. Inot. uoh rn ncil 1934, no. 4:2~3-265; C. A. 29:7650.

The tcnrlnnS stron.,,th of paper produced fron a mixture of chLenical and nechanical pulps depends on the tcerinC strength of the two component pulpc.. It is ;lossible to clccrease tho contents of chemicol iulp in the compositiono of paper without impoiring its n~charnicol pro-portics by o. Horo cfficient boating of the chemical pulp or by 'in.:proving the quality of the mechanical Tralp. El

4 1. osifications for white, unbleached, and colored Papcrs i for railroad ;7rintings and writings. Papaterio 56, no. 21:1118, I 1121-1122(Nov- 10, 1934); B. I. P. C. 5:1-57.

The official method for &otcrr1JninC the breaking loagth is -ivan. 1

708.Ouornoistr, Erwin. The Elmondorf tearing test anrd its relation to the burotinjn test. Paper Indl. 5, no. 3:477-479(june) 1923); C. A. 17:2645; T. S. 77:161. 'd C6 0to 1-. 0~~~P m 0-P) 0 C)I 4,4 0 4) 0) P4 0 o4'- O 4,d o1 14C $4 00 03 4) 0 r 0 C) C- PIO' P 020 0C $4P 4~ 10 4SHr- CD 0) 02 *-lco C) -' *0 0 a Q40- 0 0 ;. '-4- C) ~ 4-3 'dp -P43 CaEr- 40 0J 'Id 02 Pt 0 0 frA 00 - 0cl C.) 0 '-4 dO 0 N1 0 co 4:0 () 0 ,-f.4) C) 043 O 0o 0 OC- 4) tdo in I O 02 '0 43 O v- 4- 0 C) aX ~00 I r-ACD$$ .04' 0W 0~h- 4: C 0 043c -P .0$ >0H C- $4 $410 4-' C) .0 - C) 0 C) 'd) 'no coc0 04~ $4 0 0- 1400 4§02.0 -H 0 i o C~d43to W - r-I .0f C1 00 P) C) C)r f. .0 P. 0 0 O .- 4 .C II 4, 00 go P.4 H9 0-b Otot C) 4~r-4 0 4) 03V- LCcI\ Wp,- C) 4- PI 0H r-4$4 C)4 w $4r a 40 C t 00' P. .04 $4- 04H~ .0 0Id (0 -4-' . to C) Q)044 -4-' ; t 0 C-4 .0 2t C' C) '-OG C 9004 'HC) .0 ~~4(ilfl .V.C H 0 PI- 0 >2,-i v-b .0 44- +3 0.ri'd4 40 4 ,-lC) 0 CQ $41 020 4, § 0 OH $4 CC) $40 0 H 0~ 0+' 030. C) 04 04 a 4- C)EC -.tf---t -0 0 4a0 0 02 X4. C3 C) 4: 14- PH -4 ) o PC $4 1 43 C)C) 000 o . p'. 4~~~~~~~~~$ $4 4A .0 0 0 4) PI3q.Id a2L, Ao ZC 4-4 10 0 o) a P4C 0-0 .0 4) 0 00 A)0 $4 - C) Ca t (a oC P.00 0 co 0- $40 4) i 0 Ht 0 to 4000 4-tO 0>2014 - 05 'vI0 0: 4-, oci tCItoO C 0 , O 4 C) v-d 4-9+W0) H-4- 4coO C) ( Zt '62 4-' $4 0 C1 4d C-) I Id 4'd 00304 0 IC: 00 .0 1 PDO 4- P.-- d0 (1. 42-00 M4: M 04') 0 0 ol 4: 0 4-) 0 C2 02 00 *'0 00 (24: 0)' 0)ad> a $4 a- 0 fP 0 0 to to 0.00 co &03 H 0 U 0~-P -PC .0 C5 m-I+ '-H4 Hi ~10 0 440 i04 gl~4C 0 a 4H '-4

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710. Szoeko, P.,, and.Fraonkol, 0. Tearing strength and stretch. Papier-Fabr. 33, no. 25:213-214(June 23, 1935); B. I. P. C. 6:578; T. S. 103:192.

- With reference to an earlier study by Reito, the authors show that neither tearing strength nor elongation stretchh) -alono-defines thc quality of b paportor its-resistanco to nechanical stresses, but that both factors are required for determining those properties. They illustrate their theory by grapha and equations.

711. TAPPI. Internal tearing resistance of paper. TAPPI Standard T 414 n-42. 1 sheet. Paper Trade J. 84, no. 4 : 4 9-50(Jan. 27, 1927); 86, no. 8:209, 211(Fob. 23, 1928); 94, no. 18:43(May 5, 1932); Tech. Assoc. Papers 15:162(June, 1932).

This method is adapted for detorining the overage force in grans required to tear a single sheet of paper after the tear has been started. This is distinguished fron the initial or cdge tearing re- sistanco. The Thwing-Elnondorf teotor is used.

712. TAPPI. Connittcee on Paper Testing. [Tearing test. Paper Trade J. 75, no. 4:4 7-48(July 27, 1922).

Includes the Knife edcg nothod developed by A. D. Little, Inc., the Withan and Case testers, the Schoppor tester and the Elnendorf toster.

713. Toating tearing strength. Paper Ind. 2, no. 9:1393, 1438, 1440 (Ioc., 1920).

This is a reply to the article by Elnendorf which appeared in the J and ust is s ofohich this Journal, in the author dis- acgrocs with the viewpoint that the tearing strength is the nost in- portant Droporty of wrapping and bag papers. It is pointed out that the consumer of paper is norc interested in the initial tear than in thc continuance of that tear.

714. Thing, Charles B. 'Initial tear testing apparatus. U. S. patent .,364,388 (Oct. 25, 1932); T. S. 97:222. Cf. Instrunonts 7: 168(Aug., 1934).

The instrunont is designed to give on accurate indication of the torsiono- strain applied to paper or cardboard at the nooant of initial tear. The construction is such thathe e graduations of the scale arc spaced so as to provide larger spaces at those portions at which initial tear ordinarily occurs, and the indication of the pointer on the scale is maintained after recession of the drive shaft during the tearing operation.

715. Thwing Instrunmnt Co. Tearing tester. Mclliandi Toxtilbor. 2, no. 7:985-986(1930); J. Textile Inst. 22:A203.

A - 9mWmeaEO aB------Tearing Strength 256

This apparatus, known as the EImendorf tearing teter, has been developed for the paper industry and is used to measure and indicate in grams the resistance to tearing of fabricated materials. An attachment to augment the capacity of the apparatus, so-that it vlll accommodate stronger materials, has recently been perfected. It measures the actual work done in effecting a tear; the personal -- element does not come into play and-no calculations are required. - --- tItschief structural details are described and illustrated.

716. Tachudi, H. The Elrendorf tearing apparatus. Wochbl. Papierfabr. 57, no. 35:964-965(Aug. 28, 1926); T. S. 84:278.

A brief description is given of the Elmendorf tearing tester and its theory. This does not give values comparable with the Schoppor apparatus, because the latter gives a mininum value with a strip 18 cm.' wide.

?717 . U. S. National Bureau of Standards. The testing of paper. Washington, Govt. Print. Off., Feb. 12, 1921. 37 p. Circular No. 107.

A brief description (page 18-20) of a modified tensile testing machine, in which the weights have been removed to give it more sen- sitivonoss.

718. Wallin, S. Tearing strength of paper. Svensk Poppcrstidn. 24, no. 18:356-357(Sept. 30, 1921); C. A. 16:645; T. S. 75:206.

A hook is substituted for the pan of the balance and the tearing is accomplished by adding weights to the other pan. The author suggests the concept "tor surface, " meaning the surface of the paper beirg tested whose weight is the same as the force needed to tear the paper. Ho also suggests "longitudinal tear surface, " cross tear surfacc," and "average tear surface." It is more difficult to obtain accurate figures for cross tearing than for longitudinal tearing.

.7j9. oells, Sidney D. Report of the Paper Testing Committee on the tearing test of paper. Paper Trade J. 76, no. 26:49-54(June 28, 1923); Tech. Assoc. Papers 6:102-106(1923); World's Paper Trade Rev. 80, no. 5:416(Aug. 3, 1923); T. S. 77:161. Bosults obtained by 16 testing stations (14 with Elmendorf, 1 with Withan, and 1 with Eastern Manufacturing Co. testers) on 12 sets of sanploe arc tabulated. Tlle factors influencing the tests seem to be related more to variations in the paper than in the in- .trumonts. WVhorecvr more than two sheets wore tooted, the results I ,·B ~ checked very closely and a deviation from the average of more than ' '10~%- vm exceptional. The ncan deviation is usually less than 5%, S'~ indicating the reguJority of the instrument. The fact that the mean deviation for the station averages usually greatly exceeded the mean variation of the individual tests would indicate variations in the instruments or in their setup or operation. The following causes 3[8,"iS ci N-1 4-' cu C) Q 0 J., cu H 0'1 Ca I 0C) C04) -H- C) dH- r-40 -'-I 4-) 4 0 0 C)i C) >0 ,0 n-t 00 pm a P4 xld 0 C-) 0 5-% 5.45-4 000 C) Id C) 00 AC H C PIC)> A~ 4-) 4,4 GI0d -~4 r- -4 P4 4 0) 4-4:4 s-I0 do 0C) C)~ P.O 4-' 4S Q 00 p .,-400 I'd $4 0. 0t C~~~~C 0 - )4~ ,0 0 042 .4-' ; . J-404. C 0~~~E40 AC) 4,. U C) C "6 4-' 0)0 ,0 P. 0 tOO 0)~ ,0 £142 o. `4 [- 0~ IO 4-'02 004~ O 04 ' PI C)d- C Id Cl c1' o7 O 0'0c 4Id A 0'd Ido$ toad 4, C a)00)00o ci 00 0D tO Od 5:142 Cl 0440 4p:.0I0 co '-I It:2 C)Wr0flr co C 0)0 C)w 5-, C')0- Ja coi -Id 4)$ 5-. ) CClr C) 04, 4-' 4- A'4C la H c 0 ) 0 00 I~d O-Pl 0 r ;4-0 o o40 0 A NO N n-i C: pr-l 0 402' Ad) 42 0) 0 1 4 00. 00 42A 0 0200 co C)0 0 4-) ~R 4204 C) ) 4-. C) P44' rip. t2 0 C 'do 4 4-C, 4) H)W" 40i ,010 CC) 4--i 4) PI o t4. 0tt,4 42d Cl 1, -d 42> ciCn a C) OP+-'C0 42m In t XC) I'd X)4C 2 C)'d on 00 00' C) to02$ ' >0 4-,W 00 ooc 0> al FAA 420 00 $ H Id Id 0 0 4)0 co C) td>) 4 d V 02 0 $40 C)$ QA'H H 43$4 P0 P. C)'0 S-i) PI 00 -l'r- [449 P.' op. Cll0 I2 IJOO Cd I o 0) 'rI a) 4H0)-.A C Cl 0 ,'i~ 0W \$(a A. CC' 0 H.- $40

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04-' P.0 $4 0 ED2 co0'Id C -'co ,3Id~ Tearing Strength 259

723. Williams, F. M. Resistance to tear and the measurement of surface friction or slip of paper. Paper Trade J. 114, no. 15: 16-17(April 9,1942);C. A. 36:3356. ..

The instrument is of the pendulum type and consists of a rovolv- ing drum mounted on ball bearings with- a suitable stand, with accurately counterbalanced pointer not rigidly attached to the drum but moved forward by contact with a pin projecting from the back of the drum. The load is applied through a similar revolving drum directly attached to a motor, which through a reducing gear applies load at the rate of 1 r.p.m. The two ends of the sample (1 inch wide) are attached to the revolving drums by placing the sample in slots and folding over ends by means of a spring clip arrangement, which holds the sample firmly in place. The load is applied by a pressing switch; as th pendulumm weight rises, the noodle is moved forward over a graduated scale intil tearing takes place. This reading may be taken as initial tear, but the test may be continued to determine thc. presence of hard spots which will advance th' noodle slightly further. This nosureos the tearing resistance of the sample in grams direct pull and not by the indirect method of indicating the absorbed energy of a falling weight. The results obtained are somewhat lower than with the conventional method of measuring tear. However, when this direct- weight method is checked by lifting a known dead-weight attached to one end of a slitted sample, the results indicate that tear tests measured by the direct method, although lower, give a more accurate indication of actual tearing resistance, because the other methods of measuring tear involve a certain amount of tensile strain as well as pure tearing resistance.

724. Winterbottom, Marion, and Minor, Jessie E. rlic test for tearing resistance. Paper Ind. 18, no. ll:928-930(Feb., 1937); B. I. P. C. 7:234; 0. A. 31:3268; B. C. A. 1937B:770; T. S. 105:371.

The number of sheets torn at one time in an Elmondorf tearing tester has an effect on the final results. The instructions "enough shooeets shall be torn at one time so that the reading on the scale shall be not less than 20 grams nor more than 40 grams" provide a too large working range. A modification is suggested to read that all tests shall preferably be made on single samples, except in those cases where such values are too low for accuracy. In no case should sheets be doubled to give a value of over 30 on the scale.

M72. Within, George S., Sr. Paper tester. U. S. patent 1,298,138 (March 25, 1919); Paper 24, no. 5:22-23, 40(April 9, 1919).

A ppoer' tester comprises noons for supporting a trip of papcr, means for fastening one side of one end of the strip to the support, a weighted lover provided winh means on one side of its fulcra 'for engaging the other side of the paper, mneoans for adding weights to the opposite side of the lever, and neons for indicating the force required to perform the tearing operation...... ~~~~~~~~~~~~~~ Is . - I~~-.

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Tensile Strength 261

direct tensile stresses. In thle casa OfPrinting papers, tensile strenztbl neasv"rements indicate the potential reoistanc to breaking when subjected to strains during 0 travel from the roll through the web I Preos nechatsno In the process of printing. In general, totiil~e strength tests ':rate n~Pers in -the sma order as the burstinge otrengh tests, sthich,'deo&pz 3t stoc-h es~ladsrtch. OMo advantage over bursting strength is that the off tensile the tesef st-eng~th Of' tile shoot in )n test can-be lnees'red and reporte-d thereby dEtecting for each direction., any nbnormal differences bet7,1cn 1.In' mI the two direction control y-orlk the termi-le termmingl the gone:'sl strength strength toot may be properties olf paper, butusdfod- it is0 not convention, nor as rapid no us -the bursting Stren~gth toot. Allth:ough tonuil6. st,'r~ngth tost aoes the not usually give such a good indicntiIon the pi-ac icaj. 'Yitrenigthi" off of parer as the bursting strength tent it fil.ls - -special need in does, the tooting of' paper subjected to ctrossec, _.22Use. tensile

72 - Anrther 5 TC AnG Inntrrsaent Co.,Ic Thilrtothesrs Ciro. No. 107. n~. ci..tsoo

T Veetpe or listed portable dial typo 269, bonchj dial type 27'0, Pendulum benhal dial tYPe 271, ~ypc20 ed. 70 re Iustrotod. and precicion mote driven 'type 250. Type 271 la const:7ructd in accordance to the TAPPI Standard P~404.

129. A-rcno~.t Albert, and Wathelot, Rnmanucl. Effect of' atmospheric humldity on the tensile strength of? writing and Dri-nting pano(rs._ pPapeterie belge 1-2:105, 1tO7-113(rcb., Mon. 1932); T. S. 95:77; C.A 26:5664; 23 . P. C. 2:_326. A gecnorol discussion of' the effect of hyd-rortetric the break-Ing conditions on lenGth Of wrTitiwi and prir-ting papers. Jj. Arneula; E. Strength and. rosictanco of' paper. Dreoking length. Paplar 25, no. 2 2 5: 09- 12(i4ay, 1922); C, A. 16:3205; 75:109. T. S.

A.discussion is given of the factors Of affecting the tensile strength paper, off the. precautions to be token tes~tor,.cand in. using -the Schiopz)rrteil of. the strength tests to be applied to various ,radea off paper. 7.Attainment of perhection in toting mochincr. World's Trade -Bov. 1,22, no. 22:1.426, 14083(ncc. Paper 1, 1939); 23. I. P. C. 10:2071. 1?sferenco is raido to the paper, testing mnchinec Goodbrand and Co. manufac Luared by for determininE the breaking strength of allI classes of paper. anid elongation The arparotus is described and. iflustrnted. 732. flaosbrg, A. The influence of' moiatur-e the streng~th and, elasticity and tempsratm'e onl of paper. Panir-J. 21, no. ll:l05-i05; no0. 22:!14-12.7; no. l5:123-lP6; no. 14:i36.139(JUly 6, 25, 3.1, 1933); C. A. 28:318; Aug. 11, n. i. P. C. 4:i6; T. S. 98:156.,

j I SI _]T1T7 li-u. . . - 'S

Tensile Strength 262

Theories of paper strength are discussed. The strength of paper reaches a maximum at 50° C. and decreases with further heating. At a constant temperature of 20° C. the maximum is attained at 1-2% moisture. At constant temperature elasticity is practically independent of the moisture ofthe papor.- When o-load-is applied in the-Schoppor i tester, tle strip shows permanent elongation or slip before rupturing. This slip does not increase with time._ Paper heated for some time. - - - at-100° C. will not recover its original moisture content. The higher the heating temperature, the less moisture is reabsorbed. This per- manent loss of moisture is accompanied-by a permanent looss of strength.

733. Borcsi, Joseph G. New method of testing paper. Method of testing and recording physical properties of paper and description of machine invented by A. Retjo. Paper Trade J. 84, no. 7:39-42 (Feb. 17, 1929); T. S. 85:141.

An instrument is described for making tensile and elongation tests and automatically registering the force-elongation diagram; the technique for its use, together with the precautions to be observed and the method of calculating the quality, is explained. A triangular rule has been devised for facilitating the measurement of the area of the diagram and the calculation of the quality of the paper.

734. Dosco tensile tester for paper. World's Paper Trade Rev. 61, no. 19:912(±May 8, 1914). tester The Bosco / operates on a strip of paper rolled into a cylindrical shell.' The two circular edges are fastened in two ring-shaped clamps, exactly concentric and located vertically above one another. If one of these clamps be turned slowly in one, the other just as slowly in the opposite direction, the paper is subjected to a torsion strain, which is strongest in the center of the cylinder. The result of this turning is a strain on the paper from every direction. The device is so constructed (along the lines of the Schopper strength tester) that the direction of revolution of the clamps can be reversed and the rotation in opposite directions is continued until the paper tears. This figure comes very close to the power of the paper to withstand crumpling.

735. Breaking length. Wochbl. Papierfabr. 70, no. 21:454; no. 27:603(May 27, July 8, 1939); B. I. P. C. 11:29.

Mean breaking lengths arc given as follow: Writing pbper of bleached puln 50 to 100 grams per square motcr; wrapping paper of un- bleached pulp, glazed on one side, 13 to 100 grams; lkrft paper, either unglazed or glazed on one side, 40 to 100 grans. Average values for writing papers range from 3000 to 5000 motors, for wrapping papers 4000 to 6000 rcters and purc kraft papers 6000 to 7500 meters. The tests were carried out vith a Schoppor tester at 65% relative humidity.

736. Brecht, W., and Blikstad, F. The tensile strength of paper perpendicular to the plano ol' the sheet. Papier-Fabr. 38, no. 8:50-51 (Feb. 23, 1940); B. I. P. C. 10:347; C. A. 34:7603. iiAL I I" e.F - - Tensile Strength 263

Tensile strength is measured in either the machine or cross machine direction of the paper' web but very little is knovn about this property in the third .ircction.--in the direction perpendicular to the plane of the chcct. Pcpt,-r· sarlJes, 20 mm. in diameter, were glued between two wode._blocksl_Qf identical size and the adhesive -wrc allowed to--- set for three houis3. ifte' this period, the blocks wore clamped in a Sciopper tensilc tcster cnd the breaking strength wct dotormincd. -When the tr-o wDur-en blocks we're-glued together rithoulr, a paper'sheet in bc-trvcn, thc bocdiinC strength of the adhesive Wo sc groat that the blocks cou d not be separated in the largest model for board testing witi a maxibvm breaking load of 150 Ikg. The tear always occurred, with..! the fibrous and never within the adhesive layers. The strength porgnndtcular to the plane of the sheet is always uxtremcly low. 0- the toon Esa3np1 tested with values of 108, 59 and 2.3 f'oamachine, cross machine, and perpendicular to plane of the sheet, and glassinc with 1090, 600 and 24 for the same direction repre- sented the lowest and highest values. Slack-sized papers from free pulps gave consistently lower strength figures than stronger and hard- sized papers from slow-boatcn pulps.

737. Coapbell, W. B. The tensile strength of single fibers. Forest Products Labs. Canada, Quarterly Rev. No. 2:70-71(April- June, 1950).

Following the technique of the Shirley Institute for measuring the tensile strength of single cotton fibers, similar measurements were nade on wood fibers. Difficulty was encountered in mounting the wood properly. Ruhloman (Paper Trade J. 82:168(April 1, 1926)) gives as the breaking load of wood fiber, around 13 grams.

738. Canadian Pulp and Paper Association. Technical Section. Tensile breaking strength of paper and paperboard. Official Standard Testing Method 10. July, 1942. 3 p.

This is practically the same as TAPPI Standard T 404 n-41.

739. Carson, F. T. Some notes on the revision of methods for measuring the strength of paper. Paper Trade J. 102, no. 19:59-42 (lny 7, 1935); Tech. Assoc. Papers 19:172-175(Juno, 1936); British Paper 4, no. 3:29-52(1936); C. A. 30:5034; B. I. P. C. 6:410; T. S. 103:269.

A discussion is given of the proposed revision of the TAPPI method under the headings: Dimensions of specimens, rate of testing, and report..

740. Clerk, Frederic C. Paper testing methods. New York TAPPI Publishing Corpn., 1920. 24 p.

Tensil strength is discussed on p. 15-16. The Schopper tester is mentioned. Relationship of other strength properties is illustrated. I.-I.- I I 404 C'S~ ~ C n40 or 0C CO' C2 t~~~~h~ ~ 4 0 C 0*40 CCr C) -I C) $1:) c CJ2 t 41 - MHC 04-' -HC aC I CO-4-) Cop ci ' . Ci *44 CC04' coU 0 Xiv .4m ci C) l -I C 0 * 4V . 0+'4-4 CC) 4 HC)02 4sg 5- 0. IC C) 4-i 104-. H C,] '42H U I 0-C 0 r -~C C * 00, C)- S)'d C41 CD $4~ Cop. Cla "I .104 le "' 4 p. Iq $4 4i CO tocio &2 Ca) 00.0 C '4 '4~ q . P4H ~4,n Ca4- +)* '.0 Hi $.4 4-) Ca -1-4 C40 "4J 00 0 z Id 0 Cs &C>000 0 0 Hf -4a *40, P. 0 43f AP H 4-H 4-I4' 6"0 C) 0 A 14 C) a c P..&H C-) '-4 C)- 4zt $04 Q. 4 .43 00 $4A j~ C;c 0 0 4~ ~4 C, 4P04b) 004~4J400 H U'\ 'd4 Id %- P4m -.0 0 P 4' 10 C $4-44 4-, '-4 Id "i Cl 'ICO rHO, 0% 0000 a 0 0

.CId 4 4-) tor 4a0 4~0-P OE Z Tensile Strength 265

744. Costello, Coleman J. Comparison of tensile testers for paper.. Tech. Assoc. Papers 7:68(June, 1924); Paper Trade J. 78, no. 15:189(April 10, 1924); Paper 33, no. 26:136(April 17, 1924); T. S. 79:147; C. A. 18:1906.

Four machines were used. Two of these were of the inclineable balance type, operated on the deadweight principle and best suited to test strips ... .. of-paper about 4 inches long and 1 inch-or-15-rm.-wide. A third machine was -- hand-propelled and tested strips 1 inch wide and 4 inches long. The fourth machine was best fitted to test strips of paper about 2 inches long and 15 - -am. vide; it was operated by a hcnd lever.- Twelvc lots of paper were tested, -the average of 10 tests being taken to determine the tensile strength of each sample; duplicate tests wore made in each case; 1900 tests wero made in all. Considering the amount of variation between individual tests made on the sample, two of the machines gave results superior to those obtained with the other two. All four machines gave good results as regards comparisonof average obtained for duplicate tests on the same machine. That is, as re- gards duplicate determinations mado on the same machine, very close checks may be obtained. When the average results obtained by the different machines anr compared, however, there is quite a wide variation. This is duc, probably. not only to differences in the mechanical accuracy of the machines, but also' to differences in the size of the paper strip tested and the rate of the application of the load. It is apparent that tensile testers of different typcs cannot be used for strictly comparative results and therefore, in re- porting results of tensile tests, the kind of machine used should be specified.

745. Dalon, Gustav. A new strength tester for paper. Mitt. kgl. Material. 1911; Erga'nzhoft 2:12-22; Papior-Fabr. 10, no. 25:713-714 (June 21, 1912); Papior-Ztg. 37, no. 39:1428(May 16, 1912); Paper 8, no. 10:17-18(Aug. 21, 1912); Wochbl. Papiorfabr. 43, no. 22:1894-1895 (Juno 1, 1912); C. A. 6:2525.

The rapid paper tester is described. The strip to be toted is 50 m.i. (2 inches) long and 10 mmn.(3/8 inch) wide. The methods of testing the strength scale, the expansion scale and the defects in the mechanical con- struction arc discussed. Tho values for the tearing length agree fairly well with the larger apparatus (30 kg.) but the expansion values arc higher.

746. Doughty, R. H. The relation of shoot properties and fiber prop- crtics in paper. I. A qualitative study of the tensile strength-solid fraction relation. Tech. Assoc. Papers 14:243-248; discussion, 90-91(May, 1931); Paper Trade J. 93, no. 2:39-44(July 9, 1931); T. S. 93:195; C. A. 24:5022; B. C. A. 19323:718.

Tensile strength at rupture in p. s. i. of original cross section is calculated from thc breaking load on a sample of known dimensions. Solid fraction by volutnm is defined as the ratio of the volume of solid fiber in the sheet to the volume of the shoot. The value of fiber was calculated from the sheet weight and an assumed density of 1.5 for fiber substance; the vblumo of the ahect was derived from its measured dimensions. The general procedure, was to prepare a number of shoots under rigidly standardized conditions, employing the most advanced tochriquo available. Those Gsheets were subjected to different wet pressures, dried, conditioned in a humidity room, and the solid frac- tion and tcnsiie strength accurately determined. The solid fraction range studied was 0.15 to 0.5. The following conclusions arc drawn _~ _:' ------.. a. 'e -< - *s r .- ,-,"*.rf;S tS^*Wv.

Tensile Strength 266

from the data presented. Tensile strength increases in a regular manner with increase in solid fraction in the test sheet, the relation approach- ing a power function. The curves of tensile strength plotted against solid fraction change in an orderly and rational Tanner when a pulp is beaten or when it is dried, the two treatments producing changes in opposite directions. Tearing and bursting strength and folding endurance

..-.- - in-an-unbeaten. pulp vary- with -solid- fraction in the- same-way that they - ' vary with.time or freeness on beating. The beating process may be divided into two parts, one in which strength increases are due to an _

- -actusl. change in the surface conditions of the fibers, and the other in which such increases are due partly to solic fraction increases dependent upon increased shrinkage and, therefore, upon decreased fiber particle size. The second of those effects can be duplicated by wet pressure but the first cannot. A means is thus provided for studying r-c;arately the effects of fineness in boating and of some other factor approximating true hydration. The regular nature of the changes observed supports the hypothesis that this sheet'strength is a function of sheet structure and fiber properties, which can be expressed mathematically.

747. Doughty, R. H. Tnc relation of sheet properties and fiber properties in .ppor. II.' The variation of ultimate tensile strength with basis weight and related factors. Tech. Assoc. Papers 15:361-367 (Juno, 1932); Paper Trade J. 93, no. 15:44-49, 54(0ct. 8, 1931); T. S. 93:275; B. I. P. C. 2:135; C. A. 25:5987; B. C. A. 1932B:718.

In socking an explanation of the fact that the breaking length of paper (ordinarily used as a measure of ultimate tensile strength) is not proportional to basis weight but, on the contrary, reaches a maximum as basis weight is increased from a low value, a series of test shoots of several basis weights, wet pressed at several pressures in order to produce various fractions for each basis weight, have been prepared and analyzed. The variation of ultimate tensile strength with solid fraction at constant basis weight and with basis weight with constant solid fraction and the variation of solid fraction with basis weight at constant wet pressure wore studied. The results indicate that the commonly observed relation between, breaking length and basis weight is governed by uncontrolled combinations of the three variables considered. Variation with basis weight is due primarily not to variation of basis weight as such but rather to fiber orientation as a manifestation of the variation in consistence when sheets of different basis weights are made, using equal volumes of stock. The following conclusions may be applied to paper sheets in general. Shoots of constant basis weight show a mathematically regular increase in tensile strength with increase in solid fraction; the increase in solid fraction is obtained by in- crease in wet pressure. Sheets of the same solid-fraction values show a regular decrease in tensile strength with increase in basis weight when the volume of stock used in their formation is kept constant and, con- scquently, the consistency is varied in proportion to the basis weight; this strcrgth decrease is primarily a result of the consistence change rather than of the weight change. Sheets made up under constant wet pressure show a'continuous increase in solid fraction with increase in basis weight, as a consequence of greater shrinkage on drying. As o result of the-two effects just noted, sheets made up under constant wet pressure and with a constant volume (variable consistence) of stock I MWAMMO I t Tensile Strength ;26

wight - first increase and then decrease in tensile strength whon base is increased from a low value. The relations involved may bo oproCoi tCll-', whore k is a characteristic of the pulp that is doeiBatod as S = s strength at unit consistence," and m and n ngy mrr naot boecrt0- "fiber an fl' Shebts of low basis weight (e.g., 21.5 pounds)-show onarnlol istic. in ---behavior that nay bo citheor specific or an effect of inaccuracy appoor to moesuremcnts. The various effects of basis weight thickness porti- be explainable from the.standpoint-of the fiber arrangement, to the cularly the concept of orientation of fibers perpendicular surface of the shoot.

Doughty, R. H. The relation of shoot properties and fibor. 748. propertioB: in paper. III. The effect of fiber length on shoot properties 1932); preliminary oxperioents. Tech. Assoc. Papers 15:137-142(Jtme, T. S. 95: Paper Trade J. 94, no. 9:29-34(/arch 3, 1932); C. A. 26:3108; 75; B. C. A. 1932B:718. separated Two unbeaten pulps--a spruce and a black gun sulfito--wore long-fiberod and short-fiberod portions; tho by vet screening into scroon a 60-mosh screen and that retained on the 32-mosh fractions paosing were mnde were used. Thcsc two fractions, as well as the whole pulp, while they wore into sheets which wore subjected to various pressures values of tho dry sheets wet and the tensile strength and solid fraction fiberod portions of were determined. Toc moan fiber lengths of the short gum pulps were 0.2 and 0.07 rmn.; of the long-fiborod the spruco-anti pulps wore 1.3 2 and J.5 nm. The mean lengths of the wholc fraction, wet from tho 1.1 amn. hects mado under any given pressure while and those iron portion are front 25 to 200% stronger than ehort-fibored fraction givos a shoot the long-fibeord faction. The short-flbered strength than one of higher solid fraction and, therefore, of greater not have a vary the long-fibered pulp. HowevCr, fiber length does of given solid fraction. influence upon the strength of sheets at any grcat structure of sheeto is a fundamental difforenco in the interrnl Theor this work by the nado of fibers of different lengths, manifested in tests other than porosity test, that nay be more evident by strength heeot-producing tensile strength. There are also differences in by fie'cr length properties between pulps that cannot be oxplainedl to the chemical nature differences alone; possibly these are ascribable of' the material. of' the tensile strength 74,. Fournicr, Raynond. Determination 1077(Sept. 10, Pap)tcric 53, no. 17:1066, 1069-1070, 1074, of paper. 29, 1931); 1931); Pulp Paper ang. Canada 31, no. 44:11 93-1194(0ct. C. A. 25:5987; T. S. 93:276; B. I. P. C. 2:136. of tonsilc When cutting out a test strip for the dotermination therefore weakened. strength, the edges of the strip nrc mutilated and represent the actual The results of the test, therefore, are too low and resulting from the strength of the original papor - les the decrease latter is inelopondnt rntilation along acah edge of the strip. 4s the wide strips arc of the width of the strip, the results obtained with up to a certain width, proportionally higher .than with :nrrow strips,

. o EEB b n Tensile Strength 268

abo-e wnich the results are practically proportional to the width. ... --. s the construction of instruments with wide Jaws offers certain difficulties, Fournier proposes that the instruments at present In use be retained but that the strips be at least twice and prefrably three or four timed as wvie as the Javw (15 in.). The toet would be simplified (less care required in preparing the stripo), the results would be higher and would more truly evaluhtfethe quality of the paper -- - . .undole th conditions of use.

- 75. -Fournier, Raymond. Dotermining the tensile strength of paper. Papicr 25, no. 10:457-440(0ct.,'1922); Paper Trade J. 75, no. 23:50-51; no. 25:58(Doc. 7, 21, 1922); C. A. 17:208; T. S. 75:306.

Fournior, after briefly discussing the shortcomings of the instrument generally used for measuring the tensile strength of paper (Schoppor), advises using a machine which could take a imch wider otrip--c.g., 15 cm. instead of 15 mm. This would necessitate the use of forces up to about 300 kg. and Schoppor typo instruments of this capacity would be too heavy, cumbersome, and expensive. A simple and efficient hydraulic type of instrument is doscribed, in which the tension is exerted by means of a piston displaced by screwing a rod into the cylinder carrying the piston.

751. Goodbrand & Co. Ltd. Goodbrand tensile testing machine for paper. Circular with no number or date.

Trnrce types are illustrated. SoC also World's Paper Trade Rev. 112, no. 22:143', 1488(Doc. 1, 1939).

752. Griffin, Roger C., and McKinlcy, Rusosll W. Studios of tensile and bursting tosts. Paper Trade J. 102, no. 2:34-55(J-n. 9, 193;); Tcch. Akssc. Papers 19:222-225(Juno, 1936); B. I. P.. . :275; CC. . 1953oB:lo; C. A. 30:2378; T. S. 103:191.

TAPI Standnrd T Il4-m specifies that the stressing Jaw shall bc onrat,,l-ct ans aod of 12 inches per minute and that the testing in- strimnnt shall be of such capacity that the tensile strength of the paper tctoed &;illnot beo svrotr than 90 nor loss than O1d of its capacity. Clar!k has proposed that the break shall occur within 10 to 0'seconds from the tine tho load is applied. Using a Schopper tensile machine (powor driven), a series of tests wra made in the machine and cross directions of seven samples. When the TAPPI method was employed, only four of 11 groups of strips tested gave results outside the time limits of 10-30 seconds proposed by Clark. Of the 11 groups of duplicate tests, the overage deviation was 2.8%; in only 2 casco was it -over5%,. eIcnall 11 groups were run within tho proposed time (10-'0 seconda, the avcraec deviation was 2.6%. The tests indicate that rapid application of the load tends to give somewhat higher toenilc strengths. The quantitative effect, however, apparently varies with the type of acpor. From present data, there do not scene to bo sufficient advantageo in the proposed modification to warrant incor- porating into the standard procedure, except as a sugcgstion. It is Esugcosted that the method require the recording for each break the Lime in seconds frao the application of the load until the break occurs,.

me-I ICCarcmnrarr-··· I . t ,·:::~'~;" s r

I Tensile Strength 269

73. Grund, E., and Weidcnrmnllor, H. The zero-breaking length of pulps and papers. Popior-Fabr. 30, no. 24:397-04(Juun 12, 1932); C. A. 26:4714; T. S. 96:136.

The breaking length of sheets rade from certain pulps. and-of ... various cormorcial papers wao determined by the use of the 'binther zero clamp" on strips of zero length. The zero-breaking length values of pulps change only slightly between 30 to 0Odegrees Schoppor, . but from 90 and above it begins to decrease. Tne zero-breaking longth of pulps is independent of the basis weight of the test shoot. By shortening the length of the strips of paper tested, the breaking length incrcascs. By means of these tests, the actual fclting properties of the fibers can be separately determined.

7j4. Harrison, H. A. [Tensile strength]. Prcc. Tech. Section, Paper Makcrs' Assoc. Gt. Britain Ireland 11, pert 1:77-79(0ct., 1930).

In a discussion of Olivcr's paper, Harrison gave figures'on the tensile strength for strips 1 inch and 15 m. wide and calculated the strength of. a strip 15 mm. wide from the values for the inch strip. The data confirm the results of Houston that decreasing the width of the strip increases the relative strength, yet this applies only to tests carried out on papers cut in the machine direction. With cross direction strips a decrease in the width of the strip causes practically no difference (in one sample of unglazed kraft a do- croase of 11.3% was observed when the narrow strip was used). There is no general agreement on the effect of the length.of the test strip. The rate of movement of the lower jaw of the Schoppor tester is men- tioned but no data are given.

755. Harrison, V. G. 11. Papcr testing. IX. Tensile strength. Patra J. 2, no. 3:l19-122(Nov., 1938); B. I. P. C. 9:254.

The Patra laboratories usc t.hc Schopper tensile strength tester. The samples arc 5/8 inch in width and not less than 8 inches long. Tosts arc made in both machine and cross rlirections. The method of making the tcot is reported in detail. The procedure follows the reconnmrndationo of i thre Paper Testing Corrmittcc of the Tochnical Section, Paper liakcrs' Association. It is rocormonded that the driviDg handle of the apparatus should be turned at the rate of 150 r.p.m. when the smaller wi'ght is in use and at 50 r.p.m. with the larger weight. The average of ton readings is taken. Thin or weak papers may have several strips broken together.

_76. TIoritage, C. C., and Doughty, R. l. The relation of shoot properties3to fiber pronorties through a shot structure. Tech. Assoc. Papers 13:21-25(Moay, 1.930).

This is a briof discussion o"' tho work of Doughty (Nos. 746-743). I I I

rrc Tensile Strength 270

. Hcrzbcrg, W. Influence of folding and printing on the strength of papor. Mitt. kgl. nech.-tech. Versuchs. 1899:269-284; J. Soc. ChCan. Ind. 19:267.

The apparatus used consisted of a heavy (7.5 kg.) iron roller - - (150 rnn. dianctcr) provided with a central flange fitting exactly into a groovcd rail, along which the roller runs. A strip of paper, 15 r. wide, likewise exactly-fitting the-groove, is folded back upon itself, laid in the groove, and the roller run over it, in both directions. After rceloval the paper is tested for tensile strength. The difference between these numbers and those obtained with the original unfolded sample expressed in percentage of the latter gives the "loss in breaking strength" and "loss in stretching powcr" of the paper on folding. Some 87 papers wore examined. The loss in stretching power was greater, both in machine and cross direction, than the loss in breaking strength. The loss in breaking strength in the ncchinc direction is greater than in the cross direction. The loss in stretching power in nst cases obeys the sane law. The lowest ncan loss in brcn!-ing strcrgth observed was 4.7% and the greatest was 48.5%. The lowest loss in stretching power was 14.3% and the greatest was 78.7%.

758. Icrzberg, W. Influence of weight per square notor on the strength of paper. Mitt. gl1. Material. 31:318-320; Papicr-Ztg. 39, no. l:3(Jan. 1, 1914).

759. Hcrzbcrg, W. Strength, stretching and folding numbers of papers in both directions. Mitt. kgl. Material. 27:172; C. A. 3:2870.

Drcaking strength, stretch and folding numbers of paper vary ac- cording to the direction in which the test is nade on the paper. A comparison of tests rado in machine direction with those in the cross nrchinc direction gives ratios front 100:18 to 100:31 between the two di'roctions in breaking length, front 100:290 to 100:455 in stretch and fr'on 100:21 to 100:1.5 in double folding tests on certain Manila pcpors. IIfrzborg advocates classifying papers, not on the average of tests ilndc in both directions, but on tle lower value found in cither direction.

760. Iouston, Paul L. Effect of length and width of test specinon on the breaking strength and elongation of paper. Paper Trade J. 76, no. 12:54-55(i;1rch 22, 1923); Tech. Assoc. Papers 6:72-73(June, 1923); T. S. 77:1.

This study was .adocof a breaking strength machine of' the inclinable ty-re wi th acuapcity of 50 kg. Ten different lots of paper wore tested; sc:-nles wcre cut 0.25, 0.5, 0.75 ond 1 inch ir width and of such length thct tlho distarnc between thc jaws of the machine was 50, 90, 100, 150, anl 180 rm. The machine was so set that the lower jaw descended, at a speed of 6 inches nor ninutc. Thc test results vary when different lengths of the salue width specimen are used; however, this variation .0I -.

S; Tensilie Strenglth 271.

was never greater than 1.5 kg.-, which is domparablo with the experi- mental error of-the machine. The percentage elengotion varied with both the width anid the length of the specimens. The elongation, is highest for the 0.25-inch strip and lowest for the 1-inch strip-- i.e., in the inverse order of the width; the some, isejtruo-of tc------__ -Whz--c-lngt.- xn~ineb~t~h~ecttha thre is a difference in stressed area as well as fiber adjustment to stresses. 'The rate of stress per unit arca _decreases nos-the--stresrjed arcw- docro"666s -- - - 1t ism-ohalulie&d that t~he !length of test spocinen t isnt important

-hn- only the breaking l1enth is desired. However, fteprbty elongation is desired, the-length and w~dth Tait bo controlled and standardized. It is suggested that aI l-enth of 3.5. inches (about 90 mm.) and & width of 1 inch (about -25 mm.) be adopted ns a standard.

761. Houston, Paul L.. Rfleltionship between breaking strength and bursting strnenth, of paper. A possible calibration of the Mullen tester. Paper Trade J. 70, no. 13:47-48Q11arch 29, 1923); Paper 1.-kors' 14o. j. 61i, n6. 5:128-189(May 15~, 1923); Tech. Azsoc. Papers 6:100-1o1 (Juno, 1923); T.~S- 77:1.

The apparatus employed was a 50-kg. breaking strength machine and a Yzzlien toster with anil attachment for measuring deflection. Jaws for the breaking strength machine were made to) use test specimens one inch in width. T1he attachment for the Matllon touter consisted of a drum, which wan gearedt to the hand wheel. A recording pen was attached to a very small rbd in such a way that it could move up, and down and describe a curve on a chart clamp-ed to the drum. A thiclamcss gage was also fastecnud to the Mullen tes2ter. flet~riminations we~re made of the brerkLng stirength, elongzation, and bi'xsting, strength. As the bursting strength wans dotermmnedi, the increasing Jciloctirn of' the paper was recorded on thel chart, fvmion which the blengantion At the~ breakcing point was calculatoti. PesuLte arc ren~orbd for eight kin-ds raaper. They- shlow that the oietg vorntioton, of' ratio of break-ing- strength to elo~iigtien and, of' rcmtib of bursting streOnLgth t- o,eongation f'_rom the mean value is vc~i'y smn1 f or each gradeo of' paper (this can be, ox- tlaifrod by experimo.nta' error~s in the initial Lest~ reandings. Tihu, it appears that there is a direct. relationship betLween breaking ami-d burstinG streng-ths. If' the rlto (break-ing; strength)/olongo1tion (bursingotrong~th)/elongatlon c-ar be checked, it th,.-1t be used. as a possible moams of' calibrating; the IMulln tester and creat'ing1 a standard bursting streng-th machine.

762~. Influence of the thickness unpon thntreng~th of paper. Wochbl. Papio:rfhbr. 49, no; 52:26&1-2682(Doc. 28,, 1918); 50, no. 3: 136-137(Jan. 18, 1919).

The tenscile s-trengths of papers, 24, IL5 and 92 -. /sq. cm).,

were 2350, 3470 6n'l 3810 meters, respectively. In the second article values for panors of sp. Fr. 1.225, 1.300, 3.tO3, 1.160, 1.120 rniV- 1.1d3 xrerc; 4604, 4734, 3233, 2809, 2881 anid 2464.

4 ____ ------~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1r" 1

Tensile Strength27

-~~~~ Institute ofl Peper Chemistry..- Measurement of the tensile -- otrengbh rif rarer. I. General considerations of the factors affecting this measurement. raper Trade J. 115, no. 5:12-18; no. 7:13-22; no. 19:16-221(July 30, Aug.- 13,.Nov. 5, 1942); Paper-Maker 104, no. 4: TS253- 60o(ot., 1942); B. I. P. C. 13:154; C. A. 37:530k

in, the sneciseon. TFolletving this clasoif'ication, pendulun, inclined- olone, hydraulic, and spring types -of instruments are described - The- . I o clirating the severaltyoofI -u sis - t p e i n tr u m n t discussed. It is bhetni that pcoidulum~-typo testers should not be calibratedd by al-lowing the test weight- to ride down on, thle lower clbmp because the follow-through of the loaded pendulum causes a serious error, porticulanily at small loads and high clamp speeds. Calculation of' the 'follow-through of the pendulum of a typical inztruncnt inthe actual testin.- of a spocirien shows the follow-through t~o uob rnch smaller than that of the pendulum. leaded with the dead weight and to be neglig-ible except when. weak papers are tested at hig~h speeds. The effects of rate of loading,, opecimon length, and specinon. width are reviewed nnd additional dataonre presented. Tensile strength in- creases as the rote of loading increases and docreasos as the specimen length inc~resces. It appears that the relative tensile strength (teonsile streng~th- per unit width of specimen) should be Independent of pecimen width for wide specimens but that it should decrease rapidly for widlths less thanr approximately half can inch. Data are given for rates of leading of 3, 6, g, 12, 15, orA 18 inches per minute, for specimens 2, 4, 6, 7 . 0 9 r and 8 inches In length, and for speeds of the stressing clamp Of 3, 6, 9, 12, 15, and IS inches per minute.

+~ ~ 76; In~itibulta, of Penner Chemistry. Meisu~rocmnt of the tensile strerrth of pe-per. II. The &cottSerig'raph, Model 35. Paper Trade Cfl 115,Y nO. 2b:14-21('Doc. 21, 1942); B. I. P. . 13:20%.

The~ lnstnz'~ient is of the pe-ndal-um type- and has two range~,s, 0 to 55 poundsI, end 0 t1o 110 nound's, -with scales g~raduatod in hfalf' around and. pO~ndS,reseetirly'. The lower range -'is effective. when onl- theo fixed weight is use-,d on the tendulum and t1)e 2irgher range is effectilve, when an ouxi1liarY we-Cigh is added to the peniduluA. The tensile scales- are rearkt d en a circular dial whorec indicator Is coupled, to the pondluithrough (•ears. The lower clamp is fastoned to a thrcreadd red. which ic motor driven throug-h a gear box and a variable, steeod nulley. Thec speed of' this lower clamp may be varied continuously 3ruto 20 inches' norl :inuto. The upper clamp is connected to tile penduluma by a chain pnssiina around and anchored to a pulley w-hich in turn is~fastenedL bethe pendulun aend is coaxial with the bearing of thes pbndulun-. The0 jaws- arecqesippcd with interchangeable anvils of' 1- ande 3-inlci wid~ths. ~he Liistrurer~t is equipped with ai recording mechanism for tree in- loa-elngaioncurves. The chart carriage is drarnn dow,,,nwrds3 bya geartrai copledt to thre lower clamp, thus assUrIng that the chart roves at speed propiortional to) the sneed of' the lower jaw. TZheper carriage" naoves hoi-rizontally and is connected! to the penrlulun by a red.

M I f1TIIlIIiiiiiIfiulinL.j IU.s..u. ' L. - ~I------~ * - _

. ----___- r·-r -L I

Tensile strength 273

The particular instrument studied is in error at a number of points along its scale. For many applications to control testing this error is not serious. For many other applications it is serious. In addition, friction causes errors of as much as 1.5 pounds. Neither source of error is due to faults in fundamental design and-both-could be eliminated by-the manufacturer.

-- 75. Institute-of Paper Chemistry. Measuremont of the tensile strength of paper. III. The Amthor universal tensile strength tester. Paper Trade J. 116, no. 6:10-12(Fob. 11, 1943); B. I. P. C. 13:279; C. A. 37:2176.

The instrument is of the pendulum type and has throo ranges: 0 to 200 pounds, 0 to 50 pounds, and 0 to 15 pounds witlh scales graduated in pounds, quarter pounds, and tenth pounds, rcopoctively. The ranges arc charged by changing the weights on the pendulun. The three scales are marked on a quadrant concentric with the axis of the pendulum, and the load is indicated by a pointer fastored to the pendulum which moves over the scale. The upper specimen clamp is connected by means of a chain to a sprocket on the shaft which supports the pendulum. The lower specimen clamp is connected to a threaded rod, called a spindle, which io motor driven through a belt, clu':ch, and gear box. In this particular instrument, the lowor clamp is drlivcn at a constant speed of 12 inches per minute. The Jaws of the clamp are one inch wide. The conpictc instrument, including the motor, is mounted upon a common base. The pcndulurm swings in a plane oprpcndicular to tho front of tho instruriment. Wnhn a pecimnon brooks,, the pcndulvm is hold at its position of mUcxtirun displacement by par.ls vhich engage tooth on the quadrant which also boars the scales. Theo ilcr jaw is brought bockc to its starting position by morin, the opocating .over to its upper position. This starting position' nay be sct at any desirod point by aljucstmrnt of thu stop on the rod which control -th^ clutch. For srccinmcr len:ths less than six inches tho up-;cr cinnmp :L:at be loavrcd by shifting its chain on the sprocket. Tlio spindle projects below bolow the level and in front -f the base during pari; of its motion, so that the irstrulont must be cst with itn base fluohlrith the edge of the table. Two scrcws are provided at the back cf the inastriunt base to pornit levelling tho inctruziont in the paine in which tho pcnduluml sa-ins. Thec instrument is equipped with a device for indicating tho elongation of the specimen. The dial of this device bears two scales, one giving the olorgation in inchos, the other giving the stretch in percentage for a six-inch specimcn. The calibration of one prcuimnably typical instrurinrt wao studied; thc greatest error found by doad-wcigit loading was 0.54i, but noasurcnents of the saall divisions indicate errors up to about 0.7% of full-scale load. This error is not serious in most applications of the inntrurecnt. It appears that the errors in the calibration are due to inaccurate divisions of the scale and arc natters that can be taken care of by the manufacturer.

M~ J 8ar - .e .. :, . ^y. y--; * .* h .--r -t.rT*:w,.

Tensile Strength 2741

766. Institute of Paper Chemistry. -Measurement of-the-tensile--- - - strcdgth of paper. TV. The Schopper electrically driven strength tester. Paper Trade J. 116, no. 9:13-l4(March 4, 1943); B. I. P. C. 13:324; C. A. 37:2933.

The instrument is of the pendulum type and has two ranges: 0 to _-……„j _ -- _ _ _ -15- pounds_an-0 .to -75--pounds-with-scales- divided-to-1/32- pouhd-andi I/4--... pound, respectively. The upper specimen clamp is fastened to a chain which passes around and is anchored to a quadrant coaxial with the ---- ' - - ._.- _ .-- --- boaring-ofrthcpon'dulum.; Th 'oier-e specimen clamp is fastened to a rod which- is draem downward.-by means of the mbtor-driven gear box. The speed of the lower clamp is continuously variable from 2 to-20 inches per minute. These clamp cpcds afford rates of loading varying approxinatcly from 0.6 to 6 pounds per second on the 75-pound. scale ard approximately from 0.12 to 1.2 pounds per second on the 15-pound scalc. The separation of the clamps is adjustable to distances of 2, 4, 6, aned 3 inches. In this particular instrument an extra hole was drilled in the rod which holds the lower clamp to permit a specimen test longth'of 7.09 inches (180 mm.). The scales arb marked on a quadrant vhich also bears teeth which engage the powlo fastened to the pendulum to hold the pendulum in its position of maxitaun dis- placement after the specimen breaks. The lower clamp is returned to its starting position by moving the operating lover to its upper posi- tion. The complete instrument, including the motor, is mounted upon a base. Errors were found in the calibration'of one instrument, presumably typical. These errors are not serious in many control problems, but they night be serious in other cases. The error appears to be due to inaccuracy in division of the scale and not to a fundamental fault in design of the instrument; therefore, it could be corrected by the manufacturer.

767. Isnard, Raymond. Analysis of cardboard. Elasticity. Paper Trade J. 73, no. 16:40, 42, 44(oct. 20, 1921); Papotcric 43, no. 13:578-586(JuJ.y 10, 1921); C. A. 15:3205.

In tho apparatus described, a strip of cardboard 1 by 10 cm. is supported on knife cdges exactly 50 rm. apart, so that 25 rm. project at either end. A graduated lever, pivoted at one and, carricu a third knifo cdec by moans of which the load is applied to. the middle of the test strip. The weight of the lever and knife cdgc is' balanced by ooans of an adjustable counterpoise and the load is varied by rnans of a rider on the lover arm. The method of calculatinr• the elasticity is given.

|. . TEsrarn, Rauynold. The analysis of cardboard. Tcnsile strength ad cori-poition. Pnpctcric 44, no. 2:50, 55-54, 57(Jan. 25, 122~); Pap-r T',ad J. 74, no. 24:51; C. A. 16:1151.

Isnardddescribes a home-rade apparatus for testing the tensilo strength of cardboard, which may be mado to indicate the elongation if desired. it is not as accurate as the instruments at pr-scnt on the market, but it is sufficiently accurate for the purpose ard is cheap and simple.

-[t --)---11·-111__

/ Tensilem Strength 275

769. Jahans, G. A. Auxiliary paper testing instruments. Zellstoff u. Papier 14, no. 9:359-360(Sept., 1934); B. I. P. C. 5:45.

Suggestions are given for the construction of'a simple bursting -_------e-and a-tensi-le strength testing-instrument-f f--uffic'ibnt accuracy for practical operation when only comparative results are required.

7'7. Kicnzl, Hubert. Breaking strength and extension. Papier- Fabr. 32, no. 48:482-485(bec. 2, 1934); B. C. A. 1935B:222; C. A. 29:6054; T. S. 101:238.

The product of breaking length and stretch of paper as a measure of its capacity to absorb work is discussed.

771. Kirchner, E. Breaking length and breaking strain. Wochbl. Papicrfabr. 48, no. 36:1581; no. 41:1792(Sept. 8, Oct. 13, i 9 17).

- Strips 15 m. and 9 mm. were tested with 3 kinds- of papers; the results with the 9-ms. strips were 2.3, 3.7, and 35.5% loss than the calculated values.

772. Korr, R. Uniform testing of' papor with reference to strength. Papior-Fabr. 27, no. 36:558'-562(Sept. 8, 1929); Wochbl. Papiorfabr. 60, no. 36:1107-1ill(Sopt. 7,. 1929); Zellstoff u. Papior 9, no. 9:612- 514(Sept., 1929); C. A. 24:3366.

! " - Seven samples of commercial papers were tested for uniformity in tensile strength, fifty tests being made in each direction on adjoin- ing portions of the sheet. Under those conditions the maximum difference in 50 tests varied between 9.4 and 33.4%h, the average deviation from the mean. being + 1.8 and + 6.1!, and the probable error of the mean between + 0.23 anl + 0.7'4. Scamplos taken from different sheets might be expectcd to show ,reator divergence than this. There appears to bo no definitely greater uniformity in one direction than in the other in the samples tested.

773. Korn, R., and Boerner, Cl. Experinents rith 'the Schopper torsion- tester for determining the number of twists in cable paper. Wochbl. Papierfabr. 65, no. 51:897-899(Dec. 22, 1934); Papior-Fabr. 33, no. 1:2-5(Jan. 6, 19355); Zcllstoff u. Papior 15, no. 2:52-54 (Feb., 1935); Papier-Ztg. 59, no. 95:1642-1644(iNov. 28, 1934); B. I. P. C. 5:1350; B. C. A. 19355:143; C. A. 29:6054; T. S. 101:238; 102:10; 103:27.

The number of twists under a definite load up to the point of rupture decreases as the paper thicknoss increases. However, no mare:d differences were shorn by papers ranging 'rom32 to 92 grams per square motor. Differentiation of such.papers is more easily carried out by determining the load of rupture in the maclino direction..

amWf Ins -- W ______------~z^~-...- = - nnr·

Tensile Strength 276

774. Landt, G. E., aid Rulon, S. A. New interpretations of structural aspects of the paper sheet. Paper Trade J. 111, no. 4:32- 36 (July 25, 1940); Tech. Assoc. Papers 23:282-286(Junoe, 1940); B. I. P. C. ]0:461; C. A. 34:8277; B. C. P. A. 1940B:783.

This paner is an exploration of- certein- fundamentals- of -p-pi struc- .. turc. It is postulated that ell the physical characteristics of a sheet of paper must be related to (a) the primary valence linkages. in the cellulose chain molecule, (b) the forces of molecular cohesion: between chains, and (c) conjugated surfaces. When a sheet of paper is ruptured in any physical test, the feltod fibers must be twisted or compressed to destroy the conjugated surfaces. When a tensile stress is applied to a shoot, the fibers will first slip whore the conjugations are dis- rupted; it will then shear along the lines of cohesion parallel to the fiber,, and finally break at the atomic linkages across the fiber. Using cotton pulps, it is shoin that the tensile strength is higher for the pulp having a reater viscosity; the tear shows the opposite ten- dency. Tvo pulps, with viscosities of 626 and 129 seconds and frccnoocs of 695 and 715 cc. had tensile strengths of 8.5 and 4.0 and tears of 114 and 14i. A rag sheet from a pulp of high viscosity and beaten for 30, 90, and 180 minutes (freoncoses of 695, 205, and 130 cc., respectively) hod tensile strengths of 8.50, 21.56 and 29.12; the tears were 1.4, 128, and 137; this represents an increase of 244% on boating. A similar change is produced by the action of zinc chloride on a shoot of waterloaf paper. Thus a sheet with a tensile strength of 15, on treatment with 68 or 71% zinc chloride for 1 minute at 60° or 120 C., had a tensile strength of 21.1 or 44.1; the tears were 67, 80, and 129, respectively. Other experiments show that the tensile strength is increased in the direction of the tension, values for the machine direction being much higher than in the cross direction. There is a theoretical discussion of the results, especially of the hydration theory.

775. Leunig paper tester. World's Paper Trade Rev. 79, no. 9:788, 790(Iarch 2, 1925).

A description is given on an improved model of the Leunig paper tester. The tester is fitted with a graphic recorder which enables the operator to detcrminc tho proportion betreoen load and elongation at any moment of the toet. The1 recorder can be applied to the motor- or hand-driven instruiont. The standard strip is 15 mm. wide and 180 nn. long. The English strip, 5/8 inch wide and 12 inches long, is the nearest equivalent.

776. Lofton, R. E., and Synder, L. W. Results with testers for measuring tonsilo strength of papor. Paper lradc J. 86, no. 24:65-66 (Juno 14, 1928); T. S. 88:199; C. A. 22:3296.

Six typos of testers wero studied; these are described briefly, but the nanmo of the manufacturers are not given. In addition to such mechanical details as runged-ncs of construction and ease of calibration, a good tensile tester should fulfil two roquircrcnto: The results obtained by testing duplicate spccinons of the same sample should check reasonably well and the average (chcclcod) results should bo reasonably near the truth.

I---- * 1 T_,si.. S-c,-h 277

The results can. harfdly be cxcte-c tchckrcCI other within. about 5c/; this

-- - figure may be tak-en. as a measure, of' the heterogeneity of the paper. Hone of' the Instruments shoved any appreciable change of' accuracy in different ,parts ci' the scale, vti the lImits exaniinod. An instrument may give results vchich chock each other closely,and. yet all the results maWy be far from the truth.

--- 777. ~~~-Messmr,7r1 11; B.'c -Pper tct~ing ntdh~hbd Pzc. Tech.,Section, Paope: Makers' Assoc. GCt. Bikitein Irelaond. 8, part l:77-87(Oct., 1927T); World's Paper TraOde fld1v._87, no. 15:1164, 1166,W.68;. no. 16:1252, 1254, 1256;'disciission, no. -17:1362, 1364-1365(Aoril 15, 2?, 29, 1927); Paper-. -Makecr 75, no. 5:486-487, 489(ilay, 19c27); Paper i-takers' Me. J. 65, no. 5: 125-l186(may, 1927); T. S. 85:240.

The Sehopper tester was introduced -into Er-,lard cc- the Inunig tester. The principle of using, dead. weight to apply the breaking load, as used Today, is exactly the some as in the first machine. Certain improvements xre detailed,. _Rcpcrine'-nts have shown that6 the results of tensile strcergth tests depend on the speed at which the load ia applied to the test cample. A menan of determ,:i7dninc the correct speed. and checking its constancy js nrujvidced in. Alt's diaphroag aj~paratuis; it coy). be used as a recorder to register the actual tcstling speed or as on apparatus for predetermiflinC; thes speed at which the test should be carried out. The ~'aphic recorder, fitted to a paper tester, records alo0ng the horizontal axis the breaking strcenth and along7 thes vertical axis the elongation. The breaking length is that length of a strip of)i paper of any uniform width and thickmcss which, if ruspended. freely at, one end, will break,. by reason of its owrn weight, at the point of suspension. This r.Iethod. of expression indicates tile specific tencilc strengthi of the sheet, irrespective of the wtdth

of the tentu strinl. The11 breaknigt lcrgth can be calculated fron the breaking strength and the subpotaces of the sheet; it is genracrlly expressed in rioters.- * If' G Wish weig~htu in ;~'an of a strip -180 =ai. long and the breaking, streng,'th in- P ,th hg thle brancing leng-th is 0.1SF/c- !Im. The Lenigr tester is ¶r-nuuatentI, in the Brlitis, system of 'Jigtland mno-asres.

77.Mcetxct, i.Graphical calculation of tearinjg lengIth and 1oat. Pm~ier 34, no. L:363-361%, ~167-36G, 371l(April, 1931).

A chart iscivcn fromn vahich can be calculated the tearin g lengtLh when the weight part square moter and the tearing load- arc known..

77. Motor driven tensile strength tester (Pnthor). Paper Trad~e J. 86, no. 11:58(March 15, 1923).

* This teste r is bult' or, the :inclination ba)lance principle with the pendulum hovinC at maximun ang-ular swingr of 45 -degrees. The load is balanced by the inclin atLion of the lover aind is reflected directly to -the quadraont scale. The pulling clamap is attached to the upper end of a guide. tube which gets its uniform linear speed of 12 i'nches per mnitrte through a chain and sprocket driven by the motor through the speed rc- duction unit. This u-nit consists of' a double sot of worm gears running in heavy annualar ball. bearing lit wi oil. 1)th. A feature of the motor- driven unit is the sealmed menrcury-to-mercury contact switch through which the current is fed-O. The operation of' the tester is~described. I

t-J - _-__ - I - - -- .-. - n.M. *'fl liii-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ITensile Streng~th 273

~.. 780. National Association of Purchasing Agents, Inc. Corrugated fib-reboaril. shipping3 containers. No. 19, 1934. £UP.

Tensileo Str-itli7(, Test. This test is only applicable to individual ~listsatinebord nd orrgatngmedium-- it cannot be applied, to Combined

board or finished bores. Tout specimens shall be cut from unrw'inkled, -

-- uncressod. anid. vmblemil.shod shocot, four each with the grain runninDg the lonc, way and the chart way of' the specimens. The specimens mist be cleanly anid i i - accurately cut, with parallel opposite edaes,- not less thtan 12.7 mnn I (0.5 inch) nor LlorLethman 25.4 mm (1.0 inch) wide, and of such length that I when clantued in the toter the distance between the jawss shall be not less Mien 5 tiesnr more than 12 times the width of the samnle, but in no cauie shall- they be loss then 140 mm. (5.5 inches) lonr. The exact size shnll. be determiynd according to the tester and itrs convenience iLn opera- tion. The specinen shall bo firinay and squarely clamped in thJe jawS of the clamps and thoe stre~ssing~clomp then operated at a constant speed of 30.5 cm. (12 -Incites) per minute until the specimen breaks under the tension. Testls in which the specimen breaks at or in one of the clamps shall be dis- regarded. The tester should be atf such capacity that all tests 1.ill fall

I within thd range franl 10 to 90% of its capacity, Tha breaking loand shall be recordedl. Lo the nearest 2%~of the total indicated reading and shall be calculated in kilog~rams per 15 =r. width of the specimen. Not more then. one of the four tests- in. each direction at' the stack nay fall below the specification, with the average aof the four tests meeting the reqlulrdnent, for compliance. However, if 'the initial tests in either or bath directions shall fail to cenply, a series of 12 re-tests of either or bothi (accord- ing to the failure) shall be naadb,. of which not more than three tests Ynsy fall below, with thea averarge of all 12 tests complying With the speci- i_'iation, for aceon3tanco.

Y(8L-. National Th'~reau of Standards. Stuructutral fiber insulting, board. 3-4 cd. Cormrercial' standard 0S42-43. 2943.-

The test -far torsile strength slhall bo as follows: Forl'nechl snrinp" Spy cincens 2 inches wide- and not les,-s than 10 inches long shall be clean cut pnrallel to the Jlong~~St direction of the board~ and at right an-les thereto. Thc: distance between. dents shall be not less than 6 :ineheC. Besults on snecimens under. test thant break, within. 0.5 zinch at' the jawls shall. be dis- regardedt. The =achine speed shall be set for the openings between the dlames at the rote of 2 inches per minute. The specimens before beingo ninced in the testing3 machine shall be assured for width and thieconcss to thec nearest 0.01 inch. The tensilo strength shall be taken as Lhe average of three specinens from eoac direction of the board.

782. National Bur-nu of Standards. The testincg, of paper.. Circular Ne. '107. Fejb. 12, 1921.

A brief discussion of tenscile strength in gi-ven on) paes 15-17, with en illustration of the apparatus.

783. 'lew tester for taper (Perk.ins tensile tester). Pulp Paper Mnag. Capada 20, no0. 18:LOI(May 11, 1922); Paper Thade J. '74, no. lC':47(Anril 20, 3-922).

M I I - I1 . I - ^1 * , .a. . ;

Tensile Strength 279

The Perkins tensile tester is of the vertical type, hydraulically operated. The cylinder is filled with a liquid which is compressed by a solid mental plunger, which fits the cylinder with a very accurately ground and lapped fit. This plunger is attached to the upper or station- ary clamp by eoans of a stirrup which brings the pull in a straight ver- tical line without cramping and without side pull. The lower or moving clamp is attached to a vertical screw vhich is operated by cars of a- .--.-- - handwhcol on-the sidc of the machih5-'--Tn- pressure is indicated on a specially radc standard gage vhich is acted on by hydraulic pressure fronm the cylilner. Rcnovablo and .intcrchangoable stop gages a-r -provided which nutor.ntica..ly separate the clamps 1, 2, or 4 inches aparb, as desired, so that strips of those lengths may be tested easily. The operation of the tester is described.

784. Nose, Folix, and Sadlcr, Hars. Testing the stronth of paper witl tlhe punctur dynanonoter of F. SchIubrt. Wochbl. Papicrfabr. 64, no. 21:360-3i3(May 27, 1933); C. A. 27:5971; T. S. 98:14; B. I. P.. C. 3:271.

The Schubert puncture dynanomotor is used in the textile industry for strength testing of fabrics, the test being a puncture of the shoot by a plunger or bolt of definite dimensions. The authors compare the application of the now instrument and of the Schoppcr tensile tester to papers and pulps of various boating degrees. Unbeaten stocks show greaterr fluctuations in results with the Schubert tester; however, uniform results arc obtained in the use of well-beaten stocks. Tables showing results with the two testers on papers of various compositions ore given.

785. Oliver, Cyril V. Variability in results net with in paper strength testing. World's Paper Trade Rev. 93, no. 8:660, 662, 714; no. 9:754,, 756, 758, 796, 798; discussion, no. 11:938, 940, 942, 994, 996, 998(Fcb. 21, 28, lMarch 14, 1930); Paper Makers' Mo. J. 68, no. 3:103- 109(.iarch, 1930); Paper-Maker 79, no. 6:595, 597, 599-605(June, 1930); Proc.' Tech. Section, Paper Makeors' Assoc. Gt. Britain Ireland 11, part 1: 53-74; discussion, 74-84(0ct., 1930); B. C. A. 19313B:582; C. A. 24: 33656, 5484; T. S. 92:157.

The electrically driven Schoppor tensile tester was studied. The makers stipulate 100 iri. per -iinutc downward movement of the moving jaw. The in- strul-cont is capable of adjustment to four different longtha of strips; weights are supplied for readings up to 14 and 70 pounds, respectively. A . strip 5 cm. long gave higher results (8.2, 8.5, 15.1) than one 18 cm iong (5.1, 7.5, 13.3). The use of different weights for testing papers with a tensile strength of less than 11 pounds gives rise to snall differences in the results; the large weight gave slightly higher results. in c series of tests on kroft paper the naxi.mun deviations were 5.6, 2.8, and 7.3^, and the avoraoc deviations were 2.2, 1.2, and 2.9%, respectively.

786. Paper Makers' Ansociation of Great Britain 8: Ireland. Tcchni- cal Section. Poper Tosting Committee. First report. London, The Association, 1937. 85 p. Also issued, with discussion, as Vol. 18,

1 :i

~-1 :M Tensile Strength P

port 1A, of' thoe Procoeding~s of twhe Technical Section. Sea also Worl(I's Pdpor ZhradoeRev., Tech. Convontion to-.,I46ioh, 1937:It-72; B. . P. C. 7:350. Speci1fications are g3iven for the tenasilu t~ot using the Schoppcr tester. Theitensile strength test gives a geoneral indication of the quality of noner rather than definite information as to its suitability for any

------npcfif toproe.- csntcessary tvbaso-the test on eny.-fundaor-- nontal consuiderati1ons o.r relate it to rrthods used for the tensile testing if other rmterials. The -iiediote roquircnents for a satisfactory spec1- - fication arc that it sh2all be convenient to -apply, allow of reasonable speed of testing, be of suitable sensitivity, and give consistent results. Tetesting condfitilons (e.g., rate of 1.oaftiig) should either be the same for different breaking 100(18 or else continuously variable. The factor neost difficult to snecify, is the rate at which the load, shall be applied. The tine rnay be shortened by usin L hohevier weiTght, (and. correspondingly fLoro rapid rate of'laig for papecrs ovecr 14 pounds, -tho ratio being,, 1:5. 'The effect of' thle changec in rate~is not very clearly known but nublishod. results indicate that a definite change in strength con be introduced. In the presentt, specification, twhe ratio of rates of loading is3:5 (that is, thec weight is Live tines greater but the speed is re- d-uced to a thirC.). A change of rate of loading with the normal type of instrui-ent can be obtalned, in the following ways: Bly using one clamp speed and different positions of' the weight on the arm; by flaing a constant speed and. a ,-weater ran-e of' weights, (e.g., in the ratio of 1:2:3:k:5); by ~:irga single euqc and. different speeds; or by a combination of weig1hts and sneoeds. Thesev aru discussed. Results rer given which show the tendency- of the strength to rise when measured on a shorter strip; their are not sufficient, however, to establish a correction factor and., in any case, varying, uniformity in the paper may be expected to affect the relation-shin. Similar results are obtained from single strips and folded strips, the rmagnitudoe of errors being of the samec order in. either case. Stubstaintially the same results are obtained. whether single or rmlt~tlicshets ore used. In the, ease of . Present data i-dicato that small vori-inions in,~the rate of loading do not affect the results. The results arc expjressed as pounds breaking strain, kilogram breaoking, utrair2 (calculated for 1 inch or 1 cm. width) or breaking lcnrelth in merters.

787. Physical testing of popor--tennile strength of paper. Tiring's P-ener Zmster 1, no).. 2:1<4,(19356).

The tonsil:- strength of paper is the load required to break a parallel strip of a stated width (usually 15 un). The arbitrary conditions ac- cenDted on; standard nrc: (1) that the test be carried out at 700 F. and

I' ®;'~" relstiv.c; ln:utdity on strips norcviously conditioned in that atmos- phere. (2) That both endse of' the strip for test be cJlamped in jaws -such thiit the strip, icuigthe clomped ends, lIe'InaI one plane. (3) That the tensile load, be tipplied along the center line anti in the nlanoe of thle strip. (4) rfllat thle distance between the edgeso of the jaws, or the actual lenJ,th of strip, under test, be 130 rn. (for pulp sheets, 100 at.). (5) That thle tennsie xoad be gradiually increased at a practically unri-- forna rate til.l fractlureo ss (6) That the load be applied at such a rote thnt fracture scours in, about 20 seconds. The tensile test Lloax~ac le'ss conniex: sot of proportion than. most other tests; the Tensile Strength 2l

result depends primarily upon, and is almost proportional to, the basis weight of the shoet; it also depends upon the degree of bonding between the fibers; to .saon extent. on the average fiber length, and to a minor-- extent upon the flexibility of the fibers and fibrous structure. The boCt strips must be cut accurately parallel and with clean edges. For un accurate test at least 10 strips should be cut from both machine and crosc directions of 1C sample shoots of paper. There are four typos of inoetruments: spring balance indicator, load applied by lever; hydraulic -diphragr.-and gage indicator, -lead applied by screw; inclined plane typo; pendulum (standard) typ.' This first type is represented by the Schopper portabtR instrument; the second.type is the Perkins instrument; - the inclined plane type (developed for textiles) has been adopted for paper testing by the Scott Co. The last is particularly adapted to the graphical drawing of the stress-strain curve and fatigue curves. A home- made apparatus is described also.

788. Radleggcr, Max. Paper testing with the Schubert puncturc- dynamometcr. Wochbl. Papiorfabr. 64, no. 39:685-687(Sept. 30, 1933); C. A. 28:1529; T. S. 98:296; B. I. P. C. 4:63.

The construction and operation of the apparatus (Noso and Sadler, Wochbl. Papicrfabr. 64:360-363(1933)) are briefly criticized. By making certain (not stated) changes in design and taking proper account of the deflections, the results obtained with either strip or round samples may be calculated to tensile strength with reasonable accuracy. The sample must have negligible stiffness.

789. Rcnnici;c, Norbert G. Manufacture of paperboard. Chicago, Fibre Containers, 1939. 47 p. Chapter of paperboard testing in Fibre Containers 24, no. 9:20, 22, 24, 26, 28, 30(Sept., 1939).

Tensile strorgth. This test is applicable only to single pieces of paperboard.. The oamplcs are 0.5 to 1.0 inch wide and of such a length that, when cllaped. ir' the testeor, the distance between the jaws will not be lceo than 5 tincs nor more than 12 times the width of the sample. Thne can3pl is clorped scuaroly between the jaws of the tester and a strlcscing frcc o:' 12 i:ichcs por minute is exerted; the point at which failure occurs is recorded. Tests in which the sampi.e breaks at or in one o0' the j.'cra'r.: disregarded.

70C. Ru'r.emn:n, Fcitz. felf-recording strength tester. Papior- 'Vbr.25, no. 577:51(1927); T. S. 89:167.

The R!hClcmann apparatus for determining the tensile strength and elasticity of single fibers photographically is described.

791. Schopper, Alfred. Apparatus for testing the tensile strength of flexible materials. U. S. patent 1,797,734(March 8, 1929); J. Tex- tilo Inst. 22:A642.

A. apparatus for testing the tensile strength of flexible materials ^ ~by inflation, comprising moans for supplying gas under pressure to one '. ~ side of the part under test and exchangeable means of geometrically - *' simrilr configuration for holdirg said part.

.'Z.VII S,1 EL6Paua58 * - .to~~~~~4i ~~~t4' -*7T

Tensile Strength22

7¶.Schopper, Alfred. Determination of' the marginal strength- o-f paper and board. Papiet-rabriK 38:157-162(i94o); C. A. 355316; B. I. P. C. 11:210.

Experiments were carried out with a Schopper torsional ctrength tester. A square test sheet is subjected to torsional strain, operat- ing at the two outur edgesa, through -t-wo ba-lanced forces which are vertical to the axis of the test shoot end which effect a marginal ter i rslsi atrina oet(termed the "marginal moment"- ,whchisautonatical-ly mceaured by arccordine device, From this the

Eithr coot~hicmos takn aoneor considered in conjunction with'

value for marginal tothicu- tflou othtetsetth concept of Lerug-bar" has boon avoiOded.

79.Schoppor, Alfred. Schopper's rapid paper tester. Vereins Zellstoff U. Papiereiiemikor, Itouptvorsain-lunr, 1911:48-53; Wochbl. Papierfabr. 43, no. 2:94-96(Jan. 315, 1912); Papior-Zltu. 37, no. 5:140& lh(ion. 13, 1912).

An illustratecd description is given of the rapid paper tester and its operation.

194. Schopner, Alf'red, and Dalen, Gustav. Apparatus for testing tensile strength. U. S. patent 1,819,719(Auge. 13, 1951); T. S. 94:280.

A Mullen-type tester is provided w-ith an elongation indicator con.- sisting of a pointer mounted on the shaft M' a pulley around which passes a thread, one end of' which is connected to a plate- restingr en a test pieces and the other end of which is cenorocted to a. coiunterweight. ThlIectrisal or mechanical means arc, provided tc apply a brake to the pulley when tlio test pioce bursts so) as to automsatically arrest the indicating pointer.

(95. Scheppor'si strength tester as a rapidL testCing apparatus. Panierf-nbr. 12, no. 17:-431-J-82(April 24, 19Th); ef. no. 20: 577(May 15, 1914); Puilp Paper Mag. Canada 12, no. 12:575(June 15, 191.4). A cormnlete strength test with thec Schopper apparatus occupie scon- siderable tinec in anay cases. The following ranid method affords, a sufficiently exact test. aut only one stbrip from each direction of the paper to be tented, add the two breaking loads (in gS.) and divide by three times the weight per square meter in. grams. In. order to obtain the breaking strength in meters, the number obtained =ist be rultiplied by 100,000. Possible errors ca-)narise owning, to only oneo strip instead- of five being used, and thereby obtaininC. Lin ave-rageC which is not sufficiently exact. In) addition, the percentagec of moisture in. the~ pener is noat taken into considcration. Since the~moisture at 65% relative humidity is ThetwOen 7 rind 10%1, tho reslts -of thle teats will be about 55 to- low. The formula on whiich the nbo;-cU test' is based is I I Tensile Strength 283

796. Schubert, Fricdrich. Cloth puncture strength tester. Leipzig. Monats. Text. Ind. 45:307-308, 347-349(1930); J. Textile Inst. 22:A155-

A description is given of an electrically driven dynamoetor in which the local strength of fabrics, paper, etc., is determined. The theory and practical value of the test and the calculation of the ro- .ults are flrthordiscussed. -

797. Schubert, Friedrich. Local examination of the tensile strength of textiles, rubber, etc. A new method inf placo of the ordinary tearing test. Cheou.-Ztg. 52, no. 94:913-915; no. 104:1018(Nov. 24, Dec. 29; 1928); 55, no. 14:134-135(Fcb. 18, 1931); British patent 301,-24(Nov. 24, 1927); C. A. 23:1187, 4103; 25:2025.

The fabric is weighted by a bolt producing a fissure of only a few rn. The new process is rapid and exact; it is very economical on account of .the suall size of the fissures, thus enabling one to do numerous tests with a snall amount of material. Cf. Radleggor, Wochbl. Papiorfabr. 64:685(1933).

198. Schubert, Friedrich. Method of and arrangement for examining the local strength of fabrics, paper, rubber, and the like. U. S. patent 1,836,621(Doc. 15, 1932); T. S. 95:75.

i The principle of the invention consists in cutting a hole in the material to be tested, hold under tension in all directions, in the main I testing direction at both sides of and close to the sides of a pressure tool, and subosquently allowing the tool to operate on the severed piece secured against sliding. Thie test is carried out with a pressure tool of rectangular cross section, which is provided with cutting edges ex- tending beyond those cnd of the to-l and corresponding in width to the siz- of the pressure tool. The test piecc is placed in a special clamp which is mounted in place of the bottom clamp of a tensile-strength tostjr, ond the pressure tool is suspordid frou the chain of the upper

i 799. Scott, Henry L., & Co. Combination tonsilo tester. Instruments 3:477-478(1.930); J. Textile Inst. 22:A313.

The combination tester for paper, etc., is built on the "dead weight" principle. The pendulum swings on ball bearings. The force exerted through tleo s3anpo raises tho pondulun, the pull in pounds being indicated by the pointer on the dial. The toothed rack is one inch wide with teeth spaced 12 per inch. Six gravity pawls travel on this rack and hold the pendulum in the position at break until reacet by raising the pawls and rcturninig the pendulun to the vertical position. The stretching screw operates smoothly and posses t!urough thec coar box without revolving. 8 This obviates hie possibility of the yarn becoming entangled in the L'.)ving parts. 'Tcnmachino is operated by two lovers, one for starting anor.d the other for rororcing and atopping. The automatic reversing and stopping of the machine is accomplished by moans of an arm attached- to the stretching screw and sliding on the reverse stop rod between two adjustable collars. Theo jaws nay be set at any desired distance apart and after each test the machine vill automatically reverse and stop ot the original starting position.

Lft f I' Llaoi ------~~~~~~~~~~~~~~~-~ ~ ~ 1~n-f

Tensile Strength 2C4

800.- Scott, Henry L., & Co. The incline plane principle as used in Scott testers. Paper Mill 59, no. 38:24(Sept. 19, 19356); B. I. P. 0. 7:52.

The most accurate-method-of- testing-fatigue,"-tcrsiil-e, elongatio n, .-...--.----... ,r other pulling stresses is by applying load to the specimen itself at a constant and uniform rate; the older machines, however, -applied------the tension-to- the samplA-in Vorying amounts per unit of time. The incline plano principle used in the new testing machines applies a definite amount of load per unit of time, regardless of whether the sample is long or short, elastic or rigid, ductile or plastic. Greater accuracy and simplicity are claimed for machines of this type.

801. Scott, Henry L., & Co. Tensile testing machine calculating attachment. Instruments 3:467(1930); J. Toxilo Inst. 22:A314.

The attachment comprises a weight adjustable on the balance arm of the tensile testing machine, making possible a direct reading on the dial in accordance with correction factors of- ny predetermined table.

802. Sindall and Bacon. The strength of paper. Testing two pieces at once. World's Paper Trade Rev. 59, no. 22:1001-1002; 60, no. 7:297-298; no. 10:437-438(May 30, Aug. 15, Sept. 5, 1915); Paper 12, no. 1:23(Juno 18, 1913).

Using a standard Lounig machine, tensile strength results were ob-. tnincd of a writing paper (16.5-lb. domy) by testing from i to 10 strips - t the sa.er tinc. The results calculated for one strip from the ob-- . sserved results wreo: 7.5, 7.25, 6.67, 6.45, 7.2, 7.1, 7.2, 7.1, 6.8, *1 'and 7.2. The results seen to indicate that the strength readings are proportional to the number of strips; the average of all readings is 7.05 pounds, whereas that for a single strip is 7.5 pounds. The gradual addition of one strip for each succeeding c.pocriomnt does not appeal' 1¶ to create any serious difficulty in manipulation, as the average readings with the greater number of strips are fairly constant. The second article shows that similar results are obtained with a wood pulp paper (6-lb. deny); the breaking weight of the paper found by testing a oiurbor of single strips was 3.J, vwlereas the average of all the readings was 3.G2. In the third article the effect of stretch is discussed. If two strips of equal length and width arc inserted in the Lcunisg machine, one being taken from the machine direction and the other from the cross direction, it is clear that, when the tension is gradually applied to both, thc mnchino-direction trip, though stronger, will break first because it sti'ctchc:; loss than the other. The weight necessary to break tho former is largely used in merely stretching the cross-direction strip.

805. Szoice, Paul, and Fra'nkel, Oscar. Brealrin strength and elongation. Papier-Fabr. 33, no. 25:213-214(June 23, 1935); B. I. P. C. 6:378; T. S. 103:192. -...... i-

Tensile Strength 2F;

-- - With reference to-an earlier study by' ci .o, the authors show that neither breaking strength nor elongation alone defines the quality of paper or its resistance to mechanical stresses, but that both factors arc required for determining these properties. They illustrate their theory by graphs and mathematical formulas.

....-- -- - 80_4 TAPPIT. Tensile breaking strength of paper and paperboard. TAPPI Standard T 404 m-44. 1 p. Paper Trade J. 83, no. 11:53-54(Sept. 9, 1926); 86,.no.-8:215(-Fcb. 25, 1928); 102, no. 8:133('cb. 20, 1936)-; 112, no. 6:33-34(Fob. 6, 1941); Toch.. Asoc. Papers 19:271(Junc, 1936).

805. TIAPP. Tensile tester testing board. TAPPI Special Reports No. 1:81-82(1926).

The question discussed related to the use of tensile testers for coarse boards, chci, as jute lincrs. Of the nine mills replying, only one usc( the tonsilc tester; this mill stated that the test was of value in 0cCtoirainirg diffterriccs between machine and cross direction; however, the test is inconveni.nt and slow to perform. It is doubtful if the tjnailc test is as useful as the Mullen for the routine and control testing of boards. .Anothor mill reported thc use of the Perkins tensile tester for corp3aring the strength of various boards from 0.2 to 0.5 inch blut did not us -itfor mill control because the desired informa- tion was obtained with the Mallon tester. The tensile tester was used for dry felts for the manufacture of prepared roofings.

806. Tensile paper tester (Marshall). World's Paper Trade Rev. 75, no. 5:k68(Fcb. 4, 1921); Paper Trade J. 75, no. 3:40.

Tho machine dep-nds for its action on the compression of the liquid contained in thc diaphragm, the pressure being produced in the diophrnsn by nooan of a tensile force applied tlirouh the paper by a hand wheel. Thile pressre is roGistcrod on a dial in-term of the weight applied to the strip of paper under test and the tensile strength is expressed in thc nurbcr of pounds pull which tle strip of paper supports up to the point of break; an inportant advantage of thelachino is that the ton- silo strength in 'oth the nnchine and cross direction can be dotcrEincd with cqual oasc and certainty; another advantage is that the width and lcCgth of the strip nay be varied at will, the rachinc being capable of dealing with strips up to 12 inches long and 2 inches wide. The stretch of the paper under tension is indicated on a graduated scale under the left-hand screw clip, front. the rcading of which the percentage of stretch nay be readily ascertained.

1925).

Of 46 mills having telsilc testers, 19 used the Standard Schopper ,'-advuatocd :in . oadLl14 in pounds; 2 used the Rapid Schopper (pounds); 7 used the Perkins tostbr (pounds); 10 the Scott (pounds); 1 the 3ickleo (pound:;); anl ihcd its o paper is primarily a dis- cucsion of the quostio;:. -f graduation in pounds or kilogramI. For com- morcial or m.ll wor- the pound was greatly favored. ' --', '- s^ ^ ...... '-~ffi,M "filf.nr, .*. *.1-. '' 71'/' 1:il.:Y1tS ,

Tensile Strength 28e

808. Tensile testing machine for cellophane, transparent paper, etc. Silk & Bayon 13, no. 6:468(June, 1939); B. I. P. C. 9:487.

An illustrated description is given of a testing instrument for _ ..-. _ _. ac-.curatoly._determining-the _b-ea!ing-strenRth and- e longation-of-c ello--- ._....- phane, transparent paper, and similar material. The machine is of the inclination balance type with a roller for the weight lever housed in - - -'ino-ball bearings and"in'whhich-the medium fromrth ujppor grip tod . . -- t le indicating motion is a-flexible steel tape. - -

80. Thwing-Albort Instrument Co. Thwing-Albert clectrohydraulic tensile strength tester. Circular M-388. n. d.

Illustration and very brief discussion.

810. Wernce, A. W. Manufacture of fibre shipping containers. Chicago. Board Products Publ. Co., 1941. 70-p.

Tonsile Toster. The tensile test, despite the several conditions specified, is one of the least arbitrary tests for the strength of paper- board and measures a less complex set of properties than most other tests in common use. The results depend primarily upon, and are almost pro- portional to, the basis weight of the sheet. They also depend upon the bonding between the fibers; to some extent, on the average fiber length, and, to a minor extent; upon the flexibility of the fibers and fibrous structure. In general, the test results parallel those from the Mallen -tcct, but the latter, in addition to the factors mentioned, are also - grcctly influenced by the ability of the paperboard to stretch during thc test. The tensile strength of paperboard is the load or weight, usually expressed in killograms (1 kg. = 2.2 lbs.), required. to break a parallel strip of a stated width, gcrerolly 15 mm. (19/2.inches). The arbitrary conditions accepted as standard are: (1) That the test be carried out at 70° F. and 5'%rolet.i.vc htumidity'on strips previously conditioned in that atmosphere; (2) 'iTlat both ends of the strip for test be claupod in jaws such that the strip, including the clamped ends, li-s in one plare; (3) That the tonsile load be applied along the center line and in the plane of the strip; (4) That tho distance between the edges of the jaws, or the actual length of strip under tcct, be 180 mm., except for pulp test sheets, for which 100 mm. is the standard distance; (5) lTat the tensile load be gradually increased at a practically uniform rate until fracture occurs; (6) That the load be applied at such a rate that fracture occurs in about 20 seconds. The tensile test is very widely used to define the "strength" of paper- board. Although it takes longer to perform and requires, as a rule, a more expensive piece of apparatus than the ITullcn or Cady test, it is better dofi.cd , is less empirical, and is a more roprodvcible test. As rnost tensile testers also incorporate a mechanism for determining the percentage stretch of the paperboard before rupture, at the camo time the tensile test is madc,. a knowledge of both may be gained without appreciable additional work. Itchl more information is then available than from the bursting strength tect only; norc especially if the two I Ue only poispcia ly if the two Tensile Strencth 28'7

properties of' tens ile strength and. stretch are determined in both the

machine (grain) and cross directions of the board. There is no informs-

L ion given by, the bursting test which may not be deduced from the te-n-

sile and stretch tests; cornegquently, for scientific work, the latter

-- -- te~~bsts are tuch rfor:2i The ratio between the tensile tests in, the

p%Žqh e nu cros 41-cc bir5 rve useful information regarding the mannol:

in witch the~ she ol'; of' panerbonrft has been s.ade, and occasionally this

rncmosusot~s~acoptrl~teu-for-board. -no~Ide-on cylinder mnchi-nes,---

or w-ith a Wourdrinier, 0or adjusting the shake and other fmeters eon-

4 trolling, the un formity of strength in both directions.

Wet Tensile Strength

8'll, ~AdI'-to W. E., a C. Measitromemnt of' wet. strength.

Foret Poducs Lboratoriese of Canada, Quarterly Rev. Rbo. 4:12-17

(Oc1t-Lee., 1,930). Processed.

A preliminary report i s -'ivanr of a method. for determtining; the wet

strength. of puln test sheets. The sheet is made on the English -sheet

machine, and pressure I's applied at any one point on the sheet. The sue-

Mosn built up by the recsistance of sheet, is measured on a manometer. As

soon as a sufficient suction is built up, the sheet bursts;. the pressure

at that point re-,presents the breaking point of the sheet. The maxim=

reading on. the r-an~ometer indicates the, strength of the sheet. No further

information about this test seems to have been published.

-812. Fineh, J. M~. Weot strehgth tester for paper. Bell Labs. Record

IC), no. 1O:309(June, 194l); D. I. P. 0. 11:417.

A 5eteip of paperis In looped under a horizontal rod. in anl assembly

which :a i.old b, the own jaws of a papecr testing moonhino. AThe two

ern"! o;' the 1oo+) are elaLalpout in the u-~pper jaws. Below the rollis a container

filled vith waterv which canL lie~ ra~isedf so as to irnorse the paper. The

o-anrora uo gives rel~nlcti -c sul-ts in - tests en wekonneimons

Lnuc` ccn absorbent nrapY- and alsao on very thin tanper like that of Condensedr

rjsewhc is,, only 0.0003, Inch 7m th-icknes~s. The1 test is important

in i>:eas rf eoui).r used fxW? making phenol fiber.

K3-I. eeE0. otrivR tile strength of paper when vet.

Pt"PC19, no. li:15-l6(Novw. 22, 1.91-6); J. Imd. - Thig. Chera. 8, no. 11:

i005,-lO,'i4(Nov., 1,916); Papcr'likers' Mdo; J. 55, no. 2:hi4-46(Feb. 15,

bIQ1); Chen. i~h.24, no. 5.23!-236(may, 1917); C. A. 11:99.

The wet strength is determined by, break~'ng a strip of a definite width,

nf rte it ha beenm iwe1rsed in waiters at a constant temperature, for a definite

neOriol of tine. A Schoppur tensle trength maloichie is used. The jaws

ci' the elanw should open in front, so that -the ends of the wyet strips,

naty be inser-ted. without injury, and ore sot 10 cm. apart, ns a short strip

01 wetl npapr can be handled noer easily. The test strips are cut 15 .

j Wet Tensile Strcenth 288L"

wide and. sufficiently lonC, to allow for clamping in thcnnchine. The strips are placed. sep-arately in a water bath at 700 F. for 20 mainutes.- After the specified, tirle they are renewed. one at a tine and tested.

strips to prevent injury~ to~, then. Date are civen showng'n thle effect of tci~oreratre of the (I0-u> 65,) 70, 75, and 1000 ".) and. of the time -oftwtting-(l0; -2073:cL -6%0 nhfr. TPh6 toWs wF dbovslhi&2~-

------tbs~tud~v-bluerririt papm-, !.Wet strength <--IF controlled by thec combina- tierl. of factors hiT1ch iaJ-x'nc~c-o other -physticalI properb.ien, such cs fiber leng,-th, beating., kind and qimslity of siz-ing, artd formation of The sheet, yet there~ is no direct relationship between the wet and dry strengths of tuner.

E14. TAPPI. Commi-fttee on Paper Testine. [Tensile1 or breaking strengthi] . Paper Trande j. 75 om. th4-b-45,(,July 27, 1922).~

DlRsuusono of' the Shopiopor tensile teetor. Wet tensile- strengtUh is also discussed.; Athe strips care ±nrnersea in water at 7Q0 F. for 20 mIinutes and, a speed of C in~che~s per minauteo is applied. to the lower jaw7.

81.5. TPGPT. Wet tensile~ breaking strenGth of pare~r and paperboard. TKPPI sttncarl T 4i55 n 44. 1 sheet. ?tper Trade J.~ 115, no. 5:51-32, (Jul1y 50, 19~p42).

The ultina be wet strejng~th moans thle strength of1 the manterial after completed s-aturation with a liquid. Iqornali wet strength means the strength of the nsabarisl af tar it hsbeen wetted te an. extent compiarable with normaal use conditions. For certain materials, such as tiussue mid unsized. raosthe two ma.-y be the acre. The. apparatus consists of a tersile butr(ci. T :0l4-n), and! a Finch we-teghdevice. The te-st is; made 4 aecndirCULg 'ho TK~rn Standard T ~,0 ml-n, sing~ strips thant have been wetted in li`qmudo t2 it The Fie tie Ig:-. E12] is usd o:? -,etting ratersJj,~' are difficult to enil II webo. For ulbnt cttrength -0a-CV0 '110UI. -10.2 - nz dUte'rnine the required UtiicA -m5nTzwi'by i-rouln0 uQst 3t-L-p for variouso rzeridos A' timuniesddt:on hi t ensile s-trength at the end of each period! u-ntil n.o i.thr igifcnt loss in tensile streongth ocus To obtain normal wet strength valUes thL ieo meso for papecr toweols shall be' 15 + 5 seconds cr1 Per, bluern)~int and. other ph~otocruphic papers 20 + 2 rtteusing water in~ ccch case. I ...- - .. 1 ,,". 1 .

I I -

289

WATER ABSORPTION

816. National Bureau of Standards. Structural fiber insulating board'.-3rd -ed. Corre.ercial-otndard CS42-43. 1943.

Water Absorption. .A specimen 12 x 12 inches-shall be dried at- 1600 F. for 24 hours and colped to roon temperature in a dry atmosphere. The thickness of the sample shall be measured and the volume calculated therefrom. The sample shall then be carefully weighed and submerged horizontally under 1 inch of distilled water maintained at 70 + 5° F. After 2 hours of submersion, the sample shall be stood on end to drain for 10 minutes, at the end of which tine the excess surface water shall be removed by hand with a blotting paper or and the sample irmcdiately weighed, the volume of absorbed water calculated, and the water absorption expressed in percentage by volume based on the initial volume.

817. National Rcsearch Council of Canada. Procedure for making physical tests of fibre building board. IRC-19-1940(tontative). Jan. 31, 1940. 2 p.

This method is the sane as that given by the National Bureau of Standards.

8138. TAPPI. Water absorptivenoss of nonbibulous paper and paper-, board. TAPPI Standard T 441 n-42. 1 shoot.

This enothod is based upon the method of Cobb and Lowe CPaper Trade J. 9c, Do. 12:43-46(March 22, 1934)] and Cobb [Paper Trade J. 100, no. 16: 42-45(April 18, 1935)]. It is suitable for dotcrmining :etor penctra- tion into paper and board 0.004 inch or moro in thiclnoss. In the test a definite area of one side of the specimen is wet uniformly at the moment that the count of time is begun. Penetration occurs only through the *1 I test area and no possibility exists of wetting the edges or other portion Ii of the specimen other than the area under test. The absorption of water is stopped at the end of the test by removal of all surface water. An. accu-rat, jirht of' the specimen ic. obtained bofore and after cxposuro to tIhe watur. Loss of roiriturc between the cxpiretion of th;: tost period and the tilo of wcishpin i's avoided. A suitable apparatus and procedure are described.

i

BCnEz-- iW990,011 &061 i I i I I 291)

AUTHOR I1l'TFDB

T~t:The nurnbers refer to the nuntered. entries in thle bibliography and not to the paoe numbers.

Abbott,. F. -F., 483 - folentson,- C., 554 - Abol, J. G., 1, 496 Berco-vitz, D.,.4 3 o, 497 Abrams, A., 67, 156), 157, 177 Bercsi, J. Gt,733 Adams, F. WA, 590 Bergene, E., 659 PAlington, W. E., 811 Berndt, K., 431, 593, 594 Ainslie, P. A., 68, 178, 377, 655, Best, A. S., 124 726 Bevan, E. J., 9 ;2-.e.xandor, 0., 81± Bialkowsky, H. WT., 498 ArLloricon Instrument Company, Inc., Bidwell' P. Wi., 184 422 Bierott, G., 185 r~,flcrictfn Society for Testing Moteri- Blanchard, F. C., 186 als, 2, 71-73, 133, 134, 179, 179A Blikoted, F., 596, 597, 7r 6 294-293, 340, 363, 378, 379, 389A, Blum, R. J., 352 395A, 423, 4a4, 529A, 656, 657, 72 7 Bode, H. L., 380,5381 Ames, B. C., Co., 299 Bo"MCke, H., 679 1znther Testing Instruneont Co., Inc., Boernor, Ch., 187, 773 135, 180, 300, 425;. 728 Booth, Hi.0., 660 "alderoon,, B., 658 Boyce, D. H., 584 Anderson., L. C-, 74 Bragg, A. 0., 595 Aono, T.; 75 Bray, G. P. R.,1 613 Ape0 igren, C. E., 173 Brecht, w., 555, 556, 596, 597, 661- PIrendt, A., 729 663, 736 ryM., 110, 143, !144, 226 Brown, D. S., 159 Arxnold, L. K., 76, 132 Brown, P. W-, 301 ;.rnoul1, E., 750 .Brown, T. M., 598 AXSOCiation. Of !Americar Railroads, Brush Developmaent Company, 557 Bmrgetanllor, P., 188 i4cYrs, L. R., 540 Campbell, J., 0o Bechnran, P.. P., 1'7]. Campbell, P., 514, 55 D~cor, 150, 267', 65a, 802 Camapbell, W. It,- 192, 737

Ba'iley, A,. J., 426 - Canadian Pain and Paper Association,. Bairtil r. K., 3, 32, 90, 1.26, 162, 302, 382, 738 I 262, 567 Carlson, T. A., 353, 354, 364, 408- Bard, P., 110 I 410, 5142, 643 Bardeen, -14. D. , -427 Carpenter, L. A., 1111, 443 I Barnhart, 4. W., 550 Carrier, ii. H., 432- Barr, G., 77 Carson, F. T., 4, 5, 47, 56', 57, 81- Basberg, A.-, 752 I (- -156, 138, 193-1.95, 303, 304, Beunwucker, W-., 550 5~87, I 4119; 433, 483, 504, 512, 599, Beach, P'. L., 182, 530-532 664, 665, 739 Beadle, C., 183 Carson, R. W., 305 Bcazlcy, W., 551 Carter, E. C., 600 Bekck, J., 78, 79, 341, 552,, 553, Case, H. u,., 666 551, 592 Chaplin, C. 4., 6 Ilellowc, J., 590 I Chttsor, 1H. "I., 67 r (Nj CM toN t"\ L-- W\ OYN 'A 'IO 'IO 01 LI\ LIN LN EN N- CMj I- tol 0 W N - C - NUNo LCN W-- 1UN EN' C CC'1 HON 6 H CM N L Q d ON r. CQ MCr H -Zt co ti ) '-. L- Od. N Z 2-i cj N I O C(N C- UrN H1rN- TNN -~ Ci WN N \ C) I UN *MO N 'ANC\ Co H .2± -Id O Cd 4) I N~' CO MC. '0~. 0 N M Ic-N~1 PI Ifi P4 n- r-i '('II EN I'* * . '4- OEC C- t.- P.C)C>l~ (N .. N * N C) tCd WI N-4g UN P*D4 - ~OLUN S-

I $4 ONP~ *- N N *0 C- N N3 C) C)$4 C-f ~i ~P H SiC0 H U3- toi o I X 0-$ $4115) $ -t ~0H tC'Si Ci z H4H .H n-i - I-i4 o H Hr- iC4P HnIi 0 0 ~ 1 - .riOOOC$4$4'~ 04 C) m

oo~ 0 o ON XI. IN1 43 Mo N- 4-) HI-I ' <1 H4 O"N ON 4) t"-N W\ 01 0 I tr\ H ..± ON 0 0 -I C-) -2 VC) 0] Mn L- MD H EN' N N--toN c- C, toi N 0 0 0 O-N Pr- 0 K>1 . D cu WN I,-N .H- LE\NC N 0 3 , ' -' . Mo N-- (0 H N- CC) .0 0 0 01 N N N C - OD I N nId dJ N H4 QN CO U C) 0] O N 4 N-- N 0 LN 42-4; -Zt Hi~ 0 P , N N .O P 7 -.t O o; ra. 'dRi El- 0tN" CC I- $4 3 \D N N~ N b I Z~ 4010 - C tH-4 Fti I NI- - ~~~ -'A O N O4 C; N i Ni' D C) O H L/> NOH0 EJ C,) CC) ENMO7MO I - C)* -'0 P N r-4- ~C) 0 Q-p -P cdi C) c, ~ P N 1 R C) .0 N- N1 H-- CN N g H I- -; r CO) 024 ;54i P :N -2 (1 :~ H -4 HA0 0 0 C) 0 0 0 00$ ~4 C, C C, C EJ C) ) C.)QC C-) C) C)l rJ3 C) C) (9 o~rL3 P In aaglmgi&& 4 ;L.-

I -

Author Inftox29 2T,

Instrument Sp)ciolties Company, Mackin, G. E., 52 1- The., 517 McKinley, R. W., 216, 752 Isnard; R., 610, 767, 763 MvNoughton, C. C., 222 Ivanov, N. D., 105) Malcoltinon, J. D., 229-233, 520, 368

Jacobson, P. M4. H., 22, 25, 456, Mnlott, iE,689 oil, 686, 687 Mulotrom, E. B., 559 Johann, G. A,., Sfl 1, 1jL.Q, '221,- mann1 -K., 650o 769 Moncgol&, E., 112, 113 Jahn, E. C., 25, 412- M~arinti, M., 507 Jarrdll, T. D., 60 Marsh, M4. C., 114 Johonsson, D., 6j88 Martin, R. I., 613 Jones, C. H. in?., 573 Marx, Rk. J., 689, 690 Masten, 'R. A., 80, 577, 614 Kontroiwitz, M'. S.Y 26, 52, 574 Il~oglitz, U1. B., 464, 465 Kaplan, A. B.,50 -Mosnomr, it. 2., 234, 466, 777 Katz, D. L., -1691., 359, 1414 Monosmr, 1I; E., Ltd., 322 }Collor, E. L., 32 micoua, Ti., 11,5, 6-15, 778 Kioly, H. u., 61, 173, 457, 458 M-i'llr, D. R., 316 Kionzl, HI., 459, 770 M-inor, C. A.; 616 Kirchner, E., 460, 406., 771l Minor, J.'E., 533 247, 616, 724, Kirkwood, 1k. S.; 57, lsS, 504 MOnzingtr, W. M., 467 Kooster, !B., 649 M~v.honcn, R. J., 617 K~orn;' B., 513 NodII;,691 Korn;' it, 271-31, 463, 772, 775 Nao'imof; K.; 469 Kott,'H., 575- UnounofP Tm 470 Xotto, -- , 612 lnational A'scociction of Purchn~in~3 xoznrovitzlki7~, L. A., icfl A~xontn, Inc., 235, 525, 569, 399, ixrU""Ucbzmr, '4.,% 141, 142 471', 6541, 692, y1o Krauss, P. A., 109 atmotinol flacoCreli Council. of Canada, Krona, 0., 62, 222 4153, 5o8, 81747 t. Krossler, J. P,,- 165 Thoumnarn, 141., 474-47

rii LbBntt, W. D., 225-225 Nluwll Tn, J. T"A,h00 Land~t, G. E., 77Th Nichols, 1.B, 9'5 'S Lorocquo, G. L., 506, 576 iBoll, A., 116 Larson, L. Cr., 4-12 Hioss, F., 784 Latham, J., 5~ Thnudon;)ak, -T., 70' Oclnrent, C., 509 theme,TI., 10,1'-, 'lac, 226 Oliver, C. V., 238, 239, 696, 7y95 LitleU1c, J. R., 3)67 Ondood, Hi. W., Jyr>, 166 !,odge, B.C., 0227 Joo)bo, IR. 14~145 onporl Makcrs ' Association of Groat memo,VT. B., 14 Britain and. Ireland, 117, 146, 2410, Loft'- n, R.- . 228~, -77 2):1, --527, 478, 697, y(86 Paris, P., 37, 38 Lortz' cntCoLtl,,~ 1 Povlotto, KC.,277 W. M., 94 Lucy, '-T 6-I Feck~han, Peek', -R. L., Jr., 174 McCarthy, J. L., 4.12 i'oirco, E". T., 621 D. F., and. Sorn, Inc.-, 2421 McoCready, D. 17., 10,' 359," ;13, 4114 Pcrkins, l~ceoP. i.,63 C'., 602 4

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E -~ ' L N -I N - \ c- K'\ NMD: MOCKN .) 200 NI- 4Zi C•% 'U - - coi CO '0 C CI co o 17% I- 0 4 OD co Z7,C HH- K'] I y~~~~a C Ci 013 CUj A -i 0Th ~ 4D f 2 '2 r. TN 0 .. 0 N-.I U N -Ma --- K'\ '~ CO '-1 H 2±1 I a* 0 N- CUNCO CN-c C) c-A -9 0 54 4 ) XIZ co CD 0% i- 4 HC~ In02 on o K> ;,ifN-i LN0 C I MON- N (Z4CiC) I co *~ ?) K' * 4 * N r- r-l 0 H-I oicyt s~ H- L S\ OC,) If C $ tc) I I W\'ic o ao K'\Cd r-4 A: NIC>LI-N CO t> H C) CC)U $4 o gj I1 -,~~-:~ -C fz, mm cc1civ x H, E-( H- PIPHE o *\

f-A 0 K'N -, -i+r g r - c-f LI> C> -o) h- 'N CO) A)C) U ' MC) 's -'K UN co IC>_ 2± CC) 0 0± ol o 4 N~ C- In'\ -2±k Co~ ~ C C) -Z~c K' c ~ ~ G -4. Ni OD El- H .~ LI-' CD co C- 11c tr\ ON Ut, 2± Lr% ON\ O1N 02J N-_ 02 UNq NZ --4- in CU .,' is- CU ON U>-IC\> C -) 2±J H- I-Ma~ Co i 0 ± -: I-1 001i CH 2±C- U-N P UNpq C- S-i 04,-I *4 S C C C)' q 4 ) Cj' 01 N) N ~ 2Ki± N , 1 N .. 0 'P4 s-i2 *~ .4 E C ) C,) O -N-d m crNLOZO - H-C) ONP Pa0 CU N CP I P-, v-i C) C) ~l 00 1 0 0 0 0 :003 .05 i C) CD PC; P 0 `~0 I fri 2i CCIrl ;7 CD C) u) C I)C I i 4

I - ______. _ __ _ _--- -__ -,-tx lrr- , I. . II I I .1-1-1-- - , - .- - - -I I - 1. . 11= -"Zlw*i-' I

Author Index 294

Wci6dcnmu~iic, nI-; 753 T~inias Olsen Testing t-lnehino ColnpanY, 540, 719-721 4 1I. I Ueili, S.LD., 53, 65, 375, k V. 7,292, 351, 361, Toledo Soi9 opn,15 ~ m obor,,enr S. W., 509~ ,,C>olto~6 pajl-. 153 529, 541, 546, 7202, Smo TorlonolacoCO., 154 576, 407, 1- 0 Thins,V 155oloS- ,t Ic `O7 Tma, v., '5I) - - ~~~~~~~~~~~11~' I I - '- -1 - ~7-linfl,Wi ' S- 33.,-5 -587 723----- 281, 359, 395- Tj. S. Anrk- Nnvy, WITIinBs Apporotus-CO.,. 5kz c.. Nojtional )3ar~COu of' 2torndards, 236-257, 324, 4w,2 4y,717, 731, Wilson, E. G., 559 Y82, 861 Wilson, K. F., 362 Wilson, T. R. C., 400) Vonduro Lkko, J5 -M1., 72,4 Co ., 553' - Wiptiorbottom, Vran Kourcn, s.,~Jr., 641. VnughaNl L.$ Jr., 640 Withcrn; a. F. m., <48'45 Withom, G. S., Sr., 725 Voitch,- 84, F., 223', 284 Worthington., F. V., BS5 194, 195, Yonnotmn, 599

Wibilin, S., 718 \T~tor L.B.,64 Young, j. H., 432 W otlib J.ot 700 Wcht 4. W, 286-290 Wate~(r, C. G., 516-51B Zipkicl2, G. S., 5P39 jf f L., 52-, 50j4 ~[u0 i z , B.

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