Patented Jan. 28, 1941 2,230,206 UNITED STATES FlCE 2,230,206 MANUFACTURE OF CERAIVHC‘ WARES Ira Elmer Sproat, Westport, Conn, assignor to R. T. Vanderbilt Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application April 14, 1938, Serial No. 202,010 10 Claims. (Cl. 106-41) _ This invention relates to the manufacture of The mineral content of several thin sections of improved ceramics. It relates more particularly this rock as determined by traversing selected to ceramic products having decreased moisture areas under the microscope is approximately as expansion and tendency to craze, together With follows: Cl 5 improved ?ring characteristics, color, and in Per cent creased economy of manufacture. Albite ______60-70 Earthenware ‘bodies are comm-only made from Microcl-ine ______5 a mixture of clay, ?int and feldspar, and may in Sericite ______10-20 clude pyrophyllite, talc; etc. The proportions of Zoisite ______l5—20 10 10 clay, ?int and feldspar used in making earthen Quartz and minor minerals 5% or less. ware bodies vary considerably depending upon While this analysis is largely an approximation it the characteristics which are desired in the ?nal ceramic products. indicates in a general way the relative distribu Most ceramic products prepared from clay, tion of minerals in the rock. A recast of the chemical analysis indicates a substantially simi 15 ?int and feldspar expand upon absorbing mois ture. This expansion causes crazing of the glaze lar distribution of minerals. Based on the chemi cal analysis of the rock the percentage composi on many products such as wall tile, etc. The tion would be very closely: present invention provides improved ceramic Per cent products having a greatly decreased moisture Zoisite: éCaOBAhOaGSiOaI-lzO ______22.0 20 20 expansion, and a corresponding decreased tend ency to craze. These new products have other Albite: 1\Ta,2O.A12O3.6SiO2 ______55.0 important advantages, such as improved ?ring Sericite: K2O.3A.l2O3.6SiO2.2HzO ______13.0 characteristics, economy of manufacture, etc. Microcline: K2O.AlzO3.6E5iOz ______5.0 In accordance with the _ present invention, Quartz: SiO2____' ______3.0 Titanite: CaO.TiO2.SiO2 ______NJ Ol ceramic products are prepared from bodies con taining zoisitic rock, which advantageously re Garnet: 3CaO.AlzO3.3SiO2 ______2D places a substantial part of or all of the feldspar Clino-zoisite: 4CaO.3Al2O3.6SiOz.H2O ______commonly used, and may even replace some of Apatite: (02.5‘) (321.4 (P04) 3 ______the ?int commonly used. The term “zoisitic rock” Since the rock occurs naturally in Virginia, I as used in this speci?cation and claims is used to have chosen to designate it as Virginia zoisitic designate materials containing a substantial pro rock, and it will be referred to in this speci?cation portion of zoisite, together with substantial pro and the appended claims by this name. Instead portions of sodium and potassium aluminum sili of this Virginia zoisitic rock, other suitable rock cates, such as albite and sericite. containing substantial quantities of zoisite to The amount of zoisitic rock used in producing gether with alkali aluminum silicates such as al the new ceramicsmay be varied; but advanta bite, sericite and microcline can be similarly geously the proportion used should be such as to used. provide from 0.3% to 5% of calcium, calculated This Virginia zoisitic rock has important ad as calcium oxide. When the zoisitic rock is used vantages as a ceramic flux and may be substituted 40 40 in these proportions in the bodies, the ceramics for all the feldspar and a small part of the ?int obtained have a radically decreased moisture in such typical white ware bodies as floor and expansion without any marked decrease in ?r wall tile, electrical porcelain, semi-porcelain din ing range. nerware, vitreous china, sanitary ware and high A naturally occurring zoisitic rock found near tension insulators. It may also be used with Piney River, Virginia, has important advantages advantage as a partial substitute for feldspar, 45 45 for use in accordance with the present inven particularly in bodies containing more than 15% tion. This rock is composed chiefly of zoisite, of feldspar. It may also be substituted for whit albite, sericite and microcline with accessory ing or marble dust when these materials are in minerals of titanite, garnet, apatite, clino corporated into earthenware bodies. The amount of zoisitic rock which is used in 50 50 zoisite and quartz. The chemical analysis of the rock is approximately as follows: making the earthenware bodies may vary con siderably depending upon the particular kind of Per cent material which is desired as a final product. In S102 ______58.72 general, the amount'of zoisitic rock may vary A1203 ______- 24.70 from a few per cent up to around 60% and even 55 55 CaO ______6.90 as high as about 70%, and it may be used in NazO ______5.58 conjunction with various other materials such as, K20 ______2.70 for example, whiting, magnesite, pyrophyllite, T102 ______01.12 talc, etc. A given amount of calcium when intro duced as zoisitic rock is very effective in de 60 60 Fe2O3__~____'____; ______‘_.."_____'..'.. ______0.30 2 2,230,206 creasing the moisture expansion. Hence but small Consequently, when such materials are present amounts of calcium oxide are required when in in a slip, it is necessary to use considerably larger troduced as zoisitic rock in order to produce a quantities of the dispersing agents. I have decrease in the moisture expansion, as little as foundthat when zoisitic rock is substituted for 0.3% of calcium, calculated as calcium oxide, in . whiting or marble or magnesite, a. much smaller troduced into an earthenware body as zoisitic rock amount of dispersing agent is needed to produce ' causing a marked decrease in moisture expansion. a satisfactory casting slip. The dispersing agents For some purposes a larger amount is desirable usually contain Various soluble salts and a de and I have found that in white ware bodies the crease in the amount of these materials present 10 quantity of calcium introduced as zoisitic rock in a casting slip increases the life of the plaster 10' may vary from 0.3% to 5.0%, calculated as cal molds into which the slip is poured. The im cium oxide. proved results. which may be obtained when The proportion of clay may vary from about zoisitic rock is used in casting slips are illus 25 to 50% and the clay may be made up in part trated in the following table: .15 of Ball clay and in part of Georgia or Florida Vztreous ch'mq, bodies 15 kaolin. Other clays such as English china clay, English ball clay and North Carolina kaolin etc. may also be used. 1 2 3 4 , Flint may be used in varying amounts and may Per cent Per cent Per cent Per cent 20 constitute from about 5 to 35% or even 40% of 6. 34.0 37. 35.0 the earthenware body. 18. 0 ______18. 0 ______. _ 17. 0 l7. 0 30. 0 30.0 The moisture expansion of ceramic bodies is 8. 0 8. 0 ______. _ commonly determined by subjecting them to a 10. 0 l0. 0 4. 0 4. 0 English ball claym- . 8.0 8.0 8.0 8. 0 steam pressure of about 150 pounds for a given Imported whiting . . _ _ __ 2.0 ______.. 2.0 ...... _. 25 length of time and then measuring the increase California Inagnesite___.v 1.0 ______. 1.0 ______25; in length, if any, which the body has undergone. Virginia zoisitic rock ______-. 23. 0 ______23. 0 The following table shows the decrease in. mois Per cent sodium silicate ture expansion produced in semi-porcelain din necessary to produce minimum viscosity. . __ 0. 606 0.281 ______nerware bodies in which Virginia zoisitic rock Per cent organic clay de- ' 30 has replaced all of the feldspar. The semi-por ?occulant necessary to 3.0. celain bodies were subjected to 150 pounds steam produce minimum vis pressure for a period of about 3 hours. cosity ______._ 0.475 0.175 Semi-porcelain dinnerware bodies The table shows that body No. 2 in which Vir ginia zoisitic rock has replaced feldspar, whiting 1 2 3 and magnesite requires about 54% less sodium silicate to disperse it than body No. 1. The table Per cent Per cent Per cent also shows that body No. 4, in which Virginia 35.0 35.0 30.0 zoisitic rock has replaced feldspar, whiting and 12.0 ______32. 0 32. 0 32. 0 magnesite, requires about 63% less organic clay 21. 0 21. 0 21. 0 de?occulant than body No. 3. - 40 ______. 12.0 17.0 This invention will be further illustrated by the Moisture expansion in percent of original length. 3 hrs. at 150# following examples showing typical body for steam pressure ______0. 123 0.071 0.062 mulae for. various‘ types of ceramic products, 45 but it is not limited thereto: The table shows that body 2 has a moisture ex 45 pansion which is about 42% less than that of Vitreous china body 1, and that body 3 has a moisture expansion which is about 50% less than that of body 1. 36. 0 31. 0 Although the above table gives data only with re 8.0 7.5 50 8.0 8.0 50 spect to semi-porcelain dinnerware bodies, it is North Carolina kao1in_. .... __ l0. 0 of course understood that the zoisitic rock will English china clay_ _ _ 28. 0 18.0 Whiting ______2. 0 ...... __

not only decrease the moisture expansion of Magnesite _ _ . _ . . . . . ______. .. _. .___._.._ 0.5 those particular bodies, but will decrease the Virginia zoisitic rock ______O 25. 0 55 moisture expansion of ceramic bodies generally. The use of zoisitic rock also has many other 55 advantages. It decreases the maturing point of 7 Sanitary Electrical white ware bodies several cones without affecting Ware porcelain other properties of the bodies. It increases the 60 ?ring range of vitreous bodies, especially those Flint ______._ . . . 20.0 Ball clay . . ______. . . _ _ _ . . 25. 0 containing calcium. . Florida kaolin.v ___ 8.0 When whiting or marble dust used in earth North Carolina kao Georgia kaolin ______._ enware bodies is: replaced by zoisitic rock, the English china clay. ?ring range of the bodies is not affected by the Whitin g ______. - Virginia zoisitic rock. ._ . .l. . _ . 65 zoisitic rock to as great an extent as it is by the whiting or marble. In addition, the zoisitic rock 55. improves the ?red color of the bodies. I have also found that the properties of clay slips containing calcium are improved if zoisitic rock is used instead of whiting and marble. In Flint ______15. 7.0 Ball clay ...... _ making casting slips, it is common to add dis Florida kaolin. Georgia kaolin.

persing agents such as sodium silicate, soda ash, Maguesite _ _ .. _ _ or the like to de?occulate the clay. It is known Virginia zoisitic . Pyrophyllite... - . that both lime, in the form of whiting or marble, 'I‘alc ______._ 75% and magnesite tend to ?occulate a clay slip. 2,230,206 3 The above body formulae are given by Way of to about cone 1 to 6. The tile may also be made example. The invention is not limited thereto, by the one-?re process in which the green tile but other formulae can be used. is sprayed with glaze and the body and glaze are The invention includes not only the use of Vir ?red at the same time, the glaze being such that ginia zoisitic rock, but also other similar zoisitic it will mature‘ at the same temperature as the rock, in making earthenware bodies. As previ body. ously pointed out the Virginia zoisitic rock need Wall tile containing zoisitic rock may also be not be used as the exclusive flux in making the prepared by the dry process, in which the various new bodies, but it may be used in conjunction components of the body are ground to about 200 10 with feldspar or other suitable ?uxing agents. mesh and are then mixed with the required It may likewise be used as the sole source of cal amount of water necessary for pressing the body. cium to decrease moisture expansion or it may be Floor tile may be formed by the same methods used in conjunction with materials such as whit that are used in preparing wall tile, but are ?red ing or marble dust. at a different temperature. Floor tile are vitre 15 The methods of manufacturing the new ceram ous and are seldom glazed, and they are ?red in 15 ic products containing the zoisitic rock depend a biscuit kiln at a higher temperature than wall somewhat on the purpose for which the products tile in order to obtain sui?cient vitri?cation with are intended. a minimum of ?ux content. The biscuit temper In making semi-porcelain dinnerware the body ature varies from about cone 10 to 13. 20 materials may be weighed out, thoroughly mixed Electrical porcelain (low tension) is also vitre with about 60% of water, lawned, ?lter-pressed ous and may be manufactured in much the same and then put through a pug mill or de-airing way as ?oor tile with a ?ring range from about machine. This pugged material may be used for cone 9 to 12. plastic forming of the ?atware and dishes. Sanitary ware containing zoisitic rock may be 25 Hollow ware such as sugars, creams and cover made by a casting process with one or two ?rings 25 dishes, may be made by a casting process in depending upon the composition and the purpose which the ?lter press cakes are blunged up with for which the ware is intended. The ?ring tem a small amount of water to which has been added perature may vary from about cone 8 to 12. a dispersing agent. The dispersing agent is added I claim: 30 to decrease the amount of water necessary to 1. Ceramic bodies made from a mixture com 30 make a fluid slip and to decrease shrinkage. The prising ?int, clay and a zoisitic rock as herein slip is poured into plaster molds, the body being de?ned. deposited on the sides of the mold as the water 2. Ceramic bodies made from a mixture com is absorbed. After standing for a few minutes, prising flint, clay and a zoisitic rock comprising 35 the excess slip is poured out and the ware is per about 22% zoisite, about 55% albite, about 13% 35 mitted to stand in the molds for a short time sericite and about 5% microcline. until it shrinks away from the sides of the mold, 3. Ceramic bodies. made from a mixture com when it is taken out, dried and ?nished. Both prising ?int, clay and a zoisitic rock comprising the dry ?nished hollow ware and the ?atware at least 15% zoisite, at least 55% albite, and at 40 may then be placed in saggers which are in turn least 10% sericite. ' placed in a biscuit kiln and ?red to about cone 4. Ceramic bodies made from a mixture com 6 to 9. On cooling, the biscuit ware is removed prising ?int, clay and a zoisitic rock as herein from the kiln and is then brushed and glazed de?ned, the amount of zoisitic rock being such either by dipping or spraying. The glazed Ware that the earthenware bodies contain from about 45 is again placed in the saggers and ?red a second 0.3 to about 5% of calcium calculated as calcium 45 time in a gloss kiln to about cone 1 to 5. oxide. Bodies for the manufacture of vitreous china 5. Ceramic bodies made from a mixture com may be formed in much the same way as those prising ?int, clay and Virginia zoisitic rock as for semi-porcelain dinnerware. However, in or herein defined. 50 der to obtain su?icient vitri?cation with a mini 6. Ceramic bodies made from a mixture com mum of ?ux, vitreous china is biscuit ?red at prising ?int, clay, pyrophyllite and a zoisitic rock about cone 10 to 12 and, after glazing, is gloss as herein de?ned. ?red from about cone 01 to 3. '7. A raw ceramic batch comprising commi In the manufacture of wall tile the body ma nuted ?int, clay and a zoisitic rock as herein terials may be mixed with water and ?lter de?ned, the amount of zoisitic rock being such pressed in much the same way as semi-porcelain that the batch contains from about 0.3 to about dinnerware. If the dry press method is used, the 5% of calcium calculated as calcium oxide. ?lter press cakes are dried and ground and suffi 8. A raw ceramic batch comprising commi cient water for pressing, usually about 10 to 14%, nuted ?int, clay and Virginia zoisitic rock as 60 is added to the ground body. The moistened herein de?ned. body is then permitted to stand in a bin for about 9. A raw ceramic batch comprising commi 12 hours and is then put through a dust mill and nuted ?int, clay, pyrophyllite and a zoisitic rock screened and then pressed into tile on hand or as herein de?ned. automatic presses. The tile are placed in saggers 10. Ceramic bodies made from a mixture com 65 and biscuit ?red at about cone 7 to 11 depending prising ?int, clay, feldspar and a zoisitic rock as on the type of body. The biscuited tile are then herein de?ned. glazed by dipping or spraying and are ?red again IRA ELMER SPROAT.