Western Michigan University ScholarWorks at WMU

Master's Theses Graduate College

6-1994

Effects of Alkaline Internal Sizing on Rotogravure Print Quality Using Waterbased Inks

Michael L. Busche

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Recommended Citation Busche, Michael L., "Effects of Alkaline Internal Sizing on Rotogravure Print Quality Using Waterbased Inks" (1994). Master's Theses. 4913. https://scholarworks.wmich.edu/masters_theses/4913

This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. EFFECTS OF ALKALINE INTERNAL SIZING ON ROTOGRAVURE PRINT QUALITY USING WATERBASED INKS

by Michael L. Busche

A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Master of Science Department of Paper and Printing Science and Engineering

Western Michigan University Kalamazoo, Michigan June 1994 EFFECTS OF ALKALINE INTERNAL SIZING ON ROTOGRAVURE PRINT QUALITY USING WATERBASED INKS

Michael L. Busche, M.S. Western Michigan University, 1994

The effect of alkaline internal sizing in improving paper smoothness and ink gloss in waterbased rotogravure printing was investigated. Papers were internally sized with alkyl ketene dimer (AKD) under alkaline conditions from slack-sized to hard-sized. Papers were printed with waterbased inks on a web gravure press. A major problem with waterbased inks is increased surface roughening of paper and a low ink gloss. Temporal surface roughening was reduced by increased AKD internal sizing with a concomitant significant increase of up to 400% in ink gloss. Surface properties were correlated with print quality. The print quality improved with increased hydrophobicity of the papers. TABLE OF CONTENTS

LIST OF TABLES...... vi

LIST OF FIGURES...... vii

CHAPTER I. INTRODUCTION...... 1 II. LITERATURE REVIEW...... 6 Environmental Regulations...... 6

Recovery Systems...... 8 A Review of Common Printing Methods ...... 10 Control of Compressibility and Ink Transfer on a Rotogravure Printing Press...... 13

Definition of Printability, Print Quality and Gloss ...... 18

Critical Rotogravure Printing Press Conditions That Determine Print- ability/Print Quality...... 19 An Overview of the Correlation of Sizing With Print Quality and Printability...... 29

Factors Affecting Print Quality and the Measurement of Print Quality ...... 31

The Relationship of Surface Smoothnes of Paper With Print Quality...... 32

Print Gloss as an Indicator of Fiber Rising and Surface Roughening...... 3 4 The Importance of Surface Compressabil- ity Along With Surface Smoothness...... 35

ii Table of Contents--Continued

CHAPTER The Effects of Sizing and Absorption Rates on Surface and Ink Film Properties ...... 3 7

Sizing Effects on Surface Roughness...... 38 Review of the Methods of Sizing, Internal and Surface Sizing ...... 38

The Effects of Sizing on Ink Film Transfer and Gloss ...... 39

Dependence of Furnish on the Effectiveness of Sizing and Control of Ink Gloss...... 42 The Importance of Ink Density Relative to Ink Gloss and Surface Smoothness of Paper ...... 42

Effects of Water Absorption and Penetration Into Paper ...... 42

III. PROBLEM STATEMENT AND OBJECTIVES ...... 47

IV. EXPERIMENTAL DESIGN...... 49 Overview...... 49

Outline...... • ..... 49

V. EXPERIMENTAL METHODOLOGY ...... 51 Preparation of Papers ...... 51 Printing Procedures ...... 55 Determination of Delta Gloss ...... 56

Statistical Analyses ...... 56

Determination of Print Quality ...... 57

List of Equipment...... 59

iii Table of Contents--Continued

CHAPTER VI. RESULTS AND DISCUSSION...... 60

Overview...... 60

Paper and Ink Film Properties Related to Print Quality...... 61 Paper Surface Smoothness ...... 61 Ink Film Smoothness ...... 68 Surface Compressibility of the Paper Substrate...... 81

A Comparative Measurement of Ink Transfer by Ink Optical Density...... 86 The Relationship of Ink Gloss With Internal Sizing and Fiber Swelling...... 90 Gloss Analysis of Printed Papers...... 91

Kraft Versus Groundwood...... 97

VII. CONCLUSIONS...... 103

VIII. RECOMMENDATIONS ...... 104

APPENDICES

A. Test Data of "USA WEEKEND" ...... 105

B. GAA Roto News Classifications ...... 107

C. An Explanation of the Statistical Analysis of Experimental Data...... 109 D. Analyses of Variance for HST Groups ...... 118

E. Analyses of Variance for the Delta Gloss of Magenta...... 122

F. Analyses of Variance for the Delta Gloss of Trap...... 127

iv Table of Contents---Continued

APPENDICES G. Analyses of Variance for the Optical Density ofMagenta ...... 132

H. Analyses of Variance for the Optical Density of Cyan...... •...... 138

I. �-Test to Analyze, for Each Paper Group, the Ink Optical Density of the Solid Printed Blocks ...... 143

J. Identification of Tested Areas ...... 147

K. Analyses of Variance for Smoothness, Parker Print Surf of 10 Kg Force ...... 1{9..

L. Analyses of Variance for Compressibility, Difference of 10 and 20 Kg Forces ...... 154 M. Analyses of Variance for Paper Surface Smoothness Compared to Printed Areas...... 159

N. Analyses of Variance for Smoothness of Un- printed Areas Compared to Printed Areas...... 163

0. Moisture Content of the Paper Immediately Following Production on the PaperMachine Reel ...... 171

REFERENCES ...... 173

V LIST OF TABLES

1. Examples of Clean Air Act Nonattainment Areas...... 7

2. Properties of Toluene and Wate�...... 23 3. Solvent Evaporation Rates Compared to Water ...... 24 4. Comparison of Sheet Thickness and Roughness From Skowrinski et al ...... 33 5. A Comparison of the Effectiveness of Sizing on Preventing Surface Roughening...... 39

6. Wet Ink Film Thickness Values...... 41 7. The Volume of Water Absorbed Relative to Time and Level of Sizing...... 45

8. Internal Sizing Dosage Levels of AKD...... 52

9. Smoothness Comparisons of Nonprinted Areas With Magenta Blocks...... 62 10. Effect of Sizing Level on Smoothness of Magenta Block and Delta Gloss of Trap...... 66

11. Smoothness Comparison of Printed and Nonprinted Areas ...... 69

12. Paper Compressibility Compared to Gloss and Smoothness...... 81

13. Ink Optical Density ...... 88 14. Hercules Sizing Test Results and Color Coding Scheme...... 89

15. Delta Gloss of Printed Solid Magenta Block...... 94

16. Delta Gloss of Printed Two-Color Trap...... 95

vi LIST OF FIGURES

1. Areas Violating the Clean Air Act-Ozone...... 7 2. Carbon Adsorption Solvent Recovery System...... • ...... 8

3. Emissions Comparison of Waterbased Ink Versus Solvent Recovery System...... 9 4. Different Printing Application Surfaces ...... 11

5. Rotogravure Printing ...... 12

6. Rotogravure Impression Roller Systems...... 14 7. Rotogravure Impression Width Calculation ...... 15

8. Impression Cylinder Nip Compression...... 16

9. Rotogravure Ink Application System...... 17

10. Rotogravure Press Register Marks...... 21

11. Two-Zone Rotogravure Dryer...... 25 12. Dryer Air Flow in One Zone...... 26

13. Air Flow in Two-Zone Dryer...... 28

14. Comparison of Sizing Levels with Surface Smoothness...... 64

15. Hercules Sizing Test Results...... 65

16. Magenta Block Smoothness Compared to Delta Gloss of Trap...... 67 17. Sizing Level 1: Comparison of Smoothness Values of Unprinted and Printed Areas...... 73

18. Sizing Level 2: Comparison of Smoothness Values of Unprinted and Printed Areas...... 74

vii List of Figures---Continued

19. Sizing Level 3: Comparison of Smoothness Values of Unprinted and Printed Areas...... 75 20. Sizing Level 4: Comparison of Smoothness Values of Unprinted and Printed Areas...... 76 21. Sizing Level 5: Comparison of Smoothnesst I Values of Unprinted and Printed· Areas...... 77 22. Sizing Level 6: Comparison of Smoothness Values of Unprinted and Printed Areas...... 78 23. Sizing Level 7: Comparison of Smoothness Values of Unprinted and Printed Areas...... 80 24. The Relationship Between Internal Sizing and Compressibility of the Papers...... 82 25. Compressibility Compared to the Moisture Level of the Papers...... 84 26. Ink Optical Density of the Solid Printed Magenta and Cyan Blocks ...... 87 27. Delta Gloss of the Solid Printed Magenta Block...... 92 28. Delta Gloss of the Printed Trap (Magenta and Cyan Ink) Block ...... 93

viii CHAPTER I

INTRODUCTION

The $2.3 billion rotogravure publication market is almost exclusively solvent-based printing, using about 396 million pounds of ink and over 500 million pounds of solvent annually (1). The portentous problem for this industry is how to improve the quality of waterbased ink rotogravure printing while reducing volatile organic compound (VOC) emissions. The lightweight publication market is not only high volume, but also quality and price sensitive. One solution is to use waterbased inks that are not composed of organically-based solvents to reduce voe emissions during rotogravure printing. Regu­ lations from the federal Environmental Protection Agency (EPA) are forcing printers in the United States to reduce voe emissions into the atmosphere. Volatile organic com­ pounds are in solvent-based printing inks and are re­ leased into the atmosphere during printing as the ink evaporates and dries onto the paper. "Rotogravure" is one type of printing process used to apply ink to a substrate. A substrate is a solid surface which receives ink. The most commonly used sub­ strate is paper. Examples of other ink receptive

1 2 materials are metal-laminated foil, corona-treated Mylar­ plastic film, and other types of cellulose materials (2). Other major printing processes are letterpress, offset lithography, and flexography (3). Items are typically printed by rotogravure when high quality print­ ing and lengthy runs are required for a particular grade of paper or substrate. An example of a coated grade of paper that is rotogravure printed is National Geographic magazine. An example of an uncoated gravure paper is a color magazine insert for Sunday newspapers (see Appendix A) •

Rotogravure publication printing in North America is typically a high volume and high quality operation. About 1.2 million tons of uncoated lightweight publica­ tion paper is printed annually by the rotogravure process (1). Lightweight publication grades of paper are defined by a basis weight/grammage of 40 to 55 grams per square meter (g/m2). Rotogravure paper is also graded by sur­ face smoothness, since a higher quality of printing is expected from a smoother surface. The largest family of uncoated rotogravure publication paper is called "Roto News" and has five categories (see Appendix B). "Roto News" is a name assigned by the Gravure Association of America (GAA) and the paper industry; it is not an abbre­ viation for "newsprint," but a family of different 3 quality publication papers (2). Printing inks commonly contain voe solvents. The inks used in rotogravure lightweight publications are almost exclusively organic-based solvents. A universal solvent that is not a voe is water.. A rotogravure cylin­ der has an image pattern composed of engraved cells. The cells of the cylinder are filled with gravure ink. Rotogravure printing is known as a direct-contact-printing. Specifically, the ink in the cells of the gravure cylinder is transfered to the sub­ strate by direct contact and pressure. Rotogravure printing requires uniform spreading of ink to obtain good print quality. Since rotogravure printing is a direct contact method of printing, the smoothness of the sub­ strate is critical to obtain good contact with the gra­ vure cylinder (2, 3). Organic-based solvent inks typi­ cally have uniform spreading and cause a minimal amount of paper fiber swelling (puffing) (4, 5). Fiber swelling will increase the roughness of the paper and thus reduce the print quality in rotogravure printing (5, 6). Poor print quality is minimized if waterbased ink penetration into the hydrophilic (water loving) paper fibers is reduced with concomitant fiber swelling and substrate roughness. One way to reduce emissions is to capture the 4 escaping volatile organic compounds and recycle them in a recovery system. Overall, the printing industry is a low margin operation and thus extremely sensitive to cost. For a high-volume four-color rotogravure printing press, a recovery system that exceeds 95% _efficiency is very costly and not always cost-effective. However, addition­ al regulations affect printers even if they have solvent recovery systems. For example, the Occupational Health and Safety Agency (OHSA) now has tougher solvent exposure _regulations for workers (7). Both the EPA and OHSA are requiring reduced human/environment exposure to organic solvents. Another way to reduce voe emissions is to switch from organic solvent-based to waterbased inks. Yet, as the problem of reducing voe emissions is solved, another problem is created. This problem is that both print quality and printability can decrease. Printability is defined as the ability of the paper-exclusive of all other factors-to accept and retain an image of ink applied by the gravure print cylinder (8). For example, missing dots on a rotogravure printed substrate cause poor printability (3). Print quality is defined as the control of the paper-ink interactions that optimize the final quality of the printing product (3, 9). Print quality can be a very 5 subjective measurement. However, most studies show that papermakers, printers, advertisers, and readers disagree on how to rate print quality except for one evaluation. This exception is typically a variation of ink gloss (mottle), due to uneven setting of the ink film on the paper surface. Variations in ink gloss and film thick­ ness can be greatly increased with the use of waterbased inks in lightweight publication rotogravure printing. Fiber swelling, from waterbased ink, primarily causes a reduction of ink gloss and an increase in distortion of the printed image (5, 10). Hence, a trade-off is caused by using waterbased inks, the trade-off being a decrease in print quality along with the reduction in voe emis­ sions. In the future, the EPA can be expected to tighten the restriction of voe emissions. CHAPTER II

LITERATURE REVIEW

Environmental Regulations

Federal, state and local environmental regulations are having a dramatic impact on the use of organic sol­ vent-based inks. The guidelines are becoming stricter in large population areas where many printers are located

(Figure 1 and Table 1) (11). The city, county and state authorities are tightening the acceptable voe emission limits, as established by federal authorities. However, if a state chooses to not fully monitor or enforce EPA regulations, then the federal government may take over the state's responsibility. The federal government will monitor and enforce the laws, with penalty and operation­ al charges being assessed to the state. The latest federal guideline is the 1990 Amendment to the Clean Air

Act, with enforcement starting in 1993 (11, 12, 13, 14). New, stricter voe emission standards may be enacted in the next four years, in part due to a new and more envi­ ronmentally conscious federal administration.

6 7

\_ '- \ ··, ..

Figure 1. Areas Violating the Clean Air Act - Ozone (11).

Table 1 (11) Examples of Clean Air Act Nonattainment Areas

Zone Classification Areas (Examples) *PPM Ozone

Marginal Kalamazoo .121 Moderate Ann Arbor, Detroit, .138 and Grand Rapids Serious Atlanta, Baton Rouge, .160 Boston, Fresno, and Washington, D. C. severe Baltimore, New York, .180 Chicago, Philadelphia, Houston, and Muskegon Extreme Los Angeles .280

*Parts per million (PPM) 8

Recovery Systems

The two major types of solvent recovery systems are both expensive and complicated (15). Both need different processing methods to handle all categories of solvents. There are two major categories of s·olvents, water soluble and water-insoluble (15, 16, 17, 18). One system is based upon carbon absorption for the separation of voe emissions (Figure 2). The other system uses an incinera- tion method to render the voe harmless (2, 15, 17).

Cl1?�nAir :o .Almosohf!r� Oun;io Aasor:1on .;yCle

cc; Tower

$t'am in .

Dring Steam• .._ inc ')CI! Fixc CJr 8;idACs-r

:iivent

Wate

Figure 2. Carbon Adsorption Solvent Recovery System. (2) 9

150 ------POUNDS ORGANIC 100 EMITTED X 1000 ,,j so

0.65 0.90 0.95 1.00

SOLVENT RECOVERY • UNIT EFFICIENCY

10 5 0

PERCENT ORGANICS • WATER BASED lNK

Legend. • • Toluene Ink -•-•- Waterbased Ink Figure 3. Emissions Comparison of Waterbased Ink Versus Solvent Recovery System. (15, 19)

A new rotogravure facility that has a solvent recov­ ery system designed for anticipated solvent inks may be inadequate. If a future printing process implements new solvents, then a costly and time consuming solvent recov­ ery modification may have to be implemented to prevent voe emissions (Figure 3) (15). Since water insoluble 10 solvents are easier to separate than soluble, a recovery system that was designed for water insoluble solvents (toluene) but switches to a water soluble (alcohols) may require additional equipment for the more complicated distillation and separation processing (15, 16, 19). The lack of flexibility of a solvent recovery system is a hidden cost. Another hidden cost can be the additional training/education required for printing press personnel on the proper processing and handling methods of recov­ ered solvents (15). Hidden costs of a recovery system need to be consid­ ered before ruling waterbased inks out as an alternative to reduce voe emissions.

A Review of Common Printing Methods

There are different printing mechanisms and methods for applying ink to a substrate. It is important to have a general understanding of printing methods to better appreciate the complexity of ink and paper interactions. The printing process being used in this study is rotogra­ vure. The rotogravure printing process originates from the intaglio printing process (2, 20). The intaglio process was developed in Europe during the 15th century (2, 20). The basic printing methods for ink transfer can be categorized into (a) engraved/etched-recessed 11 surface, e.g., intaglio; (b) planographic-planar sur­ face, e.g., offset lithography; and (c) relief-raised surface, e.g., letterpress (See Figure 4).

(relief/raised) (recessed/engraved) Figure 4. Different Printing Application Surfaces (2, 2 0)

Intaglio is still used today for high quality limit­ ed editions or to implement hand engraved plates as impression cylinders to make image copying and printing difficult. For example, United States of America curren­ cy is printed at the Bureau of Engraving and Printing with the intaglio method as an attempt to prevent coun­ terfeiting. Intaglio evolved into rotogravure at the end of the 19th century, about 1877 (2, 20). Printing from a recessed surface is the common element of both processes. The recessed surface (etched or engraved) of the gravure cylinder transfers ink under pressure by direct contact 12 with the substrate (2, 20, 21) (See Figure 5). A printing method which transfers ink directly from the printing image to the paper is defined as direct-contact­ printing.

uc.:�u1£k "J;\lrk�JO� kO._i..t:K

All:\l T [. (.;.CLLS ►· l,;LL ot-· l�h

-�------.... CMAVl.au; CYLJl\l>CK -···--···----....·

Figure 5. Rotogravure Printing (15).

Interestingly, the rudimentary rotogravure process was invented only about ten years after the letterpress was invented by Gutenberg, often called: "the father of modern printing" (20). The letterpress is also a direct impression printing method (direct-contact-printing) but uses a raised (relief) surface instead of a recessed (engraved) surface for transferring ink (Figure 4). Today, applications are very limited and as letterpress machines wear out they will be replaced with a newer printing method. 13 Planographic printing transfers ink from a planar surface with the printing image, as typical in offset lithography, to an intermediate surface and then to the substrate. Therefore offset lithography is different from most other printing methods, e.g., rotogravure, and as defined is not a direct-contact-printing method. Rotogravure has a large variety of recessed cell sizes which gives a large variation of dot sizes on the substrate (21, 22). Yet, a common problem to rotogra­ vure, flexography, and offset printing methods can be fiber puffing (swelling) caused by a waterbased ink or waterbased fountain solution (5, 6, 10, 23, 24, 25, 26, 27) •

Since rotogravure uses a direct-contact-printing method with recessed cells containing ink, it is critical that the gravure cylinder makes good and uniform contact with the surface of the substrate (21, 2) (Figure 5).

Control of Compressibility and Ink Transfer on a Rotogravure Printing Press

To give good contact between the engraved cylinder and the paper, the pressure is controlled by a hydraulic unit or a stepper motor located above the rubber coated impression roll (Figure 6). The substrate is compressed between the impression roller and the gravure cylinder, 14

LEGEND: 1= Graure cliner 2- Impression roller 3= Back-�p roiie' 2 4= Presire appkato

- ...... -. - - ... -- - ... -.

8 r-----� 3 ... -. -. -... -.... - . - .. - .. .1====:======i~ 2 ...... -~

X ...... A

Figure 6. Rotogravure Impression Roller Systems. (2) usually between 50 and 100 pounds per line�X inch (pli) ( 2) •

The contact area of the substrate with the gravure cylinder (impression width) is determined by the com­ pressibility of the rubber coated impression roll (Figure 7). The compressibility is determined by the applied pressure on the impression roll and the hardness (duro­ meter) and thickness of the coating material (Figure 7) (2). Too much pressure on the rubber coated impression roller causes de-formation (Figure 8). A distorted image is the result, if the substrate does not break causing a 15

101% 101¾ �-o t:J"O (/) (1) .... a.

[(/) .--I- ct! (1) 100 . - -. - 100 a. CJ ro - Web o61: .... - :, :]) Impression Velocit 0(1)"'9 Profile � 99 0:--=O Roll C 99 �U ·-o 0 (/) - Q) (/) '"O I... �(1) '), QJ ::i Cl. 11) ;:C, ◄ ► a.-.... 98 98 -E (/) (.9 Impression Width

• • - .... 200 200 100 100

0 -----0

.600 .400 .200 0 .200 .400 .600 Distance from Center of Nip (inches) Rubber Thickness · .500 inches Rubber Hardness • 80 Ourometer Impression Pressure • 72 lbs./inch

Figure 7. Rotogravure Impression Width Calculation. (2) 16

8 Figure 8. Impression Cylinder Nip Compression. (2) shut-down of the press. A small increase in surface roughness can reduce the quality of the image dramatically (2, 28). Yet, rotogra­ vure typically gives the best tonal image since the size of the dots, which represent a continuous tone of a photograph, can be varied by very small changes in the size of the engraved cells to release different amounts of ink (29). If the dots are small enough, these changes appear as gradations of color or darkness to the human eye. Rotogravure is the most reproducible printing pro­ cess. This is because the ink amount is determined by the cell size and not by the metering of a certain ink film thickness to the roller surface. Also, the process is more reproducible since there is less chance for human error. The excess ink is simply wiped from the surface of the gravure cylinder by the doctor blade (Figure 9). 17 This allows for photographic quality of gray scaling of one color, often 256 different shades of black, and color shading (continuous tones) for multiple color applica­ tions. The rotogravure printing press_ is versatile since the gravure cylinders can be varied in size for

Backing ~--7--- roller

Impression --Hfr----- roller

Ink Doctor---,- ..,;:~---feed blade

Ink Gravure trough cylinder

Ink return---.

Ink pump

Figure 9. Rotogravure Ink Application System. (22) 18 different print image lengths or widths (2). Chrome plating is the most expensive print imaging process. Yet, the higher initial cost is offset by the durability of the chrome plated engraved copper impression cylin­ ders, which have a longer cycle of print quality and printability than any of the other printing methods. If high quality photographic reproduction or high volume printing is required, rotogravure can have the best quality/cost ratio of all the printing methods.

Definition of Printability, Print Quality and Gloss

In the Graphic Arts Technical Foundation (GATF) book written by William Bureau (3), print quality and print­ ability are categorized together as ''Printability" and then defined independently: The terms of printability and print quality are not easily defined or measured. Printability has been defined as the extent to which properties of paper lend themselves to the true reproduction of copy by the. printing process used ... Print quality has been defined as the degree to which the appearance and other properties of a print approach the desired result. Print quality is determined by the degree to which all the many variables involved in print­ ing, including paper, combine to achieve the desired result. The desired result itself is difficult to define, since it is a subjective assessment and will differ among various observers. Paper properties that relate to printability can be classified as appearance and chemical, structural, and surface properties. Print quality as defined by Bristow and Ekman (6) is: Quality in a gravure print is a many faceted 19 property... print quality contains qualitative as­ pects which can only be assessed subjectively, quan­ titative measurements are needed... variation in density of the print... the print unevenness is re­ lated to the surface roughness of the paper and to determine which surface roughness parameter is of the greatest value for predicting the print quality. Bureau in the GATF book (3) defines gloss: ...that attribute of a paper surface that causes it to be shiny or lustrous. As a paper surface approaches optical flatness ...light rays striking it are primarily reflected as parallel rays ...known as specular reflection. A matte paper ... very low gloss, reflects much of the incident light diffusely ... When specular reflection appreciable exceeds diffuse reflection for a particular viewing angle, the paper appears to be shiny or lustrous [high gloss). Because specular gloss is a function of surface-reflected light, it is not affected by color... Gloss is related to smoothness, but there is no simple correlation. Gloss is an optical property and smoothness is a physical property... The gloss of an ink can also be affected by paper absorbency •.. Printability and print quality in this study were considered synonymous. The variation of ink gloss was used to judge print quality/printability. A higher ink gloss constituted better print quality in these experi­ ments.

Critical Rotogravure Printing Press Conditions That Determine Printability/Print Quality

What happens on the press during printing is criti­ cal to printability and print quality. To obtain good print quality in rotogravure, the swelling of fibers and the evaporation of the waterbased ink must be carefully monitored and controlled on the printing press. Both the 20 ink and the paper/substrate on the press must be con­ trolled interactively to ensure good print quality. Smoothness is one of the most critical parameters of the paper substrate (2). Therefore fiber swelling (puff­ ing) must be prevented or minimized _during printing to maintain substrate surface smoothness and the desired print quality and printability (30). Roughened surface areas cause cells to miss releasing/transferring ink from the gravure cylinder to the substrate (20). This is commonly called missing dots or also known as "skips," "snow" or "speckle" which reduce the overall print quali- ty ( 3) . Ink film setting is critical to form a high ink gloss in all printing methods. Yet, since rotogravure is a dry trap printing process, the ink must be dried and set before the next colored ink is applied to prevent improper trapping and misregistration. Improper rotogra­ vure trapping occurs when the ink of the next color printing unit is applied onto a "wet" ink instead of a dried ink surface. Misregistration is when the images and register marks of the different printing units are not in align­ ment (2). A different register mark (bead) is printed in the margin for each printing unit, and the placement of the mark (bead) to the target (ring) shows the alignment 21 of each printing unit (Figure 10). Misregistration can occur in two directions. One direction is the machine direction-the direction in which the continuous web is

COLOR REFERENCE

MACHINE DIRECTION

PRINIG EDE

Figure 10. Rotogravure Press Register Marks (2). traveling-and typically can be corrected by tension adjustments. The other is the cross direction-across the width of the web at ninety degrees to the machine direction-and is usually more difficult to correct since tension can only be adjusted in the machine direction (2). Misregistration is often caused by expansion or shrinkage of the cellulose fibers during wetting and dry­ ing. A waterbased ink can magnify the directional-es­ pecially cross direction-misregistration of an unsized light weight rotogravure paper (31, 32, 33). This means that the ink drying rate must be compatible with the 22 press speed and dryer capacity to prevent poor print quality caused by fiber swelling and trapping. Waterbased inks have several disadvantages. The primary problem with the use of waterbased inks in roto­ gravure printing is that fibers swell and cause surface roughness (4, 5). An interrelated problem is the increased drying re­ quirements of waterbased ink. Water requires about seven times as much energy-heat of vaporization in BTU/lb-to evaporate as a commonly used organic solvent, toluene (Table 2) (10, 18}. A British thermal unit (BTU) is a measurement of energy; specifically it is the quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit (2, 18). Rapid removal of water by evaporation from the sub­ strate surface immediately following the printing nip helps to reduce fiber swelling of the hydrophilic paper substrate (34). As printing press speeds increase, the problem of drying becomes even more critical (4). As in the paper industry, a printing press can become dryer­ limited. A method which has been used to reduce the dryer demand is to increase the evaporation rate of waterbased inks by an addition of an organic solvent (Table 3). However, using this additive defeats the 23 Table 2 Properties of Toluene and Water (10, 18) UNITS CONDITION TOLUENE WATER

Formula C6H5CH3 H20 Molecular 92.15 18 Weight Boil Pt. oc 1 Atm 110.6 100 2 Vapor Pr. lbt/in 77°F/25°C 1.064 0.46 Heat of BTU/lb 1 Atm-77°F 156 1050 Vaporization Flash Pt. OF 45 purpose of reduced voe emissions (17). This additive is typically alcohol, usually isopropanol, which increases the evaporation rate and reduces the British thermal unit (BTU) drying requirements (Table 3). Increased drying requirements of waterbased inks can also cause poor print quality and printability. High press temperatures can change the compressibility of the rubber coated impression roller which can then change the pressure and the resulting substrate contact area (2). These press temperature changes reduce printability and print quality. If temperatures are decreased to prevent these problems, then another problem of reduced produc­ tion speeds is created by these lower temperatures and longer dryer dwell times. 24 Table 3 Solvent Evaporation Rates Compared to Water (35)

CATEGORY SOLVENT NAME RATE

Water Water 1.00 Glycol Ether Dipropylene Glycol 1.17 Glycol Ether Propylene Glycol Methyl 2.30 Alcohol n-Propyl Alcohol 2.39 Alcohol Isopropyl Alcohol 4.00 Aliphatic Naphtha VM & P Naphtha 4.10 Alcohol Ethyl Alcohol 4.40 Alcohol Methyl Alcohol 5.75 Ester n-Propyl Acetate 5.78 Hydrocarbon Toluene 6.67 Ester Isopropyl Acetate 9.50 Ester Ethyl Acetate 10.86 Aliphatic Naphtha Heptane 13.50 Aliphatic Naphtha n-Hexane 27.67

Presently, waterbased inks have not been successful­ ly used on publication rotogravure presses at speeds of 2000-3000 fpm (4, 5, 36). The rotogravure web printing press usually have separate drying units for each of the color stages (2, 15) (Figure 11). Another drying method is to have a single gas burner with a blower to force the air into a 25 manifold located on the top of the press (Figure 12). After drying, the web needs to be cooled closer to the

\ \ \ \ \ \ Q_�

Figure 11. Two-zone Rotogravure Dryer. (2) ambient temperature for the next print application (37) (Figure 11). The applied pressure of the rubber coated impression roll is changed if a constant temperature is not maintained (2). 26

Exhaust ',f, '

Burner @§� Recirculation

Ext,ausl Fnn •

Suµply Fnn

i ,iftralion I/Capture I o . r'" .-- ...."�- "--

Figure 12. Dryer Air Flow in One-zone. (2)

The fibers swell due to wetting by waterbased inks and shrink on drying repeatedly throughout the printing 27 process. This causes registration problems and thus reduced printability (2). The repetitive fiber swelling (cycling) can also cause poor print quality because of increased substrate roughness and decreased substrate compressibility (3, 30). Even if a printing press dryer system is designed properly for the evaporation of waterbased inks or is retro-fitted with auxiliary infra-red (IR) dryers, rough­ ening of the substrate surface is only minimally prevent­ ed unless the paper fibers are chemically treated (sized) to reduce their hydrophilicity (water loving) (37). Figures 12 and 13 show the air flow system for forced hot air drying of a typical rotogravure press; this was similar to what was used in this experiment. Paper is typically subjected to dryer air temperatures that can exceed 160 degrees centigrade. The paper is then cooled on chill-rolls before the next impression section. The repetitive thermal cycling at high press speeds places stress and strain on the paper. This is even more complex and difficult to control with water­ based inks and hydrophilic cellulose fibers of light­ weight papers. Print quality may be affected by temporal fiber swelling and surface roughening caused by water­ based ink. 28

Exhaust . t '

' Burer . . Recirc11l.1tion ' ' ' ' ' tjS� -

t + . ' I

J ; __--- -J-o /''"''

Figure 13. Air Flow in Two-zone Dryer. (2) 29 An Overview of the Correlation of Sizing With Print Quality and Printability

Interaction of water with a cellulose substrate needs to be carefully controlled in printing. Specifi­ cally, waterbased inks in rotogravure, flexography, and waterbased fountain solutions in offset printing cause problems with print quality and printability (5, 38, 39, 40). The common problem of all three is that water penetrates the hydrophilic cellulose fibers of the paper substrate causing increased surface roughness by the swelling of fibers (41, 42). Rotogravure and flexography are direct impression methods but the smoothness of the substrate more directly affects the quality of rotogra­ vure printing (20). In offset, the swelling of fibers from a waterbased fountain solution can also reduce print quality. This is primarily caused by the picking of fibers. Picking occurs when the high tack (strong adhe­ sion) offset ink pulls fibers onto the printing press image {plate/blanket) and causes deffects in the printed image. Picking in offset is increased by weakened fiber bonding. Poorer fiber bonding is caused by repetitive fiber swelling from water-paper interaction that is similar in waterbased flexography and rotogravure print­ ing (3, 25, 43). Since high tack offset inks are not used in waterbased rotogravure, sheet strength is not as 30 significant in determining print quality or printability. The critical factor for rotogravure printing is the initial substrate smoothness and the prevention of rough­ ness during the waterbased rotogravure printing process (30, 44). Ginman (45) found that uncoated beater-sized paper, which was printed with rotogravure waterbased ink, had the least amount of wrinkle formation. The next sample (unsized) had a wrinkle formation value that was worse by more than 300 percent. Wrinkles reduce the substrate surface area that is in direct contact with the impres­ sion cylinder and thus give poorer print quality and printability (2, 20). Also, this sample (sized) had the least amount of misregistration for uncoated papers; only one of the coated samples was better. Misregistration on a press is measured by directional markers that need to be lined up from one printing image (color) to the next (2). If not, the final image is misaligned and not in registration (misregistered) (2). In the Ginman study (45), the next "best" uncoated sample had a misregi­ stration value that was almost 40% worse than the ''best" sized sample. For the uncoated papers, there seemed to be a direct correlation between water absorbency (STFI rapid moistener) values and the formation of wrinkles and misregistration (45). The uncoated, sized paper had the 31 lowest water absorbency value and the best (least amount) wrinkle and misregistration values for the rotogravure waterbased ink printing process (45). Additional studies have been done on water and paper interaction. However, many published studies have been done for lithographic (offset) or flexographic printing and not for lightweight publication rotogravure. There­ fore, it is important to study the prevention of water absorbency and fiber swelling of a rotogravure sheet by internal sizing. Then correlate this with print quality and printability of lightweight publication paper in rotogravure waterbased ink printing. The topic of water and paper interaction is reviewed in the following sec­ tions. The next section deals specifically with a review of the factors affecting print quality in rotogravure printing, such as the importance of surface smoothness of the paper.

Factors Affecting Print Quality and the Measurement of Print Quality

The prevention of surface roughening of the sub­ strate in rotogravure printing is critical to print quality. Surface smoothness and surface compressibility of the substrate (paper) in rotogravure printing are typically listed as the most important factors that affect print quality. To maintain a smooth surface of 32 the substrate during and after printing can be considered the most important factor affecting print quality. Several measurements, including surface smoothness and ink gloss, can be used to estimate the final print quali­ ty.

The Relationship of Surface Smoothness of Paper With Print Quality

The importance and definition of smoothness of the surface was explained by Bureau and Ekman (3) that: "The sectional smoothness of the paper existing at the instant of printing is described as its 'printing smoothness', and that a change in compressibility changes the gravure 'printing smoothness'. Also, the resiliency of the paper is important in a multiple color press." Paper require­ ments for gravure printing were identified by Bureau and Ekman (3) as: "·· .softness and compressibility are essential requirements, particularly so for uncoated pa­ pers... " Skowronski, Lepoutre and Bichard (42) made several important findings and statements regarding how different pulping methods affected the water/cellulose interaction. They found kraft pulp fibers to have good reversibility from water swelling, and partially explained this by: "Kraft handsheet ...fibers are already well-collapsed into ribbons." Yet, it was found that groundwood and TMP pulp 33 fibers have poor swelling/roughening reversibility. Specifically, the experimental data of Skowronski et al. showed that there was a correlation between the percent­ age of irreversible change in thickness and the percent­ age increase in surface roughness (Table 4).

Table 4 Comparison of Sheet Thickness and Roughness from Skowronski et al.*

Paper Type Increase in Increase in Sheet Thickness(%) Surface Roughness(%)

Kraft 34 30 Handsheet (calendered) Kraft 1 1 Press Dried

Machine Made 55 50 Newsprint (GW) Machine Made 65 70 Newsprint (TMP)

*Data has been reorganized from the article by Skowronski et al. (42) and placed in table form.

Dunfield, McDonald, Gratton and Crotogino (44) showed that a smoother surface (PPS measurements) gave better print quality and, conversely, that higher surface roughness (PPS) gave lower print quality. Their study was specifically on the evaluation of gravure printing of steam-treated machine calendered newsprint (44). A 34 definite correlation between surface roughness/smoothness and print quality was exhibited. However, the study also showed, "··· [that if] changes in the surface structure were caused at the wet end or by changes in furnish properties this will alter the roughness/printability relationship." PPS measurements of surface roughness may predict print quality but the accuracy or sensitivity of this method may be dependent upon the furnish and paper­ making process.

Print Gloss as an Indicator of Fiber Rising and Surface Roughening

Hoc (30) states that changes in surface structure caused by water and high temperatures give poor print quality. Specifically, fiber rising increased surface roughness and decreased ink gloss. Hoc used newsprint, supercalendered and lightweight-coated paper for STFI fiber rising testing, and printing was done on a GFL Lithotester. There was a better correlation between fiber rising and ink gloss than with surface roughness. Also it was demonstrated that a loss of gloss, caused by fiber rising, was less with paper primarily containing long wood fibers and greater for paper with short fibers. Chemical (kraft) paper had less surface roughening and more fiber bonding strength than paper containing mechan­ ical pulp. Beland, Nguyen, De Silveira and Lepoutre (46) 35 found that the best correlation with fiber rising was gloss for all papers and printing methods, and not PPS roughness measurements.

To understand surface roughening from the applica­ tion of water, and principally waterbased ink in rotogra­ vure printing, fundamental research on water/fiber inter­ action done by Hoc was reviewed. Hoc (30) explained that fiber rising is a problem caused by water from surface sizing, coating, or printing inks. Hoc found that fiber rising caused an irreversible change in the surface structure-roughening. Irreversible surface roughening also caused variations of print density and a loss of gloss in halftone images as determined by a GFL Litho­ tester. The amount of fiber rising was shown to be dependent upon the amount of water applied to the surface of the paper. Hoc (30) also demonstrated that long fiber length was better in the prevention of fiber rising. Specifically, paper that contained short wood fibers had the greatest surface fiber rising. Thus, short-fiber rising caused a reduction in gloss.

The Importance of Surface Compressibility of Paper Along With Surface Smoothness

Surface compressibility and roughness of paper are defined by Bristow and Ekman (6): "Surface compressibil­ ity ... is the change in surface roughness accompanying 36

the application of pressure to the surface." (6). Bristow (47) found for sheets of 2 microns to greater than 8 microns of surface roughness: "Printability is dependent not only on the surface roughness achieved but also on the compressibility." However, the printing pressure may be important: "Printing pressure require- ment is the pressure required to achieve a PPS rough- ness level arbitrarily chosen as being a level which is compatible with good printing quality ... " In Bristow's experimental work (47) there was a higher correlation between increased surface roughness and poorer print quality, with a higher than normal test­ ing applied pressure of 6-7 MPa (approximately 60-70 kgf/cm2). Parker Print Surf surface roughness measure­ ments are typically made with three applied pressures, 5, 2 10 or 20 kgf/cm • Bristow found that both compressibility and roughness should be considered in a correlation with the print quality of a coated stock: ...if steps are taken to take into account not only roughness but also the compressibility of the sur­ face a better resolution of the data is obtained and an explanation is found from widely different print quality results are some times obtained for materi­ als having very similar PPS roughness values. In other words, papers with the same roughness values but with different compressibility and different printing press conditions may result in different gravure print qualities. Bristow also stated it this way: " ...the 37 roughness and the compressibility [is) in a manner rele­ vant to the printing situation and is thus of value in predicting gravure print quality. A paper having a high pressure requirement will clearly tend to be difficult." Aspler and Lepoutre (48) also found experimentally that smoothness and compressibility of the substrate affected rotogravure print quality: In gravure printing, surface smoothness is essential to ensure transfer of the ink from the cells on the engraved cylinder ... The good performance of bulky coatings in gravure printing ... because they fill more of the volumetric roughness •.. they deform more easily to conform to the planar gravure cylinder. Several other groups of researchers (49, 50, 51 and 52) found that bulky coatings typically gave good print quality. The next section reviews how good print quality may be maintained.

The Effects of Sizing and Absorption Rates of Paper on Surface and Ink Film Properties

When a paper is sized, it typically means an in­ crease in hydrophobicity (water-hating). Fetsko (38) defined highly polar materials as hydrophilic (water­ loving) while materials with low polarity were either hydrophobic or oleophilic (oil-loving). Fetsko also stated that: "If water from the formed solution (lithog­ raphy) that contacts the paper is minimized then 38 "problems such as curing and expansion will be prevent­ ed." Ofcourse, this also applies to waterbased rotogra­ vure printing or any other printing operation, such as waterbased flexography, which applies water to a cellu­ lose substrate.

Sizing Effects on surface Roughness

Both increased rosin and alkenyl succinic anhydride (ASA) sizing reduced surface roughness of the paper after printing with waterbased ink, as demonstrated in Table 5. The sizing was measured by the Cobb water absorption sizing test. The rosin sizing was for an acid paper of pH 4.5 and the ASA sizing was for a neutral paper of pH 7 (53). Rosin sizing is typically used in acidic paper making conditions, while both ASA and AKD are typically used in neutral and alkaline sizing conditions. The sizing and surface roughness values are summarized in Table 5. The values are a compilation from several Tables in the article by Aspler, DeGrace, Beland, Maine, and Piquard (53) except for the calculated percentages.

Review of the Methods of Sizing. Internal and Surface Sizing

Krueseman and Beck (37), and Tompkins and Shepler (54) found that without sizing (i.e., internal or surface 39 Table 5 A Comparison of the Effectiveness of Sizing on Preventing Surface Roughening

Sizing Slack Sized Hard-sized Reduction Agent (Unsized) PPS-10 of Surface PPS-10 (microns) (microns) Roughness(%)

Rosin 4.34 3.61 17

ASA 4.35 3.42 21 sizing) the amount of water pick-up was much greater and required more evaporation drying when water was applied to the surface of the papers. The conclusion that can be reached from these studies was that a combination of internal and surface sizing was the most efficient (lower total dosage). Also, it was more effective in reducing water pick-up, drying, and subsequent fiber swelling from water/paper interactions. The improved efficiency of the sizing process was not an issue in this study. In this experimental study at Western Michigan University, only the effect of internal sizing (AKD) as a primary component on print quality was studied.

The Effects of Sizing on Ink Film Transfer and Gloss

The influence of water absorbed in waterbased gravure ink transfer was small for handsheets of bleached 40 softwood kraft. Aspler et al. (53) used Cd in the ink to quantitatively measure ink transfer. A decrease in sizing resulted in an increase in surface roughness. Aspler et al. did a quantitative study of ink transfer by measuring Cd on the printed samples� They also measured surface roughness and ink density for different sizing levels. Aspler et al. correlated surface roughness with changes in ink transfer and ink density measurements. Aspler et al. found that wood species was the dominate property influencing ink transfer and penetration for either oil or waterbased inks. Oil and waterbased inks had the same fraction of penetration for commercial ink film thicknesses. Commercial ink film thickness (dried) for all print­ ing methods are typically 1 to 3 g/rn2 (53, 55). Aspler concluded that water absorbency had an effect or impact on ink penetration when 10 times (extreme) the normal amount of water in an ink film was applied to the paper. Dried ink film of different printing methods is about the same thickness although "wet" ink film thickness is significantly different (Table 6). The "wet" volume is critical for the determination of the amount of water that is applied to the surface of the paper (3). Bureau found that if enough water in the film was applied to the paper, a critical point was reached where the water 41 Table 6 Wet Ink Film Thickness Values (6)

Type of Ink Thickness* Thickness (microns) (mils)

Offset 2 0.08 Letterpress 3 0.12 Gravure 12 0.5 Screen 60 2.5

*Ink at full strength and printed as a solid on smooth paper.

inhibited the penetration of the ink (pigment) into the paper (3). Other films that apply water to the surface of paper are aqueous paper coatings. Aqueous paper coatings have a dried film thickness of 6 to 12 g/m2 • Since these paper coatings typically have "wet" films that contain higher levels of water than "wet" ink films, they can be better indicators of the critical water levels. The critical water level can be used to deter­ mine the effective penetration rate into the paper. Ginman and Visti (56) showed that with an increase in water absorbency, an increase in the dried coat weight from approximately 3 g/m2 to 8g/m2 , there was a relative drop in ink gloss by 40 percent. 42 Dependence of Furnish on the Effectiveness of Sizing and Control of Ink Gloss

Skowronski et al. (41) stated that paper and coating gloss was not affected by AKD hydrophobic sizing. They determined that AKD sizing did not stop adsorption into the fiber walls but inhibited capillary migration. However, capillary migration can be important to the set­ ting of a thin film such as waterbased ink. The furnish contained mechanical pulp fibers and the paper was pro­ duced on a handsheet former, not a paper machine. Both Aspler (57) and Triantafillopoulos, Serafano and Rosinski (5) stated that hydrophobic sizing had little effect on print quality of waterbased gravure. Triatafillopoulos et al. used 100% hardwood kraft, and Aspler (57) used paper containing mechanical pulp.

The Importance of Ink Density Relative to Ink Gloss and Surface Smoothness of Paper

Print density can be an important indicator of the ink film and thus a factor in print quality. Maley (55) stated that: Ink density is a measure of the percent of pigment that is contained in an ink film. This pigment loading accounts for most of the density, with paper absorption contributing a small amount. It is not density that produces ink gloss ... If papers are being tested for ink gloss with ink containing the same pigment loading, then density can be used as an approximation. 43 Again, the furnish used can be critical on the experimen­ tal results. Aspler's study used mechanical pulp (57). Specifically, part III of Aspler's research series (57) showed that as the surface roughness increased the print density decreased in letterpress and flexographic print­ ing of newsprint (mechanical pulp fibers). Aspler et al. (53) found that flexographic ink density increased with an increase in ink transfer. Both ink transfer and ink density increased with increased water absorbency, resulting in an indirect correlation between ink density and ink transfer.

Effects of Water Absorption and Penetration Into Paper

Hutchinson (58) stated that absorption of water and smoothness of the paper determined the print finish and print gloss. The lowest waterbased ink print gloss was correlated to the substrate which had the highest water absorbency (Cobb test). Bassimer and Krishan (59) found that in offset lithography the formation of the ink film was affected by the absorption rate of the paper. In particular ink film properties were influenced, e.g., gloss. Theoretically, Bassimer felt that instantaneous gloss changes would correlate to the water absorption rate. However, the change of gloss was not used to approximate the 44 absorption rate since a series of gloss measurements could not be made within seconds of printing. Salmimen (23) made significant observations about the effects of water on paper, a continuation of the work of Eklund and Salmimen (60). Salminen concluded that: "Diffusion is probably the most important transport mechanism in hydrophobic (sized) paper qualities under no external pressure,'' and "Pressure penetration is also affected by the degree of calendering, the liquid temper­ ature, and the degree of sizing." Salminen's data showed that an increase in the hydrophobicity lowered the amount (volume) of water that was transferred into the paper at short intervals from .0025 seconds to .0625 seconds. Salminen's data has been reformatted into Table 7 and shows the effectiveness of hydrophobic sizing in reducing water penetration at a pressure of 0.5 atmospheres (0.52 kg/cm2). In summary, waterbased inks typically give poorer print quality than inks containing toluene in publication gravure (5). This is true despite attempts to optimize ink properties and press operating conditions. In addi­ tion, the surface sheet properties can be controlled to maximize smoothness and uniformity. These techniques improve the effectiveness of ink transfer (61, 62) and assist in uniformly spreading the ink on the paper while 45 Table 7 The Volume of Water Absorbed Relative to Time and the Level of Sizing (23)

3 2 Sizing Volume ( cm /m ) Volume Absorbed Level at at Increase (%) 0.0025 sec. 0.0625 sec. (%)

0 8 24 300 1.1 6 10 67 minimizing missing dots. Although, print quality and printability depend on many of these factors, paper and ink interaction chemistry also plays an important role ( 5) •

Paper sizing can be an important factor as a control for wetting, penetration, and drying of the ink. Inter­ nal sizing was the controlled variable for study in this experiment. However, there are many complex factors involved in ink/paper interactions. These include dynamic wetting, penetration and absorption into the substrate for an uncoated basesheet. For an uncoated paper substrate, wetting and penetration into the fibrous matrix of the paper substrate take precedence over other phenomena. Ink gloss can be a key factor in determining print quali­ ty and was in these experiments. So, this experimental work attempted to control or modify these phenomena to 46 improve ink gloss and optical density of the waterbased gravure printed impressions by reducing ink penetra­ tion/absorption rates into the paper. CHAPTER III

PROBLEM STATEMENT AND OBJECTIVES

It is hypothesized, based upon -the previous review of the literature, that increased internal sizing of machine-made paper will improve print quality of papers printed by gravure printed waterbased ink. The problem of controlling the printing process to achieve good print quality is more complex for waterbased than for organic solvent-based inks. Ink gloss (mottle) is typically ranked as the most important judgement factor for print quality, so optical ink density was measured to validate the final print quality results. Further improvements in water based printability and print quality need to be considered with respect to • alkaline sheets, the current trend in papermaking. There previously has been no comprehensive and systematic study on improving waterbased ink print quality and print­ ability by controlling fiber swelling with alkaline internal sizing. Therefore, the focus of this work was to study the effects of internal alkaline sizing on print quality of "Roto News" printed with rotogravure water­ . . based inks. A major print quality problem for these grades is fiber swelling from water during printing. The

47 48 swelling can cause surface roughening of the printed areas, and thus reduced print quality/printability. The nonuniformity of fiber swelling and water penetration of the paper network can adversely affect the print quality. The objectives of this experimental study were as follows: 1. To evaluate fiber swelling by comparing the sur­ face roughness of paper surfaces, before and after roto­ gravure printing, and, ink gloss with magenta and cyan waterbased inks for seven internal sizing levels, from slack-sizing to hard-sizing. 2. To correlate paper absorption and penetration values by Hercules sizing test (HST) measurements with rotogravure optical ink density for the seven different internal sizing levels using a waterbased ink. 3. To correlate rotogravure press printability and print quality with surface roughness and ink gloss mea­ surements. CHAPTER IV

EXPERIMENTAL DESIGN

Overview

The basic concept of these experiments was to vary internal sizing of paper (increase hydrophobicity) to study the effects on print quality. Ink gloss is a sensitive indicator of surface changes as shown by Hoc (30) and Beland et al. (46), and was used in this experi­ ment to measure print quality of waterbased rotogravure printed papers.

outline

The paper utilized in this study was an alkaline, internally-sized sheet made on a pilot Fourdrinier paper machine. The paper sizing ranged from unsized (minimum) to hard-sized (maximum) paper. This paper represented the heaviest of the commercial Roto News publication grades (basis weight, 55 grams per square centimeter). The paper was printed on Cerutti rotogravure press with waterbased ink. The interactions studied were between alkaline waterbased ink rotogravure printing and alkaline rotogravure paper of varying hydrophobicity.

49 50 Smoothness measurements and HST (sizing test) results were recorded. These measurements were compared to printing properties (a) gloss and (b) ink optical densi­ ty. These printing properties were then analyzed to determine print quality. Print quality was then corre­ lated with changes in internal sizing properties. Poor ink receptivity tends to be defined strictly as a paper problem, not an ink problem. It is important to look at small changes in the ink density of the print area of the paper, and to compare across the sheet for minor variations over a large area. The tested samples were printed on the Cerutti gravure press and the ink density values were measured by a densitometer (optical ink density) on the solid color blocks. An attempt was made to elucidate the effects of fiber swelling and surface roughening, as well as water penetration, on the print quality of waterbased rotogra­ vure for publication papers. Variations of surface roughening and penetration rates were achieved by alter­ ing internal sizing. CHAPTER V

EXPERIMENTAL METHODOLOGY

This study consisted of four parts. In part one, the paper was made on the Lou Calder Fourdrinier paper machine of Western Michigan University, at seven differ­ ent internal sizing levels. Part two was the super­ calendering and testing of the machine made paper. During part three, the paper was printed on the pilot plant Cerutti rotogravure printing press of Western Michigan University with two alkaline waterbased inks of magenta and cyan color. Finally, sizing properties of the paper were correlated with print quality.

Preparation of Papers

In part one, a blend of bleached softwood and hard­ wood kraft (chemical) fibers were used to produce light­ weight publication paper under alkaline conditions for Runs 1-6. Run 7 had groundwood (high-yield mechanical pulp) added to the kraft. A total production of 45,500 linear feet was made on the paper machine. Each of the seven sizing levels contained 6,000 linear feet with a . 500 linear foot process stabilization section. The pulp . blend was chosen to ensure that smoothness was controlled

51 52 to 2.8 Parker Print Surf (10 kgf) soft backing measure­ ment. The pulp blend consisted of 84% bleached kraft hard­ wood and 16% bleached kraft softwood. The hardwood was composed of 45% maple (early-wood), 25% birch, 15% beech, and 15% aspen. The softwood was composed of ponderosa pine. Five percent precipitated calcium carbonate filler was added to the furnish for smoothness. Internal siz­ ing, alkyl ketene dimer (AKO) and a cationic polymer retention aid, was added at seven different dosage rates, as shown in Table 8. This paper was wound as a continu­ ous web on a roll with a 24 inch trim width.

Table 8 Internal Sizing Dosage Levels of AKO

AKO AKD AKO Sizing Dosage Dosage Run (lbs/Ton) (%)

1 0 0

2 6 0.3

3 10 0.5

4 14 0.7

5 18 0.8

6 22 1.1

7 40 2.0 53

The kraft hardwood dry lap (sheet) pulp was pulped and then refined separately in the pilot plant beater and disk refiner. The Canadian Standard Freeness (CSF) was 225 to 245 ml for kraft hardwood. The kraft softwood dry lap pulp was also refined separately in the pilot plant beater and disk refiner, but down to a freeness range of 400 to 420 ml CSF. The mechanical pulp was a never-dri�d slurry of stoneground northern hardwood. The kraft pulp was bleached, but not the mechanical pulp. The mechanical pulp received no further beating or refining. The two pulps and the calcium carbonate were blended in the stock chest to produce the furnish for the paper. The pH was adjusted for alkaline papermaking conditions with either sulphuric acid or sodium hydroxide, approximately to pH 7.5. In this experiment, the pH of the paper machine white-water was held constant to reduce any possible sizing varia­ tions due to pH variation. Paper chemistry changes, by an alteration of the internal paper pH, did have an effect on alkaline waterbased print quality in other experiments (5, 63, 64). So, to reduce variables, the paper pH was held constant at alkaline conditions while the internal sizing of paper was modified to increase the hydrophobicity of the paper from low (slack-sizing) to high (hard-sizing). The pilot plant paper was produced 54 at a basis weight of 55 g/m2 at a moisture content of about 5 percent. The maximum number of paper machine calender nips (three) were used for maximum smoothness. The smoothness target of 1.5 to 2.8 Parker Print Surf (10 kgf soft backing) was achieved using the pilot plant supercalender. It was critical to allow the paper to condition at printing press conditions. Normal TAPPI controlled temperature and relative humidity conditions ° of 70 F and 55% were used. The basic characteristics of all seven papers were that they were uncoated and supercalendered to the same approximate smoothness of 2.8 Parker Print Surf (10 kgf soft backing). In part two, the sizing level of the paper was determined by the Hercules Sizing Test (HST). Smoothness (roughness) was measured by the Parker Print Surf tester after production on the Lou Calder paper machine and, if supercalendered, after this operation. The roughness ex­ ceeded 2.8 PPS (10 kgf with a soft backing plate), so supercalendering was used to obtain a lower roughness of the paper. The supercalender was run with 5 nips, 1700 pounds per lineal inch (pli), and a steam temperature of ° 175 to 180 F. All of the seven different sized papers were measured for sizing. 55 Printing Procedures

Part three of this project involved printing the paper on a Cerutti pilot plant rotogravure printing press. The same magenta and cyan waterbased inks were used for all printing. These inks were similar to com­ mercial waterbased alkaline ink with a 9.0 pH and about 4,000 µMHO/cm conductivity. The two inks, cyan and magenta, had approximately the same solids content: 55 , percent. The composition of the cyan waterbased ink was 24.7% Phthalocyanine (cyan) pigment emulsion, 50% acrylic emulsion, 3% polyethylene wax, 0.3% organic defoamer, and water. The magenta ink had a similar composition but contained a different pigment emulsion. The static sur­ face tension of the two inks was measured (32.8 dyne/cm) and compared to a standard toluene based rotogravure ink, approximately 32 dynes/cm. Printing was carried out at ambient conditions (74 degrees Fahrenheit and 55% relative humidity) with 5 to 6% sheet moisture. The press speed was 500 fpm (65.3 m/min) and had a hydraulic applied impression roller pressure of about 100 pounds per lineal inch (pli). With the applied pressure, the nip (impression) width was calculated as 1 cm on a 85 durometer (hardness) rubber coated impression roll. Electrostatic assist (ESA) was available and was set on automatic as a constant for the 56 Cerutti print trial. Industrial printing uses ESA to aid in ink transfer, thus it was used in this experiment. Helio engraved cylinders that were specifically designed for waterbased ink was used. The cell dimension of the cylinder for magenta ink was 30 microns deep and the cylinder for cyan in was 32 microns. The drying was done at 160 degrees Fahrenheit by forced hot air, gas fired, at a flow rate of 9,000 cubic feet per minute (cfm) to simulate a full size drier at 160 degrees Fahrenheit.

Determination of Delta Gloss

Paper and ink gloss were measured by a light re­ flectance instrument at an angle of 60 degrees with a Hunter Print Gloss meter. Measurements of ink and paper gloss were used to calculate the delta gloss by differ­ ence. The delta gloss was used to compensate for any possible variation of paper gloss.

Statistical Analyses

Statistical analyses of data was done using Statis­ tical Analysis Software (SAS) for the standard variation and simple linear regression methods (65, 66). In SAS, several specific methods of analysis were used. The Bonferroni �-Test, the Scheffe's test, and univariate procedure (including skewness of the dependent variable) 57 were implemented for data analysis. A comprehensive analysis of the data is in the Appendices. A general description of each of the appendix is in the "Results and Discussion" section. Explanations of the analysis methods are in Appendix c.

Determination of Print Quality

Printability and print quality were determined and correlated with the internal sizing values and fiber swelling as measured by surface smoothness variations for each of the seven AKO sizing levels. Print quality was determined by the evaluation of the following: 1. Ink optical density assessed the uniformity of ink receptivity. A reflectance optical densitometer was used to experimentally measure the ink density of the solid printed cyan and magenta areas. The ink densitome­ ter used in this experiment measured the reflectance of light from the ink film. A higher pigment loading in the ink film reduced the amount of reflected light, thus a higher density value. For example, a density reading of o.oo means that 100% of the light is reflected and a 1.20 reading means that approximately 6.25% of the light is reflected from the ink film (43). Williams suggests that the maximum density reading for any printed ink film, 58 including rotogravure, which can be achieved with an un­ coated paper is 1.35 (maximum density reading of gloss­ coated paper is around 2.0, which means that less than 1% of the light is reflected) (43). 2. Surface smoothness was experimentally measured and paper compressibility was calculated from smoothness measurements to determine their possible effects on the variation of ink film transfer. Parker Print Surf (PPS) airleak surface roughness measurements were taken with a soft backing at both an applied pressure of 10 Kgf/cm2 and 2 20 Kgf/cm • The surface compressibility of the 7 experi­ mental papers was calculated by PPS 10 Kgf/cm2 smoothness values minus PPS 20 Kgf/cm2 smoothness values. For data on how compressibility was calculated from PPS measure­ ments, see Appendix L. 3. Experimental optical ink density measurements were used to estimate variations of ink film thickness and the relative thickness of the ink film. These esti­ mations were possible when surface smoothness and com­ pressibility of paper were held constant between sized kraft paper runs. 4. Increased delta gloss values were related to the improvement in print quality. Delta gloss is the difference between the ink and paper gloss. Specifical­ ly, delta gloss was determined by subtracting the paper 59 gloss from the ink gloss to remove any possible variation between the basestock of the different sized papers.

List of Equipment

Equipment of Western Michigan University used in this experimental work was: (a) Parker Print Surf Sur­ face Smoothness Tester (Digital), (b) Hercules Sizing Tester (HST), (c) Hunter Print Gloss Instrument, (d) Lou Calder Pilot Plant Fourdrinier, (e) Pilot Plant Supercalender, (f) Cerutti Model 118 Rotogravure Printing Press, (g) Ink Optical Densitometer (X-rite Model 404). CHAPTER VI

RESULTS AND DISCUSSION

Overview

The HST values relative to internal sizing levels form the centerpiece of the experimental results. These results are presented in Tables and Figures which include corresponding values of smoothness, gloss, compressibil'­l. ty, and ink optical density. The method of statistical analysis for each test is briefly described in the main text, and additional details of the statistical methods used appear in Appendices C through I and K through N. The major conclusion of this experimental work was that, within the range investigation, an increase in the internal sizing increased the delta gloss. Also, the ink gloss was improved with higher internal sizing dosage levels. Optical print density values were compared to PPS surface smoothness measurements for the seven papers. A correlation of these measurements between the different papers existed and thus the ink film thicknesses was estimated as equivalent (55). Although the differently sized paper prints had the same approximate ink film

60 61 thickness in the solid printed areas, they had variable delta gloss values for different internal sizing levels. Compressibility of the paper had a minimal effect on the ink gloss of the papers. Internal sizing presumably did not reduce or in­ crease ink transfer but did dramatically improve ink gloss.

Paper and Ink Film Properties Related to Print Quality

In this section paper and ink film smoothness and compressibility of the paper, are evaluated for their effect on final print quality.

Paper Surface Smoothness

Table 9 shows that standard deviations of smoothness measurements were typically less than 0.06. This is a coefficient of variation of about 2% that is considered low for this method of measurement. The Parker Print Surf roughness tester measures in units of microns and a change of more than 2/10 (0.2) of a micron can be signif­ icant. There was an initial decrease in surface roughness from Run 1 (unsized) to the other sized kraft runs with the addition of AKD. The exception was Run 3; the stan­ dard deviation value exceeded 0.12 and had an 62 experimental measurement variation that was between 0.1 and 0.2 microns for the smoothness of the printed magenta blocks. There were high and low voltage electrostatic assist (ESA) values at random intervals while printing Run 3.

Table 9 Smoothness Comparisons of Nonprinted Areas With Magenta Blocks

Nonprinted Areas Single Color Statistics*

AKO Smooth. Smooth. Smooth. Sizing P.P.S.** P.P.S.** P.P.S.** SD*** SD SD Run Never Unprint. Mag.Blk Never Unprin Magenta

1 3.11 3.27 3.28 0.0811 0.0613 0.0567

2 2.73 2.85 2.88 0.0407 0.0881 0.0433

3 3.08 2.93 3.12 0.0498 0.0589 0.153

4 2.75 2.88 2.87 0.0669 0.0481 0.0508

5 2.80 2.89 2.83 0.0489 0.0539 0.0566

6 2.70 2.91 2.79 0.0642 0.0363 0.068

7 2.74 2.85 3.12 0.0577 0.0739 0.0818

*A complete statistical analysis is located in the Appendices M and N. **Parker2 Print Surf smoothness values tested at 10 Kgf/cm • ***Standard deviation of PPS measurements.

Thus, the ESA system was unable to maintain a constant charge, possibly contamination of the paper of Run 3. 63 ·Overall, Run 3 had the roughest surfaces and the greatest statistical variation in data for the mechanical proper­ ties of all the internally sized 100% kraft papers (Runs 2 through 6). Run 3 data are listed in Tables 9, 10, 11, 13, and in the Appendices M and N. It is critical to have the same surface smoothness to obtain the same ink transfer for all of the runs (56). The surface smoothness values (see Table 9) for each of the papers were within a range of 10% of the mean value of all values. The ink optical densities for each of the papers (see Appendices G and H) were within a 10% range of the mean value of all values. Thus, even with the same approximated ink film thickness, the ink gloss in­ creased with an increase in HST seconds. Surface rough­ ness (Tables 9 and 10, and Figure 14) and compressibility (Appendix L) values were not skewed and were within a range of 10% of the mean value of all sized kraft paper values, except run 3. A very important condition of the experiment was that most of the paper surface smoothness values of the sized kraft papers were approximately the same. However, papers which had lower delta gloss values also had marginally (i.e., 10 percent) rougher surfaces. Therefore, an increase in internal sizing improved ink gloss within the limits of this experiment. Runs 2, 4, 5, and 6 had smoothness values that 64

varied less than .09 micron (3% variation) for never­ printed, unprinted and printed magenta block areas (Table

9 and Figure 14). A trend of moderate roughening was

present from "never-printed," to the "unprinted," to the

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Legend. X Never-printed section of paper,

� Unprinted area of image (printed) area, ■ Printed Magenta Block Figure 14. Comparison of Sizing Levels With Surface Smoothness.

"printed magenta block" was present in all runs except 65 Run 3 (Figure 14). "Never-printed" was the paper that was not printed on the press, and "unprinted" was the area of the printed impression that contained no ink. The smoothness of the first color down, magenta, affected the delta gloss of the trap for sizing levels 1, 2, 4, 5, and 6 (Table 10). With an increase in HST values (Figure 15), the surface roughness· of the printed magenta block for Runs 2, 4, 5 and 6 decreased as the gloss increased (Table 10 and Figure 16).

50U

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Figure 15. Hercules Sizing Test Results. Table 10 Effect of the Sizing Level on Smoothness of the Magenta Block and Delta Gloss of the Trap

AKO AKO HST Smooth. Trap sizing sizing Time P.P.S.* Delta Run Level (%) (sec) Mag. Blk Gloss**

1 0 0 3.28 1.190

2 0.3 75 2.88 2.246

3 0.5 117 3.12 2.400

4 0.7 170 2.87 3.212

5 0.8 207 2.83 3.852

6 1.1 268 2.79 4.788

7 2.0 459 3.12 3.042

* A higher value is rougher. **A low value represents a low ink gloss relative to the paper gloss.

O'I O'I 67

SL 6 (268)

SL 6 (207)

0.e I. I- SL 4 (170) GI CSL 7 (450) .::.., 3 (271 Groundwood)

e s ◊ -" SL 3 (117)

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Sising Level (SL) 1 1

Z,7 2,8 1,1 3.0 3,1 3,Z 1.3 3,4 SIDothness of the�ta Block (1icr)

Figure 16. Magenta Block Smoothness Compared to Delta Gloss of Trap. 68 Four of the 100% kraft papers (Runs 2 and 4-6) surface smoothness values varied by less than 0.02 of a micron with an increase in internal sizing from 75 to 268 HST seconds. With the same printed surface roughness of the Magenta Block, a correlation between increased HST and delta gloss is shown in Table 10. The other inter­ nally sized kraft paper, Run 3, had a greater change in surface roughness (0.20) micron. If the PPS smoothness value of the "unprinted" image area are compared to surface smoothness of the solid printed magenta block of the image (see Appendix N, Table 11), then Run 7 paper did not fit the pattern of not exceeding an increase in surface roughness by 0.20 of a micron. Run 7 had the highest sizing value of 459 HST seconds, but in the comparison example had a 0.27 micron increase in roughness. Run 7 paper contained 27% stone groundwood, and highlighted the importance of furnish composition on surface roughening (Table 11 and Figures 17-23).

Ink Film Smoothness

Trap analysis was important in this study for ink to ink, and ink to paper interactions. Trap in this experi­ ment was determined at the print location where the cyan ink was printed on top of the magenta ink. In general, Table 11 Smoothness Comparisons of Printed and Nonprinted Areas

Nonprinted Areas Printed Areas -- AKD Smoothness Smoothness Smoothness Smoothness Smoothness sizing P.P.S.* P.P.S.* P.P.S.* P.P.S.* P.P.S.* Run Never Unprinted Magenta Cyan Doors

1 3.11 3.27 3.28 3.29 3.16 2 2.73 2.85 2.88 2.78 2.75 3 3.08 2.93 3.12 2.80 2.82 4 2.75 2.88 2.87 2.80 2.74 5 2.80 2.89 2.83 2.80 2.78 6 2.70 2.91 2.79 2.75 2.76 7 2.74 2.85 3.12 3.20 2.95

*Parker Print Surf smoothness values tested at 10 Kgf/cm2.

°' \D Table 11-Continued

Statistical Results*

AKD Standard Standard Standard Standard Standard Sizing Deviation Deviation Deviation Deviation Deviation Run Never Printed Unprinted Magenta Cyan Block Doors (Cyan and Magenta)

1 0.0811 0.0613 0.0567 0.0579 0.0757 2 0.0407 0.0881 0.0433 0.0665 0.0501

3 0.0498 0.0589 0.153 0.126 0.0537 4 0.0669 0.0481 0.0508 0.0513 0.0467 5 0.0489 0.0539 0.0566 0.0478 0.0472 6 0.0642 0.0363 0.068 0.0406 0.0703 7 0.0577 0.0739 0.0818 0.0486 0.0533

*A complete statistical analysis is located in the Appendices K-N.

-..J 0 71 the rotogravure printing process prints the next ink on top of the previously dried or set ink, not wet on wet. It was important to determine the effects of the first color down (magenta) on the final properties of the trap (Figure 16). In Figure 16 there we�e three groupings from the smoothest to the roughest; (a) kraft papers Runs 2, 4, 5 and 6 had 2.8 to 2.9 microns of roughness; (b) kraft paper Run 3; and (c) unsized paper Run 1. In smoothness groups (a) and (b), the gloss increased with an increase in sizing. The increased surface roughness of the paper of group (b) partially negated improved ink gloss from higher internal sizing relative to group (a). Overall, surface smoothness of the magenta ink had a negligible effect on gloss, and thus sizing was the key factor affecting ink gloss. For most of the kraft papers, smoothness of the single ink and trap printed areas were statistically equivalent. The exception was the groundwood containing paper, Run 7, which continued to have an increase in surface roughness as more ink was applied; the surface roughened by more than 0.2 micron after the printing of first ink (magenta) but less than a 0.1 micron after the printing of second ink (cyan on top of magenta-trap) (Table 11). This is consistent with roughening of me­ chanical pulps compared to chemical pulps. 72 Appendices K, M and N show the details of measure­ ments and analysis. Appendix K analyzes the variance of data from the air-leak method (Parker Print Surf) of measurement on surface roughness. Appendix M analyzes the variance of data for PPS 10 kg/cm2 force smoothness measurements between various tested areas of the seven papers. The specific tested areas are displayed in Appendix J. The surface smoothness of various printed areas is compared to unprinted regions of the printing impression. Tested regions are identified by color (e.g., printed red block is actually the magenta ink and the printed blue block is actually the cyan ink block). Appendix N compares the variance of surface smoothness measurements for the unprinted regions of printed impres­ sions to paper which has never been printed-"never­ printed" (no printed impressions). Data analysis was first done on surface smoothness variation for each run independent of other runs (Figures 17-23). If there had been too much variation a pair wise comparison would have been difficult. The surface rough­ ness data did not vary significantly within each run (e.g., between the never-printed areas and single color printed areas). The exception was Run 7 that contained groundwood in the furnish (Figure 23). 73 3.4

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Figure 17. Sizing Level 1: Comparison of Smoothness Values of Unprinted and Printed Areas. *Appendix M. 74 3.4

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Legend. D Never-printed section of paper, • Unprinted area of image (printed) area, llll Printed magenta block, I Printed cyan block, Printed door photograph (magenta-cyan)

Figure 18. Sizing Level 2: Comparison of Smoothness Values of Unprinted and Printed Areas. 75 3.4

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Legend. D Never-printed section of paper, □ Unprinted area of image (printed) area, � Printed magenta block, Ill Printed cyan block, ga Printed door photograph (magenta-cyan)

Figure 19. Sizing Level 3: Comparison of Smoothness Values of Unprinted and Printed Areas. 76 3.4

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Area of Measurement Legend. D Never-printed section of paper, [] Unprinted area of image (printed) area, lllD Printed magenta block, II Printed cyan block, Printed door photograph (magenta-cyan)

Figure 20. Sizing Level 4: Comparison of Smoothness Values of Unprinted and Printed Areas. 77 3.4

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Figure 21. Sizing Level 5: Comparison of Smoothness Values of Unprinted and Printed Areas. 78 3.4

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Figure 22. Sizing Level 6: Comparison of Smoothness Values of Unprinted and Printed Areas. 79 Appendix J is a reduced copy of the gravure printed impression where the tested areas are identified. Run 7 had an increase in surface roughness of 12% and 9% for magenta, and 14% and 11% for cyan for never-printed and unprinted surface smoothness values, respectively (Figure

23) • The supercalendered paper which had mechanical pulp, i.e., 27% stone groundwood containing furnish (Run 7), had the largest increase in surface roughening from the application of the waterbased ink. Even though Run 7 had the highest internal sizing, the effect of mechanical furnish dominated surface roughening of the paper. This may have been caused by fibers swelling and bonds relax­ ing in the "z" direction causing hygroexpansivity which lead to surface roughening-a problem harder to control with mechanical pulps. This problem of mechanical pulps, which is different than with chemical pulps, reflects water and fiber interactions as discussed by Skowronski et al. (42) and in several other experimental works-already reviewed-by Aspler et al. (53), Aspler

(57) and Hoc (30) for surface roughening, and by Bobalek for differences of furnish in overall hygroexpansive properties (31).

Since this experimental furnish was different, the results of print quality with alkaline internal sizing in 80 this experiment were expected to be different from that of other experimental work already discussed (5, 57).

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• • Unprinted area of image (printed) area, 1111 1111 Printed magenta block, II II Printed cyan block, CJ CJ Printed door photograph (magenta-cyan) Note: Different furnish than runs 1-6, has groundwood. Figure 23. sizing Level 7: comparison of Smoothness Values of Unprinted and Printed Areas. 81 Surface Compressibility of the Paper Substrate

Surface compressibility can be an important factor in rotogravure printing. Rotogravure is a direct-con­ tact-printing method since the ink is transferred direct­ ly from engraved/etched cells to the paper. The surface compressibility of experimental papers is listed in Table 12 and displayed in Figure 24.

Table 12 Paper Compressibility Compared to Gloss and Smoothness

Compressibility Factors

AKO HST PPS SD Trap of Magenta Sizing Value 10 - 202 Delta Block Run (sec.) (Kgf/ cm ) Gloss Smooth

1 0 0.440 0.125 1.190 3.28

2 75 0.319 0.086 2.246 2.88 3 117 0.424 0.074 2.400 3.12

5 207 0.419 0.080 3.852 2.83

4 170 0.390 0.067 3.212 2.87 6 268 0.390 0.088 4.788 2.79 7 459 0.497 0.072 3.042 3.12

Five of the papers had similar compressibility values but two papers were different. Run 7 (27% stone groundwood) and Run 2 had the highest and lowest compressibility 82

values, respectively. The average compressibility values for the kraft papers had a range of approximately 13%.

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SmneI.tvet HSi (�.)

Figure 24. The Relationship between Internal Sizing and Compressibility of the Papers.

Run 1 had a zero HST value and a desired reel moisture 83 value of 4.7 percent. However, as the internal sizing increased from Run 1 to Run 2 (HST values changing from o to 75 seconds) the reel moisture decreased to 3.2 per­ cent. The problem could also haven been created by process/control system dead time, which can delay a change or correction of process conditions. For example, as the dryer temperatures of the paper machine are changed to control the reel moisture, the resulting increase or decrease may not occur until the next inter­ nal sizing condition/run (Appendix 0). When the moisture increased in Run 3, the control system was changed to reduce the reel moisture of the sheet which affected the next run. As a result, Run 4 produced a drier sheet and, therefore, the moisture control was adjusted to increase moisture for the dry sheet of Run 4. But the Run 4 mois­ ture control adjustment increased the moisture of Run 5 (not Run 4) and again the moisture was corrected to reduce moisture, but the desired result was delayed until Run 6. This moisture cycling, on the paper machine, was di­ rectly related to the surface compressibility data (Fig­ ure 25). In another study, Dunfield et al. (45) found that changes in the amount of moisture added to paper (95% chemical thermomechanical pulp and 5% kraft) by a steam shower on a supercalender did not change the 84 a.s T ..

0.48

0.46 ·

0.44

0.42 > •.-t .--I •.-t ..Cl •.-t � 0.4 QJ H

0 CJ 0.38

0.36

0.34

0.32

0.3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 Moisture of the Paper

Figure 25. The Effect of Moisture on Compressibility of the Papers. 85 surface compressibility of the paper (calculated in their 2 2 study by the ratio of PPS 10 kgf/cm and 20 kgf/cm ) after supercalendering. They found that for changes in surface compressibility to occur that moisture needed time to enter and permeate the sheet of paper. Thus, in this experiment the moisture variance was already present throughout the sheet of paper. Therefore the cause for variations of surface compressibility may be directly related to the moisture of the paper at the take-up reel of the paper machine, within the limits of this exper­ iment. Appendix L analyzed the variance of data for surface compressibility. Even though the compressibility mea­ surements were taken at TAPPI standard conditions and the moisture was equalized in the samples at that time, the moisture was not equalized between the paper machine and supercalender. The moisture content of the papers at the time of supercalendering influenced the final compress­ ibility of the papers, irregardless of standard TAPPI test conditions as described in the ''Procedures" section of this thesis. A furnish partially consisting of un­ bleached stone groundwood typically has a higher com­ pressibility than a low yield bleached chemical (kraft) pulp. Run 7 had the highest paper machine reel moisture and compressibility as compared to the six 100% kraft 86 runs, as expected since it contained stone groundwood pulp. Appendix O lists the laboratory data of the paper moisture at the paper machine reel. However, the surface compressibility in this experi­ ment appears to not have had a major effect on either ink gloss or surface smoothness of the kraft papers (Table 12) .

A Comparative Measurement of Ink Transfer by Ink Optical Density

For a valid comparison of the delta gloss measure­ ments, among the six (100% kraft) sizing levels, the printed ink optical density needed to be in an equivalent range (Figure 26 and Table 13). The skewness of each run and composite comparison in the appendices shows that the data for ink optical density was not skewed and had a 6% or less variation for the mean values of all kraft val­ ues. The magenta process color ink was applied before the cyan process color ink. Also, the ink film thick­ ness, determined by ink optical density of the magenta ink was less than for the cyan ink. Since the ink densi­ ties for both the magenta and cyan were statistically equivalent, as compared within each color group for all six sizing levels, gloss comparisons between sizing levels could be made. Appendices G, H and I show a detailed analysis of 87 optical ink density measurements. Appendix G analyzes the variance of the data from ink optical density mea­ surements of the solid printed magenta block. The

1.4

1.35

1.3

_c1.25 ·rl {/) C Q) Cl 1.2 rl c u ·rl .w 1.15 0, 0

,..!( i::: H 1.1

1.05

0.95 0 10 200 30 4 50 Sizing Level, HST (sec.)

Legend. ■ Magenta Printed Block, ':IC cyan Printed Block Figure 26. Ink Optical Density of the Solid Printed Magenta and Cyan Blocks. 88 Table 13 Ink Optical Density

AKO HST Ink Ink Sizing Value Density Magenta Density Cyan Level (Sec.) Magenta* SD Cyan SD

1 0 1. 094 0.0184 1.290 0.0189 2 75 1. 073 0.0907 1.286 0.0175

3 117 1. 065 0.0147 1.279 0.0213

4 170 1.060 0.0216 1.284 0.0258

5 207 0.997 0.0272 1. 252 0.0227 6 268 1.013 0.0205 1.255 0.0266 7 459 1.004 0.0196 1.191 0.0368

*The densitometer digital readings were to 4 significant figures. tested area is identified in Appendix J. Appendix H ana­ lyzes the variance of the data from ink optical density measurements of the solid printed cyan block. Appendix I implements the �-Test procedure to analyze the variance, for each paper group (e.g., Black is Run 7, Yellow is Run 2, etc.), of the ink optical densities for the printed solid blocks of magenta and cyan inks. The paper color codes corresponding to the seven internal sizing levels are listed in Table 14. 89 Table 14 Hercules Sizing Test Results and Color Coding Scheme

Increasing sizing values Color Scheme

Sizing Sizing Color HST Level Level Ident-. (seconds) Code (lbs/Ton) Code

1 0 red 0

2 6 yellow 75

3 10 blue 117 4 14 purple 170

5 18 brown 207

6 24 green 268

7 40 black 459

The areas which were measured for density, gloss, and smoothness are identified in Appendix J (printed

solid magenta block, solid cyan block, trap, and doors).

The magenta process color ink had a lower optical ink

density than the cyan ink since, typically, less magenta

ink is applied in a four color printing process. As already stated, the gravure cylinder in this experiment had a cell depth of 30 microns for the magenta and 32

microns for the cyan; a greater cell depth means that

more ink can be transfered to the substrate. Addition­ ally, to increase accuracy, the delta gloss was used as a 90 comparison to help factor out any possible differences of basesheet gloss values. Optical ink density measurements, as analyzed by the "General Linear Model", did not have a trend (linear, quadratic or cubic) with increased AKD internal sizing (Figure 26, Appendices G and H). Even with increased internal sizing, the ink transfer from the gravure cylin­ der to the paper surface appeared to give a constant film thickness with a maximum 6% variation of the mean value for all kraft values of ink optical densities for magenta and cyan. Skewness for all kraft ink optical density values was normal, and sample calculations are shown and explained in Appendix c. Thus internal sizing in this experiment dramatically improved ink gloss-a significant finding for potential ink gloss improvement. Ink gloss improvement is especially significant when the applica­ tion of more material (ink) to the finished product (printed paper) is not required-the same ink film thick­ ness and ink optical density (55). For example, with no significant variation in ink optical density, Run 6 had an improvement in delta gloss of 30% for a 50% increase in HST seconds when compared to Run 4.

The Relationship of Ink Gloss With Internal Sizing and Fiber Swelling

There were negative delta gloss values for one color 91 (magenta) printing. Negative values were observed for the two papers which had the lowest internal sizing levels (Runs 1 and 2) (Table 15). Negative delta gloss is also a problem in industry for waterbased printing with rotonews grades of paper. The low gloss values for the lowest size level papers may be explained by the faster ink penetration into the paper (67).

Gloss Analysis of Printed Papers

Delta gloss of the trap showed a dependence on internal sizing levels. Alkyl Ketene Dimer (AKD) inter­ nal sizing increased the Hercules Sizing (HST} recorded time from zero to approximately 270 seconds for a 100% kraft sheet, and 450 seconds for a stone groundwood/kraft sheet (Figure 15). Appendix D has details of these mea­ surements and gives the analysis of variance of data for the Hercules Sizing Test. This analysis showed seven separate groupings of data. The data groupings are displayed by "Bonn Grouping" from Bonferroni !;.-Tests, and "Sheffe Grouping" in the appendices. Each of the seven papers are analyzed independently. Table 14 associates the color codes with each of the seven sets of papers. For example, as the AKD dosage levels increased from Run 1 to 7, so did the hydrophobicity of the paper (Figure 15). 92

Printing with rotogravure waterbased ink increased the delta gloss by more than 400% as paper sizing levels increased from zero to 268 seconds. As internal sizing increased so did the delta gloss for both the solid magenta printed block and the trap_ (Figures 27 and 28, Tables 15 and 16). 2

1.5 C/) C/) 0 rl CJ � l � H

C/) � ·.---l 0.5 E

C/) C/) 0 rl CJ 0 100 200 300 400 500

-0,5

-1

Sizing Level, HST (sec.)

Legend. ■ Softwood and hardwood kraft furnish, � 27% stone groundwood added to furnish Figure 27. Delta Gloss of the Solid Printed Magenta Block. 93

6,------

5 •

4

UJ UJ 0 r-1 c., ro .w 3 r-1 • Q) 0 • 2

Delta Gloss = 0.0132*HST + 1.1090 1

0.------,-----,------.------.------l 0 100 200 300 400 500 Sizing Level, HST(sec.)

Legend. Fitted data of kraft funish, •■ Experimental data of kraft furnish, 27% stone groundwood added to furnish Figure 28. Delta Gloss of the Printed Trap (Magenta and Cyan Ink) Block. 94 Table 15 Delta Gloss of the Printed Solid Magenta Block

AKD HST Delta Gloss Sizing Value % Level (Seconds) (Mean)

1 0 -0.58 2 75 -o. 28 3 117 0.10 4 170 0.52 5 207 1.06 6 268 1.51 7* 459 0.39

*Contains 27% stone groundwood in the furnish.

Appendices E and F show statistical analysis of one color and two color ink gloss. The correlation of a high "F" value with a probability of fit (Pr>F) indicates a very good fit for both the magenta and trap gloss data. Higher delta gloss values showed a linear improvement in ink gloss that corresponded to a linear increase in HST. In this study the cyan block was printed on top of the magenta block and designated as the trap. A desired print gloss increase was achieved with an increase of internal sizing (Figures 27 and 28, and Tables 15 and 16). Ink gloss is normally greater than 95 Table 16

Delta Gloss of the Printed Two-Color Trap

AKO HST Trap Delta Trap Gloss Sizing Value Gloss % Std. Level (Seconds) (Mean) Dev.

1 0 1.19 0.196 2 75 2.25 0.281 3 117 2.40 0.306 4 170 3.21 0.192

5 207 3.85 0.248 6 268 4.79 0.300

7* 459 3.04 0.183

*Contains 27% stone groundwood in the furnish. paper gloss, so a negative delta gloss value is signifi­ cant. Negative values indicate low ink gloss and thus poor print quality. The lowest sizing levels, Run 1 at o

HST seconds and Run 2 at 75 HST seconds, had negative delta gloss values (Table 15 and Figure 27).

Gloss measurements of a thin waterbased ink film are a better predictor of temporary surface roughening caused by temporal fiber swelling than a thick aqueous paper coating (30, 46). Ink gloss readings for waterbased

rotogravure are primarily better indicators because of the film thickness. A one micron increase in surface roughening is typical and is approximately the dried ink 96 film thickness for publication rotogravure printing. A thick paper coating typically ranges from 6 to 10 g/m2 • In this experiment, gloss measurements were a more sensi­ tive indicator of changes in hydrophobicity than PPS smoothness measurements; possibly because of the film thickness, and that temporal fiber swelling occurs while the ink film is setting and leveling which disrupts the ink formation pattern. An increase in the disruption of the surface of the paper during the setting and leveling of the ink results in a lower light specular reflection reading (gloss). A pattern is formed in the dried ink film which interfers with the reflectance of light. This is exactly what appears to have happended in this experi­ ment and explains the pattern of lower ink gloss with lower hydrophoicity of the paper. A possible mechanism for the interaction between sizing and gloss is as follows. High values of paper internal sizing decreased the absorption and penetration rate of inks. Also, the ink optical density measurements showed that the amount of pigment on the surface of the papers was approximately the same (Table 13) (55). Increased internal sizing resulted in an increase in spreading of the ink film due to a delay in liquid loss to the paper. The film splitting pattern of a dried ink film is important to gloss since this pattern affects the 97 reflectance of light. As Maley (55) summarized, the leveling of the ink film and reduction of the internal ink film splitting pattern improved light specular re­ flection and thus ink gloss, which explains the pattern of results in this research. In the scope of this exper­ iment, the most critical factors for improved light specular reflection (ink gloss) were the spreading and leveling of the waterbased ink film. Gloss reflectance values increased with increased HST values. Thus, hydro­ phobic internal sizing controlled the spreading and leveling of the waterbased ink, and determined the delta gloss of the inks. The increased HST values corresponds to an increase in delta gloss for both magenta (first color down) and the trap (Tables 15 and 16, and Figures 27 and 28). Specifically the linear correlation between the HST second values and the delta gloss of the trap had a correlation average of 0.992.

Kraft Versus Groundwood

The groundwood paper (Run 7) had a higher delta gloss than a kraft paper of the same magenta ink surface smoothness, but had lower sizing (Run 3). A comprehen­ sive comparison cannot be made among the six kraft papers and the groundwood paper since only one groundwood paper was produced. Yet with this fact understood, general 98 observations can be made. The unsized kraft paper (Run 1) had a higher roughness and a lower trap gloss than the groundwood paper, Run 7 (see Figures 14 and 28). Inter­ nal sizing improved the ink gloss quality of the 100% bleached kraft uncoated papers but was not as effective for the one paper (Run 7) which contained mechanical pulp. The different mechanisms between mechanical and chemical pulps was demonstrated when the paper of Run 7 and Run 4 had approximately the same trap delta gloss values, although the mechanical paper (Run 7) had about triple the HST sizing level as the 100% kraft paper (Table 16). Factors affecting the mechanisms were in­ creased surface roughness and a different pore structure due to more fines in the mechanical (groundwood) pulp. Another comparison (Table 13) was Run 7 (groundwood) which had approximately the same ink density values as Run 6 (100% kraft). Between Run 6 and 7 there was about a 10% (less than 0.2 microns) surface smoothness differ­ ence for the color image of the doors (see Table 11), and a difference of 0.107 microns in paper compressibility. Yet, Run 6 had 150% higher delta gloss of the trap while having only about 60% of the Hercules sizing value. If the surface smoothness, compressibility, and ink optical densities are approximately equal, then a varia­ tion of ink gloss can be primarily attributed to the 99 spreading and leveling of the ink film on the paper (55). Within the limits of this experiment, the more hydro­ phobically sized mechanical paper (Run 7) may have had greater temporal fiber swelling (41) which interrupted the spreading and leveling of the waterbased ink and thus reduced the ink gloss as compared to the less hydro­ phobically sized chemical paper, e.g., Run 6. Some experimental work has not found sizing, at any level, to be effective in improving gloss. For example, Skowronski et al. (41) did not find an improvement in 75 degree coating gloss measurements when a 60% ground­ wood/40% kraft basestock was hydrophobically sized. However, their study used very rough (5 micron PPS 10 kgf/cm2) handsheets that were formed, dried, and then sized by dipping them into an AKD solution, not internal­ ly sized or completely aged. Also, in their coating methodology they applied large amounts of water-up to 2 12.6 g/m -with apparently no accelerated drying. The two control handsheets (containing mechanical pulp fibers) were rough, the PPS surface smoothness values varied from 4.65 to 4.9 PPS (10 kgf/cm2). In addition, with an approximate dry weight of 6 to 2 7 g/m , the thickness of the 50% latex pretreatment may have been sufficient to reduce the 5 micron surface roughness of basestock (paper). It cannot be stated from 100 the experimental data of Skowronski et al. (42) that the only reason for less surface roughness, in the case of the 50% latex, was that less water was applied to the paper. A combined effect of a thick latex pretreatment coating and less water was what probably reduced the surface roughness. Skowronski also stated, but showed no data, that paper gloss was not affected by sizing (41). The effect of temporal surface roughening on a thick-film paper coating gloss can be significantly less than for a thin-film ink (print) gloss. In fact, ink film gloss may have given different results for the various air dried coated handsheets that were produced by Skowronski et al. Skowronski et al. reported only two sizing values (no sizing and infinite sizing) for the handsheets. Variations of the physical and optical properties of the handsheets may be due in part to the variability of the handsheet and size dipping processes. Also, numerous different pretreatments and coating formulations may have introduced variability into the experiment of Skowronski et al. (41). It is difficult to apply the experimental work of Skowronski et al., the effect of tub-sizing on paper gloss, to what effect sizing may have on a thin film indicator (ink gloss), e.g., a waterbased ink. In the present experiments, internal sizing was 101 varied while the two ink films and traps were estimated as constant in thickness and ink optical density to illustrate the effects of internal sizing. However, Skowronski et al. showed that groundwood interacted differently than kraft pulp with water and, in principle, they may explain some difference in surface roughness and delta gloss in this experimental work between kraft and groundwood containing paper. Since groundwood (mechani­ cal) fibers swell more readily than kraft (chemical) fibers (41), the groundwood paper may have had more temporal swelling of the fibers that disrupted the ink film formation pattern by altering the waterbased ink setting and leveling as compared to a kraft (chemical) paper that had lower internal sizing. From the work of Skowronski et al. and this experimental work, it can be said that a high internal sized mechanical-chemical paper has less temporal surface roughening than an unsized or slack sized 100% chemical paper. Yet it appears from these experiments, an internally sized chemical paper may only need to have 30% of the HST seconds of a sized chemical-mechanical paper to achieve the same gravure waterbased ink gloss (Figure 27). However since only one mechanical paper sizing level existed, no definitive conclusion about the effect of varying the internal sizing of a paper containing mechanical furnish on 102 temporal fiber swelling or thin film ink gloss can be made in this experiment. Yet, this work confirms the work of Beland et al. (46) that ink gloss was a better indicator of fiber rising (temporal surface roughening) than PPS surface smoothness measurements. More specifi­ cally, this experimental work correlated with Hoc (30). Hoe's findings agreed with Beland, but also demonstrated that long wood fibers (e.g., softwoods) and chemical pulp (e.g., kraft) had less fiber rising (temporal surface roughening) and higher ink gloss than short wood fibers (e.g., hardwood) and mechanical pulp (e.g., groundwood). Combined with Salmimen's work with hydrophobic sizing (23)-water penetration into paper was reduced with increased hydrophobic sizing-and the difference between chemical and mechanical pulp fibers, this study shows that sizing may reduce temporal fiber swelling as mea­ sured by a thin waterbased ink film but is dependent upon the normal swelling characteristic of the fibers used in the furnish to produce the paper. CHAPTER VII

CONCLUSIONS

1. The data clearly showed that permanent (not temporary) surface roughening for four of the five AKD internally sized softwood and hardwood kraft papers did not occur. 2. Ink gloss was significantly affected by sizi1g. 3. Delta gloss was significantly improved (up to 400%) with increased internal sizing (hydrophobicity of the paper), especially for solid print areas. 4. It appeared that a reduction of temporal (not permanent) surface roughening during the formation of the first ink film was critical in improving ink gloss for both single color and trap areas (second ink film). 5. A thin film waterbased ink was a more sensitive indicator of temporal (not permanent) surface roughening as measured by light specular reflectance (ink gloss) than a PPS smoothness tester, as demonstrated in the limits of this experiment.

103 CHAPTER VIII

RECOMMENDATIONS

Further study is needed of the factors of internal sizing which will improve ink gloss, especially for single­ color rotogravure waterbased ink printing. A continuation of the ink and paper interaction study would be to do scanning electron microscopy {SEM} to deter­ mine the ink penetration into the basesheet of different internal sizing levels or different sizes, e.g., alkenyl succinic anhydride (ASA). The effects of different furnishes on ink gloss could also be studied with internal sizing since groundwood (me­ chanical pulp} and kraft (chemical pulp) have such dramatic differences. This experimental study addressed a significant problem of negative delta gloss for waterbased• gravure printing. Further laboratory studies on the hygroexpansivity could be done with equipment developed by the U.S. Forest Products Laboratory in conjunction with the Treasury Department, Bureau of Engraving and Printing called a Vacuum Constraint Apparatus.

104 Appendix A Test Data of "USA WEEKEND"

105 106 Test Data of "USA WEEKEND" Sunday Newspaper Supplement (68)

2 Basis Weight 51.33 g/m 3 Density O. 66 g/cm _ Brightness - ISO 50.48% Opacity 76.68 Caliper 3.05 mils Appendix B GAA Roto News Classifications

107 108 GAA Rote News Classifications (Updated, source: GAA*)

Paper Name Bright. Parker Values are Class TAPPI Print s. Approximations Super-cal end- SC Rote 66-67 1. 4-2 .1 ered for high Group A News gloss & smoothness Superior Group B Hibrite 66-67 1.5-2.5 smoothness & Rote News brightness

MF Roto Premium Group C 60-66 1.8-2.8 Machine News Finished

Std Rote 55-60 2.7-3.7 Economy Group D News Groundwood Same as Group E Newsprint 54-57 3.6-4.4 commercial newsprint

* Each year Parker Print Surf (PPS) values are typically being upgraded. An "upgrade" is a decrease in PPS values for each grade--a decrease in surface roughness. Brightness values are typically increasing in value-­ higher brightness levels. Appendix C An Explanation of the Statistical Analysis of Experimental Data

109 110 An Overview on the Importance and Significance of Statistical Analysis of Experimental Data

If the data have a Normal {Gaussian) distribution then the data are symmetrical around the mean value. Also if the data are distributed in a limited range-smaller the better-then the mean value can be valid for comparison (see Figure Cl). A valid mean value was critical for

••va11ts• .>-SMA�ao cu•ve s.-.- cuava ■ XT_ ... POSIT1va MOOElltAT• ..OSITIV. SICE-SS SICE-ESS

ST-•Tlttc.AL cv•v•

Sit-CV.VE a,oo,oa11tAT■ Ml!�TIVI! -•-•-

Figure Cl. Frequency Distribution of Various Shapes {69) these experiments in order to compare values of the seven paper runs. Most experimental data are not perfectly symmetrical and some skewness (asymmetry) is acceptable. An acceptable range for skewness in most statistical 111 analysis computer software programs, such as SAS or Systat, is defined by the Systat Handbook on page 8-19 (70) :

... we requested SKEWNESS and KURTOSIS in addition to mean, standard deviation, and standard error of the mean. Extreme values of SKEWN_ESS {Gl) indicate departures from symmetry: -large positive values of Gl mean the distribu tion has a long right tail. -large negative values indicate a long left tail. How large is large? Statisticians often con­ struct a standard error for Gl using:

where n is the sample size. If the interval 11does not11 include zero (O), Gl is considered 1arge or extreme. The interval is defined as:

G1±2x� ( ! ) Equation Cl.

If distribution of the data are in this range, it can be considered normal (69), and the mean value can be consid­ ered to represent the data. The skewness and homogeneity of the data in these experiments were displayed numeri­ cally and graphically by the Univariate procedure in SAS. It was easier to use graphical displays, principally 112

"Boxplots", but "Normal Probability Plots" were also helpful in viewing data (see Figures C2 and C3).

0

♦----♦ I I •-----• +----+ •-•-•tI + I 1..:. .1 ♦----+ I

Figure C2. An Example of Boxplot(s)

1.042.5• +♦h ++ ++♦ * ♦H tt trUt♦.... Ut+♦ H+♦♦ ttH Hit♦ u+ HHt++ +tu Ht ♦♦ t +H * ++ + * 0.9475 ♦---♦•--+-•--+----+----+-•--♦ ♦--•-• -2 -1 O -•--+----+--- +1 +2

Figure C3. An Example of a Normal Probability Plot

In the case of the "Boxplots" (e.g., Appendix Hon Page 140) 'the total distance from the top of the line to 113 the bottom of the line-including the box-represented the distribution of the data. A smaller total distance-the two lines and box-that the data were more homogeneous-smaller distribution. For example, page 135, Run 1 had a smaller distribution of data (boxplot distance) than did Run 4, still both runs were in accept­ able distribution limits. For a more complete explana­ tion on "Boxplots", please see pages 116 and 117. Pages 116 and 117 were used with the permission of the author, Christopher s. Soderquist (a statistician at the Bureau of Engraving and Printing in Washington, D.C.). The symmetry or skewness was examined by viewing the relative positioning of the four parts of a "Boxplot". If the size of each of the four parts was equal, then the data were symmetrical and not skewed. The boxplot was divided into four parts, 25% of the data for each part. The first of the four parts (25%) was represented by the top line of the diagram. The box represented 50% of the data, split into two 25% parts. The final part 25% was represented by the bottom line. An example of data symmetry comparison was Run 1 and Run 2 for optical ink density measurements on pages 136 and 137 in Appendix G. Run 1 had data that were less skewed than Run 2 for the optical ink density of the solid printed magenta block. Yet, both runs in Appendix 114 G were within acceptable skewness range. An example of sample calculations of the extreme values of SKEWNESS were computed below using Equation Cl to verify acceptable skewness for Run 1 and 2. In Appen­ dix G on page 136, Run 1 was measured for the ink optical density of the solid block printed with magenta ink. The skewness range of Run 1 was computed by: Gl (Skewness value)= -0.02093 n (sample size) = 50 Equation Cl gives,

-0.02093±2x� ( 6) --0.02093±0.6928 50

Gives: Interval {-0.714, 0.672}

The calculated range for Run 1 was from -0.714 to +0.672, which means that zero lies in the range. Therefore as defined by systat (70) and Equation Cl, the skewness

(Gl) was not "large" for Run 1. Run 2 had values listed on page 137 and the skewness range was also computed by Equation Cl: Gl (skewness value) = -0.65764 n (sample size) = 50

-0.65764±2x� ( 6) --0.65764±0.6928 50 115 Gives: Interval {-1.35, 0.03518}

The extremes of Gl were from +0.03518 to -1.35, which means that zero lies in the range. Therefore as defined by systat (70) and Equation Cl, the skewness (Gl) was not

11 11 1arge for Run 2. A Normal probability plot is when a plot is linear, as in the example, when the "*" and "+" are lined-up to­ gether. Another example is on page 140, the data of the ink optical density of the solid printed magenta block was linear. Similar observations were made for the rest of the test data and can be quickly reviewed in the Appendices, using the above described procedures. Another data analysis test used was the 1-Test. It was implemented in Appendix I to analyze the ink optical densities of the solid printed magenta and cyan blocks. The magenta ink printed from the gravure cylinder was designed to apply less ink to the paper than the cyan ink, and was confirmed by the data analysis. Run 2 had a mean value of 1.284 for cyan and 1.060 for magenta. Run 4 had a mean value of 1.284 for cyan and 1.060 for magen­ ta. 116

As previously mentioned on page 113, the comments below were written by Soderquist:

A box plot is a very useful ___ l00tperent graphical tool. It displays a wealth of informationin a truly simplisticplot. From _.T. ___ 75tpere� this plot you can examine distributions of different variables (Isit normal? Is it skewed?Are there outliers? etc.), compare ,--- 1q1perJU1fx:k distributions among different categories of a variable, detennine significant differences among thesecategories, and look for evidence of sub groups inyour data. Thistool should be used routinelyin the examination of datawithin BEP. --- lowerJU1fx:la The differentparts of a box plot are displayedin Figure 1 at right. This is a typical lookingbox plot, but other plots outi nu could have differentshapes with pieces in *--- an entirely different order. Below the 100th percentile at the top of the plot, is 0--- & outi nu the 75th percentile or upper hinge, which as the nameimplies, means 75% of the data fall below that line. Below that is the uppernotch. The upper and lower notches are the boundaries of the 95 % confidence intervalaround the median. Each notch occurs at the point where the non-vertical Figure Al lines end and become vertical. Below that is the median (50th percentile), and the The distinction between the two is only the 25th percentile or lower hinge. It can distance eachis from the median. These occur below, above, or on thelower points almost always require further notch; inthis case it is above. As you can examination. see, the 95 % confidence intervals do not have to bewithin the middle 50% of the One of the things you should look data. Below that is the lower notch, which for in a box plot is the shapeof thebox is definedabove. The small, unlabeled itself. If it looks highly symmetric, as horiz.ontalline below the notch is the Category A does in Figure 2 on the lower fence.The fences border the data followingpage, then the distribution is that are not outliers. Theupper fence in approximately nonnal as long as theplot this graphhappened to be the 100th doesnot have unusually long or short tails. percentile, or thelargest value, as well. Longtails as in either B or C, show that Theoutside value andfar outsidevalue the distribution is negativelyand positively simply show points that may be outliers. skewed respectively, andtherefore not 117

significantly different at the 95% level. However, because the upper notch of C is below the lower notch of both A and B, we can state with 95 % confidence that the 0 median of C is less than that of either A or B.

It should be obvious the exploration ' of box plots can yield much needed ' information. You should almost never do an analysis without doing preliminary graphs such as histograms, scatterplots, and box plots, and the use of them in your analytical work is recommended. Most statistics packages, like SY STAT, Statgraphics, and S + can produce these graphs.

A B C

Figure A2

normal. Much of the data is compressed into one end of the box plot in both, and both contain outliers; one of the points in C is a far outside value. Because the variances of these three plots do not appear to meet the homogeneity of varianceassumption, assumingthat a single SD applies to all categories could be a mistake.

The differences between the group medians are also important pieces of informationthat can be gained from this graph. Because the upper notch for A is above the lower notch of B, then by definition these two groups arenot Appendix D Analyses of Variance for HST Groups

118 119

The SAS System . 1 13:53 Tuesday, June 1, 1993 Analysis of Variance Procedure Class Level Infor1ation Class Levels Values COLOR 6 BE BK BR GR PU YE

Nu1ber of observations in data set= 120

Analysis of Variance Procedure Dependent Variable: TIME Sum of Mean Source OF Squares Square F Value Pr> F Hodel s 1870329,054 37-4065. 811 1085.28 0.0001 114 . ·, -� Error 39292,591 34�.672 Corrected Total 119 1909621,646 R·Squ are c.v. Root MSE TIKE Mean 0,979424 8.595828 18. 56534 215.9808

Source OF Anova SS· Mean Square F Value Pr> F COLOR 5 1870329,054 374065,811 1085.28 0.0001 120

The SAS System 3 13:53 Tuesday, June 1, 1993 Analysis of Variance Proce�ure Bonferroni (Dunn) T tests for variable: TIME NOTE: This test controls the type I experimentv1se error rate, but generally has a higher type II error rate than REGWQ, Alpha= 0.05 df= 114 NSE= 344.6719 • Critical Value of T= 3.00 Mini1u1 Sign;ficant Difference= 17.603 Means with the same letter are not significantly different. Bon Grouping Mean N COLOR A 458.960 20 BK 9 267,620 20 GR C 206.715 20 BR D 170.380 20 PU E 117,380 20 BE r 74.830 20 YE 121

The SAS System 13:53 Tuesday, June 1, 199i Analys1s of Variance Procedure Scheffe's test for variable: TIME NOTE: This test controls the type I experimentwise error rate but ge�erally has a.h;gher type II error rate than REGWF for all pa1rwise coapar1sons Alpha= 0.05 df= 114 MSE= 344.6719 : · Critical Value of F= 2,29391 Miniaua Significant Difference= 19�883 Means with the same letter are not significantly different, Scheffe Grouping Mean N COLOR A 458.960 20 8K 8 267.620 20 GR C 206,715 20 9R D 170,380 20 PU E . 117 I 380 20 BE F 74,830 20 YE Appendix E Analyses of Variance for the Delta Gloss of Magenta

122 1 123 The SAS systu 11:51 Tuesday, June 8, 1991 General Linear Models Procedure ·class Level Infor■ation Class levels Yalu es COLOR 7 123456 7

Nu1ber of observat;ons In data set= -350 Dependent YarfaJlt: DEL6lOSR Su• of Rean Source 1lF Squares Square F Value Pr > F Model 6 159,3418857 26.5569810 6�9.02 c.0001 Error 343 14,9570000 0,0436064 Corrected Total 349 174,?988357 R•Squart c.v. aoot JISE DEUlOSI llean 0.914U8 -53,46563 0,208821 -0.390571 Source DF Typt I S$ 'lean Square F Value Pr> F coLo, 6 159, 3418857 26,5549810 609.02 0.0001 Source DF Typt Itt SS '1ean Square F Value Pr > F COLOR 6 159,3418857 26,55H81C 609,02 0.0001 Contrast DF Contrast SS Mean Square F Value Pr> F Unear 1 98.89986429 98,89886429 2267.99 qua ratic 1 2S.28828810 o.oor cubf c 1 26, 14403333 U:UHHU lbl:H i:�� I Scheffe•s test for variable: DELGLOSI NOTE: This test controls the type I exp1ri1entvfse error rate but gener lly has a higher type II error rate than RE&VF for all pairv fse co,,artsons Alpha= df• 343 11se• 0 043606 Crfto oscal Value o F• 2.1,5041 "tnt1u1 Sl gnfffcant Df fference� C.1491 "•ans vfth tht sa1e letter are not significantly different. Scheffe Grouping Mean N COLOR A 0,57900 50 1 8 0.27600 50 ? C -0.10000 so l D ·0.39200 7 D 50 -0.52400 4 D so E -1.06400 50 5 F -1.soaoo 50 6 124 Look for Skewness in Dependent V1rf1blt 19 - 11:51 Tuesday, June 8, 1991 Univariate Procedure Sche■atic Plots Varfable=DELGLOSR 1 l 0 3,751 ♦•----•--+ o.s I 1 .. !... l

0.2; 1 ! [�i 1 0 1 ·-r ..._ 0 LJ♦---♦ -0.25 I I t••+-•t...... 0 •-•-• -c.s I 1-+--1 !---l •0,7S Li I I ., i, t--..r�i -,.25 I -1.s I 1-.. -1 ... _. l-·--l .,.11 I I -z I o COLOR -----···----+------+------•+--•1 2 3 •---·· ..•------+------+-•---··----+--- 4 5 6 7 -- Look for Skevness in Dependent YJ,hble 4 12s 11:51 Tuesday, June 8, 1991 ••------•-•••--••••••--••------COLOR=1 -•------�----••------•••----- Univariate Procedure Variable=DEL;LOSR "o■ents N 50 Su• \lgts 50 "ean �-578 Su■ 28 9 Std Dev 0.2 2323 Variance 0.0409 5 Skewness -0.07209 lurtasis -0.5001 1 USS 18.71 css 2.0058 T:MeanCV =O 15- 0402 Std Plean 0.025613 �0073 Pr>lll 0.000150 MUI A: 0 ..o. 50 lUI > 0 K(Si nl 25 Pr 0.0001 Sgn Jant 637.5 Pr>=t'IS 0.0001 W:Noraa\ 0.954075 Pr= 0.0B77 ...... - ...... COLOR=1 ...... Univariate Procedure Variable=DELGL�SR Ste• leaf Box lot 10 0 9 1, &9 0000 4 .,8 000010 6 •----+ 67 0000�� 6 s6 00000000�00 11 1--l l 0000000000 10 l-�--l ! 00000 5 l2 000 3 2 0000 4 0 ··•·+-•··+---+--+ �ultioly Stea.Leaf by 10tt•1 Nor■al Probability ,tot 1.025• ft♦ t tttt ••

UUt♦ ++ ft tttt+ +++ tHUt 0.62� +++ ttt+++t tt **** +o ttt

t U♦++ o.2i5 ♦ t ♦ ----+·-··+-··•+-t••-➔----♦--•+--•♦---+---• •2 -1 0 +1 +2 126

...... COLORs2 •··•-•·······•-••-•·•·•·-----••••• Univariate Procedure Variable=OELGlOSl fto■ents II 50 Su11 \lgts · 50 Kean o.276 su■ n.a Std Dev 0.243746 Varian;e 0.059412 Skewness 0.370367 turtos1s 1.302965 USS 6. 72 css 2.9112 CV 88.31387 Std "fan 0.014471 T:"ean=O s.�0674 Pr>IT O.OCf Nu■ "-= O 4I Nu1 > 0 l M(Silnl 20 Pr>=jP.) o.ooof Sgn ank 460.5 Pr>= S W:Nor■al 0.949566 Pr

Univariate Procedure Variable=OELGlOS� Stea leaf ? 00 Boxglot .,S 0 ' r6 000 00 +----+ 4 0000000000 10 6 i �����0000000 l--+--1 1 00000 ♦-----+ 3 000000 ')6 0 -:¥ 1 I -J2 -4 0 1 0 ··--•---•---+---+ Multiply Ste■,leaf by 10•t•1

Nor■al Probability Plot -t t 0,95+ t ++t+ +++♦ tt♦t++ Htttt tt♦+ Ut+♦ ttHtU 0.25 ttt+++ ** uu++ ♦* ++++ ++++ +++ ++ t -0.45 •-•-·+--•--•♦--+-•-♦---.. --...... -- ♦•-··• -2 -1 o +1 +z Appendix F Analyses of Variance for the Delta Gloss of Trap

127 128

1 The SAS 3yster 11:43 Tuesday, June 8, 1993 General Linear �odels Procedure Class Level In1ormation Leve ts Values Class ., C�LOR I 1 2 � 4 5 6 7

Numher of obs�rvations in data set= 350

General Linear Models Procedure �ependent Variahle: �ELGLOST 5um of �ean Source !)f 3quares �quare F Value Pr > F Model 6 408.1878357 69,0313143 1099.59 0.0001 Error 343 21,2 2140CO 0,06187JO Corrected Tot a l 349 4i9.4092857 �-Square c.v. Root MS� OELGlOST Hean 1, �515�0 -9,39?215 o. 248737 -2. 961429

Source OF Type I SS )lean Square F Value Pr > F COlO� 6 408.1878357 68,0313143 1099,59 o.ooc1 Source �F Type III SS Mean Squ3re F Value Pr > F COlOR 6 408.1878857 68.0313143 1099.59 C,0001 Contrast DF Contrast SS :,ean Square F Value Pr > f linear 1 261, 10082S6 261, 1 OC8236 4220,15 O,OOC1 quadratic 1 64,9268667 64. 9268667 1049.41 0.0001 cubic 1 38,234 7300 33. 2347000 617.98 c.ooc1 129

The SAS Systu J 11:43 Tuesday, June a, ,��J General Linear �odels Procedure Scneffe's t�st for variable: DELGL�ST NOTE: ihis test controls the type I experimentwise error rate but Je�er�lly has a.higher type II error rate than �EGWF for all pa1rw1se co�par,sons Alpha= 0.05 df= 343 MSE= 0.06167 Critical Value of F= 2.12504 Xinimu� SiJnificant Difference= C,1776 �eans with the sa�e letter are not si�nificantly different. Scheffe Grouping �ean ij COtOR A -1.19000 50 1 B 50 8 -2. 24600 0 -2.40000 J 50 ., C I C -J.04200 50 C -3.21200 50 4 0 -J.35200 50 5 C .. -4. 78800 50 � 130

Loo\ for Sk��ness in Oependent variable 21 11:43 Tuesday, June a, 1993 UnivariateScheaiatic Procedure Plots Variable:O:LGL,sT -o.s ! Q -, I I •--+--•+-----+

-,., l 0 J ! +----+ •··+--·•I I ♦-----I l ! t--+-•t♦ -l,5 I ----- l-----! I 0 I •--+--•+-----+ J I ♦-----I a •--+--•♦ ! ..... ! I -J.5 j I •-----• -ii l--�-.! I 1 0 -,. 5 ♦-----I •-+··•♦ .l L... I -5,5 j ------+------+------♦------+------+------+------♦----- COLO� 2 3 4 5 6 7 131

Look for Skewness in Dependent Variable 4 11:48 Tuesday, June S, 1993 ------COLOR=1 •••••••••••••••••••••••••••••••••••

Univariate Procedure Variable= OELGL05T Moments N 50 Sua llgts 50 �ean -1.19 Su11 J,033469-59,5 Std Dev 0 .196136 Variance Ske!IMSS -0.02705 Kurtosis ·G,49693 USS 72.69 css 1,885 CV ·16.482 Std >lean 0.027738 T:�ean=O ·42,?017 Pr>IT 0.0001 �U11 ": 0 50 Nu111 > I Q H(Si · t> - 25 Pr> 0.0001 S3n ank 637 .s Pr>== 1�S1 O,OC01 W:Nor"at J,9S3537 Pr<� 0,0811 Variable=OELSL03T � Ste1- Leaf 3 aoxgtot _.,·8·J OOJ -o 0 1 ·? - 3 -101J 000010:io -11 00000010�00 ♦-----+ ·1 11 + - t 0 I I 1 L cooooooa ., •-----• -1? -n-13 00000000 a i. ....! -14 0OJO-1 5 - -1514 00000 5 -15 -16 0 1 0 ----+----+----+--- ♦ �ultiply Stem.Leaf by f0••-1

-IJ,825+ Nor�al Probability Plot * •+ * H+ tUHU++ +♦ tuuu +♦ UHH -1.�25 *****+H ****+++ * .....+H , +++ * ++ -1,6l5 +++ +----+---+----+----+----+----♦----+----+- -+ ---• -2 -1 0 +1 --+2- Appendix G Analyses of Variance for the Optical Density of Magenta

132 133

1 The SAS 3ystn 11:43 Tuesday, June 8, 1993 General Linear �odels Procedure Class Level Infor1at;on Levels Values Class ., COLOR I 1 2 3 4 5 6 1

�umber of observations in data set= 350 General Linear Models Procedure �ependent Variahle: �ELGLOH Sum of >!ean Source DF Squares Square F Value Pr> F Model 6 408.1878357 6,.031314� 1099,59 0.0001 Error 343 21,22140CO 0,0518700 Correct ef To1a l 349 4i9.4092357 �-Square c.v. Root MS� neLGLOST Mean 1. n1s,o -s.39?21 5 0.248737 -2.961427

Source DF Type I SS "lean Square F Value Pr> F COLOR 6 408,1873357 68.0313143 tOQ9.59 O,OOC1 Source DF Type III SS Plean Squ1re F Value Pr> F COLOR 6 408.1878857 68.0313143 1099.59 c.0001 Contrast DF Contrast SS :,ean Square F Valn Pr> F linear 1 261,10082S6 261, 10Cd236 4220.15 0.ooc1 quadratic 1 64,9268667 64.9U8667 1049.41 0.0001 cub;c 1 38,2347)00 33.2347000 617.98 C.0OC1 134

The SAS Systu 3 11:43 Tuesday, June a, 19�3 General Linear Jodels Procedure Scheffe's test for variable: DELGL�ST NOTE: This test controls the type I experime�twise error rate but ]e�er�lly has a.higher type II error rate than �EGWF for all pa1rw1se c0Npar1sons Al?ha= 0,05 df= ]43 MSE= 0,06187 Critical Value of F= 2,12504 Minimu1 Si,nificant Difference= C,1776 �eans wtth the sa�e letter are not si�nificantly different. Scheffe Grouping �ean ij COlOR A -1,19000 jQ 1 B 8 •2,24600 50 8 J -2.40000 50 ., C 50 ' C •J.o4ioo C -3.21200 50 4 t> -1,!5200 50 3 C: .. -4.78800 50 � 135

Loo\ for Sk�vness in Oependent variable 21 11:43 Tuesday, June 8, 1993 Univariate Procedure Sche111atic Plots Variable=O:LGL?ST -o.s ! G -, I I +-----+•--+••tr

-,., l ! 0 +----+ i ..•.. 1 ♦-----♦I - i .. 1 1 I i .. r::::i �: •-----+I I j 1 •··+••t O :: :: ! .....I ! ·l.l l T l--�--l•·---·• -4 I ·I, s I ! I

5 - 1 f�;�i -5.5 ------+------+------•♦-•------+------•------•------♦-----· COLOR 1 2 3 4 5 6 7 ·,,, ., .,

.· •. "·, 136 ;.at ,����·

.. -','• Look far Ske�ness tn Dependent Variable 5 14:09 Friday, June 18, 1993 .1';· ------·--- COLOR=1 -·------·········-·--·-·····-······ ·. �: :·· .. Univariate Procedure Variable=O£N�ITYR �oments N 50 Sun Wgts 50 Mean 1 06454 Sui 5 3. 227 Std Dev 0.014726 Variance ).000217 Skewness -O.02093 Kurtosis -0.18501 us s 56.6729 css 0.010626 CV t .383354 Std Mean 0.002083 T:Mean=O 511.1537 Pr>tTI o.oco1 IIUII A: Q so �URI) 1 50 f1C Si n) 25 Pr>= ' 0.0001 SJn jank 637.5 Pr>=j S f 0.0001 V: �or■al 0.981566 ?r

Normal ?robability Plot ♦t+♦ l 1.0975+ tt♦+ .....t+t++ l ***** tt+ Ht♦ Ut+ l ....tt+t Uh u+ I ++++ 1.0}25 +t+ t +---♦----+----+----+----+-·--+----♦---·+----♦-•--♦ I -2 -1 0 i1 +2 137

Look for Skewness in Dependent Viriablt 7 14:09 friday, June 18, 1993 COLOR=2 Univariate Procedure ------Variable=OENS1TYR ------·•·------••--•------Mol!lents N 50 Sum •,;ts 50 Hean 1,01)356 Su11 50.178 ' Std Oev o.0195q3 Variance 0.000384 Ske.,,ness -0.65764 Kurtosis 0.15 5 USS 50.31544 css 0,01881 CV 1.952346 Std Mean 0.002771 T: Mean=j 362.1832 Pr>ITI 0.0001 l Nu■ A: n SO Nu111 > 0 50 !1(Sign) 25 Pr>= '- 0.0001 Ssn Rank 617 ,5 Pr>= j S 1 0.0001 l W:Nor111at 0,962Z05 Pr

138 139

1he sAS System 1 14:10 Friday, June 18, 1993 ure General Linear Models Proced Class Level Information Class Levels Values 6 7 COLOR 7 1 2 3 4 5 set = 350 Humber of observations in data n this 340 observations can be used i NOTE: Oue to missing values, only analysis. General linear �odels Procedure �ependent Varia�le: DENSITY3 Sum of Mean Square F Value Pr> F Source DF Squares 6 n. j5893 34 2 94.32 0.0001 Model 0.05983140 J33 0,00063436 Error 0,21124164 ""9.;J a. 51021006 Corrected Tot al Root HSE DENSITY9 Hean �-�quare c.v. 1,261321 �.629550 1, 996,g35 0,025186 Square F Value Pr> F Source DF Type I SS Mean 6 o. 94,32 o. 0001 COLOR 35898342 0.05983140 Type III SS Square F Value Pr> F Source vF }lean 6 0,05983140 94,32 0.0001 COLOR o.1sqn342 Pr> F DF Contrast SS �ean Square F Value Contrast o. 0001 1 C,03300160 0,03300160 52,02 o. linear 1 0.00389702 6.14 0137 quadratic 1 0.0038?702 36.11 0.0001 cubic 0.02290656 0,02290656 140 Look for Sk�wness in De en en p d t VfI!f�l�riday, June 18, 19�J Univariate Procedure Schematic Plots Yariable=DEMSITYB

, ,351 0 0 1, ]251 3

1.J +··--+ +··-·+ I I +·····+ I I t··+••t +·-···+I I t••+•·t ...... 1.m l. .... l ♦·•···+ t••---• l ♦ 1. .... l -•··+ ♦-•--+ !----1 t---t +·····+ 1.15 I L'.. .I L�.l 1.111 I +----+

1,l I •--••t C 0 1.1751 [.I 1. 11 I 1.m I

1.1 I ·····-··-·�--······••f ··········+··· .... + • . ... + •••• _••••• ...... +.-•···-·- �---·· COLOR 1 � 3 4 l 6 7 141

Look for Skewness in Dependent Variable 5 14:10 Friday, June 18, 1993 •------COLOR=1 ------• Unlvariate Procedure Variable:DENSITYB Moments N 50 Sum \l-3ts 50 �ean 1.27888 Sum 63.944 Std Dev 0.021344 Variance 0.000456 Skewness -0.74873 lCurtosis o.2oas62 USS 81.79903 css 0.022323 CV 1.66898 Std Mean 0.003019 T: l'\ean:0 423.676 Pr> IT I 0.0001 Num A: 0 50 Nurn > 0 50 11(Sign) 25 Pr>= 0.0001 Sgn Rank 637.5 Pr>: 1�1 S 0.0001 W: Normal :l.936406 Pr

Normal Probability Plot * 1.3175+ +♦♦* ♦♦* ••++u • ♦♦ * u ** **•+++ UH •**++ UHH 1. 2725 * ++ ++ ++• ++• +++t+ +* ** ♦♦ * ++ 1,2275 +++• +---+----+----♦----♦----♦----+�---+·�--f•---+•�--f• -2 -1 0 +1 +2 142

for Skewness in Oependent V�ri�ble 7 Look 14:10 Friday, June 18, 1993 ------·------COLOR=2 ------�------••••-••• Univariate Procedure Variable=DEHSITYB lo1ents N Sul Wgts 50 Hean 1, 19058so Sum 59.529 Std Oev 0,036846 Varian�e 0.001353 Skewness -0.315 49 Xurtos,s -0.64506 USS 70.94056 css 0.066524 CV 3.094804 Std Mean 0.005211 T:Mean=O Pr>ITI 0.0001 Nua "= 0 Nu11 > 0 50 MC Si in) 25.s Pr>=f 0.0001 �. 959204617 Pr= MS I 0.0001 W:Nor::at us.4819 0.1450 Variable=DENSITYB 50 Ste111 Leaf I 126 Sgn2 ank 1 125 04 2 124 1?3 J6 2 Boxr 122 0244489 7 - - 121 0011379 7 +- - + 120 1358 4 I - -I 119 135678 6 • -+- • 11 349 3 11 , 17? J 116 019 3 f_ ___ J 115 699 J 114 168 3 11!. 079 3 112 1 1 111 77 2 ----+----+----+---+ Multiply Stea.Leaf by 10tt•2

Normal Probability Plot t 1.265+ .+t ♦t♦ +++ 1 1.235 ·••+••++t t ** ** 1.205 1 ·••++ ****♦ **+ 1.175 l **+ Ht ++u l �+*** 1.145 ♦t+H +++t 1.115 ! t++ t +----+----+----+----+----+----•----+----♦----♦----♦ -2 -1 0 +1 +2 Appendix I -Test to Analyze, for Each Paper Group, the Ink Optical Density of the Solid Printed Blocks

143 144

The SAS Syste1 1 color code = red 16:CB Wednesday, June 2, 1993 TTEST PROCEDURE Run 1 Variable: DENSITY ·················GROUP N ·······---Hean -----·-·-·---Std Dev ---- Std-·------·-·- Error ------·--Minimu, "ax1mu1--- 1 50 1,28988000 0,01894529 0,00267927 1,25800000 1.13700000 2 50 1.09378000 0.01840174 0,00260240 1,02800000 1,1,900000 -Variances------T ------DF ?rob>ITI----- Unequal 5?.,5-020 97,Q 0.0001 Equal 52,5020 98,0 0,0000 For HO: Variances are equal, F' = 1,06 OF= (49,49) Prob>F' = C.8394 COLOR CODE· = YELLOW Run 2 Variable: DENSITY ------�GROUP N ·------Mean------Std Dev ------·-·------·····Std Error Nini1u1 ---·-----Maxt1u1 1 40 1 28425000 0 017 7332 0.00279440 1.25100000 1,337000CO 2 . 40 ·1:05995000 0:018 f6403 0.00291942 1.02200000 .. . ..1,10400000., ··-·------·-·---·---·-······----Variances T DF ·. · Prob>111 Unequal 55.5027 77,9 o. 0001 Equal 55,5027 78,0 0.0000 For HO::Variances are equal, F' = 1,09 DF = (39,39) Prob>F� = 0,7860 _COLOR_CODE = BLUE Run 3. . .. · Variable: DENSITY ...... GROUP ______N �ean Std Dev ______Std Error______"ini1u1 Maxf1u1_ _ 1 so 1.11sssooo 0.02114425 0.00101353 1.12soo000 1.31900000 .-. 2 50 1,06454000 0,01472636 0,00208262 1,01100000 1,09600000 . T DF : . ------Variances -�--�------Prob>ITI . ... ' . unequal" ... 58,4468. · 87.0 : 0,0001 . Equal 58,4468 98,0 · 0,0000 For HO: Var;ances are equal, .F' = 2.10 DF = (49,49) Prob>F' = C.0106 145

The SAS Systel 1 COLOR CODE = PURPLE 16:09 Wednesday, June 2, 1993

Run .4 TlEST PROCEDURE Variable: DENSITY ----GROUP------·- N ·-·------Mean ·-·-·------Std Dev ------·--Std Error ------Mini1u1· ·--·------"axi1u1 1 so 1.2sJ66000 ·o.02sa3354 0.00365341 1,23000000 1,35100000 2 50 1,05970000 0,02162316 0,00305798 1,00700000 1.10200000 ------·-·Variances T -·-·------DF . Prob>------IT) Unequal 47,0078 95,1 ' 0,0001 Equal 47,0078 98,0 0,0000 For HO: Variances are equat,.F' = 1,43 Df = (49,49) Prob>F' = C,2165

COLOR CODE = BROWN

Run 5

Variable: OEHSITY GROUP N Hean \Ii nimu11 ------Std--- Dev------·--Std --Error------1 50 0,25208000 0,02272178 0,00321334 0,1B1000GO 0.28700000 2 50 0,51654000 0,43572043 0,06869124 O,C0100000 C,99900000 ···········--·-·-Variances ·--T ------OF ------Prob>ITI Unequal -3,8458 49,2 0,0003 Equal ·J,8458 98,0 0,0002 1 For HO: Var;ances are equal, F = 456,97 DF = (49,49) Prob>F' = 0.0000 146

1he SAS System 1 COLOR CODE = GREEN 16:07 Wednesday, June 2, 1993

Run 6 TTEST PROCEDURE Variable: DENSITY ----GROUP--- ·-·------N ------Hean---·-·------Std --Oev------Std-- -�--Error------�inimu�------Maximum , 50 1.2s4soooo a.02653314 0.00375942 1.1a900000 1,29200000 2 50 1.01336000 0.02054836 0.00290598 0,94400000 1,05600000 Variances------T ------OF ?rob>lTI---·- Unequal S0.7489 92,2 0,0001 Equal 50.7429 98.0 0.0000 For HO: Variances are equal, F' = 1.67 OF: (49,49) Prob>F' = C.0745

COLOR CODE = BLACK Rµri 1 Variable: DENSITY -GROUP------N Kean------Std------Dev Std------Error· ------Mini1u1------Maxf1u1···--- 1 50 1.19058000 0,03684612 0.00521083 1.11100000 1,26200000 2 50 1.00356000 0,01959296 0.00277086 0.94900000 - 1,04100000 ---Variances------�----·---T-.-----. ------OF Prob>ITI Unequal 31.6890 74.7 0.0001 Equal 31.6890 98.0 0,0000 For HO: Variances are equal, f' = 3,54 DF = (49,49) Prob>F' = 0.0000 Appendix J Identification of Tested Areas

147 4 5 148

3

2

-,...... - �----. ·••·.. -- .. ..- --. -- . .

1

Legend. 1 = Magenta (red) block, I p. I 2 = Cyan (blue) block, - .. 3 = Trap (eyan ink printed on magentai 4 = Doors ( CVan and magenta ink. ) Appendix K Analyses of Variance for Smoothness, Parker Print Surf of 10 Kg Force

149 150

The SAS Systen 1 11:53 Tuesday, June 8, 1993 General Linear Models Procedure Class Level Information Class levels Values COLOR 7 1 2 3 4 5 6 7

Nuaber of observations in data set= 140

Dependent Variable: SM0OTH10 Sum of Mean Source DF Squares Square f Value "r > F "odel 6 3.64000429 0.60666738 169.77 0.0001 Error 133 o. 47527000 0.00357346 Corrected Total 139 4.11527429 R·Square c.v. Root MSE SKOOTH10 Mean o. 884511 2,102970 0.059778 2.842571

Source DF Type I SS Hean Square F. Value Pr> F COLOR 6 3.64000429 0.60666738 169.77 0.0001 Source DF Type III SS Mean Square F Value Pr> F COLOR 6 1. 64000429 0.60666738 169. 77 0.0001 Contrast DF Contrast SS Hean Square F Value Pr> F linear 1 1. 5857 8571 1. 58578571 443.77 0.0001 quadratic 0.11041929 0,11041929 30.90 0.0001 cub1c 1 0.00520083 o.oos2ooa1 1.46 c. 2298 151

Look for Skewness in Dependent Ytriable 18 11:53 Tuesday, June 8, 1993 UnivariateScht11atic Procedure Plots Yariable=SMOOTH10

3.3 l 0 3.1 I I I +----+t---t +·-···+ 3., I !--�-l l--+--l l .•... 3 l I I ! J 0 t I 1 0 •••f,••i+----+ 1.81 +---·+ +-----+ •-+-·• +---•♦ ♦-•--+ +---·+ t••+•-t +---·+I •·····•I + I J l..!-! +·--·-+ I ! +----♦ ul 0 J I ---·-····-+······-----+-··-···----+·--··-·-+········-+--·-----♦-••---·--·-+-···-··--- COLOR 1 2 3 4 5 6 7 152

The SAS Systu 3 11:53 Tuesday, June 8, 1993 General Linear Models Procedure Scheffe's test for variable: SMOOTH10 NOTE: This test controls the type I experiientwise error rate but generally has a higher type II error rate than REGWF for all pairwise comparisons Alpha= 0,05 df= 133 "SE= 0,003573 Critical Value of F= 2.16742 Nini1u1 Significant Difference= C,0682 Means �ith the sa1e letter are not significantly different. Scheffe Grouping �ean N CJlOR A 20 1 A 3.10850 A 3.07850 20 3 B 5 B 2.79750 20 C 8 20 2 C B 2,74650 C 8 20 7 C B 2, 73850 C 8 20 4 C 2.73150 C 2.69700 20 6 153

Look for Skewness in Dependent Vari11:53 able 4 Tuesday, Junt 8, 1993 ------�------COLOR=1 ------····-··•--·--·•-•·�------•- Univariate Procedure Yar;able=SMOOTHtO Moments N 20 3.1085 Sum Wgts 62.1720 MeanStd Dev 0.081064 Sum o.o 06571 -0.17709 Variance 0,687606 USSSkewness Kurtosiscss 0, 124855 193.2.607806 3803 o.01a,u; CV 171.4904 Std Mean 0 .0001 T:Mean=O 20 Pr>ITI Nua A: 0 10 Num > 0 0 .000120 11(Sijn) 105 Pr>= Sgn ank Pr>::( MS ( o.ooot W:Nonal o. 972105 Pr

Normal Probability Plot +t++H 3.275+ +-flr+-f♦ Hh+• *•++++U+ ♦HHh + + +++++• + t tt 2.925 +++♦+H +----+----+----+----+----+----♦----+----+-·--+-�--i -2 -1 0 +1 +2

•

Stem Leaf ' Bo,c�lot 32 8 1 3231 3678 3 •-·-·+ 8 •·-+-·• ·3031 69901122334 3 +·-·-·+ 30 03 2 29 93 1 ----+----+----+----+ I Multiply Stem.Leaf by 10••·1 Appendix L Analyses of Variance for Compressibility, Difference of 10 and 20 Kg Forces

154 155

The SAS Systn 1 11:52 Tuesday, June 3, 1993 General Linear �odels Procedure Class Level Information Class Levels Values COLOR 7 1 2 3 4 5 6 7

Number of observations in data set: 140 Oependent Variable: 'MOODIFF Su111 of Mean Source OF Squares Square F Value Pr> F �odel 6 o. 35716714 o,c5qs2136 7,93 C.0001 Error 133 0.99825)00 0.00750564 Corrected Tot al 119 1.35541714 R-�quare c.v. Root HSE S�OODIFF Hean �-�63511 -21.07177 O,Of6635 -0.411143

Source OF Type I SS '1ean Square F Value Pr> F COLOR 6 0,35716714 0,05952786 7,93 0 ,0001 Source OF Type III SS �ean Square F Value Pr> F COLOR 6 C,35716714 0.05952786 7,93 o .ooc1 Contrast DF Contrast SS Mean Square F Value Pr> F linear 1 J,06732071 0,06732071 �.97 0.0033 quadratic 1 0,08514331 0,03514331 11.34 0.0010 cubic 1 o. 00024083 0.00024083 0.03 C.8581 156

The SAS System 1 11:52 Tuesday, June 3, 1993 General Linear Models Procedure Scheffe's test for variable: JMOOOIFF NOTE: Th;s test controls the type I experimentwise error rate but Jenerally h�s a higher type II error rate than REriWF for all pairwise comparisons Alpha= :.05 df = 133 MSc= 0.007506 Criticdl Value of F= 2,16742 Mini�um SiJnificant Difference= 0.0988 Means �ith the same letter are not significantly different. 5cheffe Grouping �ean N cnto� A 20 'C. � -0.31900 J A 20 6 3 A -0.38950 fl A 4 3 -0,38950 20 3 C 20 5 ] C -0.41000 � C 20 3 a C -,),42400 a C 20 C -0.44000 C -0.49700 20 7 157

look for Skewness in Dependent Yjriabte 18 11:SZ Tuesday, June 8, 1993 Univariate Procedure Scheutic Plots Yariable=SMOODifF �0.1 l -o.J

•O,l I -0.15 I +··•-•♦ 0 -o,J I + ♦-•-·+ t-••t •-·••• -a.is j •---+ 1___ .f +--·+ I I ♦••···+ -0.4 I I --- ♦ +·····+ t-+-• t-••••It .L'.) .-.. .I r··j .o.45 I l----l LJ -- -o.s I ♦ t••··· •1,551 l----l -o., I

-o.,s I · ·· ···· - · - - · · -+ --· ·····+ - -······•··· ..······ +··········-+-····-··-•·+·······--·-+-·•·-·--·· COLOR 2 3 4 5 6 7 158

Loo� for Skewness in Dependent Variable 4 11:52 Tuesday, June 8, 1993 ------·•0•··-·------COLOR=1 --·------Univariate Procedure Variable:S�JODTF� Moments N 20 Sum W�ts 21 lie an -0.44 Sum -s,g Std D2v 0,125068 Variance 0.015642 Skewness 0.475648 Kurtosis -C.1?652 USS 4,1692 css 0.297� CV ·2P..4246 Std Mean 0,027966 T:Mean=1 ·15,7333 Pr>ITI o.oco1 Num A: 0 20 Num > 0 0 �(Sign) -10 Pr> 0.0001 Sgn Rank -1 cs Pr>== j"j S O.JC01 W:Norl!lal 0,?64333 Pr

Univariate Procedure Variable=SMOOOIFF Normal Probability Plot -0.15+ HHH♦ • t+tHH++ Hut♦♦+ h+t++Htho++u -o.J hHHH +----+----+----+----+----+------+- - -♦ -2 -1 0 +1 + ---+---+2+---

Stem Leaf # ot -1 6 1 BOKr -2 5 1 +---··+ -3 9500 4 t--+--t -4 �544211 7 +-----♦ . -5 85551 5 -6 31 2 ----+--·-+----+---•+ �ultiply Stea.Leaf by 10••·1 Appendix M Analyses of Variance for Paper surface Smoothness Compared to Printed Areas

159 160

The SAS Systell 1 15:03 Tuesday, June 8, 1993 Correlation Analysis 1 'WITH' Var;ables: BLXPAPER 1 'VAR' Variables: 8LKREDBl

s;mple Statistics Variable N Mean Std Dev Median Hinhlu11 P1axiau1 BLKPAPER 20 2,8470 0.0739 2.8450 2,7300 •�.0300 BLKRED8X 20 J, 1215 0,081! 3,1150 J,0000 3.3000

Pearson Correlation Coefficients I Prob> IRI under Ho: Rho=O / N = ZO BLKREDBK BLXPAPER ·0,03663 0.8782

Spearaan Correlation Coefficients/ Prob> IRI under Ho: Rho=O / N = 20 BLKREDBK BLKPAPER •0,09607 0.6870 161

The SAS System 2 15:03 Tuesday, June 8, 1993 Correlation Analysis 1 'WITH' Variables: ·sLKPAPER 1 'VAR' Variables: BLKBLUBK

Simple Statistics Variable N Mean Std Dev Median "ini1u1 Maxi1u1 BLKPAPER 20 2,8470 0,0739 2,8450 2�7300 3,0300 BLKBLUBK 20 3,1940 0,0486 3,1950 3,0900 3.2700

Pearson Correlation Coefficients/ Prob> IRI under Ho: Rho=O I H = 20 BLKBLUBK BLKPAPER ·0,20158 0,3941

Spearaan Correlation Coefficients/ Prob> IRI under Ho: Rho=O IN= 20 BLKBLUBK BLKPAPER •0,22167 0,3476 162

The s�s System 15:03 Tuesday, June 8, 199i Correlation Analysis 1 'WITH' Variables: BlKPAPER 1 'VAR' Variables: BLKDOORS

Si1ple Statistics Variable N Mean Std Dev "edian Mini1u1 Maxi1u1 BLKPAPER 20 2.8470 0,0739 2.M50 2,7300 3,0300 9LKOOORS 20 2,9485 0,0533 2.9500 2,8400 3.0700

Pearson Correlation Coefficients I Prob> l�I under Ho: Rho=O IN= 20 BLKDOORS 3LKPAPER ·G,40033 0.0803

Spearman Correlation Coefficients/ Prob> IRI under Ho: Rho=O / N = 20 BLKDOORS BLKPAPER ·0,40144 0.0794

:-·

.. :. ti;'.(� Appendix N Analyses of Variance for Smoothness of Unprinted Areas Compared to Printed Areas

163 164

The SAS system 1 14:40 Tuesday, June 8, 1993 Correlation Analysis 1 'WITH' Variables: YELLP10P 1 'VAR' Variables: YELPAPER

Siaple Statistics Variable N Mean Std Dev i.edian �ini1u1 ftaxi1u1 · YELLP10P 20 2. 7315 0,0407 2.7300 2.6500 2.8200' YELPAPER 20 2.8505 0.0881 2.8450 2.1100 3,0200

Pearson Correlat;on Coefficients/ Prob> )RI under Ho: Rho=O / N = 20 YELPAPER . . YELLP10P -0.07216 ' 0.7624

Spear1an Correlation Coefficients I Prob> JR) under Ho: Rho=O I H = 20 YELPAPER . . : ... •. '• ·.":'.· .. ·' · · .. · · · · ... . YELLP10P · 0106327u. 7910 .,:.:.:. . '.

,. ···. .... :! ., 165

· The SAS System 2 14:40 ·Tuesday, June 8, 1993 Correlation Anatisis 1 'WITH' Yar ables: REDP10P 1 'VAR' Var1 ables: REDPAPER

Si1ple Statistics Variable H ftean Std Dev Median Mini IIUI J11axhu1 REDP10P 20 3.1085 0.0811 3, 1150 2,9300 3,2800 REDPAPER 20 3. 2735 0,0613 . 3,2700 3,1700 3.4200

Pearson Correlation Coefftctents I Prob> (RI under Ho: Rho=O IN= 20 REDPAPER REDP10P ·0,482720,0311

Spearaan Correlation Coefficients/ Prob> IRI under Ho: Rho=O / N = 20 REDPAPER

.· · ·- ·: _-:-�· ·- R£DP1 OP. 0.64932 ' . 0.0019 . . '

.. 166

The SAS Systea 14:40 Tuesday, June a, 199i Correlation Analysis 1 'WITH' Variables: PURP10P 1 'VAR' Variables: PUltPAPER

Si1ple Statistics Variable N flean Std Dev Median · Min11u1 Maxi1u1 PURP10P 20:. 2.7465 . 0.0669 i. 7600 2.6000 2.8700 PURPAPER 20 2. 8790 0.0481 2,8800 ,.7800 2.9900

Pearson Correlation Coefficients/ ?rob> IRI under Ho: Rho=0 / N = 20 PURPAPER PURP10P 0,04137 0.8625

Spear1an Correlatio� Coefficients/ Prob> IRI under Ho: Rho=O I H = 20 PURPAPER

·• . PURP10P,. -0.04252.. 0.8587 ,.•,

. I

.(::·.::--._ 167

The SAS Syste1 , 14:40 Tuesday, June 8, 1993 Correlation Analysis 1 1 · 'WITH Variables: GRENP10P 1 'VAR' Variables: GRNPAPER

Si1ple Statistics Variable H Mean Std Dev Median �tni■UI Maxi■UI GRENP10P 20 2,6970 0,0642 2,6850 2.5800 .. · 2.8100 GRHP�PER 20 2. 9070 0,0363 2. 9100 2.8300 2,9600

Pearson Correlation Coefficients/ Prob> IRI under Ho: Rho=O I H = 20 GRNPAPER GRENP10P ·0,17812 0,4524

Spear1an Correlation Coefficients/ Prob> IR) under Ho: Rbo=O / H = 20 GR"PAPER

GRENP10P ·0109174 .... :. . : . .. .. u,7005 . ...

' -,-

•• i . , , 168

The SAS System 14:40 Tuesday, June 8, 199� -Correlation Analysis 1 'WITH' Variables: 8RWNP10P 1 'VAR' Variables: BRWNPAPR

: Si1ple Statistics Variable N Mean Std Dev Median Miniiu1 Maxi IUI ..... ·. . .' -- BRVNP10P 20 :· 2.7975 . 0 • 048 9_· 2,7900 Z,7000 2.aaoo- BRVNPAPR 20 2.8940. 0 • 053 9 2,8900 2.8000 2,91O0

Pearson Correlation Coefficients/ Prob> )RI under Ho: Rho=O / N = 20 BRWNPAPR BRWNP10P 0,43328 0,0563

Spear1an Correlation Coefficients/ Prob> )RI under Ho: Rho=O / N = 20 BRWNPAPR

•BRVNP10P i . 0,45806 .. .· ·. , . 0.0422 1-. j. : .

:,

•.·· .. 169

The SAS Syst ea 6 14:40 Tuesday, June 8, 1993 Correlation Analysis 1 'WITH' Variables: BLUEP10P 1 'VAR' Variables: BLUPAPER

. Siaple Statistics Variable N: Hean Std Dev �edhn �inbu1 Maxhua · 8LUEP10P . 20 ! 3.0785 0.0498 . · 3.0850· 2.9900 3.1400 ...... BLUPAPER 20 ·2.9270 0.0589 2.9400 2.s100- 3.0200

Pearson Correlation Coefficients/ Prob> IRI under Ho: Rho=O I H = 20 BLUPAPER BLUEP10P -0.31918· 0.1102

. . Spearaan Correlation Coefficients/ Prob> IRI under Ho: Rho=O IN= 20 DLUPAPER . ·•.. -. ·.· . .. . ( . _ BLUEP10P - _,_·,, . ... -. _ ..:. _�0.40121· 0,0796 . . ·l. -_ 'I :r ,· : :. _- ... • f· I . .. � (..

... ·. . _

- ; 170

The SAS Systn 7 14:40 Tuesday, June a, 1993 · Correlation Analysis 1 'WITH' Variables: BLKP10P 1 'VAR' Variables: BLXPAPER

:· Siaple Statistics Variable N ' Mean Std Dev Nedhn Mi ni■u1 Maxhu1 BLKP10? 20 : 2. 7385 ..· 0.0577 · 2. 7300 2,6000 2,8300 BLICPAPER 20 . ·2�8470 . 0,0739 2,8450 2,7300 3,0300

Pearson Correlation Coefficients I Prob> IRI under Ho: Rho=O / N = 20 BUPAPER BUP10P 0,03468 0.8846

Spearaan Correlation: Coefficients / Prob> I RI under Ho: Rho=O / M = 20 BUPAPER 0 0 .. �-��,1 ,_ . _. . - 0��iU . . . ·. 1 i··.- . ;. . . ·-·

; , . . . . . Appendix O Moisture Content of the Paper Immediately Following Production on the Paper Machine Reel

171 172

Run Number Aged HST Value (seconds) % Moisture-Paper

1 0 4.7

2 75 3.2

3 117 4.9

4 170 3.3

5 207 4.8

6 268 3.5

7 459 5.0 REFERENCES

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