Inks

Inks Ink Properties The purpos purposee of thi thiss sectio section n is to help establish a common language between the maker can ink compounder and the printer. These are properties that the ink maker the informed printer it allows a fast  identify and assign a repeatable range. For the varietyy of ink inkss with a minim minimal al amoun amountt of tes testin tingg. comparison of  a variet evolu olutio tion. n. The  We are in an industry with no standards and this is slowing our ev  We after time and is rarely  printer cannot count on the ink printing the same time after suree if the ink sur ink is at fault fault or if the caus causee is the the balanc balancee of th thee prin printt proc proces esss. Su Such ch is our world world without standards. standards. For all other applicat applications ions,, the plastisol plastisol manufacmanufacturerss offer a Certifi turer Certificate cate of Analy Analysis sis that that describes describes any normal or special variance of the product product that has has been been purchas purchased. ed. Iro Ironic nicall allyy none none of the these se alte alternat rnatee processes is more complex or more more variable than screen printing. printing. Ask your vendor if you are a large enough enough account account to warrant warrant a CofA with your your ink. ink. market. et. Far too There are a variety variety of probl problems ems with some some ink currently currently on the mark press ss ran slo slow w, often,, these are often are remedie remedied d by an adjustm adjustment ent on the the press press.. If the pre M&R would expect that you would call and we would would do something about the , reali realize ze that ink solutions solutions from from the proble pro blem. m. If the ink ink is forci forcing ng you you to run slow  slow  press may be costing you productivity and and quality. The point is that what you dont know about your ink may may hu hurt rt you you.. If in fa fact ct th thee ink is problematic, problematic, the best solution is to fix the ink ink not to use use the press press,, mesh mesh,, Ink  Problem

Build-up  After flash tack Low opacity Screen hang-up Blade hang-up Over plasticized Excess tack Thermal sensitivity Dilatent white High viscosity Poor grind

Press Compensation

Record Lost Dozens per Hour

Flash cure Cooling station or fans Double stroke, second screen Higher off-contact  Lower angles, wider gap Longer flash time Higher off-contact, tension Periodic cooling breaks Slower blade speed Higher blade pressure Periodic cleaning breaks

Figure 3.1 Use the table above to record the number number of dozens per hour you lose, due to the press fix used to com- 

 pensate for ink problems. This will give you a more concrete idea of what problem ink costs you in downtime and leverage  to discuss the issue with your ink manufacture. PAGE 3 . 3

Chapterr 3 Chapte stencil or anythi anything ng else. else. The proble problem m is, is, you may not alwa always ys know know if the ink  meets mee ts your specif specificati ications-y ons-you ou may be be laboring laboring with art, scree screens, ns, stenc stencils ils,, press press,, flash or dryer to solve a problem caused solely by the ink. Ink,, as For our test purposes we used white ink manufactured byHaden-Horn byHaden-Hornee Ink used d color. color. Eac Each h  white is familiar to all readers and by far the most commonly  commonly use d of wh whit ites es an and d som somee of  of the manufact manufacturers urers in the marke markett place has a boatloa boatload use. Once you you understand understand the companies are hard pressed to tell you which t o use. the availab available le data on each each of the whites whites and get comparable data from your supplier,, it is simple plier simple to determine why why and where and where you should select a white or any  listed tests, tests, nor do they encourage encourage other color. color. Not all manufacturers manufacturers perform all listed facets of of ink performance performance can be listed listed on on a publishing publi shing the results results.. All of these of  these facets Certifi Cert ificat catee of Ana Analys lysis is.. The properties listed below are offered as a starting point  divided ded into four categori categories: es: optica optical,l, rheol rheological ogical,, therm thermal  al  in your search and are divi and physical. Optical

The opti cal cal propertie propertiess of the white white are very very important, important, as it is the color color most  most  toften ofte n used as an underbase. underbase. As such it may may have a strong affect on the overprin overprinted col colors ors,, part particu icular larly ly if the theyy are are tra transp nspare arent. nt. Furt Further her,, the aes aesthe thetic ticss of a w hite are criticalcritical- it must must not look dirty or yellowe yellowed. d. Fo Followi llowing ng are the stand standard specifications for white plastisol ink.

L*

a*

B*

92.04

-2.81

-2.65

H-Cote 9000 Optical Specifications Delta Peak  Gloss Opacity E Spectral Pctg. Per Mil

<1

480 nm

50

75% @ 1 mil 

Bleed Resist

3

x

y

.3372 .3562

Figure 3.2 This table lists the the optical properties of the H-Cote 9000 white white ink. The test test was done on a 1.5 mil deposit 

on a black tee shirt. The Luminosity indicated not total opacity on the tee shirt, 100.00 would be totally white. The a* and  b* read slightly toward a blue-green cast, away from a yellow-red cast. The Delta E was not measurable but that should be  expected batch-to-batch variation variation of white inks. inks. The peak spectral supports the the a* and b* data, it was 480nm, 480nm, a slight  bluish green cast. The gloss level was very low at 50%, which indicates a desirable printing surface. On a drawdown, the ink develops 75% of its opacity at a one-mil deposit. The bleed resistance on a one to five index was was a three, this series is not  intended for bleed resistance. The chromaticity coordinates are very near daylight at .3372 and .3562, once again they indi-  cate a slight shift toward the blue-green.

L*a*b*

The L*a*b* opponent color syst em em is an industry industry wide standard, standard, used to comcomparee the accur par accuracy acy of of col color or matches matches.. Opponent systems gauge the color between a seri se ries es of ax axes es.. The ax axes es have two two poles each; as the color specimen specimen gets closer to PAGE 3 . 4

Chapterr 3 Chapte stencil or anythi anything ng else. else. The proble problem m is, is, you may not alwa always ys know know if the ink  meets mee ts your specif specificati ications-y ons-you ou may be be laboring laboring with art, scree screens, ns, stenc stencils ils,, press press,, flash or dryer to solve a problem caused solely by the ink. Ink,, as For our test purposes we used white ink manufactured byHaden-Horn byHaden-Hornee Ink used d color. color. Eac Each h  white is familiar to all readers and by far the most commonly  commonly use d of wh whit ites es an and d som somee of  of the manufact manufacturers urers in the marke markett place has a boatloa boatload use. Once you you understand understand the companies are hard pressed to tell you which t o use. the availab available le data on each each of the whites whites and get comparable data from your supplier,, it is simple plier simple to determine why why and where and where you should select a white or any  listed tests, tests, nor do they encourage encourage other color. color. Not all manufacturers manufacturers perform all listed facets of of ink performance performance can be listed listed on on a publishing publi shing the results results.. All of these of  these facets Certifi Cert ificat catee of Ana Analys lysis is.. The properties listed below are offered as a starting point  divided ded into four categori categories: es: optica optical,l, rheol rheological ogical,, therm thermal  al  in your search and are divi and physical. Optical

The opti cal cal propertie propertiess of the white white are very very important, important, as it is the color color most  most  toften ofte n used as an underbase. underbase. As such it may may have a strong affect on the overprin overprinted col colors ors,, part particu icular larly ly if the theyy are are tra transp nspare arent. nt. Furt Further her,, the aes aesthe thetic ticss of a w hite are criticalcritical- it must must not look dirty or yellowe yellowed. d. Fo Followi llowing ng are the stand standard specifications for white plastisol ink.

L*

a*

B*

92.04

-2.81

-2.65

H-Cote 9000 Optical Specifications Delta Peak  Gloss Opacity E Spectral Pctg. Per Mil

<1

480 nm

50

75% @ 1 mil 

Bleed Resist

3

x

y

.3372 .3562

Figure 3.2 This table lists the the optical properties of the H-Cote 9000 white white ink. The test test was done on a 1.5 mil deposit 

on a black tee shirt. The Luminosity indicated not total opacity on the tee shirt, 100.00 would be totally white. The a* and  b* read slightly toward a blue-green cast, away from a yellow-red cast. The Delta E was not measurable but that should be  expected batch-to-batch variation variation of white inks. inks. The peak spectral supports the the a* and b* data, it was 480nm, 480nm, a slight  bluish green cast. The gloss level was very low at 50%, which indicates a desirable printing surface. On a drawdown, the ink develops 75% of its opacity at a one-mil deposit. The bleed resistance on a one to five index was was a three, this series is not  intended for bleed resistance. The chromaticity coordinates are very near daylight at .3372 and .3562, once again they indi-  cate a slight shift toward the blue-green.

L*a*b*

The L*a*b* opponent color syst em em is an industry industry wide standard, standard, used to comcomparee the accur par accuracy acy of of col color or matches matches.. Opponent systems gauge the color between a seri se ries es of ax axes es.. The ax axes es have two two poles each; as the color specimen specimen gets closer to PAGE 3 . 4

Inks one pole, pole, it automatical automatically ly moves moves away away from the the other. other. Fo Forr example, example, th thee more samee holds holds  white a color contains, the less black it can contain and vice versa. versa. The sam true with red versus green, and yellow versus blue-there blue-there are no reddish greens or bluish yellows yellows.. between een a high of of white and The L* is the the luminosi luminosity ty of the color color or its its position position betw position n of the color color betw between een a low low of bla black ck.. The a* a* horiz horizont ontal al axis axis is the positio ertical axis is is the positio position n of the color color absolute red and green and the b* v ertical between absolute yellow and blue. blue. colorless ess or achromati achromatic, c, it has attribut attributes es of  Even though white ink ink is seen as colorl modeled. ed. A white white that has has a bluish bluish cast, cast, such as as the one one shown color that can be model observer. It is an indication indication that that the white in figure 3.7,will 3.7,will appear whiter to the observer. nt used has been been altered with a blue tint, which negates the the yellow cast  pigment pigme

Figure 3.3 The L*a*b* Solid Color Model is the de facto standard map for color consistency. It is an opponent based 

model in that as the position of a color approaches one pole, the the influence from the opposite pole is lessened. lessened. Primary color  attributes can be specified between between the three axes. axes. Photograph compliments compliments of Hunter Labs. PAGE 3 . 5

Chapterr 3 Chapte Color Matc hing  We have all been asked to make  We sure the image color matches on all seve seventy nty-tw -two o of the garment  garment  colors. For you colors. you who have never never been asked, asked, we offer offer a few  caveats; there are two phenomephenomenon called simultaneous contrast  and adjacency contrast that may  keep you from delivering as needed. The first one implies that we do not see the the color color of image imagess as isolated entities. entities. Rather we we see the entiree image; our impression entir impression of  the color color is a composite composite of all  other surrounding surrounding colors. colors. The second phenomenon implies that our impressio impr ession n of a color can can change change radically depending on the color that is immediately beside it.  Assuming the ink is opaque enough to hide the garment color, you may still have a radical difference. It will most often be with the peri perimete meterr colors colors.. If ther theree is a hard border, border, you may may get away  away   with little trouble-but consider the following example: example: You need to to print a yellow sun in the background on both white and violet  T-Shirts.. On the white T-Shirts white T-shirt  T-shirt  there is little value contrast  between the shirt color and the sun. Printed on on the violet violet shirt the contrast is overwhelmi overwhelming, ng, because the two are complimentary colors,  which creates extreme extreme contrast.  Your  Yo ur focus will be forcibly taken to the perimeter and it will overpower most everything in the image. ima ge. Bew Beware are of bor border derles lesss images and complimentary hues  when the garment color is changed.

PAGE 3 . 6

inherent in the raw TiO² (titanium dioxide) dioxide) pigment. The bluish cast makes a cleaner looking white and this cast will  show up on an L*a*b* L*a*b* color model. Delta E

The delt deltaa E of a color color is a mea measur suree of the dist distanc ancee fro from the ultt of th thee color match to the sample or target color. color. It is a res resul less ss of an L*a*b* opponent opponent color parameter parameters. s. The delt a E is le issue with a white as white is opaque and and less sensitive to a lta E is the resulting variance shift with with a change change in deposit. deposit. De Delta in all three L*a*b* attributes that indicates color variance in anufacture cturers rs have have a range of of toler tolerance ance that th at ba batc tch h of in ink. k. Al Alll manufa

Figure 3.4 "Essentials" is a T-shirt-print of a fiduciary image used to diagnose 

 print parameters. The ink sets can be used for a variety of applications including delta e  measurements. Delta Delta e is the resulting variance of data developed in the L*a*b* color  model. The Hi-Res AccuColor© AccuColor© garment is provided compliments compliments of Target Graphics. Graphics.

Inks in the color and a lower number is better. Not all colors will  fare as well as a white. The range can be due in part, to the thickness of the test specimen. Peak Spectral

The peak spectral response of a color is its dominant wavelength. The visible spectrum ranges from approximately 400 to 700 nanometers and within that range a color will have a peak  indicating its hue. In the case of our white the peak is 435 nanometers at 95 percent reflectance, which indicates a blue tint. If the white is to be used as an under base, its cast should be minimal and only to the blue side or it can quickly alter the appearance of transparent color overprints with colors such as PantoneÒ or process yellow.

Hue, Saturation & Intensity -7257 + 50.26*x - 0.1255*x

  e   c   n   a    t   c   e    l    f   e    R    t   n   e   c   r   e    P

2

3 4 + 0.0001351*x - 5.31E-008*x

100

100

90

90

80

80

70

70

60

60

50

50

40

40

30

30

20

20

10

10

400

450

500

550

600

650

Color Matc hing (continued) Further there is the issue of gloss. Before you try to discount the effect of gloss on color, look at a PMS book-coated and uncoated-and think again. The  white T-shirts typically would have less ink on them and thereby may  have a lower gloss. Find a neutral gray card and punch a hole in its center. Use this to isolate questionable colors by  laying it over the printed shirt. This will allow you to see if in fact you matched the colors-you may not be able to match the appearance of the image due to the effect of the perimeter color.

700

 Visible Wavelength

Figure 3.5 Spectral Response Curves are the "tell-all" for color analysis. Shown here are 

three primary attributes of color identified, as the curve would depict them. This color is a cyan   plastisol printed at less than one mil. You can see that it peaks at approximately 460 nm, has  a moderate reflectance of 86 percent at that peak and that the red component (21 percent) in  cyan gives it undesirable grayness. This grayness desaturates the color to 64 percent. Graph com-   pliments of First Aid Ltd.

Gloss

The gloss of the plastisol is taken at 60° and our white drawdown has a low gloss of 30 percent. Be cautious of higher PAGE 3 . 7

Chapter 3 Bloody Myst er y There are three times when y ou may be surprised to see dye bleeding. First when the color of the bleeding does not match the color of the garment. Second when your reds and maroons arent a problem but the blues and greens are. And third when the bleed resistant ink stays white but the overprinted color turns. First as an example, you print a black tee, but the bleeding is a totally different color than the shirt because the garment has been over dyed. It was another color previously but left over, so the garment people said, lets dye this one black and ship it anyway. There is a limit to the amount of  dye that can attach to the garment. It is based on the propensity of that dye to fill the available dye-sites (microscopic nooks and crannies of the fiber). The problem is the original color should have been at, or near, the limit  already. Over dying is a risky business because of the availability of  the dye at the surface of the garment, and the ease with which it  can be detached from the fibers. Second, the manufacturers use bleaches like organic peroxides to neutralize the color of the dyes. The functionality is totally different for reds and blue T-shirts, as different as addition and subtraction. If the bleach is adding when it should be subtracting you may  end up with a bleeding dye. The ink manufacturer may need to use a combination of bleaches to neutralize both colors. The problem arises when the printer has solved the problem for the red bleeding 

PAGE 3 . 8

gloss levels if you intend to use the ink as an underbase. Higher gloss is indicative of a smoother finish, perhaps due to higher plasticizer level, which indicates lower surface energy 

Printers Color Wheel

Too much cyan or not enought  magenta.

CYAN

Too much cyan or not enought  yellow.

GREEN

BLUE

Too much magenta or  not enought  cyan.

Too much yellow or not  enought cyan.

MAGENTA 

Too much magenta or not  enought yellow.

YELLOW

RED

Too much yellow  or not enought  magenta.

© 1999, First Aid Ltd. Figure 3.6 The Printers Color Wheel is a model for process color balancing. This is a color 

wheel based system for printers to use as a guide when trying to balance colors on a process job. It not only shows primary and secondary colors, but in addition it shows both sides of a colr  shift of CYMK and RGB colors. A laminated version of this color wheel is available from  First Aid Ltd. for press-side use. Image compliments of First Aid Ltd.

and poor ink trapping (refer to page 3.37 for details). Also there is the aesthetic value of the ink,and by far the public does not want gloss unless the print is athletic numbering or related images. Note that the gloss should be determined with

Inks a drawdown, not a print as the texture of the print would give an artificially low reading.

Bloody Myst er y (continued)

Opacity per Mil

The opacity of an ink color should be noted per mil and a one-mil deposit i s typical and indicative of a 305-mesh

and not the blue or visa versa. Just  because one is solved, the printer may assume both have been solved, but it all depends on the type of bleach the garment manufacturer used. Third is when the white doesnt  bleed, but a color printed over the  white does. In this scenario the overprint color is highly plasticized, probably containing more (and different) plasticizers than the white. Its plasticizers migrate over time into the white film, plasticize the polyester yarns, and allow a river of plasticizer for the tiny dye molecules to swim to the top. The over-print colors on a bleeding T-shirt should have a minimum of plasticizer and if  they are highly transparent fluorescentscheck twice.

Figure 3.7 The GATF test image shows the results of fast recovery and high opacity white 

inks when used as an underbase. The reflection density of the white is 0.01, for near total  whiteness. The fast recovery and high mat-down kept virtually all fibers below the ink surface  through a 305 mesh. HiRes AccColor Ócompliments of Target Graphics Ltd.

deposit. The printer needs a white that will develop opacity at  t he thinnest deposit possible. This is a real-world measurement, because all whites are opaque if you pack them on the shirt  thick enough. The opacity is given as a percentag e of total  opacity (at a one-mil deposit) and a higher percentage is always preferable.  An ink drawdown and an opacity card are used to evaluate per mil ink opacity. The top half of the opacity card is white and PAGE 3 . 9

Chapter 3 How To Instructions

Testing For Sublimation There are many causes of "bleeding" on synthetic garments containing polyester. They all relate to how much the printer is willing to pay for garments. The problem is the quality of garment dyeing. Manufacturers know  how to stop it, but it would raise the price of the shirt. So the ink makers must try to compenstate for a problem that is solely the gar ment manufacturers doing. Sublimation occurs when dye becomes a gas without  liquefying first and "gasses" through the ink. There is a technique where you run the suspect garments through the dryer prior to printing in an attempt to fix the dyes in the garment. Those who preheated their T-shirts  were often disappointed because the dye fell right back  on the garment. The pre-setting is a waste of time and energy. After investigation we learned that sublimation occurred at 250°, but the plastisol ink goes into gel at  150°. Further, dyes do not sublimate until 250°, they  remain below the plastisol until that point. Meanwhile, plastisol becomes an insulator at 150°, insulating the dyes in the shirt from additional heat. So most of the dye-bleeding problem is not directly related to sublimation. To see if dyes are being released from the garment, use a white Pellon® stock approximately two-inches square and punch a hole in it. Temporarily secure the sheet to the garment and put it through the dryer at normal  speeds and temperatures. If the dyes are available the Pellon will pick them up and upon inspection, you will  see traces of the dyes. You have two options at this point. First, if you ran your test with higher-than-fusion temperatures, reduce the heat, this should eliminate sublimations. Second, you could look for different ink  one that passes this test.

the bottom half of it is black. The white ink is drawn dow n on an opacity card to a prescribed thickness. A colorimeter or densit ometer is used to measure the whiteness (reflectance) of the ink on both ends of the card. Total  opacity would mean that the ink looks the same on the  white and black ends of the card. If there is a variance in the two the percentage of the  white and black ends is taken at the thickness of the drawdown. Lets say that the deposit is one mil and the white ink on the bottom (black end) of the card has 71 percent reflectance.The white ink at the top of the card (on the white end) has a reflectance of 95 percent. The resulting opacity  is 75 percent at one-mil or 1600 square feet per gallon. Bleed Resistance

There are a variety of methods the ink manufacturer uses to ensure the white will stay   white on a variety of colors of polyest er-containing garments. The most commonplace method is to bleach the dyes to a neutral color, with the use of organic peroxides. Just as a hair stylist bleaches dark hair to light, they can turn the dyes to clear. Typically the t ype of peroxide used on red garments is different than the ones that neutralize blue dyes, so the manufacturer may resort to the use of a pair of organic peroxides in tandem.

PAGE 3 . 10

Inks More important than how to stop the dye is now to avoid triggering the dyestuff. There are two methods of achieving  such a product. First is by the selection of a plasticizer that  is less likely to plasticize the polyester fibers. Certain plasticizers are literally used as carriers for dyestuffs and they  can act as a conduit for the dye once it i s released from the garment fibers. This family of plasticizers should be avoided. The second point is to use the minimal amount of  plasticizer that the application  will permit and most of the inks contain more than is desirable. Bleed resistance can also be achieved with the use of  blowing agents comparable to those used in puff inks. These create a cell structure that accomplishes two goals, to keep the fibers below the ink surface and to construct a maze that the dye will have to navigate to reach the surface. Note that much of the bleeding is from the top of the garment. Finally, there are manufacturers that use cross l inkers to tie-up the i nk film so that  the dye cannot pass through.  All of these adaptations tend

Testing For Migration

How To Instructions

Migration is the permeation of the dyes through the plasticizer due to the compatibility of the ink, dye and garment. Plasticizers are literally used as carriers for dyes in many cases also plasticizers invade the (polyester) yarn structure and while it was once relatively  thermo set, it now becomes thermo plastic and flows under the application of heat. The flowing causes it to release the dyes into the inviting plasticizer of the ink. Unlike sublimation, which is assumed to come from the garment below the ink, triggered during the cure cycle, migration can emanate from above or below the ink  film. Consider that the manufacturer uses bleaches that  decompose with heat. Your garment looks snow white for a while and then begins to bleed. There is more than a fair chance that the fibers on the top of the ink film have been plasticized by the ink and released their dyes into it. After all there are no bleaches left over to neutralize the dye color. Use a snow-white business card and punch a hole in it. Compare this whiteness to that of the ink film immediately after it is printed. Then keep a continued eye on the ink for any change. The comparison to the card will  allow you to detect the least change. As soon as you see a shift toward the garment color, cut a slice in the test  sample and use a 10X loupe to observe if the dye stemmed from the top or bottom of the print. If it is from below you may not be totally fused, recheck your settings. If the other extreme occurred-over fusion, the bleach dies off and allows the liquefied dyes to enter the plastisol, and bleeding occurs. Be sure that if you are flashing then you check the dryer exit temperature with a heat gun before entrance. If the top of the ink film is stained with dye and the internal segments are virgin, then your goods bled from the top down. Your ink problem may be mat down.  You can select ink / mesh / blade combination that  mats the fibers better. Or you can print flash print, your choice.

PAGE 3 . 11

Chapter 3 to make ink that is more difficult to print and cure. Also they are traditionally  more finicky and exhibit less shelf stability. It is best to use bleed resistant ink  only when printing garments that contain synthetics such as polyester. The specific white that we selected has some inherent bleed resistance but is not recommended for polyester printing. xy Chromaticity Coordinates

The xy-chromaticity coordinates indicate the position on the color locus and gauge its hue as well as saturation. This model is most often used for process colors but if y ou intend to use a white for underbasing process colors, you will want  to know its relative position from this model. For example if the white is excessively cast to the blue side, it will drag every overprint color to the blue side,  which may be a consideration in your separation.

Figure 3.8 The Chromaticity Diagram is the classical 1931 color locus. It is a plot of the hue and saturation 

components of a color and was used for relative comparison of closely related colors. The x and y axes are used to  plot color. It has been updated to a more intuitive 1976 version where the distance between colors more closely  approximates their differences. Compliments of Photo Research. PAGE 3 . 12

Inks Rheological

The rheological properties of plastisol ink indicate how much force you need to apply to get the ink moving, how the product will flow through the mesh once it  is moving and if and when it will stop flowing w hen printed on the garment or on top of another ink.

Relative  Viscosity

(cPs)

1,120,000

H-Cote 9000 Rheological Specifications  Yield Plastic Shortness Thix Tack  Stress  Viscosity Ratio Index Percent (D/cm) (cPs)

180,000

480,000

2.67

5.9

20

Severs (cPs)

3059

Figure 3.9 This table lists the rheological properties of the H-Cote 9000 white ink. The relative viscosity is high, meas- 

uring 1,120,000 cPs, which gives it a bodied consistency. The yield stress is low,measuring 180,000 dynes/cm, so the ink begins to flow with little effort. The plastic viscosity measures near the midpoint, 480,000 cps, making it thin enough to flow  through the mesh, but able to recover its body quickly. The shortness ratio is also near the midpoint at 2.67, while the  thixotropic index is 5.9. The shortness ratio and thixotropic index here, describes a bodied ink that thins readily and yet  holds its shape under shear. The tack level is 20 percent, which is very low, and the Severs test indicated excellent fluidity at  100 psi.

Unfortunately, the standard viscosity instruments are not particularly informative  when it comes to on press perf ormance. The equipment used for the readings below included several types of laboratory instruments. If you are looking into a low cost viscometer for in house QC efforts with plastisol inks, you may find t hat  only extreme di fferences are measurable. We recommend that you rely on data from the manufacturers and subsequent press performance. Relative Viscosity

 A viscometer measures the resistance t o flow of the ink and is used to establish thix index. It runs at one of very slow speeds between two and 20 rpm (revolutions per minute). The spindle-type viscometer senses the resistance of the spindle as it turns in the cup of ink  thicker ink means more resistance. The measure of viscosity is centipoise (cps) and that is the scale that the resistance is converted to. Relative viscosity is measured at a low rpm and accordingly has a higher resistance and consequently a higher viscosity. Preferably t he relative viscosity (low shear stress viscosity) is high. Ink with a low relative viscosity would tend to pour from the container and not hold the imag e once it is printed-however there is no assurance that it would flow through the screen mesh properly.

PAGE 3 . 13

Chapter 3 Quick Test To Check Ink Flow Properties

 Y ield Stress

 Yield stress indicates the amount of force required to get the ink to flow. It is not an indicator of viscosity, rather a device

The in plant testing of plastisol  performance is difficult because even the standard viscometers used by most of the manufacturers are not particularly representative of the performance of the ink on press. There is a simple and informative method of ink  testing that you should incorporate into your daily schedule. Do not mix the ink before you begin the test. At one edge of the top of the ink pail, push a stainless steel spatula into the ink  about two inches in depth. Now  cut a channel into the ink, two inches deep, the width of the spatula across the diameter of the pail and observe the spatula as it  crosses the pail. If the spatula bends severely, the relative viscosity and yield stress are too high and you will need excessive force to transfer the ink  through any screen mesh. If the channel flows together immediately, the ink will transfer sufficiently, but it will not hold its position on the garment. It will perform poorly when printed on an underbase. If the ink remains in the shape of  the channel for a time, the results  will not be as bad, but caution should be applied. The best ink   will cut the channel easily and never allow it to fall or lose its shape. The test is subjective meaning that  the results are not transferable from one person to the next. But  the impression gained about the performance of the ink for each individual is priceless.

PAGE 3 . 14

Figure3.10 This is a macro view of the Rockport logo is a high-density T- 

shirt. The relative viscosity of high-density inks is extreme, due to its high resin  and filler loading. If you are using high-density inks, we recommend the Turnabout  H.D. for complete low shear mixing. Printed garment compliments of Liberty  Screen Print.

Figure 3.11 This is a micro version of the Rockport T-shirt accentting the ter- 

raced relief structure of the garment. The ink is less fluid than the standard plasti-  sol and maintains its shape quite well after it is printed. Gar ment compliments of  Liberty Screen Print.

response to initial resting viscosity. Since you want the ink to have initial body but become fluid i mmediately with a gentle push of the blade, you want a low-yield stress. Low yield stress

Inks ink allows a minimal squeegee angle, speed and pressure to cause the ink to flow. If the yield stress is high, it will require too much warm-up time getting the ink  to flow and this indicates you will have a color shift over the first few dozens prints. Yield stress i s a factor in the calculation of the shortness-ratio index. Plastic Viscosity

Plastic viscosity is the fluid property of the ink at its t hinnest point. This is where the spindle type viscometers fall shortest of an accurate number. Ideally you want  the ink to be at its plastic viscosity and the plastic viscosity must be low enough to allow the ink to transfer through the screen mesh. If the plastic viscosity is too high you will be forced to run very high squeegee pressure and a very low angle just to get the ink to clear the mesh. This will be Ink Shortness Ratio Scenarios Ink  Manufacturers Problem

Excessively  High Shortness Ratio

Ink  Characteristics 1Low force, 2high flow 

(half-tone extender) 3High force, 4high flow  (fluorescents)

Effect (one or multiple)

 Appears that the ink  should transfer, but  does not.

Short-Term Solution

Use larger mesh opening.

Deposit changes as ink   Warm-up ink on  warms up. Turnabout, before print run. Ink wont hold image. Use thinner mesh. Inadequately  Low force, low  Transfers mesh easily. Use higher mesh Low Shortness flow (violet) count. 5Lower shear rate. Ratio Ink wont hold image. 6Higher shear rate, High force, low  Trouble transferring  flow (aged-up ink. add reducer.  white) 1Low force is technically low yield stress, meaning it requires little effort to get the ink moving. 2High flow is technically, low viscosity, meaning the ink is thin. 3High force is technically high yield stress, meaning it requires more effort to get the ink moving. 4Low flow is technically high viscosity, meaning the ink is thick. 5Higher shear rate demands more squeegee pressure and lowering the blade angle. 6Lower shear rate permits less squeegee pressure and raising the blade angle. Figure 3.12 Use the table to verify ink problems. It offers short-term solutions, but more importantly, it gives you the 

accurate launguage to the discuss the problem with your ink manufacturer. If you tolerate the type of problems listed above, it will eventually affect your bottom line. Work with you ink manufacturer to solve the pr oblem or find an ink that doesnt  exhibit these problems. PAGE 3 . 15

Chapter 3 How To Instructions

Matting Down Surface Fibers To mat-down the surface of a T-shirt, you need to follow these steps. 1. Select ink with a low-yield stress. 2. Select ink with a very high-relative viscosity. 3. Select ink with a moderate plastic viscosity. 4. Use a thin, flat screen mesh with a large opening. 5. Set tension to the required off-contact distance (refer to page 4.4). 6. Use an 80-durometer blade with a sharp edge. 7. Set speed and angle for zero-mesh-lag and image stretch.

particularly evident in the center of the screen where the blade contact pressure is at its lowest. If the plastic viscosity is too low , as the squeegee injects the ink into the mesh it wants to splatter onto the substrate. Such a flaw will be particularly noticeable when printing  on an underbase. Ink with a proper plastic viscosity transfers the mesh cleanly at high speed and still holds the shape of the i mage. Shortness Ratio

The shortness ratio is an index that can offer insight  into the way that screen-printi ng inks will perform on press. It is a ratio of the inks initial resistance to f low, and its final resistance to flow. Based on empirical  evidence, the shortness range for screen-printing inks should be between 1.5 and 3.5. A higher ratio would characterize inks that were not shear-thinning and a lower rat io would profile inks that would not recover their body aft er the ink  had transferred. Either of these scenarios would not be conducive to quality or high-speed printing. There are four possible extreme, ink-shortness scenarios. Please review the table shown in figure 3.12 (previous page). This aspect of the inks performance is a delicate balance of force to cause the ink to flow and its viscosity once it is flowing. To control shortness, the ink maker must accurately control or anticipate aging. Thixotropic Index (Thix)

Thix index is a numeric scale that allows the ink formulator (or the printer) to determine general tendency of the ink to be shear thinning. The operator will  run the ink at two different rpms on a spindle vi scometer, a low rpm and one that is 10 times as high. For example, two and 20 rpm measurements are taken and the low rpm reading is divided by the high rpm reading. If it were 1,000,000 cps (centipose) at two rpm (revolutions per minute) and 200,000 cps at 20 rpm, PAGE 3 . 16

Inks you would divide the two to find the thix index. 1,000,000 / 200,000 = 5 as the thix index.

The two-rpm reading (low-rpm reading) indicates how t he ink   will lay on top of the shirt. The 20-rpm reading (high-rpm reading) indicates how it will transfer through the screen. The thix index of five indicates the degree to which the product is shear thinning (stir it and it gets thin). Generally, you will want  the highest thix index that the manufacturer can build. The typical range of plastisol inks is from a low of three to a high of 12. If the thix index is too low it indicates one of two extreme possibilities, a runny ink that flows too fast and wont hold an image or print on an underbase. Or it is tar-like, stiff in the container and wont transfer well through the mesh. If the thix index is too high the ink may appear fluffy but con-

End Caps These accessories fit on the ends of your squeegee blade and keep the ink from spewing out from around the ends of the blade. Of  course they are very convenient  on press, they allow you to run longer without adding ink and will  save you the embarrassment of  poking an ink knife through a screen during a production run. One ripped screen more than pays for End Caps for the entire press (refer to figure 3.13 for details). Here is the less apparent value: they allow you to compact the ink  and take advantage of the fact  that in mass, the ink will not react  as fast to heat. These attachments allow you to put more ink  between the blades and the ink   viscosity will be more stable. If  you do a lot of flash curing these  will help keep the print colors consistent and reduce the need to stop and clean up or change inks. End Caps work at any tension level, on any M&R holder with any blade at any angle or pressure. Simply wash them off when you need to change colors.

Figure 3.13 The end caps shown here, compact the ink and by keeping a more dense area of 

ink, reduce the impact of thermal-viscosity drop. If you are flashing, try using end caps to pre-  vent the inks low viscosity from plummeting and prevent premature gelation. PAGE 3 . 17

Chapter 3 Af t er-Flash Tac k  After-flash tack is an ink and flash issue, but there are other facets of  the process that you can pursue to improve the condition. Unfortunately a flat-coated screen or capillary film is the worst possible surface, however we strongly  suggest that you look elsewhere for answers and make the best  stencil possible. If you are running high strength twill-woven mesh, you are creating more problems than you need for two reasons. First, twill mesh has the highest surface area so more mesh is in contact with the hot ink at  any one time. Second, it has a smaller opening so it forces you to use a greater blade-contact area to transfer the ink. Review the press calibration and flash settings sections of this book and then use a plain-woven screen mesh with a large opening.  Yes, continue to make a flat stencil. Use a rigid blade, with a sharp edge, set at the most vertical angle possible. If this is not enough, M&R offers the Animister to cool the ink prior to the next screen and eliminates the need for a cooling station.

 vert from thick to thin and back, too fast to transfer through the mesh. Tack Percent

There are a variety of methods for the analysis of tack, which may be the most important single variable of all. In all printing  and imaging processes tack is necessary so that the ink will  hold to itself at various times dictated by the process. The formulator knows this property by the name visc o-elasticity and can typically measure it with a sophisticated viscometer. Generally  the lower the tack level, the faster you can print and the higher the quality. If the tack is too low the liquid and solid phases of the ink   will separate and build-up-mottling and wick ing will result. If  the tack level is too high (and this is most often the case of  high solids dispersions such as pl astisols)-the ink is difficult to transfer at low shear rates. (The shear rate of the screen-printing process includes the blade contact area, flexure and speed.  A low blade angle with a low contact area and high speed is the highest shear rate). Most of the time excessively high tack  plastisols are a result of aging after the product is made. The best analogy is honeychill it and it becomes high viscosity and high tack,-warm it and it becomes low viscosity but remains high tack. Thinning the ink tends to drop the viscosity, but  leave the tack level as it was (refer to page 3.28 for details on ink tack). Severs Viscosity

Severs is a capillary-tube viscometer with a specific orifice on one end and air pressure on the other. When the tube is filled  wit h ink, the application of air pressure forces the ink throug h the orifice at the other end of the tube. Viscosity is measured by the time that it takes a given quantity of ink to flow  through the orifice, specific to the pressure applied. This test  method draws a high correlation between the lab and the transfer of ink through a printing screen. If the viscosity is too high, the ink will not transfer well at all. If the viscosity is too low, there is a likelihood of phase separation, which w ould result in build-up, mottling and wicking.

PAGE 3 . 18

Inks Thermal

The thermal properties of plastisol inks have a serious impact on the optical and rheological aspects. Generally as the ink is warmed, t he plasticizer thins and eventually begins to solvate or fluxes the resin. Each of the significant plateaus of  thermal change is listed below for your ev aluation. By understanding this time temperature relationship you can use these properties to your advantage.

Low   Viscosity

40,000 cPs

H-Cote 9000 Thermal Specifications Peak  Gel Fusion Re-melt Wavelength

150° F

300° F

375° F

2.3m

Hot-Tack  Index

3

Figure 3.14 This table lists the thermal properties of the H-Cote 9000 white ink. Low 

viscosity indicates the ink, as do all plastisols, thins when they are warmed. The degree of thin-  ning is well within acceptable margins. Gel point is a typical 150°, fusion (cure) at 300° and  remelt at 375°. It has a low gelation point and sufficient distance between fusion and remelt to be very user friendly. Its peak absorption wavelength is 2.3m, with a hot tack index of 3, on a  one to five scale. The hot tack is higher due to the smoothness of the print. Low Viscosity

Low viscosity is the first phase that the ink passes through, due to temperature elevations. At temperatures below gel, but above room temperature, the plastisol  becomes very thin. This phase occurs in plastisols around 110° to 130°. The point at which it occurs is less significant, than the viscosity the increase in temperature produces. If there is a severe viscosity drop, you can be certain you will  have printing probl ems. These would be most apparent with dark-blue ink printing on a white underbase. It is also this factor that causes a color shift during various stag es of production. As the ink warms it fills the mesh cavity to a different  level. There can be a very noticeable color shift, particularly with transparent colors. The high limit for this low point would imply that the viscosity of the ink   was unaffected by heat-but this is never the case. Gel Point

The gel point of the ink i s reached when the ink is no longer fluid at operating  temperatures. On press this is an indicator of how flash efficient the ink will be, so in general, a lower number is better. In the real-world the ink is subjected to infrared energy-the panel or tube temperature will be significantly higher and the exposure much shorter than our test data. If the gel point is too low, shelf stability is an issue; the ink will probabl y not ship PAGE 3 . 19

Chapter 3 How To Instructions

Eliminating Gel In The Screen Stop Gelling In The Screen by following these step:.

or store well at all. If the gel  point is too high, you will  have a difficult time running  at high speeds due to a longer flash time or higher flash temperature.

1. Calibrate the press and flash units. Fusion

2. Do not double stroke. 3. Run as-fast-as possible at all times. 4. Minimize the flash temperature. 5. Do not use flash additive. 6. Add curable reducer. 7. Add plasticizer, only as a last resort.

The fusion or cure temperature is the point at which the performance properties of  the ink have reached their maximum higher temperature and longer retention time will  not improve the performance of the ink. Elasticity, abrasion resistance, light and color fastness are at an optimum. For standard plastisols this occurs if and when the entire  ink film  reaches 300° to 320°. The variables that effect curing plastisol ink are extensive; garment entrance temperature, i nk fusion temperature, i nk deposit thickness, garment fabric mass, garment  specific heat, dryer temperature, and dryer retention time. Thats a whole lot to control, but the results will be worth the effort.

Figure3.15 The photo shows an incremental gap in the squeegee and 

 floodbar. If your screen length and stroke adjust permit, you can invert  the floodbar and increase the spacing between the squeegee and floodbar. For high tack-level inks, coarse meshes or long runs with a high coverage  area, this is a very helpful technique. The adaptation is very simple on  the Challenger II. PAGE 3 . 20

Infrared dryers have more  variables, including the wavelength and distance from t he garment to the panel or tube. The emissivity of the ink and the garment is a factor.

Inks Cure or fusion is a time-temperature balance, which means that you can make up for a shortage in one with an abundance of the other. If the time is long enough, the temperature can be lower. The 300° listed i n table 3.14 is not nominal, but it is a real world number that can typically be achieved with industry equipment. Plastisol inks fuse from 200° to 2000° but the former would require an impractically long dryer retention and the latter would prove to be dangerous. Flash curing is a preheating station for some of the garment  and some of the ink. If you flash cure, the part of the garment under the fl ash gets hotter. The ink printed on the shirt  prior to the flash becomes hotter when flashed and remains hotter t han those colors printed on top of the flashed inks. They may be closer to room temperature. The flash can ensure that the ink is totally cured, but relying upon it to do so, is risky business. For example, the first time you stop and dont  put the shirt into the dryer immediately after flashing, it cools, and its dryer exit temperature is lower than the balance of the shirts. A consideration at the other extreme is the fl ash can superheat the ink and lead to bleeding, sublimation and shrinkage. For information on how to evaluate fusion refer to page 3.20 for details. Remelt

Remelt is the level beyond fusion or cure, when the resin begins to soften and flow i n dependent of the influence of the plasticizer. It is this property that prevents ironing plastisols, as  well as makes heat transfers a viable product. The remelt point  of the ink should be the maximum possible for direct-print  plastisols, so this threshold is not crossed in production. Should this happen the inks may become very thin, you risk  both dye bleeding from sublimation and migration,and hot  tack at this stage can weld the inks together at the end of the dryer. Hot Tack

Hot tack is known in our industry as after-flash tack. It is determined by the combination and type of resin, plasticizer and fillers. It is a form of temporary adhesion known as diffu-

Fusion Tips There is no need to sustain the fusion temperature once the ink  has reached it, but there are issues that need to be recognized. The garment will act as a heat-sink, specifically in the case of fleece. The fabric mass of a T-shirt is often less than 25 percent but a sweatshirt is often over 75 percentmore of it is fabric and less is airspace. Before the entire ink  film can be brought to cure temperature, the garment temperature must be sufficiently high, so that  equilibrium is reached. In practice, this means that the ink on a sweatshirt will generally exit the dryer at a lower temperature than a T-shirt under the same conditions. You will want to doublecheck the sweats for cure, particularly if they are run at T-shirt settings. High humidity has an affect on the curing level of the ink; due to the fact the garment holds moisture. The moisture regain of cotton is 35 percent and that moisture must be dealt with before the ink will cure. In high humidity  environments you may want to double-check the cure of the ink. Some synthetics will take more energy than others. This is based on the specific heat of the composition of the garment. The specific heat is an indicator of the rate of increase in temperature. For example, a nylon garment of  the same construction as a polyester garment will take more time or temperature to elevate it to a given temperature point.

PAGE 3 . 21

Chapter 3 sion bonding. To make ink that has very high hot tack, one would start with a soft (co-polymer) resin and add an equal amount of high-solvating plasticizer (over 50 percent). The hand would be very soft and the ink would level and penetrate as soon as it was heated. Inks similar to this, used on highly elastic materials such as SpandexÒ, would have a rating of five on the hot-tack index. Most pigments and fillers are inert  and are unaffected by the gelation or cure of the ink. As pigments and fillers wi ll  appear on the surface of the ink, they act to reduce the hot tack, but are not as influential on the hot tack as the plasticizer/resin ratio. Note that a smoother surface is more prone to after flash tack, but produces higher quali ty prints. Room Temperature 72 Greater than 72 110 125 150 175 250 Total Ink Film Reaches 300 350

° ° ° ° ° ° ° ° °

è

Ink remains as it appeared in the container. è Ink drops in viscosity as on a Turnabout mixer. è Ink reaches its low viscosity point. è Plasticizer becomes aggressive, fluxes resin surface. è Resin gels, plastisol becomes dry and immobile. è Fluxing continues at a slower rate. è Dye sublimation begins. è Fluxing complete, optimal ink properties achieved. è Resin softens and ink re-melts.

Figure 3.16 The details listed in the table above are generic; they do not necessarily describe a particular ink brand or 

series. These properties are offered as a "thermal timeline" of events as the plastisol is exposed to heat.

Physical

There are dimensions of plastisol inks that do not fall into optical, rheological or thermal. These are categorized as physical properties and include; the si ze of the particles of ink, its reaction to infrared energy, its ability to wet a surface and to be wet once it is gelled. Included is the percentage of plasticizer because lower is better and the hardness of the cured ink film. All of these play a critical role in the aesthetics and performance of the ink and are listed below. Grind

The grind of plastisol ink is a measurement of how fine the agglomerates (collections of particles ) have been reduced in size. Although the test method does not  gauge viscosity, the relative viscosity of the ink nonetheless, influences the test. The standard grind gauge runs from zero to eight with eight being the finest  grind. This fineness index can be converted to a nominal agglomerate size. Each  whole number is approximately equal to a 12m increase in diameter. For example, a grind of four equals a 51m diameter, while a five equals a 38m diameter. If this PAGE 3 . 22

Inks dont seem like much of a disparity, consi der that the 38m particle has a surface area of 4536m² and the 51m particle has a surface area of 8171m²-and these are only one number apart on the grind gauge. Grind is a reasonable predictor how easily the ink particles will  transfer through the mesh. Of course the particle shape,  weight, size and pigment loading are significant factors that  aff ect ink transfer, but a coarse grind will make matters worse. If the grind is poor, the plasticizer continues to migrate into the agglomeratesthe ink gets very tacky and thick. Once this happens nothing  known to man will reverse the process. Poor grind is the primary cause of thick, tacky inks; build-up; mottling and after-flash tack. Emissivity

Emissivity is ratios of an objects tendency to reflect versus absorb energy. This is a real-world factor if you are using a non-contact, infrared pyrometer. These heat guns should ideally be calibrated to the emissivity of the surface they are about to measure. Emissivity is affected by the texture, gloss and color of the product, as well as its chemical make-up. Emissivity also changes over a range of temperatures. For example, black ink, at gel, will have an emissivity ratio around 0.70, while whites, at fusion temperatures, are around 0.95. Most of the default settings are 0.95 and there is no problem unless you are looking for absolute readings. SpG (specific gravity)

Specific gravity of ink is the ratio of ink weight to an equivalent volume of control  water. This data allows the manufacturer to easily determine the weight of any volume container. Because whit e pigment (TiO²) is small and spherical, it packs  well so the density and specific gravity of whites are very high, making white pigment heavy. A 1.49 ratio would mean that t he ink weighs nearly one-and-a-half times the same volume of   water. It is advantageous to have white ink with a high weight  to ensure two things: there are no air pocket s and there is a relatively high volume of pigment in the ink.

Ink Grind Grind  A pharmacist uses a mortar and pestal to breakup clumps of dry, powder particles and make a more homogenous prescription. The ink  manufacturer has to achieve this grind twice with your plastisol ink  before it is finished. There are grind parameters for the pigment  dispersion stage, and also for the finished ink. Though the two approaches differ radically, the goal for each is the samereduce the size of the clumped particles.  A generic description of pigment  dispersions follows. The pigment and plasticizer are premixed into a slurry or paste on a high-speed dissolver mixer. Surfactants and fillers are added at  this time. This "premix" is not  finely ground and must be put  over a milling machine. There are sand mills; ball mills, colloid mills and three roll mills to name a few. The choice of mill is based on the needs of the pigment and its abrasiveness. Whites for example are so hard they will nearly destroy a three-roll mill and the shear thickening nature of the dispersion makes it unsuited for some mills. The premix is taken to the mill  and under specific time, pressure,  velocity and clearance the clumps of the pigments are broken down.  What is left is a smooth paste that  requires less addition of dispersion to develop color. This efficiency has several advantages; lower raw material cost ink, series  with print properties that are more similar and colors that are cleaner, brighter and more intense.

PAGE 3 . 23

Chapter 3 Constructing Plastisol There are two major components in plastisol ink; resin and plasticizer. The resin is a powdered, dispersion-grade polyvinyl chloride and the plasticizers are liquids, specifically high boiling esters.  When the two are combined they  react in a particular manner, which is described below: 1. The resin and plastisizer are blended. 2. The plasticizer solvates the surface of the resin. 3. The plasticizer is now diluted  with solvated resin. 4. The diluted plasticizer cannot  continue to solvate. 5. Equilibrium is reached and maintained if: a. the plastisol is not exposed to heat. b. the fillers do not continue absorb plasticizer. c. there are no resin cavities for the plasticizer to migrate into. 6. If equilibrium is not achieved, tack increases due to aging.

Surface Tension

The surface tension of the ink is i ts ability to wet-out a surface. At times this has little relevance-but at other times it is critically important. When the plastisol is printed directly onto the garment, wetti ng is a non-issue. The adhesion is mechanical and the substrate is absorbent so the ink cant creep across the surf ace. But when the ink is printed on an underbase or ov er another color, all rules change . The compatibility of the tw o inks is gauged by the surface tension (liquid) of the liquid ink  and the critical surface tension (solid) of the flashed underbase ink. Lower-surface-tension inks wet our more surfaces better and faster than inks with higher surface tensions. In fact, if the liquid has a higher surface t ension than the gelled or fused ink, the two are incompatible, image stability and adhesion can be at risk. And if youre printing a process job, color balance just  flew out t he window. The surface tension of the ink is dictated initially by the surface tension of the plasticizer, but this can be altered with additives. The lower the number the better. Typical however, additives used to reduce surface tension tend to reduce critical  surface tension as well. The ink maker must be wise in his choice or the result will be ink that wets-out a gelled surface better, but is more difficult to wet once it is gelled (see sidebar on pag e 3.32 for more information on surface tension). CST (critical surface tension)

Critical surfacetTension is a measurement of the tendency of  the gelled or fused ink surface to be wet-out. The best example is the slick surface of TeflonÒ that nothing sticks to. Teflon® has a very low surface energy, around 13 dynes per centimeter, and most liquids like eggs have a surface tension higher than 13, so they cant wet the surface. When they evaporate they stick to them selves, but not to the skillet, so they  fall right off.  Youve probably seen the results of incompatible surface tensions, when the ink does not want to stick to the underbase. There is a balance that can be disturbed if the underbase is

PAGE 3 . 24

Inks taken over its gel point and too close to cure. As the ink is heated the critical surface tension decreases to a point beyond fusion. Eventually, it will begin to increase with sustained or incremental temperatures. The range of critical surface tension in white plastisols is from 30 to 44. The higher number allows overprint inks to trap (stick) easily and the l ower number is  very resistant and difficult to print on. (Refer to page ___ for details on surface tension). Percent Plasticizer

This is one of the most critical aspects of the plastisol ink, and its excess is triggered by a poor grind. Far too often the manufacturer does a poor job of blending the ingredients in the ink, and knowing before hand that the ink will age-up in  viscosity, he adds plasticizer to retard the aging and reduce the final viscosity. The ink ages (or thickens), then it meets the standards set with viscometers, but viscometers dont inform us how the ink will perform on press. The lowest practical percentage of plastisizer is 35 percent and the goal of the manufacturer. More plasticizer creates a multitude of problems. It retards the gel rate, creates after-flash tack, reduces the critical surface tension, increases the chance of dye migration, sacrifices opacity, promotes build-up, rai ses the fusion temperature and makes ink that is low viscosity, but  high tack. Like warm honey-and it still wont pri nt well. Shore A

The hardness of the ink is an indicator of the drape and flexibility of the print ed material. It is established on a Shore-A scale for elastomers, and a higher number indicates a harder product; less likely to drape. This property is dictated in part  by the type and percentage of resin in the ink. More resin makes for a harder product, while some types of resins are harder than others. Hardness is indirectly proportional to the quantity of plasticizer in the system. More plasticizer means softer ink. The hardness is checked against a totally fused thick-film (at  least 1/8 inch thick) deposit. Employ the same meter used to check the durometer of squeegee blades. It operates similarly 

Base vs. Clear These vary from manufacturer to manufacturer and there is little consistency. The only common denominator is they dont contain pigment. There are three terms that give you an indicator of the performance of the transparent  ink; unfinished ink, finished ink  and ink modifier. There are unfinished inks that are intentionally short of their plasticizer balance and are to be used in conjunction with pigment dispersions for color matching convenience. Be cautious, as these are  very often unstable and ageupfaster due to the reduced amount of plasticizer. Once ink  has aged, there is no turning back. There are finished inks that will  not accommodate color concentrates, but can be used to overprint an image for durability or gloss control. Some finished inks are intended to mat-down garment fibers and serve well as transparent underbases. Another course of action is to add these, in virtually any amounts, to an existing color to increase its transparency. Of course the properties of the color are compromised by  the properties of the additive. Finally the ink modifiers, which are marketed under a variety of  names, but usually intended to solve a specific problem. These include hand modifiers, which at  the cost of opacity, improve penetration and increase drape. Some of these are highly plasticized (refer to page 3.25 for details), so be cautious. There are also modifiers that are recommended for process-color printing to control  the balance of the four colors. PAGE 3 . 25

Chapter 3 Flash A dditiv e If you are having problems with flash times and after-flash tack, you have an ink problem and should find ink that is suited for flash-curing applications. Meanwhile the fix is to add blending resin, which is known to our industry as flash additive.

to a tension meter, except it has a pin on the bottom of the meter, rather than a foot. Hold the meter with the pin facing  the printed sample; firmly press the pin into the fused i n k. The meter will register the hardness. This number should be evaluated along with the fused deposit thickness y ou normally print  for drape and hand acceptability. For example, the first ink has a hardness of 50, but must be printed at a five-mil deposit to

 As is the case before you add anything to the plastisol, it should be stirred thoroughly-not a quick  spin with a spatula. It is wise to use a Turnabout Mixer allowing  the low-shear to gently reduce the  viscosity of the ink in a minute of  stirring, without generating excess heat, typical of high speed mixers.  Volume mixing (quart, gallon, etc. measurements) is a very risky  business, so we recommend that  the resin be added by weight. Use a scale that measures to a tenthof-a-gram for quarts, to one-gram for gallons and to five-grams for five-gallon pails. High viscosity  and subsequently high tack will be your limiting factors, but begin at  a quarter-percent of resin, by   weight, to the ink. Add it slowly, as the Turnabout continues at  slow speed. The additive will partially combine  with the plasticizer in the ink, so if  you must add, do so in advance of  the press run. After all if you have had problems before, you can expect to have them again. So mix the additive a minimum of 24 hours, but ideally 72 hours, before the press run. This allows the ink  to reach equilibrium and you will  find fewer additives will do the job. If you over shoot the mix, the best advice is to dispose of it  PAGE 3 . 26

Figure 3.18 This HiRes AccuColor© print has an extremely soft hand due to the inks 

used for the underbase and the fact that they were printed at less than one mil deposit. Red Hot   Mama, image rights liscensed by Blue Chicago and T-shirt printed by Target Graphics Ltd. © 1995 John Carrol Doyle.

be opaque. A second type of ink, of the same hardness, prints at three-mils and matches the opacity of the first ink -the thinner deposit will have a better hand.

Inks Troubleshooting Ink  If you have read the preceding pages on the nature of the plastisol inks, it will help you identify ink problems, and other related issues, when a problem occurs. This section demonstrates how to put your newly gained knowledge to work by  dividing i nk troubleshooting into four categories. These categori es are the most common issues associated with plastisol  performance; ink tack, build-up, ink adhesion and surface energy, test for fusion, test for temperature, ink mileage. Tack

Screen printing is unusual when it comes to ink tack. Most  other ink transfer processes need , and even flaunt, the tackiness of the ink. But we have a hydraulic pumping system that transfers ink; high tack level is a problem. It is more difficult to transfer higher tack level ink- such ink requires a higher shear rate. Shear (rate) is the force applied to the ink on the surface of  the screen-it is intended to cause the ink to become thinner. At  this state of lower viscosity, the ink should be easy to pump through the mesh openings. Shear (rate) increases in direct  proportion to the following: 1. Higher off-contact or peel. 2. Higher mesh tension. 3. Lower squeegee angle. 4. Higher squeegee speed. The higher the shear rate, the thinner the ink becomes over a relevant range. Plastisols and virtually all printing inks need to be shear thi nning. That is, as a shearing force is applied (like the squeegee or the Turnabout Mixer) the ink drops in  v iscosity. To cause this shear-thinning drop, with high tack ink, requires excessively high shear rate and a mesh with an excessively high flow rate. In the vernacular we say, Use the coarsest mesh you

Flash A dditiv e (continued) properly. Do not try to reduce the ink and run it on press. Its performance will be the worst possible and downtime is the enemy of  profits-dont risk it.  Adding this flash additive resin  will alter all of the properties of  the ink on press and on the printed image. On press the grind (Refer to sidebar page 23) will not  be as high and the mesh can act as a strainer by filtering out particle clumps. Be particularly cautious if  you are on a mesh with a small  opening, either higher count or thicker threads. If this is a problem you will find that it gets worse as the run continues. Temporarily  you may need to run a lower blade angle and a higher squeegee speed. Flash additive may worsen buildup as it raises the tack level of the ink. Your response to this will  necessarily be more force and if  so you may see perimeter build up. If the ink tends to build up in the central areas, the addition of  flash additive will not adversely  affect this and may slow it down. But our best advice here is to get  ink that works, don't get caught  up in ink repair. Flash additive will reduce the gloss level of the ink and stiffen the hand or drape of the printed film. It is not a solution for dye bleeding but will not encourage bleeding. All things considered, flash additive is a temporary fix so that  you can stay in production by  compensating for ink deficiencies.  Asking more from the product is unwise. PAGE 3 . 27

Chapter 3 Whit e Hang-up Hang-up There is by far, more white ink  used by the textile printer than any other color of plastisol screen ink. It is very unfortunate for screen printing, which is a pumping process, that white ink is absolutely the most difficult color ink to pump.  And at times the ink seems more difficult than others, for example, in the middle of a press run. Unless you are new at the game, you have seen where all is well, and all of the sudden the white starts hanging up in the screen.  Well its occurrence was probably  not sudden at all, only its appearance was sudden. It was probably  the long-term result of one of the following factors. 1. Screen tension loss from fatigue. 2. Gelation in the screen from heat. 3. Dilatency (shear thickening). Number one occurs frequently. If  you need to retention after every  press run, it may well be your problem. Review the sections in this book on press calibration, off-contact set tings and squeegee pressures. The warning signs will  be registration problems, smearing  and image stretch. If you stop the press, wait and then start it again, the condition will be the same. Number two is unavoidable if, and when, your heat gets out of  control. Review sections on flash curing and plastisols. The warning  signs will be; as the ink warms-up the deposit changes, and you per-

PAGE 3 . 28

can find and crank down on the squeegee, hardly good advice for quality printing. However, high-tack inks are prevalent in our industry (refer to the how-to on page 3.30 for detai ls). Tack versus Viscosity

Do not confuse tack with viscosity. The best analogy is Cool   Whip desert topping and honey. Cool Whip is high viscosity  and low tack. Honey is low viscosity and high tack. The best  printing inks are more like Cool Whip and less like honey.  With honey, no amount of shear will successfully transfer it  through the screen and such excessive shear will cause a lot of  problems on its own: 1. Premature stencil breakdown. 2. Premature tension loss. 3. Premature mesh ripping. 4. Oversized image distortion. 5. Perimeter ink build-up. 6. Smearing and blurring. It is always best to cure the illness and not only the symptoms. Figure 3.19 The 

Turnabout is available in  three configurations for every  budget and viscosity of ink. Each Turnabout comes with  a single and five-gallon blade  that are very easy to clean. The DC version allows you to mix slowly, so there is no heat   generation. Once the ink begins to flow, you can speed it  up for a quick and thorough  mix. All Turnabout mixers  clean the bottom and sides of  the pail automatically. They  are ideal for mixing colors or   for stirring thick white ink, so that it flows properly on the  very first shirt.

Inks If the tack in the ink you are currently using is too high, talk  to your supplier. Some printers will resort to modifiers to reduce the appearance of tack-but there is no way to eliminating tack in plastisol, which means a compromise in the performance of the modified ink is inevitable.

Whit e Hang-Up Hang-Up (continued) ceive a lower gloss level. If you stop the press for a while, and start again, this one goes away.

Cause of Ink Tack

The primary cause of ink tack is in the manufacturing stages, in the selection of raw materials and their assembly. No one builds ink that is difficult to printit becomes that way in time and aging is an indication of poor manufacturing. The test  for tack is varied and unfortunately not often used by the ink  manufacturers. One test that is universally used and a g eneral  gauge of high tack is the grind of the ink. The gri nd of the ink is a measure of how well all of the particle agglomerates are reduced in size and distributed in the liquid vehicle (plasticizer) of the ink.  A poor grind would leave the resin agglomerates (particle collections) too large and over time (72 hours plus) the plasticizer  would migrate i nto these clumps of resin and change everything. When the ink was first made, it may have been creamy  because the plasticizer acts as an ink system lubricant  allowing the particles and clumps to pass by each other, with minimal friction. If this (plasticizer) lubricant is absorbed into the clumps, and the ink is put under a shear, the fri ction will be  very high  we call it excessive ink tack.

Number three is subtle and may  be missed if you are not obser vant-there are no warning signs. Dilatent fluids resist flow and  whites are very dilatent. The percentage of pigment is high  between 17 and 27 percent is typical. Further it is very small, spherical in shape, and very heavy. Just  like a set of billiard balls on the pool table, white pigments tend to settle, collect and push up against  each other. White ink acts the same way, but in three dimensions, and when the ink gets  warm, the particles can begin to settle. Run the squeegee blade at  the highest angle possible and use a moderate speed. Keep your operating temperatures in control; use a thinner mesh with a larger opening, and a faster flood stroke. If you stop and start again this symptom will disappear.

Conversely if ink is finely ground, the amount of plasticizer needed is minimal and the ink achieves a system equilibrium   it doesnt get thicker or thinner. Initially when the resin is mixed with the pl asticizer, the surface of the resin is attacked and becomes a part of the plasticizer. Now the plasticizer has changed  it is thicker and less aggressive to the resin. The goal is for it to reach equilibrium- so at room, shipping, and storage temperatures, the plasticizer stays where you put it. If  the goal is achieved, there is no aging after the initial wetting  period of 72 hours. Such an ink mixture will require less plasti cizer-that is good news, because excess plasticizer will rui n the ink (refer to page 3.25 for details). PAGE 3 . 29

Chapter 3 How To Instructions

Dealing With Tacky Ink Follow these steps to avoid tacky-ink problems: 1. Add the proper amount of the surfactant, as suggested by the manufacturer. 2. Use End Caps to compact the ink. 3. Calibrate the press. 4. Calibrate the flashes. 5. Sharpen the squeegee blade. 6. Use a thin mesh with a large open area. 7. Optimize the off-contact distance. 8. Lower the squeegee angle.

Poorly dispersed resin results in clumps of resin agglomerates in the ink and there is no  way to improve the dispersion. Mixing would cause  ve heat and gel the ink, excessi  long before it would reduce the sizes of the agglomerates. Plasticizers (that do not  encourage tack) or surfactants (wetting agents) can act as lubricants and may improve some performance properties, but they do not solve t he problem of a poor grind and resin agglomerates that are  welded together. That is the exclusive responsibility of the ink manufacturer.

Before Modifying High Tack Ink If

you are to about to modify your ink, first you want to review the list below, to see if in fact the problem is the ink. Ink hanging up in the screen can be the press operators first inclination that the ink is not performing to specification. The list includes a variety of symptoms that may occur when the ink fails to transfer cleanly. 1. Is the ink fast fusing (refer to page 3.20)? 2. Does the screen mesh have an adequate flow rate (refer to page 1.14)? 3. Is the screen tension adequate (refer to page 4.8)? 4. Is the off-contact distance high enough (refer to page 4.5)? 5. Is the ink tack exhibited all over the screen (refer to the how-to on this page and review the informati on on page 3.29)? 6. Is the top of the screen clear (refer to pages 3.32 through 3.36 for further information)?

PAGE 3 . 30

Inks If you can confidently answer yes to all of the above points, then adding something to reduce the tack level of the ink may be the only alternat ive. But before you do, the ink should be put on a Turnabout (or other mixer) and thoroughly  mixed. The reason is simple-at rest the ink particles al ign and form a temporary  barrier. The barrier can be broken down easily w ith the application of shear for a short time. If the ink has aged, then this fal se-body condition will exist, despite the shearing force. If you add a liquid without stirring first, it causes the ink to become far too thin and creates many other problems. The problems associated  with over reducing inks are dependent on the particulars of the ink, the quality  and type of reducing agent, but in general the results are as follows: 1. Loss of opacity. 2. The ink becomes harder to flash and fuse. 3. The ink becomes harder to overprint. 4. May visibly increase ink gloss level. 5. Assures the operator of after tack. 6. Leads to ink build-up, particularly due to absorption. 7. Likelihood of bleeding on polyester content garments. 8. Possibility of premature image fade. If there is a need to adjust the ink, follow the manufacturers recommendations. Do not exceed the limits without expecting a compromise in the performance of  the product. Build-Up

Ink buil d-up, the accumulation of ink on the underside of subsequent screen, is due to poorly made ink, which has lost plasticizer through ei ther or both absorption or excess hydraulic force.  Although there are actions, which you can take to retard build-up, the real solution is the ink. The lists below suggest that you find out why you are having  build-up by observing its location on the underside of the screen. The first thing  to do if you are experiencing build-up is to watch closely to see if the ink begins to build-up around the perimeter of the screen or the central areas. Build-up will  not occur if the ink does not lose its plasticizer, but it can lose it for more than one reason. PAGE 3 . 31

Chapter 3 Plasticizer s vs. Su r factants There are no real-world universal additives. Total compatibility  of one modifier with all plastisol  inks is a fallacy, so before you adjust the properties of your ink, talk to your supplier or directly to the manufacturer of the ink. There are two thinners for the ink that has become too thick to flow well and transfer cleanly  through the mesh. The two are plasticizers and surfactants. Plasticizers are the most common and the most dangerous in the hands of the press operator. They  are chemically compatible with the ink but that is not the issue; they  are inefficient and at a level of  overflow. There is physically no room for them in aged up ink.  When added they act as independent lubricants, just as if you put  one extra quart of oil in your carit gets blown out after the damage. The overload is easily  separated from the ink and then the only option is build-up. Surfactants do a far better job at  dealing with ink tack but dont  forgetonce plastisol ink has aged up there is no way to reverse it. The manufacturer can and must  prevent the aging. Surfactants are  very efficient wetting agents and for mild tack on press they can make it manageable. Also they  have a lesser affect than plasticizers on the thermal stability of the ink. Consult with your supplier and adhere to the limits on the products that you are using and stir thoroughly before adding anything.

PAGE 3 . 32

Perimeter Build-Up (shear rate)

If the ink build-up initiates or is w orse around the perimeter, then your build up is due to excess force. This type of buildup is relatively insensitiv e to different garment types, brands or constructions. The solutions to reduce the effect follow: 1. R aise the squeegee angle. 2. Slow the speed of the squeegee blade and ensure that there is clearance between the flood bar and screen mesh. 3. Reduce the squeegee pressure, unless the ink  is refusing to clear the central areas of the screen. 4. Reduce the off-contact distance, unless you have st roke direction image stretch. 5. Use a mesh with a higher flow rate and a greater percentage of open mesh area. 6. Test a fresh batch of ink  one that has not  accumulated lint or been subjected to heat on press. 7. Use a prescribed amount of a surfactant  added to the ink only after it has been thoroughly stirred on a Turnabout or other mixer. 8. If the press is running hot due to a lot of  flash curing, the v iscosity of the ink may be too low and lead to phase separation, where the resin and the plastisizer break their bond. St op the press and allow it to cool. Recalibrate the press before you begin printing again. 9. Of course flashing or running the build-up color last will totally resolve the problem. 10. Printing on an underbase will not help.

Inks Central Build-Up (absorption)

If ink build-up initiates or is worse around the central areas of the screen, then your build up is caused by phase separation, due to absorption. This type of  build-up is very sensitive to different garment types, brands or constructions. The solutions to reduce the effect are follows: 1. Increase screen tension to a recommended level for the count  and thread diameter of low-elongation mesh. 2. Ensure that the off-contact distance is sufficient to eliminate positive-screen lag (the lack of snap back). 3. Minimize the contact edge of the squeegee blade on the screen mesh and be sure that you are not forcing ink onto the platen. 4. Use a higher mesh count; it will restrict the transfer of ink, pre venting it from absorbing into the garment as readily. 5. Speed up the printing blades and reduce the dwell time between print cycles, this  will reduce absorption time. 6. Under no circumstance should you add any liquids to the ink, they will not help and can actually hurt the absorption. 7. If the press is running hot  due to a lot of flash curing, the viscosity of the ink may  be too low and lead to accelerat ed absorption. 8. Of course flashing or running the build-up color last   will totally resolve the problem.

If there is a trace of ink build-up, all of  the detail is lost immediately. Shown is a five color 120-line   process print. Dropas is another HiRes AccuColor© T-  shirt print, printed by Target Graphics Ltd., artwork is by  will  Tim and Scott Etters. Figure 3.20

9. Printing on an underbase totally resolve this problem.

PAGE 3 . 33

Chapter 3 Perimeter and Central Area Build-Up

If ink is building up initially, and equally, at the perimeter and the central areas of  the undersides of the subsequent screens, then you have an ink problem. Short  of flashing or running the color last, the only cure is another ink. Before you blame the ink, be sure to consider that there are inherent properties in various colors that may be a build-up problem. Altering the resin/plasticizer ratio can definitely lead to build-up-as well as flashes, lint and a few other things. 1. Whites are dilatent (shear thickening) and tend to build up due to phase separation. Of course to run at high speed is your goal but with whites, particularly on thick thread mesh, they fight back. The harder you push, the more the white resists. In this battle the white ultimately  breaks down and the solid phase (resin) and the liquid phase (plasticizer) separate. In this state, the plasticizer can be absorbed into the garment or float on an under base, either way the result is build-up. Use a thin fabric with a large mesh-opening, raise your squeegee angle and you may have to reduce your speed. 2. Whites are often added to create pastel  colors or to improve the opacity of  another color. If white ink is added, it can be a problem. If it is white pigment, the problem may be worse (refer to number one). If you are working with finished inks, add a small amount of the strongest  of the color family to the white. For example, if you want a light blue add reflex to white. Similarly, if you are using  color concentrates, add a small amount of  dark blue pigment dispersion to the finished white ink. 3. Fluorescents are tacky and contain excess plasticizer. They also require excess force to transfer and are prone to rapi d absorption into the garment. Use the recommended surfactant (refer to the sidebar on page 3.32 for details), on a thin mesh with a large opening, and a near-vertical  squeegee at a moderate speed. PAGE 3 . 34

Figure3.21 The M&R KoolMist fits 

between two heads; it is the ultimate solution  to after tack. It sprays a mist of water con-  taining 5% food grade silicone to prevent the   flashed ink from sticking to the next screen. It maximizes color capacity on your press;  eliminates the need for a cooling station.

Inks 4. Fluorescents are often used to punch-up another color, that is to increase its saturation. If there is fluorescent and white in t he color, review numbers one and three and consider running t his color last. 5. Black and blue pigments require higher shear rates to transfer and they  are loaded with plasticizer. These colors may separate phases (refer to number one) and may absorb readily into the garment. Use a mesh count with the largest possibl e opening for the hand and detail that  your image demands. 6. If the problem is related to the blue and or black ink, and not the processing conditions, the two may exhibit a higher gloss level than other colors at the same deposit. Your only alternatives are to run them last, flash them, or talk to your ink supplier about the problem. 7. If you have added color concentrates there can be a problem. The pigment dispersion contains between 22 and 80 percent plasticizer. So  when you add color concentrate between 1/5 and 4/5 of the addition is plasticizer. The resin may not be able to accommodate the overload. If so, the excess will separate from the ink and build-up is imminent.  Your only alternatives are to run it last, flash it or talk to your ink supplier about the problem. 8. If you are using a base (unfinished ink) and its viscosity has increased (aged-up), its use may lead to severe build-up. Run the channel test  (refer to side bar on page 3.14 for details), or ask your supplier for stable product. It is unlikely that anything will help hereother than proper ink. 9. Is the (finished) ink aged-up (increased in viscosity) and requiring  excess force to transfer? Lay the squeegee more horizontal and speed up the 80° -durometer blades. This increases the shear rate and pressure on the ink. 10. Has the ink absorbed too much lint from use? Lint, in excess, will  absorb the plasticizer and virtually turn into glue. There is no way to save the ink. Dispose of it properly and save your profits; put fresh ink in the screen. 11. Is the ink too hot, thin and runny from a flash (refer to chapter five for details)? If so, it is very prone to both separation and absorption into the garment. Either case will cause build-up at an accelerating  PAGE 3 . 35

Chapter 3 rate. Adjust your flashes as prescribed and properly dispose of the ink. Once it has separated it cant be repaired. 12. Has the ink gone into gel state from continued exposure to heat? If  so, it must be disposed of. The cycle will thicken the ink, and you will  be forced to increase the shear rate. Build-up will be at the perimeter, not through absorption into the garment. 13. Has the viscosity been altered, either w ith plasticizer or curable reducer? There is no guarantee there was room in the ink for the amount of  plasticizer/reducer you added. If there was no vacancy, the added plasticizer will move at a different rate than the balance of the ink, causing phase separation. The excess plasticizer is prone to absorption and will act as a wick to draw the original plasticizer into the garment. 14. Have you cross-mixed brands of ink? If so, there is no one that truly  knows what you have. There are no generic recipes that are marketed universally. There are fundamental and unique dif ferences that can actually cause a mixture to build-up; when in fact, neither of the two  virgin colors would have. 15. The purpose of this list is not to suggest that you tolerate ink buildup but to help you properly identify its cause. If it is the ink, then you must fix the problem, t he cost of downtime is devastating and the quality suffers on the way. Adhesion And Surface Energy

Graphics screen printers are far more familiar w ith the concept of surface energy  than T-shirt printers, but to any of you who flash cure ink and then overprint it, the issues are the same as for the graphics printer. The study of surface energy  pertains to the ability of ink to attach to a surface. That surface might be the raw  substrate or another ink. Before reading any further please read the sidebar, Taking The Mystery Out Of Surface Energy . Plastisols adhere to a T-shirt primarily through mechanical adhesion. The knit of  the shirt is a series of loops with a massive surface area onto which a plastisol  can fall. Once the ink is fused, it cannot be torn from the garment  its imbedded into too many nooks and crannies. Plastisol does not penetrate into the indi vidual fibers, only dyes do that and plastisol is a coating. Conversely, if you put that same plastisol onto a coated transfer paper, the ink  can be fused and still peeled cleanly f rom the surface without leaving a trace. The PAGE 3 . 36

Inks reason is the coating on the paper has a very low surface energy, and the surface is so smooth that there is little area for the plasitsol to mechanically lock-on to. The wet plastisol having a higher energy level; likes itself far more than it likes the sheet  of paper. If the energy of the liquid has a higher dyne level  than the substrate, the ink will not properly wet out the substrate.  You have seen examples of this when you print on an underbase. The slick glossy white ink looks great, then you try to overprint it with Royal Blue. At worst, mottling, pinholes and color shifts are obvious, even with a thicker deposit. The white is tending to repel the blue- they dont like each other. The following paragraphs explain that all surfaces have mi croscopic pockets, no matter how smooth they seem. And that   wetting is the extent to which the inks fill those micro nooks and crannies. Further, they detail the nature of the inks, how  to tell if this is a problem in your plant, and what to ask the manufacturer for- to alleviate the problem. Surface Tension

This is a measure of the tendency of the ink to resist wetting.  W etting at the point of initial contact is the degree to which the liquids of the ink, change places with the gases in the microscopic pockets on the surface of the flashed print. Surface tension is measured in dynes per centimeter energy  units and is established on the ink whi le it is in its liquid form.

Taking aking The Myst er y Out Of Su r face Energy Surface energy is the umbrella term for the phenomena of surface tension and critical surface tension. The term surface tension is used when measuring something in a liquid or fluid state. Critical surface tension refers to something measured in the solid state. Both are measured in dynesper-centimeter. To avoid color trapping, mottling and ink adhesion problems, the surface tension of the over-print ink (liquid) must  be a lower number than the critical surface tension of the flashed and cooled ink film (solid) to be printed on.  You must rely on the ink manufacturer to provide the surface tension levels (liquid ink), but  dyne pens can be used in-house to test for critical surface tension on flashed ink film.

The surface tension of the ink is determined primarily by the surface tension of the pl asticizer that constitutes nearly half  the ink. If a low surface tension plasticizer is used, the ink will  tend to have a low surface tension and will wet out effectively. If the plasticizer used has a high surface tension, the ink will  adopt this performance and not wet the surface below it well. If the plasticizer chosen for the core of the ink has a high surface tension, the ink manufacturer may select surfactants to reduce the surface tension of the ink. If not, you are likely to experience some of the wett ing-out  related problems covered in this section. PAGE 3 . 37

Chapter 3 How To Instructions

Preventing Surface-Energy Problems How to prevent surface energy problems: 1. Ask your supplier for the surface tension of  the inks that you are using. 2. Be sure you get surface tension levels on all  colors. 3. Remember, surface tension and critical surface tension aren't the same (refer to sidebar page 3.39). 4. Use dyne pens to test for critical surface tension of flashed cured inks. 5. Six pens from 30 to 40 dynes per centimeter are sufficient. 6. Store the pens as recommended in a cool  dry area. 7. Do not keep a pen set longer than five months. 8. Ask your supplier for proper surfactants to adjust problematic colors. 9. Stick to the guidelines of the manufacturer for limits of addition.

These are the worst-case  colors, those that tend to have high surface tension: Whites, due to the nature of t he plasticizers used for anti-migration properties and in the pigments used for dispersion. Blues and blacks use specific plasticizers in their dispersion state, and these are often poor wetting agents. Fluorescents are notorious for poor flow and tend to have higher-than-normal surface tension and much of the time they reduce the critical surface tension of the gelled ink. Laboratory equipment is needed to measure the surface tension of the inks  whether by critical angle or  with the use of a tensiometer.  You will want to leave this up to the ink manufacturer but  ask for the results. You may  find that some of your troubles are due to low surface tension inks. Critical Surface Tension

This half of the surface energy phenomena is a measure of the tendency of  the gelled ink (substrate) to be wet out by another color. The best analogy is Teflon® (ptfe), it has a critical surface tension of 13.9 dynes per centimeter. The reason that nothing sticks to it is that most common liquids, foods, inks and chemicals have a surface tension that is higher than 13.9 dynes per centimeter. If the surface tension of the liquid is higher than the critical surface tension of the solid, then wetting will not occur.

PAGE 3 . 38

Inks The critical surface tension of plastisol inks will typically range from low to high thirties. At a critical surface tension in the low thirties, not many ink colors will wet-it-out. Pinholes, color shifts, mottling and smearing are likely issues with this as the substrate. When critical surface tension reaches t he high thirties, the ink is a dream to overprint even wi th contrasting color combinations such as Royal on White. Testing The Critical Surface Tension

There is a quick, low cost and simple test for the surface energy of the gelled (flash-cured) ink. It uses special felt-tip pens that contain measured liquids at a specific surface tension. The pens are swiped on the flash-cured ink and the critical surface tension is related to the time, in seconds, it takes the pen solution to beads up. Lets say that you want to evaluate the surface energy of your  white underbase. Print the underbase under normal conditions; flash it and let it cool thoroughly. Hot inks will react differently  t han cool and give you an erroneous reading. Start with a pen at a dyne level of 30. Swipe the pen on a clean, dry sheet of paper, three times. This action allows the f luid in the pen to clean itself. Then swipe the pen on the flashed, cooled underbase. The solution will probably flow out  and cover the underbase in a continuous line of fluid. In two seconds, if the fluid has not beaded up, then you know that  the critical surface tension of the underbase is higher than 30 dynes per centimeter. Now select a pen that has a reading of 40 dynes per centimeter. Swipe it on paper to clean the tip and then onto the same flashed cooled under-base. It w ill probably bead up in two seconds or less. If so, this means your under-base has a critical  surface tension of less than 40 dynes per centimeter. You now  know the critical surface tension is more than 30 and less than 40 dynes.

 Vi su al Cl ues sual Identifying Sur faceEnergy Pr oblems The following is a list of what you  will see if you have surface-enery  problems: v

 White looks glossy, feels slick  and overprints poorly.

v

Coverage over underbase leaves pinholes.

v

Some colors cover much better than others.

v

Blues and blacks tend to mottle or reticulate on the surface.

v

Halftones cannot be printed on an underbase.

v

Halftones on an underbase have erratic color shifts.

v

Fluorescents do not flow out  onto an underbase.

v

The ink climbs the squeegee and flood bar.

v

v

 You cant print anything on top of a metallic. Extreme color loss when overprinting.

The pens are available in increments of two dynes: 30, 32, 34, and so on. By testing one lower and one higher pen number, you can establish the critical surface tension of the flashed PAGE 3 . 39

Chapter 3 color. This will allow you t o determine if the problem is due to an under printer or an overprint color. Fusion Testing

Testing for fusion or total cure is divided into two parts; a calibration stage that  allows you to set your standards and ensure results and second, a monitoring  stage. Once you have calibrated you can then use quick tests at press side and be confident of the accuracy of those tests. The tests and how to use them are described in detail below. Swipe test

Total cure or fusion is based on the type of ink, its deposit, entrance temperature (as from a flash or not) and the dryer parameters. The possibilities are expansive.  Are you near the upper or lower edge when you cure your plastisol? If you do not  know, there is a quick test to allow you to develop a sense of posit ion. Take a scrap, which matches your normal goods; tack the cloth to the platen. Use a spatula and swipe a gradient  of white ink two-three inches  wide and six inches long, from wafer thin to over 1/8i nch thick.

Figure 3.22 Get Exotic (print compliments of Target Graphics) is a 

65 Lpi halftone four-color-process print. There is no underbase and the  colors are deposited at one mil each. Thin film deposits are more likely to exhibit problems with both the wet and dry crok test, but this shirt passed  the test with flying colors.

PAGE 3 . 40

Then put the scrap through your dryer as usual. When it  exits you should see the following results: The thick end of the swipe is still wet, or nearly so, and indicates undercure. The thinnest end is

Inks burned, or very glossy, indicating over-cure. The middle areas appear to be reasonably  fused. Time, and then record the retention in the heating  chamber, as well as the set  and point temperature. If the entire swipe is fused, either your time is too hi gh, your temperature too hot or both. If the entire swipe is still wet either your dryer is turned off or you have serious under-cure problems. You now have a quick index of  deposit and cure times.

Testing With Ethyl Acetate

How To Instructions

To test with EA follow these steps: 1. Print and cure a swatch or T-shirt. 2. Turn the shirt inside out. 3. Apply several drops of EA to the inside of the print. 4. Fold the printed image onto an unprinted area. 5. Press with a blunt edge for two minutes. 6. If there is ink transfer, the print is not fused. 7. If no ink transfer, the print is fused.

Compare this test swatch to the opacity of a normal white print. Find the point on the swatch that matches in opacity or density to your normal print. This is the area that will alert you to the need to increase or decrease your retention time or temperature. Make the required change and repeat the test until the correct density is cured properl y. EA (ethyl acetate) Test

Testing for total ink cure is a case where more is bet ter advice. Use the information about cure ranges you learned doing the swipe calibration to assist you with this test. This test is for calibration (not used to monitor results). It is fast and  very accurate but destructive; you w ill ruin the shirt or swatch. Ethyl acetate is a  very flammable solvent use caution as prescribed in the MSDS. Never put a shirt  or swatch in the dryer af ter you have applied ethyl acetate to it. Take a printed sample shirt or swatch and put it through the dryer twice to be positive that it is cured. It is better to be over cured than under cured. This swatch will be the control  swatch. Then put a second sample through the dryer at  normal retention time and heat. This will be the print swatch. Use the first t o check your cured ink against the EA test. Use the second sample to check for cure of your production conditions. Please refer to the flow chart on page 3.42 to review the testing process.

PAGE 3 . 41

Chapter 3 Figure 3.23 This is the step-by-step pro- 

cedure for using Ethyl Acetate (EA) to establish a control or standard for testing  degree of fusion and testing a printed gar-  ment, once your standards are set. Establishing the control requires certainty of   fusion send the garment through your  dryer two times rapidly, back-to-back. Be  sure the garment is back to room tempera-  ture, before testing. Use caution with EA, it is a highly flammable solventplease  study the MSDS sheets. This is a very  thorough test and should be completed as a  calibration for scratch, stretch and crock testing.

Cautionbefore you proceed with this test, contact your ink manufacturer to confirm compatibility of your plastisol with the E.A. test . PAGE 3 . 42

Chapter 3 Stretch Test

Since plastisols are good thermal insulators, stretching the print to look for cracking can be inconclusive. The reason is that you are observing the portion of the garment that got the most exposure to heat, so it is the part that will be least likely to crack. The ink can be totally cured on top and not on the inside. Nonetheless this test will help y ou to identify blatantly under cured results. Be sure that you rely on this test as a monitor-only-test, after you calibrate with the EA test and then double check with laundering. Then you can use stretching  as an effectiv e monitor of the results. Crock Test

This test is used for both calibration and moni toring. Wet and dry crock testing is a textile-industry standard, with very specific procedures, that do not fit the plastisol, T-shirt community very well. Crock resistance is the likelihood that the color will not transfer from the print, either when dry or wet. The test is to suggest that the print will wash and wear well. Use the inside of  the shirt or a white T-shirt and scrub the image forcefully with several strok es and look for color transfer. If you see color transfer, y our ink is under cured. Try putting it through the dryer one more time and retest. If there is any transfer of color, check the following: 1. Proper curing conditions. 2. Plasticizer level of the ink. 3. Use of reducers or curable reducers. 4. Presence of fluorescent colorants. 5. Pigment overload. The only part of the ink that is strong is the resin. Anything that is added to reduce the percentage of resin weakens the ink film. If the resin load is high enough, then we would suspect either a pigment problem or a curing problem.  Wet crock is a launder monitoring test and about as harsh as the w ashing process can be. Laundering is one of the most harmful elements the printed image needs to withstand-you should be able to anticipate its affect. Periodic wash tests are highly recommended. Meanwhile, the following test will simulate washing a perspiration-stained T-shirt. Use a 50 percent mix of glacial acetic acid (white vinegar) and water. Soak the printed image in this solution for 15 minutes and then PAGE 3 . 44

Inks perform the dry crock test as described above. Perspiration is very hard on the print and the vinegar simulates the effect of perspiration. Laundering:

If the shirt passes all the other tests, then there is every  reason to believe it will do  well in laundering. There is a standard for performing laundering tests that can be obtained from the American  Association of Textiles Color & Chemicals (AATCC), should you decide to add this test to your process. The tendency for a garment  to with stand repeated washings is affected by the wash standards and the following  print parameters.

Calibration and Monitoring Of Ink Cure

How To Instructions

Calibration must be completed before monitoring can be reliable. The following tests must be done in the order listed, and each test must pass before moving  onto the next. The swipe test gets you in the ballpark for the EA test. The EA test is the real-calibration test. The swatch, stretch and crock tests need to be done on a sample that has passed all the previous tests, to provide you with a reference for knowing what to expect during  monitoring. Calibration

1. Swipe test for dryer retention and temperature ranges. 2. EA test to verify ink cure. 3. Scratch Test to establish pressure required for monitoring. 4. Stretch Test to establish results of stretch for monitoring. 5. Crock Test to establish results of crock for monitoring.

1. Cure level.

Monitoring

2. Ink deposit.

1. Scratch Test 

3. Degree of adhesion to the garment.

2. Stretch Test  3. Crock Test 

4. Plasticizer level of  the i nk. 5. Filler level of the ink. If the print on the garment is not fully cured, washing (which is intended to remove dirt, grease and grime from the micro pockets of textiles) removes the excess plasticizer from the ink. What is left is a brittle and very thin sheet of  plastic, which will crack and peel from the garment. How ever, it may not be the printers fault; if the ink was over plasticized, and many are, then you may not  PAGE 3 . 45

Chapter 3 have been able to fuse the ink at a reasonable time and temperature. The ink may  have been defective. Standard plastisol cannot be dry cleaned for the same reason; the solvents used in dry  cleaning can, and will, extract  the available plasticizer from the print. What is left is brittle and very thin; it cracks and flakes off of the shirt.

Figure 3.24 The GATF test image shows the results of fast recovery 

Ironing is never acceptable, and though there is hardly an epidemic of ironing in our  wash and wear society, you must caution your customers that ironing will melt the ink  and do its best to ruin the iron.

and high opacity whites when used as an under base. The reflection density  of the white is 0.01for near total whiteness. The fast recovery and high  mat down kept virtually all fibers below the ink surface through a 305  mesh. Garment compliments Target Graphics Ltd.

Turning the shirt inside out is a tough sell to the consumer, but a great idea, nonetheless.  Wash in warm  water with mild detergent and not   with other garment  types is the same dilemma; most people dont want to t ake the time, the Tshirts are seen as expendable until  their favorite is eroded and then the Figure 3.25  A "Heat Gun" is ideally suited for checking gelation under a flash. The   print on denim (compliments Promotions Chicago) should be checked for flash to insure  printer gets blamed. sufficient penetration into the woven (not knitted like T-shirts) material. If the platens  are not acting as a heat sink, adhesion can be compromised.

Keep in mind the gauge for minimum dryer retention time and temperature is print durability- max i-  mum is absence of bleeding, blistering and penetration. PAGE 3 . 46

Inks Dryer Temperature Testing

To gain a sense of position use the swipe test as described on page 3.40. You dont test the flash or dryer for cure or fusion; you test  them for temperature-this is important to understand. Cure is a result of time, temperature, and the cooperation of the ink. And that cooperation should not be assumed. Use a CofA confirm the fusi on temperature or contact  your ink manufacturer to acquire this information.

Profiling A Dryer

How To Instructions

To profile the dryer follow these steps: 1. Get a stopwatch and an assistant. 2. Start the donut through the dryer. 3. Record the digital temperature every five seconds. 4. Ideally you will aim for the printed shirt to exit the dryer in the exact retention time and temperature standards developed in the EA test.

Donut Probe

This system uses a meter and a cable attached to an insulator and a thermocouple. The insulator is shaped like a donut and this probe runs through the length of  your dryer. The thermocouple is relatively fast in its response and indicates an elevation in temperature similar to that experienced by the ink and garment. The leads are to be laid in or on the wet ink so this is a destructive test. Note that if your dryer is infrared, the donut probe is inaccurate unless the leads are imbedded in the ink. The beauty of the system is that it gives continuous feedback on the relative heat at a specific position. With a bit of record keeping you can profile any  dryer and begin to optimize its settings. The downside of the system is that it is bulky and not as convenient as other methods, we recommend that you tolerate the wires and profile the dryer. Finally most of these units that we see in the field have not been accurately calibrated. Calibration should be done according  to the manufacturers directions; keeping the wire leads taut, or the readings are  will be erroneous. Heat Gun

These units are non-destructive, ultra conveni ent and if calibrated to a standard, can give nearly instantaneous readings w ith great accuracy (generically called non-contact infrared pyrometers). The meter reads the emitted energy from  what ever it is aimed at. Few of these units have been calibrated to the complexPAGE 3 . 47

Chapter 3 ity of the calibration procedure. It is best left to the ink manufacturer to calibrate these units to his ink parameters. Gloss, texture, color, ingredients and range of  Figure 3.26 The macro

shot shows the striking  effect of an award quality  high-density print. The rea-  son for its inclusion here is  caution regarding the  mileage you might expect. With a twenty to thirty  mil deposit, you will get  approximately 50 to 80  square feet per gallon.  Aesthetically and financial-  ly high density is best  served in small doses. Figure 3.27 The micro

shot shows the relief of the  high density Addidas   print. Ink mileage is based  on both the area of the  image and the height of the   print. In this case the area  is quite small, but the  height is extreme, adding to its effectiveness. Garments   for both photos are compli-  ments of Liberty Screen  Print.

Figure 3.28 The graph 

Ink Mileage Based on Deposit 1600   n 1400   o    l    l   a 1200    G 1000

  r   e    P  .   t    F  .   q    S

800 600 400 200 0 1.0 1.5 2.0

2.5 3.0 3.5

4.0 4.5 5.0

Mils of Ink Deposit  PAGE 3 . 48

5.5

shows ink mileage based on  mils of ink deposit. The  deposit (horizontal axis) runs from one to five and  one half mils. The square   feet per gallon (on the verti-  cal axis) goes to 1600  square feet, equivalent to a  one-mil deposit. A 3 mil  deposit would yield 535  square feet of image per   gallon.

Inks temperatures all affect the emissivity of the ink and therefore the readings of the heat gun. These do not need to touch the part, but focus on a narrow field even from a distance. For flash-cure testing, these guns are indispensable. Keep them away from direct  exposure to heat and if you have not calibrated the gun, real ize that the numbers may  be sufficient but not absolute. Temperature Tapes

These are gray plastic, which are used one time only. When exposed to heat the gray turns black. They are available in ranges of temperatures that   will allow you to test for temperature in a dryer. They are expensive, but con venient and fast-they will not interrupt  product ion. Do not get confused and think you are testing for cure, this tests for temperature only.

Ink Mileage

Estimating Ink Mileage

How To Instructions

Estimating By Weight

1. Cut a swatch of the material. 2. Run swatch through dryer. 3. Weigh swatch on very precise gram scale (tenths of a gram). 4. Immediately print ink color onto swatch. 5. Immediately run printed swatch through the dryer. 6. Re-weigh the swatch. 7. Subtract unprinted swatch weight from printed swatch weight. 8. Divide the resulting weight by the weight of a gallon. 9. This is the percentage of a gallon used per print. Estimating by Area

1. Refer to Approximate Mils per Mesh chart, figure 3.22. 2. Find your mesh count on the vertical axis. 3. Find the approximate mils on the horizontal axis. 4. Refer to Ink Mileage Based On Deposit , figure 3.23 5. Find the square foot per gallon. 6. Find the square footage per color. 7. Divide the results of # 5 by the results of #6. 8. Refer to Dozen Per Gallon at 50% Coverage , figure 3.23.

There are three ways to estimate the ink mileage on a Tshirt and the most accurate occurs after the job has ended. The second most  accurate requires a very sensitive gram scale and the third

8. Compare the results to 50% coverage at your deposit. Notes: For greater accuracy on ink mileage, estimate by  area. Some graphics software packages offer a pixel  count for extreme accuracy of computing image area. Measuring the wet and dried ink film thickness will be more precise than the table provided. PAGE 3 . 49

Chapter 3 How To Instructions

Calculating Ink Mileage To calculate ink mileage follow these steps: 1. Select a container of ink to print multiple shirts. 2. Weigh the container of ink prior to run. 3. Print the job, stop prior to completion of the container of ink. 4. Take a shirt count at the point that you stop. 5. Return all unused ink to the container. 6. Weigh the leftover ink. 7. Subtract the leftover ink weight from the original   weight. 8. Divide the total weight by the number of shirts printed. 9. This is the weight-per-shirt. 10. Divide the weight-per-shirt by the weight of a gallon. 11. This is the percentage of a gallon used per print.

is a ballpark number, but it  is immediate and can be run in your office or that of your customers.  Actual ink mileage is predicated on nearly all of the variables discussed in this book. Mesh parameters, stencil  impact, press settings, virtually all of the blade properties, all of the temperature conditions, t he substrate specifications and the image itself-all  have a bearing on the actual  deposit. The three methods in order of accuracy are: Method One  weighs the ink prior to, and after, production. The number of prints divides the ink  consumed and the result is the weight per print. That   weight is taken as a percentage of the gallon. This method is far and away the Figure 3.29

 Approximate Mils Per Mesh

   h   c   n    I   r   e    P   t   n   u   o    C    h   s   e    M

350 300 250 200 150 100 50 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

 Approximate Mils Deposit  PAGE 3 . 50

Viscosity, shear rate and  screen / stencil geometry  all interrelate to determine  the actual deposit of the  ink. This graph is offered  as a quick estimator of  mesh and ink deposit. Since the ink cost is near-  ly always a less significant  of the unit cost, we feel  that mileage and cost can  be approximated in most  cases. A 300 mesh  deposits a nominal 1 mil  of ink.