Clarke Joe, Lynch Colleen C. M&R Professional Screen Printing Series

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Chapter

INKS

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PAGE

. 3

Ink Properties

The purpose of this section is to help establish a common language between the

ink compounder and the printer. These are properties that the ink maker can

identify and assign a repeatable range. For the informed printer it allows a fast

comparison of a variety of inks with a minimal amount of testing.

We are in an industry with no standards and this is slowing our evolution. The

printer cannot count on the ink printing the same time after time and is rarely

sure if the ink is at fault or if the cause is the balance of the print process. Such

is our world without standards. For all other applications, the plastisol manufac-

turers offer a Certificate of Analysis that describes any normal or special variance

of the product that has been purchased. Ironically none of these alternate

processes is more complex or more variable than screen printing. Ask your ven-

dor if you are a large enough account to warrant a CofA with your ink.

There are a variety of problems with some ink currently on the market. Far too

often, these are remedied by an adjustment on the press. If the press ran slow,

M&R would expect that you would call and we would do something about the

problem. If the ink is forcing you to run slow, realize that ink solutions from the

press may be costing you productivity and quality.

The point is that what you dont know about your ink may hurt you. If in fact the

ink is problematic, the best solution is to fix the ink not to use the press, mesh,

Inks

Ink

Problem

Press

Compensation

Record Lost

Dozens per Hour

Build-up

Flash cure

After flash tack

Cooling station or fans

Low opacity

Double stroke, second screen

Screen hang-up

Higher off-contact

Blade hang-up

Lower angles, wider gap

Over plasticized

Longer flash time

Excess tack

Higher off-contact, tension

Thermal sensitivity

Periodic cooling breaks

Dilatent white

Slower blade speed

High viscosity

Higher blade pressure

Poor grind

Periodic cleaning breaks

Figure 3.1 Use the table above to record the 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

. 4

stencil or anything else. The problem is, you may not always know if the ink

meets your specifications-you may be laboring with art, screens, stencils, press,

flash or dryer to solve a problem caused solely by the ink.

For our test purposes we used white ink manufactured byHaden-Horne Ink, as

white is familiar to all readers and by far the most commonly used color. Each

of the manufacturers in the market place has a boatload of whites and some of

the companies are hard pressed to tell you which to use. Once you understand

the available data on each of the whites and get comparable data from your sup-

plier, it is simple to determine why and where you should select a white or any

other color. Not all manufacturers perform all listed tests, nor do they encourage

publishing the results. All of these facets of ink performance can be listed on a

Certificate of Analysis. The properties listed below are offered as a starting point

in your search and are divided into four categories: optical, rheological, thermal

and physical.

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The optical properties of the white are very important, as it is the color most

often used as an underbase. As such it may have a strong affect on the overprint-

ed colors, particularly if they are transparent. Further, the aesthetics of a white

are critical- it must not look dirty or yellowed. Following are the standard specifi-

cations for white plastisol ink.

LL**aa**bb**

The L*a*b* opponent color system is an industry wide standard, used to com-

pare the accuracy of color matches. Opponent systems gauge the color between a

series of axes. The axes have two poles each; as the color specimen gets closer to

Chapter 3

H-Cote 9000 Optical Specifications

Delta

Peak

Spectral

Gloss

Pctg.

Opacity

Per Mil

Bleed

Resist

92.04

-2.81

-2.65

480 nm

75% @

1 mil

.3372

.3562

Figure 3.2 This table lists the optical properties of the H-Cote 9000 white ink. The 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 of white inks. The peak spectral supports the a* and b* data, it was 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 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.

PAGE

. 5

one pole, it automatically moves away from the other. For example, the more

white a color contains, the less black it can contain and vice versa. The same holds

true with red versus green, and yellow versus blue-there are no reddish greens or

bluish yellows.

The L* is the luminosity of the color or its position between a high of white and

a low of black. The a* horizontal axis is the position of the color between

absolute red and green and the b* vertical axis is the position of the color

between absolute yellow and blue.

Even though white ink is seen as colorless or achromatic, it has attributes of

color that can be modeled. A white that has a bluish cast, such as the one shown

in figure 3.7,will appear whiter to the observer. It is an indication that the white

pigment used has been altered with a blue tint, which negates the yellow cast

Inks

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 influence from the opposite pole is lessened. Primary color

attributes can be specified between the three axes. Photograph compliments of Hunter Labs.

PAGE

. 6

inherent in the raw TiO² (titanium dioxide) pigment. The

bluish cast makes a cleaner looking white and this cast will

show up on an L*a*b* color model.

DDeellttaa EE

The delta E of a color is a measure of the distance from the

color match to the sample or target color. It is a result of the

L*a*b* opponent color parameters. The delta E is less of an

issue with a white as white is opaque and less sensitive to a

shift with a change in deposit. Delta E is the resulting variance

in all three L*a*b* attributes that indicates color variance in

that batch of ink. All manufacturers have a range of tolerance

We have all been asked to make

sure the image color matches on

all seventy-two of the garment

colors. For you who have never

been asked, we offer a few

caveats; there are two phenome-

non called simultaneous contrast

and adjacency contrast that may

keep you from delivering as need-

ed.

The first one implies that we do

not see the color of images as iso-

lated entities. Rather we see the

entire image; our impression of

the color is a composite of all

other surrounding colors. The sec-

ond phenomenon implies that our

impression of a color can 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 differ-

ence. It will most often be with

the perimeter colors. If there is a

hard border, you may get away

with little trouble-but consider the

following example: You need to

print a yellow sun in the back-

ground on both white and violet

T-Shirts. On the white T-shirt

there is little value contrast

between the shirt color and the

sun. Printed on the violet shirt the

contrast is overwhelming, because

the two are complimentary colors,

which creates extreme contrast.

Your focus will be forcibly taken

to the perimeter and it will over-

power most everything in the

image. Beware of borderless

images and complimentary hues

when the garment color is

changed.

Chapter 3

Color Matc

hing

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 e is the resulting variance of data developed in the L*a*b* color

model. The Hi-Res AccuColor© garment is provided compliments of Target Graphics.

PAGE

. 7

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.

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The peak spectral response of a color is its dominant wave-

length. 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.

GGlloossss

The gloss of the plastisol is taken at 60° and our white draw-

down has a low gloss of 30 percent. Be cautious of higher

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.

Inks

Color Matc

hing

(continued)

400 500 600 700

450 550 650

Visible Wavelength

100

Percent Reflectance

Hue, Saturation & Intensity

-7257 + 50.26*x - 0.1255*x

+ 0.0001351*x

- 5.31E-008*x

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.

PAGE

. 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

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

There are three times when you

may be surprised to see dye bleed-

ing. 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 gar-

ment. It is based on the propensi-

ty of that dye to fill the available

dye-sites (microscopic nooks and

crannies of the fiber). The prob-

lem is the original color should

have been at, or near, the limit

already. Over dying is a risky busi-

ness because of the availability of

the dye at the surface of the gar-

ment, 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 differ-

ent for reds and blue T-shirts, as

different as addition and subtrac-

tion. 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 neu-

tralize both colors. The problem

arises when the printer has solved

the problem for the red bleeding

Chapter 3

Bloody Myst

Too much cyan

or not enought

magenta.

Too much cyan

or not enought

yellow.

Too much

magenta or

not enought

cyan.

Too much

yellow or not

enought cyan.

Too much

magenta or not

enought yellow.

Too much yellow

or not enought

magenta.

CYAN

RED

GREEN

BLUE

MAGENTA

YELLOW

Printers Color Wheel

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.

PAGE

. 9

a drawdown, not a print as the texture of the print would give

an artificially low reading.

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The opacity of an ink color should be noted per mil and a

one-mil deposit is typical and indicative of a 305-mesh

deposit. The printer needs a white that will develop opacity at

the 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 percentage 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

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 manu-

facturer 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 plasti-

cized, 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 fluo-

rescentscheck twice.

Inks

Bloody Myst

(continued)

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 AccColorÓcompliments of Target Graphics Ltd.

PAGE

. 10

the bottom half of it is black.

The white ink is drawn down

on an opacity card to a pre-

scribed thickness. A colorime-

ter or densitometer 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 draw-

down.

Lets say that the deposit is

one mil and the white ink on

the bottom (black end) of the

card has 71 percent reflect-

ance.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.

BBlleeeedd RReessiissttaannccee

There are a variety of meth-

ods the ink manufacturer uses

to ensure the white will stay

white on a variety of colors

of polyester-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 styl-

ist bleaches dark hair to light, they can turn the dyes to clear. Typically the type

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.

Chapter 3

There are many causes of "bleeding" on synthetic gar-

ments 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 prob-

lem that is solely the garment 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 sublima-

tion.

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 sub-

limations. Second, you could look for different ink

one that passes this test.

Testing For Sublimation

How To

Instructions

Clarke Joe, Lynch Colleen C. M&amp;R Professional Screen Printing Series

Подождите немного. Документ загружается.

Clarke Joe, Lynch Colleen C. M&R Professional Screen Printing Series