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

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. 41

burned, or very glossy, indi-

cating 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 high,

your temperature too hot or

both. If the entire swipe is

still wet either your dryer is

turned off or you have seri-

ous under-cure problems. You

now have a quick index of

deposit and cure times.

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 properly.

EEAA ((eetthhyyll aacceettaattee)) TTeesstt

Testing for total ink cure is a case where more is better advice. Use the informa-

tion 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 will 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 after 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 to

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.

Inks

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.

Testing With

Ethyl Acetate

How To

Instructions

PAGE

. 42

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 manu-

facturer to confirm compatibility of your plastisol with the E.A. test

PAGE

. 43

Take the control garment and turn it inside out (or in the case of a swatch to the

back-side of the print). Be sure the swatch and ink are cooled for the EA to work

properly. With an eyedropper apply several drops of the EA solvent to the inside

(or back) of the swatch directly behind the printed image. Using the area of the

swatch covered with EA drops put the front (printed image) into contact with a

non-printed area of the swatch. Press firmly with a blunt instrument from the

point where the EA was applied. Hold the surfaces in contact for two minutes

and peel apart.

The EA test will produce one of two things on the control swatch; it will transfer

ink to the non-printed area or it wont. If it transfers ink you will need to repeat

the test, but run the sample through the dryer three times. If you cannot get the

control swatch to pass the test and you are positive the ink is more than cured, it

is possible that the ink you are using will not withstand the EA test period. Using

the swatch that went through the dryer three times, find a spot unaffected by pre-

vious testing, apply the EA solvent. This time when you contact the printed

image to the non-printed area, reduce the time to 90 seconds. If you still transfer

ink, then the ink has a bleed problem that cannot be controlled with cure time.

Contact your ink manufacturer to solve this problem or find another ink that will

pass this test.

Now test your print swatch with the same method used on the control swatch. If

the print swatch does not transfer ink, leave your retention time and temperature

as it is. If the EA test failed, you need to adjust your dryer retention time or tem-

perature. Repeat the test until you have a sample that doesnt transfer ink. Do not

over compensate, or you will be running your dryer at higher temperatures than

necessary or longer retention times than necessary-either will add cost to your

bottom line. Now you have found the correct dryer retention time and tempera-

ture for the tested ink at the tested film deposit.

SSccrraattcchh TTeesstt

This is the standby test, which is used most often because it is convenient, but

many times it is inaccurately done with fingernails. We suggest that you first run

the EA test (see opposite page) and then launder the test prints so you can have

confidence of pass and fail. The nails or any sharp tool can cut through a plasti-

sol even once it is totally fused. By calibrating with the EA and laundering tests,

you will know just how hard to scratch the surface. The amount of pressure

required to scratch the surface will become your standard for monitoring. After

you have calibrated your print curing you can rely on the scratch test to monitor

pre-established results.

Inks

PAGE

. 44

SSttrreettcchh TTeesstt

Since plastisols are good thermal insulators, stretching the print to look for crack-

ing 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 like-

ly to crack. The ink can be totally cured on top and not on the inside.

Nonetheless this test will help you 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 effective monitor of the results.

CCrroocckk TTeesstt

This test is used for both calibration and monitoring. Wet and dry crock testing is

a textile-industry standard, with very specific procedures, that do not fit the plas-

tisol, 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 sug-

gest 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 strokes and look for color transfer. If you see color transfer, your 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 washing 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 per-

spiration-stained T-shirt. Use a 50 percent mix of glacial acetic acid (white vine-

gar) and water. Soak the printed image in this solution for 15 minutes and then

Chapter 3

PAGE

. 45

perform the dry crock test as

described above. Perspiration

is very hard on the print and

the vinegar simulates the

effect of perspiration.

LLaauunnddeerriinngg::

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 laun-

dering 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 wash-

ings is affected by the wash

standards and the following

print parameters.

1. Cure level.

2. Ink deposit.

3. Degree of adhesion

to the garment.

4. Plasticizer level of

the ink.

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. However, it may not be the

printers fault; if the ink was over plasticized, and many are, then you may not

Inks

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.

CCaalliibbrraattiioonn

1. Swipe test for dryer retention and tempera-

ture 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.

MMoonniittoorriinngg

1. Scratch Test

2. Stretch Test

3. Crock Test

Calibration and Monitoring

Of Ink Cure

How To

Instructions

PAGE

. 46

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 rea-

son; 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.

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.

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 peo-

ple dont want to

take the time, the T-

shirts are seen as

expendable until

their favorite is

eroded and then the

printer gets blamed.

Keep in mind the

gauge for minimum dryer retention time and temperature is print durability- maxi-

mum is absence of bleeding, blistering and penetration.

Chapter 3

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

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.

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

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.

PAGE

. 47

DDrryyeerr TTeemmppeerraattuurree TTeessttiinngg

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, tem-

perature, and the cooperation

of the ink. And that coopera-

tion should not be assumed.

Use a CofA confirm the

fusion temperature or contact

your ink manufacturer to

acquire this information.

DDoonnuutt PPrroobbee

This system uses a meter and a cable attached to an insulator and a thermocou-

ple. 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.

HHeeaatt GGuunn

These units are non-destructive, ultra convenient and if calibrated to a standard,

can give nearly instantaneous readings with 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 complex-

Inks

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.

Profiling A Dryer

How To

Instructions

PAGE

. 48

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

Chapter 3

200

400

600

800

1000

1200

1400

1600

Sq. Ft. Per Gallon

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

Mils of Ink Deposit

Ink Mileage Based on Deposit

Figure 3.28 The graph

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.

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.

PAGE

. 49

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 nar-

row field even from a dis-

tance. For flash-cure testing,

these guns are indispensable.

Keep them away from direct

exposure to heat and if you

have not calibrated the gun,

realize that the numbers may

be sufficient but not absolute.

TTeemm

ppeerraattuurree TTaappeess

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 tem-

perature in a dryer. They are

expensive, but convenient and

fast-they will not interrupt

production. Do not get con-

fused and think you are test-

ing for cure, this tests for

temperature only.

Ink Mileage

There are three ways to esti-

mate the ink mileage on a T-

shirt and the most accurate

occurs after the job has

ended. The second most

accurate requires a very sensi-

tive gram scale and the third

Inks

EEssttiimmaattiinngg BByy WWeeiigghhtt

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.

EEssttiimmaattiinngg bbyy AArreeaa

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.

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.

Estimating

Ink Mileage

How To

Instructions

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 predicat-

ed on nearly all of the vari-

ables discussed in this book.

Mesh parameters, stencil

impact, press settings, virtual-

ly all of the blade properties,

all of the temperature condi-

tions, the substrate specifica-

tions 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 num-

ber of prints divides the ink

consumed and the result is

the weight per print. That

weight is taken as a percent-

age of the gallon. This

method is far and away the

Chapter 3

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 con-

tainer 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 gal-

lon.

11. This is the percentage of a gallon used per print.

Calculating

Ink Mileage

How To

Instructions

100

150

200

250

300

350

Mesh Count Per Inch

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Approximate Mils Deposit

Approximate Mils Per Mesh

Figure 3.29

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.

PAGE

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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