Impressions - June 2018 - 38
When Matte Ink turns Glossy
It should be easy to know ink is overcured if it should be a matte
finish but is glossy instead. But this can be deceiving because the ink
also can look glossy when it is undercured.
In the case of a white underbase that will have other colors printed
screen from overheating. This ensures the screen peels away
from the print as the squeegee passes over, thus minimizing
contact with the heated print.
on top, it is important to only flash the ink so that it is only dry to the
touch (gelled), not fully cured. I often hear complaints of instances
where colors printed on top of a white underbase disappear during
laundering. This can happen when the white underbase has been
overflashed, meaning the top colors won't bond with it.
Inks Cracking, Washing Off
The Cure: Let's be clear: Heat is your enemy and friend in
the screen-printing process. Using too much and too little can
harm your print. The average, industry-agreed-upon curing
temperature and time is 320˚F for one minute.This is a guideline, and doesn't mean you can't cure a four-color (halftone)
process design at 360˚F for 45 seconds.
The thicker the ink deposit, the longer it will take to cure.
Some special inks can cure at lower temperatures, though printers
must use caution when working with them.
How can you be assured ink has cured sufficiently? The
general rule is to stretch the print after it has come off the dryer
and cooled. If the print cracks, it's not cured. Be careful not to
stretch a print until it cracks. Rather, take a 1-inch-wide print
and stretch it to 2 inches at most to see if it cracks. To make
doubly certain that all the ink has cured, wash the garment.
Undercured Prints: Curing, or lack thereof, probably is
the primary culprit of all the complaint calls I receive about
inks.To avoid undercuring issues, ensure the entire ink layer is
cured at the prescribed temperature.Time is your friend when it
comes to curing.A steady run of about one minute through the
dryer at the correct temperature will save you a big headache.
A White Print Becomes Color
The ragged edges in
this print possibly are due
to lack of emulsion on the
screen's print side, thus
allowing ink to seep through.
Ink Going Through the Shirt: If you see ink being squeezed
through to the inside of a shirt, then there is too much pressure being applied to that screen. Perhaps the ink is too thin,
the squeegee is too hard, too much pressure is applied or the
substrate fabric's weave is too open.
Always test squeegee pressure by lowering it to where it almost
won't print, then add just enough to where it prints just right
- with visible details and even coverage - and then stop. Look
at the garment's underside and you should see much less ink.
Ink Drying in Screens
Over-Flashing: Printers often refer to ink "drying in screen"
when it becomes hard and clogs the screen mesh's open parts.
This usually is caused by using excessive heat during printing,
most likely after the flashing process. If the ink isn't given
enough time to cool after flashing, laying the screen down on
top of the heated print could partly cure the ink it contains,
thus clogging the mesh.
Using proper off-contact also can help keep the ink in the
i m p r e s s i o n s m a g . c o m JUNE/JULY 2018
Dye Migration: Dye migration typically only occurs on polyester or polyester-blended garments.When the polyester fabric
is dyed, it is "set," cured or dried between 280˚F and 300˚F.
Therefore, when a screen printer cures inks at 320˚F - a higher
temperature than the polyester dye's cure temperature - those
dyes get released.
Dye migration can happen when dryer settings aren't reset
from a previous job involving cotton shirts, which can involve
temperatures between 330˚F and 340˚F. The white ink in
a design can turn pink on red fabric or gray on dark fabric,
or perhaps other colors due to excessive dyeing. Sublimated
camouflage fabrics are prone to heavy dye migration, making
them some of the worst fabrics for printing, so be cautious.
To avoid dye migration, use a low-bleed, low-cure underbase
ink or a low-cure additive. When printing on fabrics known
to bleed, try a special gray or black blocking ink specifically
formulated to absorb the dye. Gray or black blockers need to be
overprinted with white if other colors will be printed on top.
If you take care of your screen-printing tools and are consistent in your methods for coating screens, and checking mesh
tension and dryer temperature, etc., your prints will look better
and troubleshooting issues will be much easier.
Kieth Stevens is the Western regional sales manager for International Coatings.
He has been screen printing for over 39 years and teaching screen printing for
more than 12 years, is a regular contributor to International Coatings' blogs and
won SGIA's 2014 Golden Image Award. For more information, visit iccink.com
and read the company's blog at internationalcoatingsblog.com.
Table of Contents for the Digital Edition of Impressions - June 2018
Impressions - June 2018
From the Show Director
Scene at ISS
Big Things Come in Small Sizes
Accelerating the Art Department
Screen Printing Production
Screen Printing Technique
Impressions - June 2018 - Intro
Impressions - June 2018 - CT1
Impressions - June 2018 - CT2
Impressions - June 2018 - Impressions - June 2018
Impressions - June 2018 - Cover2
Impressions - June 2018 - 1
Impressions - June 2018 - 2
Impressions - June 2018 - 3
Impressions - June 2018 - 4
Impressions - June 2018 - 5
Impressions - June 2018 - First Impressions
Impressions - June 2018 - 7
Impressions - June 2018 - 8
Impressions - June 2018 - 9
Impressions - June 2018 - From the Show Director
Impressions - June 2018 - 11
Impressions - June 2018 - Overheard
Impressions - June 2018 - 13
Impressions - June 2018 - 14
Impressions - June 2018 - 15
Impressions - June 2018 - 15a
Impressions - June 2018 - 15b
Impressions - June 2018 - First Look
Impressions - June 2018 - Scene at ISS
Impressions - June 2018 - On Design
Impressions - June 2018 - 19
Impressions - June 2018 - Big Things Come in Small Sizes
Impressions - June 2018 - 21
Impressions - June 2018 - 22
Impressions - June 2018 - 23
Impressions - June 2018 - 24
Impressions - June 2018 - 25
Impressions - June 2018 - Screen Printing Production
Impressions - June 2018 - 27
Impressions - June 2018 - 28
Impressions - June 2018 - 29
Impressions - June 2018 - Shop Talk
Impressions - June 2018 - 31
Impressions - June 2018 - Embroidery Production
Impressions - June 2018 - 33
Impressions - June 2018 - 34
Impressions - June 2018 - 35
Impressions - June 2018 - 36
Impressions - June 2018 - 37
Impressions - June 2018 - 38
Impressions - June 2018 - Screen Printing Technique
Impressions - June 2018 - 40
Impressions - June 2018 - 41
Impressions - June 2018 - 42
Impressions - June 2018 - 43
Impressions - June 2018 - Sublimation
Impressions - June 2018 - 45
Impressions - June 2018 - 46
Impressions - June 2018 - Ad Index/Classifieds
Impressions - June 2018 - 48
Impressions - June 2018 - Cover3
Impressions - June 2018 - Cover4
Impressions - June 2018 - IO1
Impressions - June 2018 - IO2
Impressions - June 2018 - IO3
Impressions - June 2018 - IO4
Impressions - June 2018 - IO5
Impressions - June 2018 - IO6