Impressions - October/November 2020 - 43

faster than light colors. Be aware of this when curing ink on white
vs. black shirts, as the dryer's temperature may need to be adjusted
accordingly.
On the other hand, a gas dryer is not affected by color, as hot
air is impervious to color changes. Note that metallic, glitter and
reflective inks can take longer to cure due to their reflective nature,
regardless of whether you're using a gas or electric dryer.
Most electric dryers have infrared panels that generate temperatures between 900˚F and 1,100˚F, and are very heat intensive.The
heat affecting the garment is controlled either by the conveyor's
speed or by lifting or lowering the panels. A slower speed raises
the garment temperature, while a faster speed lowers it. Similarly,
the temperature can be lowered by raising the panel or increased
by lowering it.This method of controlling temperature works but
can cause headaches when trying to cure heat-sensitive fabrics.
For the most part, raising an IR panel and slowing the conveyor
speed is the better and more controllable method for controlling
electric dryer temperatures.Take time to assess which dryer type
is ideal for your shop and your current operations.
If you have outgrown your dryer and find yourself lowering
panels and speeding up the conveyor belt to match your production
speed or cure a larger print area, you may be taking unnecessary
risks.A higher temperature with less dwell time can cause the ink
film to be insufficiently cured.When it comes to curing, time is
your friend; don't rush the process.

24 hours.This waiting process is especially important when using
an adhesive catalyst, which will continue to catalyze for 24 hours
before becoming fully cured.
Testing is especially important for low-temperature curing
because there's always a high chance the ink is undercured.Therefore,
don't skip this important step.What comes off the dryer ultimately
is the screen printer's responsibility.
Kieth Stevens is the Western regional sales manager for International Coatings. He has been screen printing for more than 42 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. He can be reached at
kstevens@iccink.com. For more information, visit iccink.com and read the
company's blog at internationalcoatingsblog.com.

Dryer Profiling
How can you know your dryer's exact temperature? Don't just
go by what the settings indicate. Instead, always profile your dryer. Use a donut probe, which is a 3-inch plastic ring with small,
crisscrossed wires in the center.This device is placed on top of a
garment's printed area and attached to a hand-held device that
shows the temperature where the wires cross.The donut ring is
connected to a thin, 10- or 12-foot cable, allowing it to go through
the dryer and read the temperature in real time.
Most dryer settings differ from the actual temperature inside.
For instance, the left side may be hotter or colder than the right
side.As long as the actual variance is determined, if any, the dryer
can be adjusted and used with confidence. A donut probe is the
only device that can perform this type of profiling.
Temperature-measuring tape is available, but it only shows how
hot the tape gets, not necessarily the type of information necessary
to profile a dryer. Laser heat sensors, available at any hardware store,
can show the temperature of the garment's ink area as it exits the
dryer. However, it doesn't indicate the temperature inside the
dryer, which is an area that can't be reached by the laser's sensor.

Glitter or reflective inks can take longer to
cure due to their reflective nature.

Testing for Cured Ink
Always test printed shirts prior to a full production run. Undercured
ink tends to crack when stretched or come off when scratched.
Conduct a stretch test by holding the image with both hands about
1 inch apart and pull the fabric to 2 inches apart - assuming the
fabric or substrate can stretch.
For fabrics that don't stretch well, such as polyester sheath, nylon
or nonwoven polypropylene-type fabrics, conduct a simple scratch
test. Lay the garment on a firm table and scratch the cured image
with a fingernail about five times to see if any ink flakes off. If
none or very little ink comes off, then it has been correctly cured.
It also may be appropriate to conduct a wash test. Afterward,
check the print for cracks or missing ink. However, the best way
to confirm ink is cured is to wait at least overnight and as long as

Light or dark garment colors can affect
the temperature in electric dryers.
Image reproduced with permission from
David Edward Byrd.
OCT./NOV. 2020

P.43

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Impressions - October/November 2020

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