Screen Print Frequently Asked Questions
Temperature, Cure, Flash
At what temperature do your inks cure?
The short answer is when the entire ink film thickness reaches
its specified cure/fusion temperature. That temperature is provided
on your specific ink's product bulletin. Keep in mind that thicker
ink deposits (e.g., High Density) take more time to reach their
specified cure/fusion temperatures. Faster fusing or low cure
inks will reach their fusion or cure temperatures more quickly
than conventional inks.
How long does it take for your inks to cure?
There is nota single easy answer. Many factors play into how long it takes
to completely cure an ink. Are you using an electric dryer or a gas dryer?
Does the print have a thick ink deposit? Are you printing on T-shirts or
fleece? Measuring the ink temperature on the garment, as it passes through
the dryer, is the best way to determine the time it takes for your inks to
cure properly. Remember that it is important that the entire ink film
thickness reach the specified cure/fusion temperature.
How do I test to make sure my inks are cured?
A "Wash Test" is the best method. Take a sample print, cut it in half,
and wash it 3 to 5 times in a conventional washing machine with 3 pairs of
jeans or towels. Set the washer for 'Hot Wash/Cold Rinse'. Set the Dryer
for 'Cotton/High' and dry for 30 minutes. Complete 3 to 5 wash cycles and
compare the "washed" sample to the "unwashed" sample. If you see cracking
of the ink film or ink loss, your inks are likely under-cured.
What temperature and what length of time are needed for your inks to "flash" cure?
Most inks will "gel" (flash) when the ink film reaches 220°F to 230°F (104°C to 110°C). There
are 3 factors that affect the "gel" or "flash" of the ink: the temperature of the flash,
the distance of the flash from the printed image, and the time the printed image is
exposed to the heat. As a rule, you want to flash the ink film until it is just
"dry to the touch". Over-flashing inks can cause inter-coat adhesion problems
and make the inks very "tacky". Check your flash cure unit to see if it has
temperature and airflow controls. These can help you better control your flash
cure process.
What happens if I don't cure the ink properly?
Many things, none of them good! Typical problems that arise from improperly
cured inks include: ink washing off the garments, cracking of the ink film,
loss of color, and bleeding of the garment color(s) into the ink film.
Why do I need to "flash"?
There are several reasons. Flashing enables you to print one coat of
ink on top of another - e.g., a color on a white base. You also might
flash an ink to keep wet ink off the back of your screens. Some inks,
such as glitters, metallics and high densities, are not designed to
be printed "wet-on wet". They should be "flashed" when printing in
sequence.
Can I cure my inks with a flash cure unit?
We do not recommend it! Although it is true you might be able to
get the ink hot enough, a flash cure unit is not a good substitute
for a properly operating dryer. Using just a flash cure, you could
easily overheat the film surface yet under-cure the rest of your
ink film, at the same time! Not a good idea - don't do it!
How do I know if my inks are cured properly?
Your printed garments pass the wash test! (See above - "How do I test to make sure my inks are cured")
How do I measure ink temperature?
There are 3 basic and easy-to-use temperature measurement devices you
can use. First, a "heat tape" can be applied to the garment before it
passes through the dryer. The tape will indicate the peak temperature of
the garment within the dryer. Second, an infrared "Ray-Gun" can be used
to measure the surface temperature of a printed garment as it exits the
dryer. All you have to do is point the gun at the garment as it comes
out of the dryer. And third, a "Thermo-Probe" can be placed in the "wet"
ink film or on the garment to measure real-time temperatures as it passes
through the dryer. Recording those temperatures at say, five second intervals,
will give you a good profile on how well your dryer is working. You may be
surprised with the results.
