Figuring out how to cure screen priting plastisol ink can be tricky. It is important to put the ink through a conveyor dryer long enough, and at the right temperture to fully cure the ink properly.
A Q&A about how to cure screen printing plastsiol inks
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 to cure Plastisol inks?
There is not a 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-cure.
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 220F to 230F (104C to 110C). 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?
You can use your flash unit to cure your inkbut 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 cure properly?
If your garments pass the wash test, then you definitely know your ink is cure properly. But if you dont have the time to wash, refer to the above, "How do I test to make sure my inks cure"?
How do I measure ink temperature?
There are 3 basic and easy-to-use temperature measurement devices you can use. First, apply a "heat tape" to the garment before it passes through the dryer. The tape will indicate the peak temperature of the garment within the dryer. Second, use an infrared "Ray-Gun" 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.?The results are surprising.