Find any old-school screen printer who has been around the block a few times and a large percentage of them will likely tell you 'just get your dryer good and hot - we never touch the temperature, we just speed the belt up or slow it down'. Well, if you are printing pretty much the same shirts and same inks over and over and over, this technique may work. For the rest of us, we might want a more scientific and researched method of curing.
At one of our recent How To Screen Print classes an industry rep from Rutland Group (manufacturer of Rutland, Union, and QCM ink lines) had a question on general guidelines on dryer temperature. His answer was, of course, that there was no set number, temperature, or belt speed. However, for most general purpose inks he recommended a temperature of 320 degrees for 60 seconds. This number was supported by research from their own chemists and R&D department. The problem comes with the vastly different quality of substrates and screen printing equipment that you use.
When your screen printing dryer is running and set to a temperature of around 300, running many shirts through quickly can dissipate the heat and make it difficult for your dryer to maintain a consistent temperature. Spacing your shirts out and running a slower belt speed can help maintain a constant temperature.
The next logical question may be 'what about polyester substrates and polyester inks?' Indeed, high heat can be the enemy of polyester material, as at a temperature usually required for standard plastisol inks, polyester material will tend to release the actual dyes in the shirt and cause dye migration issues. Well, one of the big innovations happening in the screen printing industry right now is the introduction of silicone screen printing ink. These are a brand new type of ink that are sold and fully supported by Texsource that are formulated to cure at a lower temperature than most polyester materials will typically release their dye at. Recommended curing temperature for silicone inks are in the 260-280 degree range. Silicone inks also offer the advantage of being extremely elastic, making them perfect for athletic wear.
dye migration issues that typically plague polyester materials and inks can be remedied by using new Silicone screen printing inks.
What about substrates that are not designed to be heated to the temperature required for a certain type of ink? What about plastics, nylons, or other materials that might melt, burn, or otherwise be damaged by such heat exposure? For those materials, Texsource recommends using an Air Dry Ink such as those from ColorFX. Air Dry Inks, as the name implies, does not require heat to cure, and has excellent adhesion to a variety of materials including plastics, woods, glass, and metals. An exact list of supported materials can be found on the subsequent product pages for those inks. They offer an excellent alternative to standard screen printing inks when heat curing may not be advised.
All of the screen printing inks that Texsource sells typically include a product spec sheet located on their product page. This sheet can offer help with topics such as curing, mesh count, additives, application, and more. Following the manufacturer specified guidelines is always the most important advice, but hopefully some of these tips will be able to stay in your memory and help as well.