A flash dryer is a useful tool that can be used in various ways, especially in small shops. While curing with a flash dryer may take some experience to perfect, it is an alternative method of curing prints without a conveyor dryer. There are several steps to follow to properly cure garments with a flash dryer. Let's go over them.
Before diving in, it's good to know that plastisol ink can be cured with any flash dryer. Water-based ink is a bit more complex. Since the water needs to evaporate before the pigment can cure, you could either use a forced air flash or mix a low-cure additive into the ink to help it chemically cure.
First, it is essential to have a tool to measure the temperature of the ink as it cures. Options include a temp gun or a donut probe. A laser temp gun provides a reflective reading while a donut probe provides a more stable reading throughout the job.
Additionally, using the proper size flash unit for the job is important. For most jobs, a 16x16 or 18x18 flash will suffice. A larger flash unit will result in a bigger area of heat on the platen, leading to a more even cure. For larger or oversized prints, a larger flash dryer may be necessary.
PREPARING FOR PRODUCTION
To ensure a full cure, the ink layer must reach the cure temperature (cure temp can be found on the ink container). Keeping the space warm, between 70-80°F, can eliminate potential issues. Airflow should also be minimized to ensure consistent cure times. Shut any doors or windows and turn off any fans.
When curing with a flash dryer, the platens are also important. Starting with warmer platens is best because it’ll help heat reach the bottom of the ink layer. Do note that aluminum platens won’t warp over time as wood platens may. If using a one-station screen printing press, a separate curing station should be set up to avoid warping platens with constant heat.
CURING WITH A FLASH UNIT
When ready to cure, make sure the flash and platens are at the proper temperature and position the flash 2-3 inches above the platen. Test to find the best flash height to cure the garment without causing damage. To cure, lift the shirt off the platen and lay it on top, allowing heat to penetrate through the ink layer. Then, swivel the flash over the shirt.
It is important to keep the platen under the flash dryer until the ink layer is fully cured, which typically takes around 30-40 seconds. The power of the flash and the distance between the flash and the shirt will affect the curing speed, so it is important to test before beginning production. Once the ink reaches cure temperature, allow it to cool down before performing a stretch test.
The stretch test is a simple way to check the curing process. Gently stretch the cooled ink, being mindful not to pull too hard and cause the ink layer to split. If the ink cracks or appears dry and cracked, it is likely not fully cured. In that case, you may need to extend the curing time for future shirts. If the ink splits evenly, it may be an indication that the shirt was stretched too far.
After the stretch test, perform a wash test by washing the garment 3-5 times and inspecting it each time. Repeat testing until you are satisfied with the results. Once you find the optimal cure time and other variables, make note of it for consistency during production. While it may take some practice, using a flash dryer can effectively cure garments without a conveyor dryer.