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Screen Printing With A Flash Cure: Advice On Flashing Tee Shirts
Using a flash cure unit to simply flash cure between colors in screenprinting is challenging enough but it is even more difficult when you are using your flash cure unit to complete the final curing of plastisol inks printed on tee shirts. Here are some quick tips for dealing with flash cure units.
Make sure to understand your flash cure unit. They can use infrared panels or quartz bulbs to produce the heat used to cure plastisol inks and they will perform differently based on their specifications. This is most critical with quartz flash units as the bulbs may be of different spectrums and therefore perform differently when curing light or dark inks. Some quartz flash cure units are specifically designed to flash cure white inks only. Infrared units are probably going to be easier to use for the beginner.
The distance between the flash cure unit and the tee shirt on the pallet will be the determining factor in flash speed. Even if your flash cure unit has a thermostat, it is very important to get the distance of the unit to the pallet correct for the dwell time you want to work with. That means if you are a slow shirt loader and printer, your flash cure unit will probably be a little higher off the pallet allowing you more time to complete your part of the cycle. The closer the unit is to the pallet, the faster the flash cure will be and it also increases the risk of scorching or burning.
It will help out a lot if your flash cure unit is level and parallel to the tee shirt pallet. This will ensure consistent curing and reduce the possibility of scorching or burning at one edge or another. In the same respect make sure your garment is loaded properly and does not have any high points that will come in contact with or even just be closer to the flash cure unit. High points in the garment during flash curing will result in scorching or complete burning of the fabric.
Infrared flash cure units take some time to heat up much like an infrared oven dryer. It is a good idea to allow the unit to heat up prior to printing. It will also take some time for your pallets to build up some heat during printing and as they do, your flash times may be reduced noticibly. Remember, you don't want them to heat up too much because it will affect printing and possibly damage the pallet.
Wind or breezes of any kind near the flash cure unit may adversely affect the curing. Make sure there are no fans, coolers or window breezes near the flash station that will prevent the ink from curing properly.
It is best to try to get in the habit of swinging the flash cure unit's head away from pallets when you are not printing. Distractions during printing while using a flash cure unit may result in ruined product or damaged equipment. Wooden and pressboard pallets will warp and burn under excessive flash cure heat.
Overheating any type of pallet adhesive will cause the adhesive to become gooey and it will not perform properly. It may even cause the adhesive to be pulled off with the garment and result in a sticky, tacky layer on the inside of the shirt. This will most often wash out on the first wash in the laundry but it is an eyesore to the customer and requires an unnecessary explanation.
When printing a multi color job especially on a white under base, make sure you give the ink enough time to cool between flash curing. Many inks like high opacity formulas may have a tendency to stick to the back of another screen as you print the next color. Having cool down stations on a manual rotary tee shirt press will eliminate this problem.
Finally, if you are using a flash cure unit to complete the final cure of your printed garment, you would be well advised to have a temperature meter or "gun". Using a flash cure unit to cure larger print areas may be inconsistent. Using a temperature gun to verify your curing temperature of at least 320 degrees Fahrenheit will ensure you product will not wash out due to insufficient curing. A belt oven to cure screen printed garments is best and will provide the most consistent and reliable results. If you are planning to print any volume of tee shirts, a belt dryer is recommended.