June '15

For the Business of Apparel Decorating

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74 || P R I N T W E A R J U N E 2 0 1 5 run on hold. Flooding over the image and leaving it for a period of time causes more drying as more surface area is exposed to the air. If the operator is away from the press too long, the simple strike method may not work immediately. To save time, drench a rag with water and lightly wipe the under- side of the screen to loosen the dried ink, and then stroke the print until it clears the image. To prevent drying in the screen during extended breaks, wet the image as described and place a wet rag in the open area to keep inks hydrated. Upon returning, the job should strike clean after a few strokes. During a print run, the ink may begin to appear thicker or duller. This is an in- dication that water is evaporating from the ink. Simply spray a fine mist of water in the flooded ink behind the squeegee until the ink looks wet and glossy again. Water-based adhesive works well on cot- ton and cotton blends. When printing on wicking fabric, such as 100 percent poly- ester performance material, select a single adhesive and stay with it. Blending wa- ter-based and solvent spray may counter- act the adhesion of the fabric to the platen. Look for water-based adhesives that are specifically made to work with wicking materials. To prevent over-flashing, use warm plat- ens at 120 degrees F. Set up the job with 80 percent power on a quartz flash with three to four seconds of heat. Flash units should allow the ink surface to reach a temperature of about 200 degrees F. Add a cooling sta- tion to allow the print to cool between 160 degrees F and 180 degrees F before pro- ceeding to the next print head. Otherwise, a tacky ink or pickup may happen. Using flash units with good air flow improves the flash time and efficiency. The keys to curing water-based ink are reaching full evaporation of water and en- suring the proper temperature for ink to crosslink. For this reason, one-and-a-half to two minutes exposure in the oven is com- monly recommended, allowing the ink film to maintain 340 degrees F for one minute. WATER-BASED PRINTING Using minimal pres- sure on the squee- gee with a double stroke provides ex- cellent results.

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