Back by popular demand, the noted trainer and consultant Charlie Taublieb shares his secrets for HD success.
In all types of HD printing, use soft squeegees with minimal pressure. I like to use a 55/90/55 triple durometer squeegee whether printing on an automatic or manual press. Use a deep squeegee angle and just enough pressure to clear the screen. One stroke is best, as a second one can cause the ink to spread under the screen and smear, ruining the effect. You can get a wonderful textured look in your print by using a wallpaper brush instead of a squeegee and cutting the bristles down (see Figure 4). This is easiest when printing by hand, of course, but you can also trim the handle in addition to the bristles and then clamp the brush into the squeegee holder to print on an automatic. Figure 5 shows a close-up shot of a print with a silver gel onto an HD black ink that was done using this technique.
FIGURE 5. In this print, silver gel was printed on top of an HD ink using a wallpaper brush to create the textured effect.
Some HD inks are very thick when printed, but surprisingly, they flash fairly quickly, not unlike standard plastisol inks. I prefer using an IR flash unit when printing manually and a quartz unit on an automatic. The temperature needed to fully cure HD inks ranges from 325-380 degrees F through the entire ink layer. Because of the thickness of the ink deposit, in addition to raising the temperature, you’ll need to slow down the conveyor of your curing unit as well to get enough heat through the print to fuse the ink.
Remember what I mentioned earlier about the different finishes of HD inks and gels after curing. Inks should have a matte finish with sharp edges. If they are glossy after curing, chances are the temperature was too high. Gels, on the other hand, should have a glossy finish with rounded edges when they are fully cured. If they are undercured, they will look just like an HD ink, with a matte finish and sharp edges.
HD special effects require a lot of heat, so white shirts may not be the best choice for this work as they could easily scorch. Dark-colored shirts are definitely more forgiving. Performance fabrics and other heat-sensitive materials are also not the best fit for HD effects. When printing a lot of complex layers, use a hand-held heat gun to carefully gel the inks as a flash may get too hot in one area and cause a problem.
This shirt features a four-color print using three HD inks and a color blend. The print was built up gradually, with about 15 layers of each color. Note how sharp the edges of the print remained despite the ink thickness and multiple passes.
Most of the shirts for this article were done by European T-Shirt Factory, Istanbul, Turkey, a very capable, high-volume producer of printed apparel. (The shirts illustrating effects with gel inks and foil were done during a workshop.) These shirts were created for technical printing competitions and were designed to test the limits of HD technology, not to produce wearable garments. But the company does a lot of production work with HD effects as well, and these award-winning shirts suggest what this technology is capable of with a little creativity. With experience, I’m sure you’ll grow to love HD inks for special-effects work as much as I do.
Read more from Screen Printing's August/September 2017 edition.
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