May '16

For the Business of Apparel Decorating

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2 0 1 6 M A Y P R I N T W E A R || 95 Thermal stability is the key to consistency and the peanut butter is so thick it will tend to have the same viscosity, tack level, surface tension, and fluid-momentum on press over a wide range of temperatures. Honey will drop in viscosity once the platens heat up during a longer press run, and bridging and matte-down will suffer until things cool off, at which point it will penetrate and be too slick to overprint. Suntan oil will behave much like the warm honey but worse. Bridging and matte-down occur only if and when the ink is printed at higher speeds, and higher speeds require low-tack ink. Shear-rate causes a shear-thinning ink to become nearly six times thinner. It whistles through the mesh, clings to the garment, and in as little as 0.5 mili-seconds recovers its body. The low viscosity covers the surface, its low tack leaves the fibers in place without "teasing" them into fibrilla- tion, low surface tension creates a smooth surface, and the elasticity keeps the ink on top, right where we want it. UNDERBASES White is the most logical color for an un- derbase. If we want a soft hand and bright colors concurrently, it must thereby remain over-printable despite how thick, opaque, or smooth the finish. Electron starved sub- strates have a surface which resists being printed upon while the secret to overprint- ing colors is to have more available electrons on the surface of the underbase. With a smooth, electron rich surface, even trans- parent blues and fluorescent overprinted colors will look good. Electron-starved underbases can be the downfall of traditional white plastisol inks. These cause color peaking and are likely to trigger build-up of the overprint col- ors. Peaking occurs when a color is nei- ther flashed nor last in the sequence, but stepped-on from subsequent screens. The overprinted ink is then rearranged into peaks, which barely increase the intensity of the color; and valleys, which immediately bleach-out the color. For example, with a reflex blue the peaks, which have stolen most of the ink, are still about the same color reflex, but the valleys they stole the ink from turn into dirty, powder blue. The reflex had more affinity for the subsequent screen than it did for the underbase. An ex- cellent underbase is electron rich so it will be far more receptive, even to the most deli- cate of overprint colors. APPLICATION In principle, a plastisol requires only two ingredients: a resin-based and a plasticizer- based liquid. When these two ingredients are mixed together, the plasticizer flows into the resin and then part of the plasticizer is absorbed by the resin. Like a saturated sponge, the swollen resin and the free plas- ticizer stay at equilibrium at room tempera- ture. At about 115 degrees F, the plasticizer thins until around 135 degrees F when it is sufficiently thinned so more of the plasti- cizer absorbed is in the gel state. Once gelled, the ink is now barely mal- The best case underbase is the one which has the thinnest de- posit, clears the mesh at lower pressure, and at maximum stroke- speed in order to bridge the T-shirt's knitted construction, and then mattes-down the fibers to produce a smooth surface for the countless halftone dots. (Image courtesy Denver Print House) TO ADVERTISE CONTACT DIANE GILBERT AT 800-669-0424, EXT. 297 DGILBERT@NBM.COM DISPLAY ADVERTISING The Marketplace Florida Flexible Products Emulsions Chemicals Adhesives Equipment Color Matching Training Classes Screen Printing Inks 305-512-2222

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