February '21

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5 4 G R A P H I C S P R O F E B R U A R Y 2 0 2 1 G R A P H I C S - P R O. C O M S I G N A G E & P R I N T I N G T H E D I G I T A L E Y E has taken hold over the past 70 years is the photo emulsion stencil. The original image can be drawn directly on a piece of clear acetate or more often than not cre- ated on a computer with graphics software and output to transparent film called a film positive (Figure 3). It is critical that the black areas on the film positive are opaque. The film positive is placed on an emulsion-coated screen. The screen is exposed to ultraviolet light in the nanometer spectrum range of 350- 420. The UV light passes through the clear areas of the film positive and hard- ens the emulsion through the process of polymerization. The areas masked by the black regions of the film positive are thor- oughly washed away with a water spray, leaving the uncoated areas of the screen for the ink to pass through during the printing process. Photographic emulsion screens can pro- duce minute detail. Multicolored photo- graphic images can be made when color- separated halftone screens are used as film positives. These screens can produce large runs as the emulsion is quite durable, and it's easy to output transparent overlays from any black and white image. USES Screen printing for certain applications is preferable to other printing methods such as dye-sublimation or inkjet print- ing because of its low cost and the abil- ity to print on many types of media and surfaces. Although textiles are the most common items that are screen printed, tens of thou- sands of other items—everything from clock faces to balloons, signage, and card- board boxes—are screen printed. Screen printing is even used for the ultra preci- sion printing of conductors and resistors on circuit boards. DIGITAL HYBRID Digital hybrid printing (DHP) combines analog screen printing and digital direct- to-garment inkjet printing. A DHP sys- tem consists of an automated screen press with a CMYK digital printer located on one of the print stations. Essentially, once the garment has run through each color station, an inkjet printer applies a printed image overlaid on the colors, in the form of a CMYK print. This technique allows for extreme speed and versatility in the printing of complex artwork. Figure 6. You see five channels each representing the four colors: cyan, magenta, yellow, and black, and the full color composite channel. Figure 7. Select Separations from the Color Handling menu. At the bottom of the screen, you see the Printing Marks area. Check the Corner Crop Marks and Registration Marks boxes. Be sure to check the Labels box so that the film will be labeled with the appropriate color.

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