Awards & Engraving

August '18

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90 • A&E THE GUIDE 2018 by a black area in the artwork, the emulsion will have stayed water soluble, while all the areas exposed to the ultraviolet light will have hardened and be less soluble. In the washout process, the areas under the black will wash away, creating the image to be blasted. This is the procedure with any of the water washout films on the market. Since the material is wet after the washout, it has to be dried. You could do this by hanging the sheet up to dry, but for production, it is best to use a dryer, which keeps a constant temperature and allows you to dry at least four full sheets at a time within a predictable time period. The sheets need to reach a drying point where there are no more moist/milky spots in the material. At that stage, the sheet can be adhered to a sheet of silicon release paper for future use. Most washout films on the market are either purple or blue. Should you decide on the dry-processed film, which is the only green film on the market, then the whole washout and drying fall by the wayside. The exposure process stays the same, even though it is quite a bit longer (1 1/2 to 2 minutes, compared to 20 to 40 seconds with the water washout material). However, there are a couple of other noteworthy differences when com- pared to the washout films. First, the printed image from your com- puter has to be a negative, meaning whatever appears as a white area in your artwork will expose and blast. This means, if you use both types of film or you started with a washout film and then decided to switch, the artwork is not interchangeable. Second, you cannot produce stencils ahead of your blasting time because this material cannot be stored. The stencils are viable within a 24-hour time period; in other words, you need to keep these qualities in mind before choosing your resist. The dry-processing resist, called Rapid- Mask, comes in two thicknesses: 2 mil and 4 mil. For regular black-and-white artwork, A larger, flatbed exposure unit that uses a different type of light source: mercury vapor lights. These units can accommodate up to four full sheets of photoresist and have a vacuum frame built in. Of course, it comes at a higher price tag (around $3,000), but if you do high production, it's well worth it. Putting the printed artwork together with the emulsion side of the film. Washing out an exposed photoresist film. The dryer most commonly used to dry washed-out film sheets.

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