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Selecting the Right Glass for Exposure Units

(July 2007) posted on Fri Jul 06, 2007

Replacing glass is a part of life for those who use exposure units. Coudray examines the ways in which various types of glass affect exposure efficiency.

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By Mark A. Coudray

All screen printers, at one time or another, will have to replace the glass in their exposure units. The procedure appears rela¬tively straightforward on the surface, but beware: Selecting the wrong glass can add thousands of dollars of cost and lost time to your operation annually. This month, we’ll take a close look at all of the options available to you and identify the ones that can save you big dollars every year.

I recently had the unfortunate task of replacing the exposure glass in one of my shop’s 53 x 60-in. exposure frames. The surface of the glass was in good condition, but the glass failed structurally after a screen frame was carelessly crashed into the edge. The impact resulted in a half-dollar-sized flake chipping off. The operator taped off the area to keep anyone from getting cut on the sharp edge. But on the second exposure, the glass cracked all the way across the frame, necessitating replacement of the sheet. I had two questions right away. Could I avoid this kind of failure in the future and what kind of glass would I need as a replacement?

The frame’s manufacturer told me to simply go to the local glass dealer and get a piece of 3⁄8-in. plate glass because that is what they supply. I called the emulsion supplier, who said, “We don’t think it really matters what kind of glass you use.” I called the company that makes our exposure lamp, and they said, “Make sure you have optically clear, high-UV-transmission glass, but don’t use tempered glass.” By now I was thoroughly confused and began the task of researching which kind of glass I would actu¬ally need.


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