Coudray identifies environmental factors and processing concerns that you need to control in order to produce reliable, high-quality printing screens.
The shop environment’s influence on the quality and usefulness of coated screens only intensifies if the light in the coating area is not controlled; however, I believe that most screen printers understand the fact that light exposes screens. Whether it’s coming in from an open doorway or a poorly filtered source, uncontrolled light affects even the best-prepared screens. But this isn’t the problem. The issue is the quality of the light present in the area.
There are two steps you should take to regain control. First, all fluorescent bulbs should be gold or yellow in color. Second, these bulbs should be encased with gold or yellow UV sleeves. This may seem like overkill, but there is a good reason to take this extra precaution. These sleeves--available from graphic-arts suppliers--do a very good job of sealing the ends of the bulbs and filtering out any stray UV light. Simply having a colored tube is not good enough, because the internal coatings do not hold up that well. It is very common for the ends of these tubes to leak unfiltered light. The amount of yellow coating on the bulb overpowers your eye and prevents you from detecting any leakage from the length of the bulb. This is where the sleeves come in.
The sleeves have special UV inhibitors built into the plastic, usually polycarbonate, and they have end caps that completely enclose the fluorescent tubes. There also is an added safety advantage to the sleeves. Polycarbonate is a very tough plastic, so it takes a great deal of force to damage it. If you accidentally hit a bulb and break it, the sleeve will retain the broken glass. The sleeves cost between $10-20, but the good news is they never wear out.
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