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Through the Looking Glass

(May 2002) posted on Thu Jun 13, 2002

Learn how and why dirt affects exposure glass and how to keep it clean.

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By Mark A. Coudray

The screen department was one of the most grungy that I had ever seen, with a thick coating of old emulsion, ink, and who knows what else covering the floor. I was shocked--it was as if I had just been told that there was no Santa Claus! When I commented on the conditions, the screen technicians laughed. They replied that the gooey, sticky floor not only captured floating dust, but it actually prevented foreign material from entering the air. It was several more years before I saw my first sticky mats at the entrance to a cleanroom in another printing operation, a high-tech version of what I had already experienced in a less sophisticated form.


Controlling dust and contamination can be a full-time job. Oddly, the situation is the worst in brand new facilities, where everything is so new and shiny that nothing will stick to it. Add to this the fact that new construction generates huge amounts of dust and dirt ranging from drywall powder and sawdust to lint, carpet fiber, and you name it. All of this debris floats through the air looking for something to land on. In the screenroom, if this dust doesn't settle on our freshly emulsion-coated screens, you can bet it will find its way to the glass of our vacuum frames.


Fortunately, we can take several steps to minimize the amount of airborne contamination we have to deal with. We begin with the air handling. If we have air conditioning and heating ducts, we should install HEPA filters in the heating and cooling system. These filters are more expensive than conventional filters, but they will capture 99.99% of visible dirt. Almost anything sucked into the air returns will be filtered out, including outside dirt or duct dirt that may have become dislodged. The filters can be purchased from virtually any major home-improvement center or hardware store.


Filtration does not stop here, however. If we are using a box fan to create air movement in our coating area to aid in drying of screens, we should tape a 20 x 20-in. furnace filter to the intake side. This will trap most of the debris that is pulled through the fan, eliminating dirt that might otherwise become trapped in the wet emulsion on your screens or drift onto your exposure unit.



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