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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

Dirt is constantly being walked into the screen-exposure area. It is on our shoes, clothes, skin, and hair, not to mention on frames that have just been stretched or reclaimed. Sweeping the floor is not the best approach for maintaining cleanliness while screenmaking activities are going on, since sweeping just agitates and throws the dirt back into the air. For cleaning during production times, it's better to use a wet mop. I recommend keeping a mop and mop bucket in the exposure area and using it to do a quick damp mop of the floor 2-3 times per day. This will eliminate almost all of the dirt that is on the floor and keep it away from critical areas. A good habit to get in is to quickly mop whenever a screen is being exposed.


You can also use quick wipes made for cleaning floors. Several brands are available and they are useful for picking up loose dirt, hair, and dust. In the beginning, controlling dirt and dust is a big job. But by applying regular cleaning practices, the work will diminish over time.


Some amount of dust will inevitably find its way to our exposure units regardless of the precautions we take. So to avoid the risk of stencil problems due to dust, we must clean the surface of the vacuum-table glass before every exposure. In the long run, this approach will have the least impact in terms of time required and the greatest impact on stencil quality.


Among other benefits, cleaning the glass before every exposure will prevent dirt, adhesive, and emulsion from building up and hardening (emulsion and adhesive will harden on exposure to UV). The process I use involves three easy steps. First, use a razor blade to gently scrape off anything that is big and stuck, including emulsion, tape, dried ink, wet ink, and frame adhesive. The second step is to use film cleaner to dissolve anything stuck to the surface that is solvent soluble. Finally, apply a quick shot of high-grade window cleaner to remove any remaining streaks or dirt missed in the first two passes. This whole sequence should take no longer than about two minutes.



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