Getting the perfect burn on a screen sits quite high on my happy list. The feeling of satisfaction and elation I felt the first time I washed out a perfectly exposed stencil is what I want you to feel.
So let’s go over a few scenarios below of what you may be experiencing and their possible causes. Once done, head over to my foolproof (and free!) exposure calculator that will help you achieve burn perfection.
Scenario 1: The image appears, but it takes forever to wash off the unexposed area of emulsion. What does this mean? You have OVEREXPOSED the emulsion. Yep, it was sitting out in the sun (or in the exposure unit) for too long. This caused the emulsion to harden up.
Solution: Cut back on exposure time, or cut back on emulsion coats. Another probable problem could be that the image print isn’t opaque enough. This allowed UV rays to leak onto the emulsion. What to do? Double it up with another print or take a Sharpie and darken the entire image.
Scenario 2: The image appears to look great at first, but peels off while you’re spraying it down. What happened? You have UNDEREXPOSED the stencil and it’s all being washed away.
Solution: Yep, you’re right, increase exposure time. Or keep exposure time and lay on another coat of emulsion on either the print side or squeegee side.
Scenario 3:. The image appears to look great, but the fine lines along the image peels away. What does this mean? Once again, the opacity of the image isn’t dark enough.
Solution: Do as you would if you’ve underexposed the screen.
The key take-away of this article is to keep on testing. Screen exposure is one of (if not the) trickiest part of screen printing, but once you get all the variables of exposure time, opacity, and emulsion coat down you’ll notice how easy it is to get into the flow of things.