Let’s face it, exposure problems can be one of the most frustrating issues in the screen printing process.
Yet, like anything else in life, screen printing is just a series of events. When something goes wrong, you have to look at each stage to figure out the source of your issue. So, when it comes to exposure, let’s break it down into events:
You created the art. You outputted the film. You coated the screen. You exposed the screen with your film. You attempt to expose the screen and either nothing will rinse out, or emulsion that isn’t supposed to rinse away is. Your screen isn’t usable, and you need to know why.
Your troubleshooting will always start with your art. Was your film positive opaque enough? If you hold it up to a light, can you see light shining through the printed image? If so, then your film is NOT dark enough and will still expose during your exposure, just at a slower rate. This can lead to not being able to wash your image area out, no matter how much patience or water you use.
If your film positive is good and opaque, then you want to think about your screen next. Since coating your screen, is there any chance that your screen was exposed to light, or is your dark room environment very hot? Screens that have been accidentally exposed or subjected to excessive heat during a drying process can expose. You will want to take care not to keep your screen drying area to warm, and keep screens out of the way of any potential stray light.
Alright, so you’ve looked at your screen storage and everything is solid there. So, next you’ll think about your exposure time.
One thing that’s pretty easy to forget is that light sources weaken over time, especially black light units. To compensate for older bulbs, you would simply increase your exposure time by a little.
If you are unsure what exposure time to use, it is suggested to use a step wedge test. This involves dividing your screen into 4 sections, each exposed at different time using an exposure calculator. You can check out a video we did on this process here.
When you’re washing out, make sure you wet down both sides of the screen. If you wet down both sides, and then let the screen sit for a couple of minutes, that can help to soften the emulsion you need to rinse away. A good, easy sign of an unexposed screen is an excessive amount of “slime” on the squeegee side of the screen, the side that was NOT directly hit by the exposure light. Because this side was not directly exposed, it will usually be softer, but if it is very slimy you may be looking at an unexposed screen.
Exposure problems can be enough to make even the most seasoned veteran want to pull their hair out. Just back trace through your process until you find the problem, and figure out how it happened! And don’t forget, if you just can’t figure it out, you can always reach out to our Customer Success team by calling 800-314-6390 or emailing email@example.com, and we’ll be glad to help you out!