Screen exposure problems can be one of the most frustrating issues in the screen printing process. These videos cover most of the common issues with screen exposure. If you are having problems exposing your screen or with your image washing out, we highly recommend watching these videos that help troubleshoot screen exposure problems.
Exposure Time / Step-Wedge Test: Like anything else in life screen printing is a pragmatic series of events, you must look at it in each stage and determine the problem. After looking at the entire series of events youll find that art, screen, printing and troubleshooting will fall effortlessly in place.
Concerning the problem of exposure and washout let's break it down into events;
You created the art, output the film and had a screen coated.
You exposed the screen, attempted to wash out with no results.
Since youre early in the pre-press stages the answers to your problem are obvious and easy to repair, dont worry that you didnt recognize them as even the most seasoned printers overlook minor details.
The troubleshooting begins at youre art;
Was the positive opaque enough? (Could you see light through the film?)
If light is creeping through the black images of your film its NOT dark enough and will expose as the rest of the screen would, only slower.
How long has your screen been sitting and has it been exposed to any light before burning?
Screens that have been exposed OR subjected to excessive heat during drying will expose. Ive had screens ruined and exposed by keeping my screen box temperature too high. Screens that have been sitting over a couple of weeks and having the door opened and closed will pre-expose as well.
Is your exposure time long enough?
Over time light sources weaken, especially HUV (Black light) units and to compensate you increase your exposure time but make sure your positive is OPAQUE!
If you are unsure of an exposure time perform a Step-Wedge test, this involves dividing your screen into 4 sections and marking each with a specific exposure starting with the manufacturers then increasing in increments of 2 minutes per section.