I'm pretty new to the forum and really new to screen printing. I've been pretty lucky so far and have not run into too many issues, but this latest has really been stubborn.
What's been happening is that the middle of my screen is exposing great. I use an exposure guide and it's telling me I'm at the proper exposure and it washes out great with excellent detail. The problem is when it gets out to the outer edges of the screen near the frame, the image gets progressively overexposed until the outer 1" won't even wash out. I'm using an 18x24 230 screen and my design is about 14" wide.
I think I may know the answer to the problem, but I thought I might see what insight I could get here first. I've been using bricks to weigh down a piece of black foam core that I wedge into the squeegee side of the screen while exposing. I've been really careful about making sure my film is sandwiched flat so I've gone up to 12 bricks on the screen which I'm assuming is about 60lbs. My glass is pretty thick at 3/8", but I'm thinking this weight might be bending the glass. I can't see a bend, but I can't imagine how else I could be getting this extra exposure on the sides.
I'm going to try less weight tomorrow, but if anyone has any other ideas I could try it would be much appreciated.