Im trying to burn a image 14 by 21 on a 23 by 31in scrren and every time i try it the egedes get all slimy and wash away while the middle is good?? Im having trouble figuring out why this is happening?? any ideas?
btw im using a 500 watt halogen light on a stand and expousing for 12:30 to 13:00 minutes.
What is the distance from your exposure light to your vacuum table? You may be too close. Measure the diagonal distance on your frame and move your exposure unit that distance from the glass. You may need to use an exposure calculator and test your time, etc.
I have a metal halide exposure unit, and I only expose for 20 seconds or less. I don't know how long halogen bulbs are used to expose, but 12 minutes seems a bit long.
this is what im using to expouse my screens. i dont have any problems with smaller images but the bigger images and bigger screens have been giving me problems
Try increasing the distance to the screen by raising the light. Your light source may have decreased over time and you may need to replace it with a new bulb.
It will be the distance from light source to the screen, buddy.
With my larger screens I usually end up disconnecting my halogen from the stand and literally stand there holding it in 4 different positions (ie: 4 quadrants of the design) to make sure that every corner of the screen gets burnt correctly. Think about the way that light travels - straight. Well, unless you've done a 10th grade Physics course, but let's not get into that. If you have a reflector that covers a certain range of degrees (pi/3 radians for those from said Physics course) area, it's safe to say that the light intensity hitting the middle of the screen is different to that hitting the edge of the screen. More photons = more chemical reactions = harder, better emulsion.
If it's fine in the middle and gooey at the outside, the outside hasn't exposed long enough. You can run the risk of overexposing the middle by leaving the light in the same position for a longer time, or move the light bulb to a better position so as to get even coverage across the entire design.
Ive used a 500 watt at a distance 32'' for 19 minutes. Coating the screen 1 coat on the non print side. I remember if I didnt expose it long enough it would get slimey,
and if the emulsion was too thick it wouldnt burn right. btw I was using speedball emulsion wich take longer to burn. I would also print on onion skin for the plates wich worked good as long as your not doing halftones. 160 and 110 mesh. I love the sound of the squeegie being pulled along the screen.
have fun.
-kage-
need help trouble expousing screen 
