Symptom: Photo resist washes out slowly and ends up ruined before I can finish.
Check list for Successful Washout:
Test: Expose a strip of film with a film positive that is know to be good. Our Letralite kits comes with a sample sheet. Wash-out should occur in about 60 seconds.
Symptom: My photo resist will not wash-out at all.
Test: Wash-out an unexposed strip of photo resist. The film should wash clean in about 60 seconds. If the mask will not wash out it has been pre-exposed to ultraviolet light. If it passes this test look at other possible problems:
Symptoms: If you're exposure blanket is worn on the edges, loose or starting to tear, you are probably having trouble getting a consistent washout with your photo resist film. You may have even said to yourself, "This vellum worked just fine last week..." and spent some time checking your toner coverage or even trying a new vellum with a new sheet of film. You probably ended up with another sheet of un-even washed photo resist film and more frustration. Upon inspecting both sheets of mask, you may have noticed the areas where the film did no wash were slightly different from the first, proving that it could not be a vellum problem. At this point, most people call us thinking it's a film problem.
When a Letralite™ blanket is loose, it can not hold the photo resist film and your film tool (vellum, etc) against the clear cylinder tightly. Light is then able to seep between areas where there is no a tight contact between the two. It usually never happens in the same spot twice and is more prevalent when exposing larger sheets of resist.
Solution: Replace the black blanket. Your blanket should have 1/2" - 1" worth of tension to clip to the other side of the cylinder.
Hint: A good practice is to leave one side of the blanket unclipped when no in use to avoid loss of tension. It's also a good idea to check the clear cylinder to see if it is badly scratched and obstructs light. You might not get accurate exposures, particularly in areas where the scratches are the worst. Another thing to look for is discoloration of the cylinder - it could be defusing critical light for good exposure.
Disassembling the Letralite™ Exposure Unit: Disassemble the Letralite™ unit by unplugging and removing the end caps and bulb. Remove the two (2) screws from right and left sides of the unit. Remove the two (2) end identification stickers and find four (4) small screws. Remove only one (1) screw for the top and the corresponding screw on the bottom. Do the same to the other side and you will be able to separate the Letralite™ into two halves.