How to tell if a darkroom is film safe?
My darkroom has a few light leaks, mainly around the door. I've proven it's safe for paper by putting a coin on paper, leaving it for 15 mins and then developing the paper. Nothing new in that.
I want to start loading my tanks in there, rather than using a changing bag. I know I need to improve my door seals (any suggestions welcomed BTW). However once I think I'm OK, how can I check it? Being a 35mm, roll film user doesn't seem to lend itself to the coin test, and would the coin test be valid for film anyway? So how does one check to see if a darkroom is film safe?
The right way to know: test it
Take some unexposed film, open it and let it hang out for about the time you expect it to be out when using film. Cover half of it and let the rest stay out for about as long again (2x total exposure). Process. Are the negs clear, or black?