I've been processing a lot of film lately but I don't have a darkroom. Instead I use a "changing bag," i.e., late at night I turn off all the lights and then crawl into my sleeping bag backwards with my feel sticking out the top. It works for loading reels into my tank, but for making prints I need a darkroom. It appears I need to use my shop for a darkroom but there are a lot of problems with doing that. Among these is the fact that I have four computers along the far wall and the monitors glow for quite a while after they have been turned off. Also, one of the computers has a light in the back which continues to glow quite brightly after it has been turned off, even if I pull the plug. I have no idea why. There's also a window along one wall. I'm thinking that a solution to this is to hang a curtain in front of the computers. After turning off the computers I can draw the curtain in front of them. My problem is that I cannot find a cloth in the cloth shops that is truly opaque. Even the black cloths pass light. So what kind of cloth do they make changing bags out of and where can I get a big sheet of it?