A while ago I tested my darkroom’s light tightness by sitting in it for a while with all the lights off, noting some leakage around the door and my blackout blind. I made a few adjustments at the door, creating a skirt out of blackout material that can quickly be velcroed to the bottom of the door and used some more of the material plus some more duct tape to improve the existing light trap around the top and sides. The door skirt takes seconds to install or remove and rolls up small enough to keep in a drawer when not in use.

I also discovered that with the window open a little, the door closed and the central fan system running, my blackout blind is pushed inward into the window opening slightly, forming a better seal. Good enough to block all outside light at night and in daytime covering most of the window with my big cardboard mat cutting sheet kills enough light to allow the blind to block the remainder of light in this way.

Indeed I was able to load a roll of Tri-X into my developing tank with early evening daylight outside with this setup a few days ago. I may still pick up another length of the blackout material or some kind of heavy felt cut to the exact size of the window interior and use velcro to allow it to be quickly installed; or cut a larger sheet of cardboard to the right size and simply insert it into the window opening. But I’ll be wanting the fan on and window opened a little for ventilation anyway, so I may not even need to do that for a while.

With those changes in place, I re-tested the room. The verdict?

It is pitch black. You are likely to be eaten by a grue.

Oh dear. I hope that safelight arrives soon or I’m in trouble. Now…uh…where was the door again…?