Light can be a photographer's best friend when it comes to capturing scenic panoramas. But when it comes to processing films in the darkroom, you should consider light to be your worst enemy! Make sure your lightproof your darkroom so that there is not a single light that can sneak up and ruin your photos.
Start by spotting all the places in your darkroom that light can go through easily, such as doors and windows. If you have windows, block the light out with two layers of heavy black garden plastics or rubble sacks. Once you have your windows closed up, go inside your darkroom and close the door. Let your eyes adjust to the darkness and have a look around.
You should be able to see some light leaking through the gaps around the door. For small cracks, close them up using felt draught exclusion strips. For wider gaps, you will need to nail down a strip of wood around the door. You can also use something lighter, such as a black plastic flap that you can overlap it to the edge of the door to prevent stray light.
If you want another layer of defense, hammer a nail into the top-left and top-right of the door frame and hang a curtain (preferably already with hoops) to cover the entire door for good measure.
Double check for light again once you have everything covered. Make sure it’s a sunny day outside so that you can spot all those tiny cracks of leaking sunlight.
Some suggestions for darkrooms is your bathroom, walk-in closet, extra storage room, etc. If you don’t have the space and you still want to develop your negatives, you can use a changing bag or a black out bag