I have used recently thick black bin bags, they are the type for garden refuse and are very thick. I stick it up with insulating tape (plastic window frames) as I have rather a lot of the tape so its what I use. It does the job but I would not use it for film. It is though a temporary set up otherwise I would go and make a wooden panel to fit in the widow recess.
Well, I happen to work in a bathroom with no windows to worry about. However, what I did for my door may be effective for your situation. I ended up using a spring tension shower rod to hang a blackout drape over the door. I think I paid about $20 total, $10 for each item. Then for a few more dollars, I got an inch diameter dowel that I cut to size and slipped into the bottom loop of the drape. It's cut so that the drap overlaps the entire door, but the part with the dowel can be wedged snugly into the frame. This keeps the drape nice and taut over the door, and ensures that the overlap doesn't go anywhere. It also pins the bottom to the floor to prevent a leak from under the door. I then picked up a roll of velcro and lined the frame where the door presses against it with the soft side of the velcro. It's easy enough to roll the drape up and secure it above the door when not in use.
You could just as easily run a lap of velcro around your window. Line an equal lap on a black out drape, and "stick" the drape to the wall over the window when you need to. Attaching a couple of dowels to wedge the drape into the window frame would help to create another corner for light to have to bend around.
Note: Those shower rods can be made much much shorter with a pipe cutter and a hack saw. Just cut equal lengths from the outside end of the inner rod, and the inside end of the outer rod. Then saw off any extra spring that protrudes when the rod is collapsed. A bit of gaffer tape is good for covering the edges to keep them from chewing holes in the drape...or a file if you've the patience.
The thing to remember is that light can't go round corners, except by reflection. how about a big sheet of MDF painted black on the outside and larger than your window. it could simply be held in place by battens and rotating wooden pegs screwed into the wall.
Thank you all so much for the tips. I was thinking that maybe a combination of board and cloth/tape would do it, but now I know it works, I can give it a go. I'm sure I can find all this stuff at the DIY store, even though I don't know what most of it is! Thanks again for the info.
Cut black foam core to block out 95% of the light. You'll still have some light leaking around the edges, but you can hang black drapes to finish the job.
Once you have it built and sealed as tight as you think is needed, get a caulking gun full of black roofing tar or other black sealant. Put a comfortable chair and a glass of ice tea or other preferred beverage in your darkroom. On a bright sunny day go in, having left all the lights on outside the room plus the sun on any outer surfaces. Sit in the chair. Sip on the tea. While away 5-10 minutes to allow your eyes to adjust fully to the dark. The older you are the longer it will take. Then carefully look around. Move around in the dark to spot holes that you might not see in the chair. Everywhere there is a bright spot you need to caulk.
I found this a wonderful way to cool off near the end of the building process. It may take more than one visit to accomplish what is needed. It will be well worth it every time you have undeveloped film out in the darkroom.
Dunelm Mill have blackout curtains - I bought a pair today for £25 for the door to a cupboard I'm using to load film holders and processing tanks. the size is 46" x 54" but there are others. My wife usually puts velcro on them and I just stick them round the door whilst I'm in there.
Yeah, I did that except with a roll of black gaffer's tape. I probably spent a half hour taping over pin holes in the paneling and covering outlets and junk. Now there are dozens of little pieces of gaff tape on the walls.
Originally Posted by jp80874
If you put a board in the window, just take a stick or a putty knife to pack foam insulation or strips of cloth in between the board and the window frame until you've filled in all the gaps.
here in florida, (hurricane territory), we have springy metal clips that hold plywood in a window. i use them for my darkroom. i have one window covered by a piece of exterior grade plywood and 4 clips hold it in place on the outside. voila, no light and the bright florida sun is shining on that window ALL day! no tape, foam caulking - light proof. they are easily removable but wouldn't recommend if it's something that you put up and remove frequently.
i had my stepson paint a mural on it, and looks great - works great - all happy.