DIY Hasselblad film back light seals, how?

How easy is it to make your own light seals for a Hasselblad a12 film back? Can you just use an exposed and developed piece of 35mm film and some foam ? On some original Hasselblad film seals there is also a curved piece of foil strip that's acts as a spring, is the foil strip necessary or can you get away with foam for the spring and a piece of film for the light seal? Is it best to store empty film backs with the dark slide out to prevent the foam from becoming compressed ? Do you wait for your negatives to show light leaks or do you change the seals annually or say after 100 rolls of film?

There are several parts of the light seal. There is the foam - with or without the rigid "springy" backing. There is the opaque plastic that's folded over - I would not use film for that but I guess it could work in a pinch. And there is a strip of felt opposite that. All of that should be replaced. I bought two different light seal kits. The first was on ebay from some Chinese seller that provided everything. The second was from the guy who, online, says he has sold 40000 of them (or some such number) and he did not provide the felt. Not replacing the felt is a mistake.

I pulled the springy backing strip from the old light seal (cleaned all the crushed foam off) and put it on the new foam (came without that strip). The Chinese kit came with that strip adhered to the foam.

One of those kits is about the cost of two rolls of film. I don't think it's worth messing with exposed film or other makeshift materials.

I believe the folded plastic piece is made of mylar which shouldn't be hard to replicate if you have the pattern. The original foam strip that goes inside the folded piece has a foil backing. The foil is not strictly necessary. Check here:


I've also read that you can store the back without the dark slide to prolong the life of the seal. Makes sense.

Also noteworthy is that the folded piece may be completely intact when you open the back, with the foam totally compressed.

Back when I needed a seal for one of my backs, I gave up on trying to figure out which ebay seller had a reliable kit, and called Hasselblad. Their price was only a few dollars more than the ebay kits, and no worries as to whether it had all the right stuff.
But Hasselblad 2024 is not the same co as Hasselblad 20-whenever. So that may not be a solution any more, but it may be worth contacting them.

Internet lore says to store the backs without a slide inserted, I’ve never done that, except for whatever back is on the camera, and it’s not been an identifiable problem for me. I’d rather risk the seal’s longevity than get dust in the back. YMMV.
As for how often to change it, If you aren’t changing backs constantly, I’d wait until a back shows a problem. That does risk some pictures though.