What camera ? I've restored a few sets of bellows over the years.It appears after testing the bellows at night with a flashlight that the source is there. Quite porous. Usage in bright sun in the last couple of months must have worn the material which was already fading. If someone can suggest a UK fitter of new bellows that would be fantastic and in the meantime would placing a cloth over the top suffice? Thanks.
I asked because I can often repair some types of bellows. I used to be able to get some thin black light proof repair tape (black or brown) I think it was repackaged 3M tape which is only available in a large quantity and is very expensive, it was great for repairs to bellows like the Toyo ones or Graflex Crow/Speed and Super Graphics and the repair is permanent and almost invisible.Toyo 45A mark 2. The bellows were initially fine at first, at least with the 180 lens. Problems occurred with the 300mm which may be down to extending the bellows and thus revealing issues. Usage in bright sun in the last month may have caused faster deterioration.