In the recent posts on bellows repair and maintenance, I haven't seen anyone men tion the liquid "Bellows Patch Sealer" sold by Bostick & Sullivan (perhaps becau se it's a relatively new product?). I just tried it with good success on an old er Arca-Swiss bellows. The compound is thick and gray-ish (though it dries blac k). I decided to touch-up all the areas where three folds intersect (all my lig ht leaks were in such intersections).

I applied four coats, letting each dry a few hours, then I let the whole bellows dry another 24 hours to be safe. The results were pretty impressive -- the lig ht leaks disappeared, and the bellows remained flexible. I only did this last w eek, and so I can't speak about long-term wear. But it sure beats paying for a new bellows.