I have used Edwal's NO-SCRATCH. It is a viscous liquid one paints on both sides of the negative. It is a bit tricky to work with. A too thick coat shows up as ghosty images on the print. Applied evenly, it seems to work well to save an otherwise nonsalvagable image. Unfortunately, you have to clean the negative afterwards. I use an organic type neg cleaner. I think the NO SCRATCH is pretty well sold at most places that carry processing supplies. Sam