I recall that several months ago there was some discussion about cleaning sanding belts and trying to get those "corns" out that sometimes form up in sandpaper when you sand soft or gummy stuff. Sometimes ya get a bit of wood sap that sticks to the paper when the temperature from sanding friction rises, as well. They sell the rubber chunks (looks like a piece of tan colored crepe rubber) for doing this at around $8 or $10 bucks a pop. One of you folks, I think it may have been @Davecam48, mentioned that cured silicone caulk might do the job, similar to the rubber belt cleaners. It seems like I'm always throwing away half-used tubes of caulking because they've hung around long enough to set up inside the tube before I have a chance to use them . Sure enough, I grabbed a tube of silicone caulk that's been sitting around half full for a year or so, and even though I'd plugged the end of the tube, it had hardened up on me. I recalled the idea we discussed, and cut the jacket of the tube off, and tried out the cured-out remains . . . The hardened up remains of the old silicone worked amazing well . .