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In the shop I help out in sometimes, while I was taking dents out of one part of a sousaphone, someone else was removing a slide crook from the valve section and when he got it off it fell onto a microfiber cloth and burnt some of the microfiber off onto the crook. The "head-repairman" there is pretty new and does not know how to get it off. What would be the best way to remove the burnt microfiber while not damaging the slide crook? Its silver.

Once many substances are carbonized, there aren't really any solvents that dissolve them very effectively, and abrasive action is usually just about the only choice.

You can try soaking it n some petroleum product ( or natural product like olive oil) and see if that carbonized substance soaks up some goo, but I'm not being encouraging about that tack.

This is the same reason that if lacquer is going to be burned, it's easier to deal with if it is stripped from that area first chemically before being burned.