noneOne way of removing soft solder from gold that I have tried and
works well is to use perchloride of iron. Dissolve 1 oz. of crocus
powder (jeweller’s polishing material) in 8 oz. hydrochloric acid. To
use, mix 1 oz. of this solution with 4 oz. boiling water. (see ‘The
Gold and Silversmith’s Handbook’, by Staton Abbey.) It helps to
remove as much solder as possible with a graver beforehand. When
dealing with acids though, please be careful and take all sensible
precautions. I haven’t tried this with silver, so test it first. If
it works, it should remove pewter as well as soft solder.
David Kelsall (UK)