I just wanted to share two recent experiences in case they might be
helpful to someone else.
First, I soldered 14k wire with medium solder around that natural
pink sapphire from an earlier post, and maybe I just got lucky, but
the stone turned a dark greyish black color when hot but cooled
slowly in air, it returned to its rosy color. Still matched its unset
brothers. Perhaps because it was a natural color in the first place?
Second, I made some sterling pieces with karat gold accents - 14, 18
& 22K - using a boric acid coating. They consistently turned the
devilish faint pink in my nearly fresh pickle, so I tried the
hydrogen peroxide boosted solution so often recommended. On all-gold
pieces, it removed the pink tint. On the combined metal pieces, it
not only did not remove the pink from the gold, but it etched the
heck out of the silver, turning it a dead, matte black. When I
re-pickled it in the plain stuff & brass brushed, much but not all of
the black came off, but the surface texture was really rough and
dull. The pieces were in the peroxide solution for about 30 minutes
(yes, I know, too long) and now I have a new ‘design element’ to deal
with. So for me, it’s super pickle for gold-only pieces in the
future. I would switch to citric acid except I can’t find a health
food store that carries it in suburban Maryland. Plenty of
McDonald’s, even horses, but no citric acid. Go figure.