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Removing brown flux stains on diamond


Fumes from gold paste solder flux apparently found their way deep
into a tubular diamond bangle I’m working on and deposited brown
stains on the pavilions of several melee about an inch from the
solder join. The stones closest to the heat were unaffected. Steam,
which has worked before, can’t quite get deep enough into the bangle
and ultrasonic did nothing except knock a few stones out (ofcourse it
couldn’t knock out the discolored ones, righti) The stones aren’t
burnt, just coated.

Is there a solvent that will work to remove these stainsi Tried
acetone and mineral spirits.


Try leaving in the pickle overnight, also try pickling in the
ultrasonic (in a Pyrex beaker!)


Hello there.

Why dont you just take the stones out and reset them after a good
salt rub.( that takes evrything off but stone has to be out.)



Hi Neil, Heat the diamonds to burn off this stain. It sounds drastic,
but is a common method in trade shops. Just don’t burn them. Use
borax or boric acid to stop the oxygen and you’ll be fine. About the
same heat as retipping.

Have fun. Tom Arnold


When this “staining” has happened to me, I have attributed it to
accumulated grime not totally removed in my pre-repair cleaning. This
is something that is difficult to avoid when the backs of the stones
are obscured. Short of removing the stones and scraping them off, a
clue to the solution is in your question. If the stones and
construction will allow for heating (apparently they will, or you
wouldn’t be in this mess) :slight_smile: What has worked for me is to apply
boric acid/alcohol fire coat as usual, but be sure an extra generous
amount gets to and on the backs of the affected stones. Then, with a
reducing flame, gently warm the area of discolored stones just to
the point the boric acid glasses and hold that temperature for a few
seconds. The metal need not be hot enough to glow at all, so most
solders will not flow at this temp. Allow the jewelry to cool, and
pickle normally. The boric acid seems to absorb the partly
carbonized grime and the whole mess devolves easily away in the
pickle. In most instances one treatment has been enough, rarely more
treatments, a higher temperature, or fluxing with Batters (or like)
has been required. If all else fails, and it sometimes does; remove
the stones, scrape them off, reset, and vow to clean longer before
using the torch next time.

Hope this helps,
David Lee


Try sulphuric acid. You can use a very diluted mixture reasonably
safely in the ultrasonic (in a plastic container). It will work.