Bruce- Please tell me that you are soldering on diamonds not colored
stones. When soldering on diamonds we always coat with boric acid
and alcohol to protect the diamonds. Boric acid and denatured alcohol
is our go to fire coating. Both ingredients easily available and very
Do not ever put anything containing boric acid on any sapphires or
When heated the flux will adhere to the stone and when dissolved
after soldering leave the stones pockmarked. Trust me on this. I made
that mistake many many years ago and will never forget that lesson.
It was an expensive one. I’ve screwed up enough in this trade to
learn what mistakes to not make. I’m whatcha call “An Expert”.
Have fun and make lots of jewelry