I occasionally re-melt a small quantity of 18K yellow scrap in a
crucible with some boric acid and paste flux and roll it to whatever
size I need at the time. These are pieces fresh from the refiner -
scrap cut off and too small to use. I am very careful about not
including scrap containing solder. I have sometimes found a pinkish
cast in the finished parts made of this scrap which looks a whole lot
like the firescale I’ve gotten on 14K (but never on 18K).
Can anyone tell me what I’m doing wrong?