I made some brass earrings. Cut them out of sheet, hammered them on
steel block, annealed a couple of times, and then put them into
pickle mixture of alum and water. Left them in for a couple of hours
and when I took them out they had some dark areas that I have to
clean off. I don’t get it? Can someone tell me what it could be. I
thought the pickle would have left the bras sparkly clean.