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Rich low Brass getting copper plated in tumbler


Hi Everyone,

I teach high school metals and the students are currently etching
rich low brass with radio shack etching mordant using PNP paper as a
resist. Once etched they are using Jax pewter black to patina the
brass. They are using steel wool to remove the patina from the high
spots and then we are puttingthem in a tumbler with steel shot and
rio super burnishing compound.

My question is that some of the pieces are coming out of the tumbler
with acopper coating on them. I know this happens if they go into
the pickle, however none of these pieces have gone in the pickle.

I would love your expertise in what I am doing wrong so that we can
preventthis in the future. Thanks so much for the forum and taking
time out of your busy days to help others.

Karen M. Gallagher
Art Teacher, BFA, M. ed