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Quenching in vinegar water


Last week I spent an afternoon working with a friend in his shop
doing some foldforming on copper. He has had decades of experience
as a copper sheet metal worker and has fairly recently started
making things small. Anyway, the point is he is has lots of
experience with copper.

The way he quenches was interesting to me. He heats the metal slowly
with a gentle flame to the annealing point. He has a little jar of
vinegar water and holding the metal in a pliers quenches by pouring
the vinegar water over the hot metal. He then dumps the quench water
back into the little jar and proceeds to work the metal. The vinegar
water gets greener and greener as he uses it. He uses it a long
time. He gets some gorgeous complex patinas that seem to last.

My questions:

  1. Does the vinegar water (mild acid) have anything to do with the
    colors he is getting?
  2. Or is it the low heat, slow annealing process?
  3. Or is it a combo?

Thanks in advance for what I know will be good


Deborah Donaghue


The green (anhydrous) or greenish blue (hydrated) is copper acetate.
By pouring vinegar over the hot metal he s forming the acetate. If
he dipped it the color would not develop as well. The patina
formation is due to the vinegar not the heating method.