Gold Filled wire turning dark in Tumbler
by Caitlin
(California)
When I put the gold filled rings into the tumbler they're bright and shiny out of the pickle. Then when I take them out they turn a dark gold/copper color... I only tumbled them for 45 minutes. It is gold filled wire- not plated. Any suggestions for what I should do or what I'm doing wrong?
Stacy's Answer:
Hi Caitlin!
The tumbling process itself will not turn yellow metal pink. But gold-filled wire and sheet are made using brass so I suspect your pickle is the culprit here.
When heated and pickled to remove firescale, brass gets coated with copper oxides while in the pickling solution turning the metal pink. (it might be clean and bright, but still pinkish) Tumble polishing will not remove this coating and might make it more obvious. Before tumbling, you want to first remove the copper oxides by soaking the metal is a Superpickle which is 3 parts white vinegar and 2 parts hydrogen peroxide for about 10-15 minutes until the oxides are lifted and the yellow metal is restored.
Superpickle will not remove firescale. You must pickle first. Long exposure of metal to the Superpickle solution will damage your metal, so don't forget about it and leave it in there! Watch the metal and remove any brownish areas that form on it by simply wiping them away. Rinse well with clean water and then tumble polish. As the solution works, it turns blue from the copper oxides just like your pickle.
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