[Jewelry making - Article 00017] - Re: [Orchid] Peroxide & Vinegar

[Len and Judy Bjorkman]

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Dear Nanz,

>     getting a copper depletion plating on their brass. 

    This is a good discussion on the safety of this type of copper oxide
    removal. However, I think that the red material on the heated brass
    is not just copper but is cuprous oxide (which is also red in color).
    Yes, some of the zinc in brass may fume off at a lower temperature,
    but I find it difficult to believe that the resulting copper-enriched
    brass will not oxidize further, as heating continues. 

    The black layer on the outside of, say, soldered brass is probably
    cupric oxide (CuO) and the inner layer (red) is cuprous oxide
    (Cu2O). The former comes off in PhMinus (=sodium bisulfate or Sparex
    No. 2) and the latter comes off in the peroxide/PhMinus bright-dip
    solution (thanks so much to Bill, from Reactive Metals, for coming up
    with that replacement for nitric acid bright-dip!). 

    Are there other chemical opinions on this?

Judy Bjorkman
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