[Jewelry making - Article 00989] - Re: [Orchid] Black Blobs in my Sterling

[Brian Adam]

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    It's solved ... it was my fault. 

    I talked to the jewellery casting company (a major precious metals
    supplier and casting house) and a man there analysed the blob
    material. I might have mis-heard but I thought he said it was a high
    proportion of copper (21.5%) in the form of cupric oxide (CuO).
    Possibly the result of uncontrolled heating during annealing. 

    That sounds right, as Ruth reminded me about what happened earlier
    in the day. I was batch-heating 5 of these rings using a stationary
    propane burner and sitting the rings on a tripod+mesh. I left them
    there for a short time leaving the gas on low! Ruth came by a while
    later to discover them, looking rather reddish. I was certain I'd
    turned the gas off! Now I'm rather pinkish with embarrassment. 

    Thanks for your replies. 

Brian

Brian Adam
Auckland NEW ZEALAND
www.adam.co.nz


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