[Jewelry making - Article 00773] - Re: [Orchid] Black Blobs in my Sterling

[Franklin Cox]

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I think that Peter is on the right track.

    I too have cut open castings to discover included flux, investment
    and horrid porosity that was not very evident from the surface. 

    There is also a possibility that the casts have a great deal of
    internal porosity that sucks pickle into it when the ring is
    quenched. When heated it would bubble out as melted salts that make
    up the pickle. This would be black as it picked up oxides from the
    porosity. The streaky like spots under the claws may suggest a
    porosity. (by the way the photos are great, they are worth thousands
    of words) 

    If it is this type of porosity, I have seen something similar. It
    was sterling silver that was contaminated by lead and or tin. This
    metal did strange things. One was to increase it's porosity as it
    was reheated. Some of the metal melted before the rest leaving a
    sponge like structure of solid metal and molten metal. When cooled
    it was very porous. 

    In any case I feel that this metal in your cast is ruined. From the
    variety of spots I do not think that the contamination came from 
    you. I would ask the caster to recast using only new metal. You do
    not want part of that old button to be included in the new cast. 

    This should be done at no cost to you as a good customer service. Let
    us know how this plays out it will be interesting. 

Franklin


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