[Jewelry making - Article 00018] - Re: [Orchid] Raising fine silver to the surface

[James Binnion]

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>     Is there possibly another reason why my pieces are not tarnishing?
>     It actually doesn't matter to me that the fine silver isn't at the
>     surface, I'm just curious. It's a bonus that there's no tarnish,
>     but it's not necessary. I think the bottom of your email got cut
>     off! 

    I was trying to say that the castings can tarnish rapidly due to
    fine gas porosity but somehow cut it off when I sent it. When
    investment breaks down due to overheating sulfur dioxide is
    generated, this gas combines with the solidifying metal and causes
    one form of gas porosity. The sulfur dioxide can end up being one
    source of the sulfur that causes tarnish. Tarnish is a chemical
    reaction between sulfur (or sometimes chlorine) and silver. If there
    is a low amount of sulfur in the local environment then the silver
    will not tarnish very rapidly and higher amounts cause more rapid
    tarnishing. So you enameled pieces may not show signs of tarnish but
    the cast pieces may be "self tarnishing" due to high amounts of
    sulfur dioxide. It is really impossible to say why one of your pieces
    tarnishes and the other doesn't without a lot more information and
    analysis but all silver tarnishes when exposed to enough sulfur in
    its environment. 

Jim

James Binnion
jbin AT mokume-gane.com
James Binnion Metal Arts
http://www.mokume-gane.com
360-756-6550


 
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