[Jewelry making - Article 00609] - Re: [Orchid] First Argentium Sterling Adventure

[James Binnion]

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Trevor,

>     The more you heat AS --assuming you don't take it above dullest
>     red-- the more the germanium will migrate toward the surface and
>     react with oxygen, thereby "activating" your AS more and more. As
>     far as I've been able to tell the net effect of more heatings is
>     deeper and deeper penetration of the tarnish resistant "skin" on
>     the metal, to the point where stock 2mm or thinner will become
>     completely "activated" such that no part of the metal is untreated,
>     regardless of whether you cut and score it or not. As ever your
>     mileage may vary. 

    The germanium is not migrating anywhere near fast enough to act in
    the way you describe. What is happening is the oxygen is diffusing
    into the crystal matrix. Oxygen atoms are much smaller than the
    metal atoms so they can slip in-between the metal atoms in the matrix
    and easily diffuse deeply into the matrix. The metal atoms however
    move much more slowly as they must either slip into a void in the
    matrix or trade places with another atom or pair of atoms in the
    matrix. So for a metal atom to move even a tenth of a millimeter
    would take an inordinate amount of time. 

    Oxygen combines with the germanium and the silver. Silver will not
    form a stable oxide compound but the germanium does. So as the metal
    cools back down the silver releases any oxygen it has picked up but
    the germanium does not. Germanium has a much greater affinity for
    oxygen than the copper in the Argentium so it prevents the copper
    combining with or holding on to any oxygen. 

    I know it is a nitpick but I can't help it :-) 

Jim

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