[Jewelry making - Article 00058] - Re: [Orchid] Black Gold

[Peter W . Rowe]

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>       Fellow Orchidites! I have a technical question to pose you all.
>     Does anyone know of a good formula for Black Gold? Traditionally
>     the only alternative was from oxidization. Hydro Tetrachloride
>     giving the richest, deepest black. But this means has proven to be
>     too carcinogenic. 


    So far as I know, and I've been looking too, all the folks
    selling/producing "black gold" are using a surface coloration, not a
    true alloy color.  Some are more durable than others.  The most
    durable I know of (I think) is a silicon nitride coating.  It is, I
    think, a vapor deposition deposit (though I'm not sure) and for
    durability over most metals, is a multi step process requireing
    several under coats of different materials to provide a secure
    attachment to metal, as a direct coating straight on the gold isn't
    well compatible, and it comes off.  Rado watchs use it on some of
    their cases and watchbands.  It's an extremely hard material which
    resists abrasion, damage, scratching, etc. very well.  It can also be
    manufactured as a solid material, such as tube sections, which can be
    incorporated into jewelry, but as it's a hard brittle material, not
    malleable or ductile, one has to carefully consider how it's used. 
    Rado (again) also uses the solid machined material in some of their
    products.  Machining is only possible with diamond tools, as it is
    the equal of carbides (or harder), in hardness, I'm told. 

    The above, by the way, also applies to blue golds, that have also
    been described and sold now and then.  They're surface colors, either
    patinas or actual coatings.  The sole real exception to this that I
    know of is the aluminum/gold alloys which produce a lovely
    purple/violet color.  This is also a brittle material that can be
    shaped only really by grinding, same as a lapidary material, though
    it can be soldered, and I'd expect, welded (laser?). 

    Now, if anyone knows that I'm wrong, and can point me to a true
    black gold formula, PLEASE do so.  My boss is just itching to find
    such a thing too, and I'd get major brownie points were someone to
    point me in such a direction with success... 

    cheers 

Peter Rowe 

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