[Jewelry making - Article 00960] - Re: [Orchid] Exotic alloys

[Peter W . Rowe]

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>        If there are no commercial sources, does anyone know where I
>     can find instructions for making this alloy?  Remember I am new to
>     alloying metal. 

    Without special equipment (induction or electric melt furnace able
    to pull a vacuum on the metal or shield it with inert gas), you can't
    practially make purple gold.  It's an 18K alloy of gold and aluminum.
     Melting it in the presence of oxygen, even traces, destroys the
    aluminum, and you get a lump of very porous and useless scrap for the
    refining bin.  Remember too, that this alloy behaves more like a
    lapidary material once you made it.  It's hard and very brittle, more
    like glass than metal.  You can't work it other than grinding it to
    shape and polishing it, and soldering to it (use a good active,
    probably fluoride flux)  It's properly called an "intermetallic", not
    actually an alloy, as it doesn't have the normal crystal structure
    associated with our normal jewelry metals.  But it is a lovely
    violet/purple color. 

    Blue golds I'm aware of are actually a steel grey color as their
    actual metal color.  The blue is a surface oxide, or patina, not the
    actual color of the alloy.  I don't know the formula.  All modern
    references to it I've seen treat the alloy, and the coloring process
    for it, as proprietary trade secrets of the producers.  Older books
    tell of a gold/iron alloy, in several karat qualities, referred to as
    blue gold.  The color is darker grey than white golds, and the
    references I've seen were to such alloys as used in multicolored
    victorian goldwork.  I'd assume that they call this blue in the same
    way they call a high silver/gold, or silver/cadmium/gold, alloy,
    green.  They're still yellow, but compared to standard yellow golds,
    they appear more greenish.  compared to standard white golds, a dark
    steely grey might seem more blueish, even if it isn't.  And a bit of
    heat color on it might well be actually blue, though again it's just a
    surface oxide.  I've never tried that, so don't know how well it
    works, but can attest that a torch melted sample of the gold/iron
    alloy (in any of several karats) produced a rather nasty cracky
    material usable only for small accent decorations, not for anything
    needing any structural strength.  This may well have been due to the
    primative melting methods I used, though.  Just a torch with a
    standard crucible. 

Hope that helps.
Peter Rowe

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