[Jewelry making - Article 00024] - Re: [Orchid] White Gold - needs some plaining

[David L. Huffman]

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Hi All;

>     Is there any great problem casting palladium white gold? Any
>     favorite alloys? 

    I need to interject here. Casting palladium gold alloys does require
    some specific considerations. First, standard investment is not
    advised. The palladium alloys have a much higher melting point, and
    the mold needs to be hotter. With conventional, crsytobalite based
    investments, this causes the sulfur in the investment to react with
    the surface of the metal, which gives you tiny cross hatched patterns
    of sulfides on the surface of your casting. This can be ground away,
    if your design alloys you to access all surfaces. Nonetheless, this
    produces a less than satisfactory casting. You should use the same
    type of investment used for platinum, or some of the new ones
    formulated for palladium alloys. Also, to cast at the lowest
    possible temperature, which is the best way to avoid porosity, you'll
    need a heavier sprue system to get the metal into the cavity faster.
    Finally, these alloys tend to absorb carbon, which contaminates the
    metal, therefore, melting in an electric melter with a carbon
    crucible is not preferred. Best to melt with a torch, using a neutral
    flame. And avoid hydrogen torches, because of the tendency to
    hydrogen embrittlement. One caveat to this information. I am not as
    expert at casting as some of our posters, so I'll defer to their
    expertise if they offer it. 

David L. Huffman

 
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