[Jewelry making - Article 00132] - Re: [Orchid] Sand Casting Advice

[Noel]

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>     I'm interested in doing things more like casting a medal in
>     bronze, gold or silver, but with provisions for mounting stones. I
>     seem to have gotten a lot of negative responses about the idea. 

    I have had a lot of good results with sand casting, but I use it
    almost exclusively for things like twigs, where it doesn't matter
    much if there's a bit of porosity or flashing. However, I had a
    student use it to reproduce a three-dimensional silver fish pendant
    (which would be much like a medal, in terms of detail), with
    excellent results-- though it took her several tries to get it
    perfect. The good news is, it is pretty fast, and the original is
    undamaged, so you can keep trying. 

    As far as tips and tricks, here's what I can think of: It helps to
    pre-heat the sand mold in an oven to maybe 350-400 degrees, to help
    reduce the likelihood of incomplete fill. You can't go hotter than
    that without burning the binder in the sand. 

    It helps to hammer the sand in *really* hard, to get good detail and
    no flashing. It also helps to put vents at the far end of the
    object-- just scratch them into the sand while you have the two
    halves separated. Curve them back around toward the top, then out to
    the edge, as the metal doesn't like to flow back the other way, but
    air doesn't mind. 

    It is important to pay very close attention to how the sand meets
    the model in the bottom half; if there is any gap around the model,
    the sand in the top half will fill it, but this produces tiny, thin
    sections of sand that tend to break off when the halves are
    separated to remove the model, causing lumps of metal where they
    were. 

    Be sure you sweep away all loose crumbs of sand before you put the
    mold back together, so they don't end up in the casting. 

    Lastly, I have actually put a sandcasting mold in the centrifugal
    casting machine and cast it, with no problems, though I always
    expect the sand to fly out (it never has). Even though it has
    worked, it makes me nervous, so I don't generally do it, and I can't
    promise that it is a good idea. I guess you could clamp a sheet of
    metal on each side of the frame so you wouldn't have to worry. 

    Sure, it is not the ideal way to cast-- that would be lost wax-- but
    it is quick and easy, and you get to keep your original. There's
    something to be said for immediate gratification. 

Noel
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