[Jewelry making - Article 01026] - Re: [Orchid] Casting small round bars

[David L. Huffman]

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>         One of the reasons that studio metalsmiths have problems with
>     casting ingots is that we work with ingots that are just too
>     small. 

    Hi James, and others . . . I agree, a small ingot is a lot harder to
    pull off than something larger. But frankly, I never had too much
    trouble with the process, and now I've got a solution that works even
    better and is very fast.  First, the way I used to do it: 

    I used one of those machined steel reversible ingot molds.  I'd wipe
    the inside of the mold down lightly with a little machine oil.  Then
    I'd hold it with pliers over my jewelers torch, lit with only the gas
    turned on and up high.  This would soot the mold and coat it with a
    fine layer of carbon. Then, handling this now quite warm mold
    gingerly with gloves, clamp it together.  Heat the outside of the
    mold from both sides until you see that oil start to smoke a little. 
    Must be around 4-500 degrees, I'd guess. Then, when it comes to
    metal, for gold alloys, I prefer Stuller's alloys, the ones
    formulated to make rolling stock.  Not so easy to hit that ingot mold
    when pouring from a dish crucible.  After it's cast, reduce it only
    slightly between annealing at first, and it doesn't hurt, as James
    says, to forge the ingot all over before any rolling.  But with this
    method, there really isn't any skin to remove that I've noticed,
    unless you're using some crappy gold that's been melted too often. 

    Now, the latest way I make ingots for rolling into sizing stock,
    wire or sheet is real simple.  I just get out my Delft sand casting
    kit, and using various shapes of "ingots" made from carving wax, I
    make a one-shot sand mold.  The hole which becomes the sprue, I've
    found, needs to be around 1/8 inch in diameter, and a brass tube of
    that diameter is great for pushing through the sand to make the hole.
     I then carve a sprue cavity big enough to hit easily when pouring
    from a melting dish crucible.  Whereas I have a 1/8 inch hole to pour
    into, on the other end of the ingot cavity is a vent hole of about
    1/16 inch.  Simple design, 1/8 inch sprue goes into one end of the
    ingot, 1/16 inch vent comes out the other.  Again, I'm using
    Stuller's alloys.  I get a nice, shiny clean ingot.  Rolling it down
    is a piece of cake. 

David L. Huffman


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