[Jewelry making - Article 00007] - Re: [Orchid] Metal set-up time

[LEESSILVER]

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    I normally remove the flask from the vacuum pump immediately after
    pouring the metal.  The button is usually still molten when I remove
    the flask from the vacuum table. I let the flask cool for between 6
    to 15 minutes depending on the amount of metal poured. 

    On the first large castings I did I quenched too soon and had jagged
    holes in the casting.  I assume the holes were caused by metal that
    had not solidified and blew up when quenched.  I no longer have that
    problem when I let the large castings cool for 15 minutes. 

    Peter is correct.  The vacuum pulls air out of the mold.  It does
    not pull the metal into the mold.  Gravity pulls the metal into the
    mold.  I cast lar ge pieces of pottery.  I try to sprue the items so
    that gravity pulls the metal down against the design in the mold
    rather that have the metal forced upward into the design. 

    Button button who has the button.  I have seen small buttons shrink
    into the flask leaving a concave button with a hole in it.  I believe
    that indica tes that the metal in the sprue button may still be pulled
    into the mold before it freezes.  I would never pour a casting with
    having a substantial sprue button. 

    As I have always said the casting art is not consistent between
    casters. What works for one may not work for others.  Generalizations
    about casting without getting down into the nitty gritty of each cast
    may not give the best results on all castings. 

Lee Epperson

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