[Jewelry making - Article 00973] - Re: [Orchid] Conditioning Crucible

[John A. Henkel]

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    Hello Sandra, Dave & All, When coating your crucible it is
    unnecessary to melt a bunch of Boraxo and swirl it around to coat the
    surface. While it does coat the surface you can also use too much and
    have it carry through with the molten metal. This doesn't happen all
    the time but it does happen. If your borax is sluggish when you're
    trying to coat your crucible it may indicate that your torch is not
    hot/large enough. Try this procedure with a new or newly cleaned
    crucible: Set your crucible up, nipple down, supported by two pieces
    of fire brick on a fire proof surface. Have some borax handy in a
    saucer or small bowl within reach, not just the box. Use powered
    ventilation like an exhaust fan or a fan at your side blowing the
    fumes away. Wear your eye protection. Use a hot , slightly hissing
    flame, heat the whole crucible until it is glowing yellow hot. In a
    simultaneous motion, take a three fingered pinch of borax and throw
    it at a specific spot in the crucible as you move the torch away.
    Return the torch after each pinch is thrown. Overlap each "throw"
    and turn the crucible on its' side and repeat. Turn the crucible to
    each side and finally to its' operating position for the final
    application of borax. You don't need gobs of the stuff. The crucible
    should have a slight shine, not necessarily a glassy enameled look.
    If you are using a bowl type crucible on a handle for pouring an
    ingot or vacuum casting you need not turn the crucible on it's side
    to glaze it. You merely turn it a little on it's bottom while you are
    applying the borax with the same "throwing pinch" method. When you
    glaze your crucibles like this you can add a thrown pinch of borax
    when you heat your crucible just before you put your metal. If you
    have an old crucible with lots of build up you can clean it by
    grinding it with a mizzy wheel in your flex shaft. Grind right
    through the old flux being careful not to sink into the ceramic when
    you break through the crust. Leave the surface as smooth as possible.
    CAUTION: a cracked crucible for a centrifuge will hold together with
    the flux when it's cool and can fly apart when hot and spinning. It
    can be quite dangerous, I've seen it happen! So discard crucibles
    with a crack or that are getting thin, even if they look like they
    are holding together.  John, J. A. Henkel Co., Inc. Moldmaking
    Casting Finishing, Producing Solutions For Jewelry Artists  

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