[Jewelry making - Article 00151] - Re: [Orchid] Vacuum casting seal problem

[Peter W . Rowe]

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>     I have been told by lifelong jewelers and casters that the
>     perforated flasks are a gimmick. I tend to believe them. I have
>     tried both perforated as well as solid and I can't tell a
>     difference. The perforated have frequently not had good seals while
>     my solid flasks have performed flawlessly. 

    Not a gimmick, but more, a timesaver and productivity improvement. 
    Especially with larger flasks, you need good air flow through all
    parts of the tree to get uniform, consistant, repeatable results. 
    Without perf flasks, you can get the same results using wax web, or
    similar products, but it's simply an extra step, and another product
    you have to buy.   While many individual jewelers used to casting
    little 2.5 x 2.5 inch  or smaller flasks don't need, nor use,
    perforated flasks, you'll find that most of the larger commercial vac
    casting machines are designed for them.  This is a more costly way to
    build a casting machine than a flat table.  They wouldn't do it if it
    didn't work better for them.  You certainly CAN get equally good
    results with solid flasks, if you prepare it correctly.  But a
    perforated flask needs less space between the models and the flask
    walls (since patterns don't have to also clear the wax web or other
    such air vent product), and the holes in the flask also grip the
    investment column securely,  which coupled with the straps across the
    bottom, reduce the potentials for an investment blowout.  All in all
    its simply an incremental improvement in the process.  The castings
    are not somehow better than equally filled castings from solid
    flasks.  It's just slightly easier to get them consistantly filled,
    and you can get more in a flask.  Plus, with manual pouring types of
    setups, locating the flask down in a casting well may offer some
    improvements in safety, as there's less hot metal exposed to
    accidentally brush against, and you can't knock a flask over by
    mistake, etc.   Minor considerations, but they all add up. 

Peter

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