[Jewelry making - Article 01627] - Re: [Orchid] Magnetic stirrer wows judges

[Jeff Simkins]

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    Cole-Parmer makes an immersion stirrer that has no moving parts and
    is incased in a block of epoxy. I used them almost 17 years ago. One
    way to maintain constant etch rates is to use a large bath of heated
    oil, and set your flask (beaker, etc.) in the oil. If you need a
    stirrer, then you set the flask on top of the immersion stirrer, and
    place a magnetic bar inside the flask. Going over the top, add a
    reflux condenser on top of the flask to keep your etchant from
    evaporating off. The immersion stirrers never seemed to last that
    long, because the oil took a long time to heat (only an hour, but
    that's too long for some). I will guess that some of the students
    left the heated bath on 24/7. The oil and spilled etchant would eat
    right through where the wiring entered the block of epoxy. 

    Older than immersion stirrers were the DC brushless motor drivers
    that Dan Orange designed at Sprague Semiconductors. 

    The judges should be impressed because so few kids enter areas of
    math and science. The ones that have an interest get discouraged for
    any number of reasons. I help my daughter any way I can. 

Jeff
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