[Jewelry making - Article 00036] - Re: [Orchid] Casting at high altitudes

[Ken Kotoski]

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Nicholas,

>      We have also been told that when we are vacuming the air bubbles
>     out of our flasks that because we are at a high altitude(6,984ft)
>     that our vacum can not physically pull enough pressure. 

    This statement is not at all true. Who ever told you this doesn't
    know what they are talking about. 

    Altitude has an effect on the vacuum gauge reading. If you are
    getting 24 in Hg at 7000 feet you are getting a full vacuum. Unless
    you spend tens of thousands of dollars you will never get a more
    complete vacuum. What is considered a full vacuum is different at
    differing altitudes. 

    Full vacuum is different at all altitudes. It ranges from about 23
    to 27 in Hg. The quality and accuracy of your gauge will also
    determine what your full vacuum reading is. The gauge you have on
    your Vic 9 is not a real good one and so if you were to put a better
    more accurate gauge on you will find a different reading closer to 
    24 to 25 in Hg. 

    BTW, your vacuum gauge is reading in inches of mercury not pressure. 

    Since you are pulling a full vacuum that is not an issue. The issues
    would be how fast are you investing? How thick is your investment?
    Are you using de-bubblizer? How fast does the vacuum pump pull a
    full vacuum? 

    Proper investing is really not that hard. Getting air bubbles on
    your waxes means either the wax is holding on to trapped air because
    of surface tension or your investment is solidifying before the
    final vacuuming is complete. 

    First try a de-bublizer. if that doesn't work then try a thinner
    investment mixing. 

    Remember, only change one thing at a time or you won't ever learn
    what has caused a change in the outcome. 

    Also if you don't do a process often be sure to keep a journal and
    write down every variable you can so you can refer to your notes
    later when there is another problem. 

    There are many factors involved in proper investing as well as every
    step in jewelry manufacturing. For investing these are some factors
    that can have an effect on the outcome. 

    Air temp., Humidity, Water temp., Water quality, investment temp.,
    investment age, how investment is stored, mixing techniques, mixing
    conditions, pouring technique, vacuuming times. 

    If your pump is taking more than 30 - 45 seconds to pull a full
    vacuum you need to either clean the lines, filters and the pump by
    flushing it and/or a complete disassembly and cleaning. Or, the pump
    may be under sized for the volume of air being removed. 

    Your Vic 9 should have a 3 cfm pump which should work fine if it is
    in proper working order but a 5 cfm pump would pull faster. Beware
    of increasing the pump size just to pull a faster vacuum. You can
    boil the water out of the investment causing it to cure very
    quickly. 

    If you have any questions please feel free to email or call me. 

Ken Kotoski
MPG Repair
www.mpgrepair.com
1-877-262-2185

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