[Jewelry making - Article 00811] - Re: [Orchid] Vacuuming investment

[Phillip Scott]

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    Jim, Running a vacuum on your investment till it "boils" is not
    usually a problem.  By letting it boil you are not putting air into
    the investment but taking it out instead.  Where you do run into
    problems is letting it boil too long.  This has been shown to
    actually take some of the water out of the mix, allowing it to dry or
    gloss off sooner than expected.   This means that you actually have
    shortened the actual working time.  Lets say that you have a working
    time of 8 minutes on your investment.  If you run the first vacuum
    for 5 minutes then release the vacuum and pour the investment in your
    flask and vacuum again you are probably running very close to your
    maximum working time of 8 minutes.  If you did your first vacuum that
    long you may have taken out some of the water making your actual
    working time closer to 7 or 7.5 minutes.  This is cutting it very
    close.  By reducing the water content of the mixture when you pour
    it into the flask, your mix is now thicker and may trap air on or
    next to your model. (This is where the myth of adding air comes in.) 
    Actual working times vary according to the type of investment you are
    using and the type of models your are investing.  Check your actual
    mixing directions for specific information. 

    A rule of thumb for investment with an 8 minute working time. 

    1. Vacuum investment, it should raise, fall, and then vacuum for
    about another 30 seconds to 1 minute. ( +/- 3 min) 

    2. Release vacuum ( +/- 15 seconds ) 

    3. Pour investment into flask ( +/- 15seconds ) 

    4. Vacuum flask ( +/- 2-2.5  minutes ) 

    5. Total working time ( +/- 6 to 6.5 minutes ) 

    6. Set flask in a place where it will not be moved for at least 1
    hour. 

    Water temperature can also play a roll in how fast it sets up as
    well. Another tip, .....take the temp. of investment (DRY), subtract
    from 156, and that would be what your water temp should be! 

    I hope this helps.  If you have any further questions please feel
    free to contact our technical support department and we will try to
    assist you with any issues you may have. 

Phillip Scott G.G.
Technical Support & Sales
Rio Grande
1-800-545-6566


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