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Specific Gravity Tests

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  • Jon P. Sullivan
    Hi, does anyone here know where I can get the machine for taking specific gravity tests? I would very much appreciate any help! Thanks Jon
    Message 1 of 3 , May 5, 2003
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      Hi,

      does anyone here know where I can get the machine for taking specific
      gravity tests? I would very much appreciate any help!

      Thanks
      Jon
    • Mike Diamond
      Hi Jon. As far as I m aware, there is no machine for doing specific gravity tests. You ve got to rig up an apparatus for each balance. Since the design of
      Message 2 of 3 , May 5, 2003
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        Hi Jon. As far as I'm aware, there is no "machine" for doing
        specific gravity tests. You've got to rig up an apparatus for each
        balance. Since the design of balances vary (e.g., platform vs.
        basket), the apparatus must be tailored to the particular design.

        In principle, doing specific gravity is simple. You need to suspend
        your coin by some kind of clip or support and immerse it in a
        container of distilled water which is independent of the balance.
        You are checking the "before" and "after" weights of the coin,
        establishing its relative bouyancy/density.

        In practice, establishing specific gravity can be difficult. You
        need a balance that is accurate to at least the nearest 0.01g,
        preferably the nearest 0.001g. You need to subtract the weight of
        the clip in doing your calculation, which is not too hard if you
        can "zero" the balance after each step. The tiniest bubble adhering
        to the coin or the clip can throw off your results. A measurement
        error of only 1-2 hundredths of a gram can erase the difference in SG
        values between silver and copper. Getting reproducible and
        repeatable results is often difficult.

        J.P. Martin, in his video "Detecting Counterfeit and Altered U.S.
        Coins", demonstrates a good design for a coin support and shows how
        SG testing is done. It's available from the ANA. Members get it for
        a reduced price.

        --- In errorcoininformationexchange@yahoogroups.com, Jon P. Sullivan
        <errcoins@b...> wrote:
        > Hi,
        >
        > does anyone here know where I can get the machine for taking
        specific
        > gravity tests? I would very much appreciate any help!
        >
        > Thanks
        > Jon
      • Jon P. Sullivan
        Hi Mike, Thanks for the help. I do have the A.N.A s grading and counterfeit detection videos, and have seen the specific gravity test demonstration. I figured
        Message 3 of 3 , May 7, 2003
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          Hi Mike,

          Thanks for the help. I do have the A.N.A's grading and counterfeit
          detection videos, and have seen the specific gravity test
          demonstration. I figured that there was a machine to do it with, but I
          guess I was wrong. Thanks for responding to my e-mail.

          Also, I do not post in this group very often, but I just thought I'd
          let you know that I enjoy reading your comments on various coins on
          Ebay. They are very educational! Thanks!

          Sincerely,
          Jon
          On Monday, May 5, 2003, at 03:10 PM, Mike Diamond wrote:

          > Hi Jon.  As far as I'm aware, there is no "machine" for doing
          > specific gravity tests.  You've got to rig up an apparatus for each
          > balance.  Since the design of balances vary (e.g., platform vs.
          > basket), the apparatus must be tailored to the particular design.
          >
          > In principle, doing specific gravity is simple.  You need to suspend
          > your coin by some kind of clip or support and immerse it in a
          > container of distilled water which is independent of the balance. 
          > You are checking the "before" and "after" weights of the coin,
          > establishing its relative bouyancy/density.
          >
          > In practice, establishing specific gravity can be difficult.  You
          > need a balance that is accurate to at least the nearest 0.01g,
          > preferably the nearest 0.001g.  You need to subtract the weight of
          > the clip in doing your calculation, which is not too hard if you
          > can "zero" the balance after each step.  The tiniest bubble adhering
          > to the coin or the clip can throw off your results.  A measurement
          > error of only 1-2 hundredths of a gram can erase the difference in SG
          > values between silver and copper.  Getting reproducible and
          > repeatable results is often difficult.
          >
          > J.P. Martin, in his video "Detecting Counterfeit and Altered U.S.
          > Coins", demonstrates a good design for a coin support and shows how
          > SG testing is done.  It's available from the ANA.  Members get it for
          > a reduced price.
          >
          > --- In errorcoininformationexchange@yahoogroups.com, Jon P. Sullivan
          > <errcoins@b...> wrote:
          > > Hi,
          > >
          > > does anyone here know where I can get the machine for taking
          > specific
          > > gravity tests? I would very much appreciate any help!
          > >
          > > Thanks
          > > Jon
          >
          >
          <image.tiff>
          >
          >
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