[Jewelry making - Article 00432] - Re: [Orchid] Disappearing diamonds fired in PMC

[nick]

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>     put a diamond in an oven and heat it at 1405 f/h or 763 c the diamond
>     will evaprate and release small amount of carbon dioxide. from this
>     finding the the methode of manufacturing synthetic diamond chemical
>     vapour deposition.

    CVD is done under high vacuum which changes the temperature that
    carbon will evaporate. At room temperature carbon will stay as a
    solid well past 1000 deg C so setting them in PMC shouldnt be a
    problem. I suspect that there is a quite simple answer to this, the
    PMC has either coated the stones or shrunk so they have popped out.
    If the diamonds had flaws in them they may have simply shattered at
    the tiny gas bubbles expanded in the heat. The gemmological
    Association of Great Britain did a couple of articles on heat
    treated gemstones a while back that are worth reading. 

    I have enveloped diamonds and sapphire in molten glass without any
    problems, the stones being small enough (2mm) that heat transfer
    didint cause any real problems but I would be careful of doing the
    same with bigger stones. The ideal gemstone for PMC is synthetic
    sapphire. 

Nick
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