[Jewelry making - Article 00265] - Re: [Orchid] Open Back or Not

[The Doctor]

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    Happy New Year to you too, Linda. 

    First, I'm going to assume that you're using a faceted stone for
    this bezel setting. This is where the study of gemology comes in
    handy. When a gemstone is faceted properly, light will enter the
    stone through the crown (the top portion), bounce around inside,
    hopefully off the pavilion, and exit back through the crown to the
    viewer's eye. This is due to the stone's crown and pavilion angles
    being cut in harmony with the stone's critical angle. For this
    reason alone, opening or closing the back of the setting will have
    no effect on the stone's interaction with light, and therefore, it's
    appearance to the eye. From this information, you'd think that an
    open or closed back would have absolutely no effect on the stone's
    appearance. 

    However, oils and grease from our bodies and the things we handle in
    our day-to-day affairs can and will be attracted to the stone,
    especially on the pavilion of it. This very different substance
    (different from the gemstone, that is), when attracted to the
    pavilion, actually changes the critical angle of the stone (makes it
    much larger) and will cause a phenomenon known as "unplanned light
    leakage". This means that light will enter the crown and, instead of
    bouncing around the pavilion and exiting back through through the
    crown, it will exit through the pavilion, thereby reducing the
    brilliance of the stone. This is why gemstone jewelry loses it's
    sparkle when dirty and regains it when cleaned. 

    Even bezel-set stones will attract dirt, oils and grease to it's
    pavilion, no matter how closely the bezel is set to the stone. for
    this reason, I recommend that, whenever possible, you leave at least
    a small open area in the back of your setting to facilitate cleaning
    so that your gems may indeed sparkle forever. 

James S. Duncan, G.G.


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