[Jewelry making - Article 00511] - Re: [Orchid] Opal Setting?

[Peter B. Steiner]

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>            ....Imagine my distress when, about a month ago, this opal
>     turned up crazed with fractures, now essentially worthless. I
>     tried opticon on it, hoping to at least use it for myself, with no
>     effect. If an opal kept in stable, humid conditions for all those
>     years can suddenly craze, how can we ever feel sure an opal is
>     stable? No, I don't know where it is from--I didn't know enough
>     then to ask. The loss is far from financially ruinous, but it is
>     disconcerting, and sad.            --Noel  

    Noel, I can indeed imagine how frustrating that would be! 

    You've discovered (the hard way) the reason why I'm wary of
    combination stones, such as doublets and triplets.  Often the backing
    material, the cap, or the adhesive used to make such a stone expands
    and contracts at a different rate than the Opal. Over time, this
    produces stress in all of the layers; and because the slice of
    Precious Opal is the most brittle component, it is usually the first
    to suffer damage. 

    There are valid reasons for making doublets and triplets.  Some
    varieties of Precious Opal are too thin to be cut into solid stones. 
    Others contain too much water to be stable when cut as solids (most
    Spencer, Idaho material falls into this category.) The risk of
    crazing in doublets and triplets can be greatly reduced by the use
    of adhesives which remain elastic over time.  Potch (common Opal) is
    a good choice for use as a backing material.  Don't hesitate to ask
    how a stone was assembled....and don't hesitate to walk away if the
    answer is vague! 

    Opal can never be guaranteed 100% stable.  The best anyone can do is
    to keep all the risk factors to a minimum.  Don't physically stress
    the material.  Don't subject an Opal to excess heat or cold.  Don't
    -ever- store an Opal in a low humidity environment (such as a safety
    deposit box.) 

    Sometimes, even when everything is done correctly, a stone will
    craze for no apparent reason.  :-\ 

    I know this does nothing to restore your damaged stone.   I wish
    that it could! 

Peace,
Peter

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