[Jewelry making - Article 00206] - Re: [Orchid] The Beilby Layer

[coralnut]

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    Oh boy....Helen, you have opened a can of worms. I thought the last
    few messages on this subject might awaken the monster but....nothing
    significant appeared. 

    Now, you have asked the single most debated question in the lapidary
    discipline. 

    G. T. Beilby's hypothesis was documented in his paper, "Aggregation
    and Flow of Solids, Macmillian and Co, London, 1912! Since then a
    great deal of research has been done, especially in the late 1990's
    and early 2000s. The best and clearest description of the polishing
    process, of which the Beilby layer is part, are papers by Stephen W.
    Attaway, Ph.D in the 2003 timeframe. You may still find some of this
    information at the New Mexico Faceters Guild site at:
    www.attawaygems.com/NMFG/preston-equation.html. In several papers, he
    discusses Fracture Mechanics, Plastic flow, Plastic process zones,
    etc., and describes in some detail the theorys of - Finer Scratch
    Theory, Flow Theory, and Chemical Polish Theory. Beilby fell into the
    second. Further, Gerry Wykoff did some significant work on these
    theories, and in his, now defunct, American Gemcutter letters,
    stongely supports the latter of the three....describing polishing as
    an electrochemical process. HHMMm interesting to say the least. 

    Supporting Dr. Attaway's research is work by Dr Scott R. Wilson,
    Ph.D whose papers are also available at the above site. 

    I hope this gives you what you need to understand the process.
    Beilby's theory currently is not highly regarded though he is given
    recognition for a possibly a correct theory for the wrong reasons. 

    I find that John Sinkankas doesn't even mention Beilby in his
    famous, Gem Cutting books describing polishing as a controversial
    subject on which few agree. On the other hand, Robert Webster gives
    some non-scientific explanations of it in his "Practical Gemmology",
    N.A.G. Press Ltd. London, 1978 reprint. 

    Chances are you will never fine a truly scientific explanation of
    this theory other than in Beilby's original paper and that is, at
    best, a theory. 

    Cheers from Don at The Charles Belle Studio in SOFL where simple
    elegance IS fine jewelry and where the July classes have commenced at
    the Boca Raton Museum of Art School!!
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