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