Hi Gerry and List ~
Actually, the most satisfactory materials for filling gemstones are
the family of UV curing photopolymers currently used as optical
adhesives. These can be obtained in a variety of viscosities and
refractive indices, and have the advantage of never yellowing and
possess a very high tensile strength. Since these compounds are UV
cured, they can be worked with for as long as necessary before curing
with a UV light source. Additionally, they are water clear and
colorless, and will also provide mechanical stabilization to fragile
materials.
One such use would be filling emerald rather than the traditional
method of oiling. Such treatment would be permanent, and would
further strengthen treated stones due to the high tensile strength of
the cured material. Photopolymers also possess a very high shore
hardness once cured which is polishable. Several sources are
available to the gem industry, but Norland Products is probably the
best known supplier of these materials. They have a web presence
which describes their entire family of adhesives including all
physical and optical properties which would be of interest to the
gemologist selecting materials for filling. Typical cost is about
$20 per ounce, but this is acceptable considering the excellent
quality of treated
Regardless of what type of filling method each individual or company
prefers to use, remember that it is ethically necessary at ALL TIMES
to disclose these treatments to your buyers. Under no circumstances
should this ever be withheld.
Paul Ahlstedt http://www.facetersdigest.org