Q:
Is there a "best"
lap and polish combination for each gem material?
A:
There are about as many approaches to getting
a decent polish as there are faceters to come up with them. Several
factors affect the reasons for that, including the individual
cutter's preferred lap size and rotational speed, the hand or
finger pressures used by him or her, and the kinds of sweeping
pattern used to keep the stone moving back and forth across the
face of the lap.
To make matters even *more* interesting, not all materials (that
is to say, all samples of a given material, from different locations)
behave the same way, all the time! (Two great examples of this
are Peridot and Smoky Quartz... While getting a decent, even polish
on some of the Burmese or San Carlos, AZ, Peridots can reduce
a grown man to tears, unless diamond compound on a tin or BATT
lap is used, the East African and Pakistani stuff polishes without
even the vaguest hint of a sniffle with Linde A or B (aluminum
oxide) on pretty much any kind of lap surface. Similarly, while
most of the Brazilian and (X-ray treated:) Arkansas Smoky Quartzes
I've tried have polished quickly and easily with either cerium
or tin oxides on tin, Lucite, phenolic or tin-lead laps, the stuff
from the Pike's Peak, CO, region will not only not polish, but
may actually splinter apart on anything less that 50,000 mesh
diamond on either BATT, copper or zinc.
Nonetheless, my general "fall-back" positions for polishing
are as
follows:
1) Soft stones, such as Apatite, Fluorite or
Calcite: use 8-10 drops of cerium oxide solition from a pharmacy
eyedropper on either Lucite, phenolic
or BATT. If using either of these two plastics, be sure to gently
abrade the surface with "000" grade steel wool, first,
then wash off, thoroughly, before using. (By doing so, you enable
more of the polishing compound to remain on the lap's surface
than would otherwise be the case due to centrifugal force.) In
most cases, I polish with about the same hand motion, speed and
pressure as you'd use if you were erasing a pencil line with the
thin eraser at the end of a mechanical pencil.
2) Medium stones, such as the Quartzes, Tourmalines,
Garnets, Feldspars, Tanzanite and Iolite: use either 8-10 drops
of an aluminum oxide solution on tin, tin-lead or BATT; my personal
preference is towards the BATT Lap. Alternately, an outstanding
polish can be had with 50,000 mesh diamond compound (or powder,
over an oil layer) on the BATT Lap. Or, if you'd _really_ like
to blow some minds with your results, try using two pump-spritzes
of Crystalite 100,000 mesh on a well broken-in Falcon (brand)
ceramic lap, moving at 2-300 RPM! (Be sure to sweep the face of
the lap with a Kleenex, first, to reduce the amount of diamond
on the lap... this keeps scratching to a minimum.
3) Hard stones, like Corundums (i.e. Ruby &
Sapphire) and notoriously, stupefyingly difficult-to-polish stones,
like Kunzite and Kyanite: 50,000 or 100,000 on either BATT, copper
or ceramic laps, only. (Actually, I've also heard good things
about the new Corian laps but, frankly, I couldn't get one to
do anything but scratch the living hell out of anything I touched
on it! Mine was sent to me, for free, by someone online... and
I soon passed it on to someone else, in the same manner!)
One footnote to all of this: my use of the
word, "solution". On my
workbench, I have six 4-oz., brown-glass, eyedropper bottles,
purchased from a pharmacy back in the 1980's. In them, I keep
solutions of cerium, aluminum or tin oxides in either a 1:1 solution
of white cider vinegar & water or a 1:4 solution of household
ammonia & water. As with all of the other variables we lapidaries
come up against, I find that most gems polish better with a change
in pH than they do, without, and that certain materials from certain
locations seem to work better than others. A great example of
this is the way Green Tourmalines from Brazil seem to come up
flawlessly, almost effortlessly, with AlO2 in vinegar on tin,
while the Pink Tourmalines from Nigeria seem to prefer AlO2 in
ammonia (or some other basic ph solution).
In the end, one big component of your personal gemological journey
will be to discover which of the wide range of combinations will
prove easiest for you. And, when you come right down to it, isn't
that what most of life's journeys are about? Welcome to the sometimes
challenging, often mystifying, frequently frustrating but imminently
rewarding world of the lapidary arts!
All the best,
Doug Turet
(This originally appeared on one of the online
listserv's on Monday, April 29th, 2003.)
