Version 1.05 March 2020
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6.0
THE FACETING PROCESS
6.0
THE BASICS
The faceting process consists of taking a rough stone (it's called "rough") grinding a series
of faces (or facets), and polishing those facets. The facets are positioned at very particular
angles so that the light reflects from the pavilion and out through the crown. The proper
angle, the one which assures reflection is different depending on the material being used--
and that's the angle used for the "main" pavilion facets (friendly name: "the Mains").
The steps of faceting consist of a rough grind, a fine grind, and then a polish. The exact
number of steps, and the sequence, can vary but it always ends with the polishing.
The discs that hold the grinding or polishing material are called Laps and most typically they have an eight inch
diameter. Grinding laps have a diamond compound of some particular size (mesh) bonded to the surface of the
lap. The higher the mesh number, the finer the particle size. For initial grinding
– shaping of the stone – 260
mesh Laps are commonly used
– although Ultra Tec recommends that 360 mesh be the coarsest Lap used –
and then, only if the shaping cannot be done with a 600 mesh Lap. (Avoidance of coarse Laps is because they
cause sub-surface damage in the stone that later show up as surface flaws, as pre-polishing and final polishing
proceeds. Typical shaping Laps (minimizing sub-surface problems) are 600 mesh or 1200 mesh. Pre-polishing
can be done with fine diamond compounds
– like 3000 or 8000 mesh diamond compound, on a suitable pre-
polish Lap (Ultra Tec recommends the high-tin-content BATT Lap). Final polish can be done with Cerium Oxide,
or Aluminum Oxide, or a fine diamond mesh (14000 to 50000 mesh) on a suitable Polishing Lap depending on
the gem material. Laps used for final polish include Tin, BATT, Phenolic, (and various others). Also, for
polishing, t
here are “Ultra Laps”—mylar films to which the polishing media is adhered.
The rough stone is cemented to a metal dop, and the dop is inserted into the Spindle which positions the stone
for grinding and polishing against the rotating lap. The pavilion side is done first, after which the stone is
cemented to another dop ("transferring"), holding to the pavilion, to complete the crown. After the stone is
complete it is removed from the dop, cleaned up--and there it is.
Now, if you are a "natural-born" faceter, you know enough to start. More than likely, you'll need some help, at
least from the various books available. If you can obtain instruction from a teacher, that will give you a fast start
(and we may be able to aim you at a teacher--call us). Most importantly, "have at it"--faceting, like 99% of
everything else in the World is best learned by doing.
6.1.1 SELECTING ROUGH MATERIAL
Almost any inexpensive material can be used for the first stone. The goal of your first attempt at faceting should
be to learn your machine's various functions and controls. Even though it is your first stone, it will be one of
which you are proud. It will undoubtedly include some mistakes, however, and it is best to save valuable mater-
ial for later on. As most beginner instructions do, we recommend quartz
—nice pieces of citrine or smoky quartz
are inexpensive and readily available. Now, a bit of caution, quartz
—in some cases—may give you some
difficulty in polishing (that difficulty usually goes away if you reverse the Lap direction of rotation). Starting out
–
could you use glass? Yes you can.
If you happen to have access to synthetic Spinel, that is a nice start-out material. It is an easy cutting and
polishes very easily. An advantage of synthetic material is that you don't have to worry about inclusions,
fractures, etc. The synthetic material will be "clean". Being a nice regular shape, it will also be easier to align on
the dop, something which is more difficult with typically irregular natural material. Synthetic materials are
formed in "boules", which are cylindrical--sort of carrot shaped. It is easy to get a slice about 1/2 inch in
diameter and about equally deep, a good size for a first-time effort.
