Wendy - Recently, I ran an extensive series of tests on polishing
PMC. The well-known PMC instructor, Cece Wire, produced the majority
of my samples. I ran the tests on all three versions of PMC from the
original to the current one.
The PMC was in various shapes, some made from embossed sheet, some
hand formed. All were fired at the recommended temperature and
duration. Some had gems fired in place.
My initial process was to simply burnish some of the pieces in a
rotary tumbler with stainless steel for varying lengths of time. The
result is obviously porous shiny metal. Then I separated the pieces
and ran them in a fine abrasive media in a flow-thru vibratory
tumbler. Then I followed the abrasive steps with another pass thru
the rotary tumbler with stainless steel. In all cases, I varied the
length of process times.
I found that the smoothest shiny finish was produced with a
three-step process. First 45 minutes in the rotary, then 2 to 4 hours
in the abrasive media, depending on the amount of detail in the
samples, and then a final run of 30 to 35 minutes in the rotary with
steel. Longer runs in the steel degrade the finish. Longer runs (over
6 hours) in the abrasive remove noticeable amounts of metal.
Prior to testing PMC, I have never observed noticeable metal removal
when finishing jewelry metals in tumblers.
So Wendy, this prologue doesn’t directly address your problem. This
is what I know about vibratory tumblers. If they are constructed so
that water cannot easily reach the motor, you can run them wet. It is
a closed system, so you need to continually check it for adequate
moisture and cleanliness. These small vibratory tumblers do not
produce the amplitude necessary to run steel. However, ceramic beads
will work; they just take a very long time. A typical polishing
session with ceramic beads is 24 to 36 hours. The only concern might
be that the tumbler will not run that long in one session.
The reason to run the PMC in steel is to work harden the surface.
Ceramic beads do not harden the surface.
Why don’t you try for another tumbler for Valentine’s Day? A small
6-pound rotary tumbler with six pounds of stainless steel would be
the perfect compliment to your vibratory tumbler.
To all the Orchidians - I ran these and other tests to update
in my book, “Tumble Finishing for Handmade Jewelry”. The
revised fourth edition is at the printer now. I anticipate that you
can find it in stock at your favorite jewelry supply house in about
Happy New Year to all