Tumbling PMC

Jewelry Discussion
1

Hi Everyone,

I am beginning (and I mean BEGINNING) to work with precious metal
silver clay. I took a class about a month and a half ago and fell in
love with it. However, being so new at it, there are about 1.7
zillion things I don’t know. In the class I took, they talked briefly
about using a tumbler to burnish the pieces after they’ve been fired
in order to get a super good shine. So my husband bought me a
vibratory tumbler for Christmas. It is a dry tumbling system and the
instructions say that steel shot and ceramic beads are too heavy for
it and will cause excessive wear and tear. Have any of you used
walnut or corn cob for shining PMC? If so, is there a trick to it?
Where do I buy it? Do I add anything to it?

Thanks so much!
Wendy

2

Wendy,

Diamond Pacific, in Barstow, California, offer a dry shine system
called, Vibra-Dry. It works exquisitely, and is a wonderful
alternative to Steel Shot wet burnishing. it just takes a longer
time, but patience is rewarded.

Diamond Pacific is a family owned store, with a catalog division,
and is a strong supporter of Rockhounds and Jewelry Artists.

They support Cubs and often can be found at Shows. They maintain a
strong presence at both Quartzsite, Desert Gardens, and Tucson, where
can be found at the Tucson Electric Park. If you have not yet come
across them, you are truly missing a wonderful experience.

Diamond Pacific is the source for many original companies, such as
Highland Park, and Mini-Sonic. They stock replacement parts for
quality machines no longer in active manufacture.

The link to Diamond Pacific is, http://www.diamondpacific.com

I know and trust them implicitly.
Hugs,
Terrie

3

There is a free tutorial about tumbling at JewelryLessons.com. Judy
Hoch’s book is well worth the money and will give you a complete
understanding of tumbling.

Walnut won’t do anything unless it’s impregnated with polishing
compound, which it sometimes is. Corn cob is generally used for spot
free drying of metal, and it won’t polish anything.

You buy both of those at Rio.

For PMC, the tumbling instructions are, stainless steel shot, water,
1 drop of dishwashing liquid or appropriate amount of burnishing
compound, 1/2 an hour.

So you may need a new tumbler that can take water.

Elaine

4

I tumble my PMC with shot in a rotary tumbler and a smidge of
dishwashing soap. They come out beautiful and shiny. I have to say
that I have never tried a dry tumble. Leslie

5 
So my husband bought me a vibratory tumbler for Christmas. It is a
dry tumbling system and the instructions say that steel shot and
ceramic beads are too heavy for it and will cause excessive wear
and tear. Have any of you used walnut or corn cob for shining PMC?
If so, is there a trick to it? Where do I buy it? Do I add anything
to it?

Your DH was sweet to buy you a tumbler, unfortunately you would find
it much easier to have a rotary tumbler instead of a vibratory. The
majority of metal clay artists use the rotary-style of tumbler to
polish and work-harden their finished projects.

Sandra Graves

6 
Diamond Pacific, in Barstow, California, offer a dry shine system
called, Vibra-Dry. It works exquisitely, and is a wonderful
alternative to Steel Shot wet burnishing. it just takes a longer
time, but patience is rewarded.

I am unfamiliar with this product, but you do need to be cautious in
what media you use to burnish or tumble silver metal clay pieces.
Polishing compounds can get embedded in the porous metal. In the
worst case scenario, the compounds get embedded in the surface of the
metal and cannot be removed, leaving you with a dull dirty-looking
piece that can never be polished to a high shine. Silver clay pieces
need to be brushed or burnished with a stainless steel or brass brush
either dry or with water (a very mild soapy solution is ok). Tumbling
with stainless steel shot in a soapy solution is an alternative many
people use.

After initial brushing or burnishing, it is generally ok to use
polishing compounds as the pores of the metal have been closed. For a
brief overview of tumbling metal clay, see:

http://www.medacreations.com/TumblePolishingPMC.aspx

As for your particular tumbler, it depends on the construction as to
whether or not you can use water with it. If you post what brand and
model it is, maybe someone here can fill you in on its actual
performance…

Mary Ellin D’Agostino, PhD
www.medacreations.com
Sr. Teacher, PMC Connection
Certified Artisan, PMC Guild

7

Hello,

So my husband bought me a vibratory tumbler for Christmas. It is a
dry tumbling system and the instructions say that steel shot and
ceramic beads are too heavy for it and will cause excessive wear
and tear. Have any of you used walnut or corn cob for shining PMC?

His heart was in the right place - my hubbie refuses to buy me tools
any more (!). You really do need something that will take stainless
shot in liquid because the metal clays are more porous after firing
than regular sterling pieces. The burnishing effect of shot gives
metal clay pieces a nice finish.

Happily, a small rotary rock tumbler can be had for a modest
investment - Harbor Freight # 46376-7VGA is $32.00. (Unfortunately,
the cost of a pound of stainless shot will about equal the cost of
the rock tumbler.) Surf eBay and the Inet for other options - I see
that Hobby warehouse.com sells a Lortone 3A jewelry tumbling kit for
$89.99 that includes the shot. Don’t forget to buy a couple
replacement belts for the tumbler. I know HF products are not the
highest quality, but I’ve been using one of these for several years
on an intermittent basis with no problems. AND, your dry tumbler
with charged walnut shell will do nicely to buff up tarnished pieces.

Happy tumbling,
Judy in Kansas, where temps are sub-freezing, but the sun is out!

8

Hi Gang,

In the worst case scenario, the compounds get embedded in the
surface of the metal and cannot be removed, leaving you with a dull
dirty-looking piece that can never be polished to a high shine.

A dip in the ultrasonic will clean the imbedded particles out.

Dave

9 
A dip in the ultrasonic will clean the imbedded particles out.

Nope. Sorry, but I’ve been there and done that. Particles that have
been embedded in the porous surface of silver clay and sealed over
with a thin layer of metal do not seem to be removed by ultrasonic
cleaning or any other method I have tried. It is best to accept an
antiqued patina look on those pieces. Maybe it depends on how well
burnished the piece is after embedding the compound…

Mary Ellin D’Agostino, PhD
www.medacreations.com
Sr. Teacher, PMC Connection
Certified Artisan, PMC Guild

10

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
two weeks.

Happy New Year to all

Judy Hoch

11

Hi, Judy,

Recently, I ran an extensive series of tests on polishing PMC.

This is very interesting, and it’s great that you did it!

However, what do you mean by “all were fired at the recommended
temperature and duration”? There are multiple choices for the
package recommendations. And the truth is, none of the PMC varieties
has any real strength unless it is fired for at least an hour at
1650.

Your tests, if done on lower-temp-fired pieces, are still useful,
but mostly to hobbyists who fire the way the company says to-- how
could they possibly know better? I’d like to think that pretty much
everyone (who is interested) on this forum is aware by now that
pieces fired to the lower temps will break in your fingers.

Obviously, this is a sore point with me, but in any case, if you did
not do tests on pieces fired to 1650, I suspect your results might
be quite fifferent. At least, I’d love to know!

Thanks for the work you are doing,
Noel

12

Judy,

Prior to testing PMC, I have never observed noticeable metal
removal when finishing jewelry metals in tumblers.

Back in 1985 I set up and managed mass finishing of cast sterling
‘fashion’ jewellery. Flow through vibratory with green pyramids for
10 hours then rotary with SS for 45 minutes. 500 - 1000 gram loads
and
they came out 2% lighter from the vibratory, no real change from the
SS.

Polishing always removes metal, a buff will yield even an even more
scary %. I seldom bother to compute it anymore, some things are best
left unknown :slight_smile:

Of course we settled, decanted, and dried the sludge for refining
with polishing sweeps.

Jeff
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand

13

Jeff - on the subject of metal removal when doing mass finishing -
Your experience of losing 2% of cast metal weight is normal.
Castings are typically rougher and finished in more aggressive media
or run longer in finer media. The standard for fabricated jewelry is
about 0.5%. In most cases the metal that is removed is not obvious
but can be observed by weighing the material before and after
tumbling.

The PMC metal removal was very noticeable. I didn’t weigh the
materials before tumbling so I can’t give you an exact percentage.
What it looked like was that patterns were partially removed due to
the material removed. I was more concerned with refining the plain or
unpatterned surfaces. Because the material is somewhat porous,
compared to milled product, I was unable to get a comparable finish.

Noel - I understand that short firing times or short cuts can result
in inferior results. The reason that I had Cece Wire make the samples
is that she is a master instructor and understood that I wanted the
best integrity possible of the fired PMC. She didn’t use short times
or low temperatures. She fired the material and the longest and best
recommended for each of PMC 1,2,3. I’m not competent in use of the
material and I wanted to have the material as recommended by the
manufacturer.

The end result of my finishing was to give the material a silky feel
without the typical small bumps that often appear in PMC art. I have
adjusted finishing times and type of media to accommodate the softer
material of PMC. Because the material is also less dense, I suggest
alternative media for finishing to avoid excess material removal.

The tumble finishing books should come from the printer today - yea!
I’ll be shipping to your suppliers this week.

Judy Hoch