I teach a silver fabrication class and one of my students would like
to meltdown her scrap from pmc projects to fabricate with.
My response was these pieces would not be hard enough to withstand
regular wear as rings, She told me that she had on a pmc ring, and it
was very hard.
The ring was a band of approximately 14 gauge. I said that as a
soldered ring it was very strong because of it’s thick gauge, but if
I were to cut it, I could bend it very easily. thinner gauges would
not be as strong. she replied that the reason her pmc pieces are so
strong is she uses technical charts to “work harden” the pieces. And
don’t I know anything about work hardening?" So my question is this.
How does metal clay become as dense as fabricated metal…or even
cast metal when it doesn’t “vitrify?” Can heat do this?
I know that work hardening was the wrong term for her to use…I am
not familiar with any metal clays. all and any help is appreciated!
Your student is misinformed. PMC is less strong (hard) than wrought
fine silver and there is no way to heat treat it to harden it. Any
hardening will be achieved by cold work like hammering. It takes a
significant reduction in thickness by hammering, drawing, rolling
etc. to harden fine silver no matter what form it is in, PMC or
wrought.
Why would PMC scrap melt down as any less dense or strong as regular
metal? Once it becomes molten any trace of the organic binder would
be long gone and it would act as any other casting made from silver
scrap when it solidified. The binder wouldn’t be there to leave
holes as the crystals formed.
Unless I misread the original post and the student is wanting to
roll out sheet from PMC to fire and use for fabrication?
Once melted and cooled, what you are left with is just fine silver
that has the density of any cast fine silver. Still pretty soft for
a ring even after pulling into wire. Add a bit of copper and she can
make a sterling ring with it.
Her PMC ring, which I assume was made using PMC and not cast or
fabricated, may be surface hardened by burnishing or tumbling, but
is not work hardened in the same way a forged piece is work hardened.
The exterior is hardened, but the interior is still soft. Cast pieces
are also surface hardened when polished, but PMC won’t be quite as
strong as a well cast piece. For more details, see
On the subject of melting down the PMC! It is very difficult to get
any drips of Fine Silver from the binder! It takes a tremendous
amount of heat to break it down. Not worth my time I realized!
So my original post was in reference to a student wanting to cast a
piece using her pmc scrap. My resopnse was it’s too soft for most
jewelry applications. Her response was that PMC could be “Work
hardened” and it would b plenty strong. I was curious if age
hardening or work hardening would even work on PMC, since I am
unfamiliar with it’s working properties. Thanks for your help!
On the subject of melting down the PMC! It is very difficult to
get any drips of Fine Silver from the binder! It takes a tremendous
amount of heat to break it down. Not worth my time I realized!
I don’t understand this…
I reuse PMC simply by placing it in a crucible and applying my
torch. It melts quickly. The binder burns off at a very low
temperature.
I don't understand this... I reuse PMC simply by placing it in a
crucible and applying my torch. It melts quickly. The binder burns
off at a very low temperature.
I don’t either. Once you’ve got the fine silver that remains after
the binder burns off, you can always alloy it into sterling or use it
“as is” for a fine silver cast or create a fine silver ingot and roll
into wire for headpins or… Gee, there’s a lot you can do with fine
silver, isn’t there?
I have had kiln fired PMC objects - that I don’t like, broken, etc.,
that I thought would yield some molten fine silver for reuse. I have
found that with the proper melting temp of the flame with the scraps
in the crucible, there are only drips of fine silver produced at a
very slow rate. There still seems to be “crap” in the crucible along
with the unmelted PMC. That was probably what you didn’t understand!
Fire the PMC in a kiln or with a torch. This burns off the binder.
You can then roll it, forge it, stamp it or otherwise manipulate it,
if you don’t want the form as it comes out of the kiln. I have used
some bits of scrap dried metal clay this way, rolling it down quite
thin and using it to make fine silver granules. I use the granules
on fresh PMC, granulating beautifully, without adhesives.
I have had kiln fired PMC objects - that I don't like, broken,
etc., that I thought would yield some molten fine silver for reuse.
I have found that with the proper melting temp of the flame with
the scraps in the crucible, there are only drips of fine silver
produced at a very slow rate. There still seems to be "crap" in the
crucible along with the unmelted PMC. That was probably what you
didn't understand!
Ok! All that is happening is that you are not using enough heat and
probably not using flux.
I am not doing a very good job explaining this. The PMC items were
already KILN fired - the binder burned off! I have rejected pieces of
FIRED in the KILN. I thought perhaps I could put them in a crucible
and heat them to retrieve some fine silver. I know all about burning
the binder off before kiln firing! Somewhere in my certification I
must have missed an explanation of refining kiln fired items.
I think I will drop the subject! This would be very easy if these
things had not been fired for the 2 hrs at 1650…that’s where I fire
everything!
PMC that has been fired has the same properties as .999 fine silver.
There are some things for which fine silver is too soft, so PMC
would be too soft. However, if it is something for which melted fine
silver would be appropriate then melted PMC would be appropriate.
I have also melted my metal clay and used in in casting. The items
are very strong. I do not understand what is meant by “drips of Fine
Silver from the binder”.
Fired PMC (or Art Clay-Silver for that matter) is Fine or Pure
Silver. Doesn’t matter how long it has been fired or at what temp.
The metal in fine silver metal clay is Fine Silver. So…no refining
is necessary to achieve a pure silver product from fired Fine Silver
metal clay. It’s already .999 parts silver. You can use it as you
would use any Fine Silver product…sheet, wire, cast, or from metal
clay. It is all the same metallurgically, though the sintered/fused
metal from metal clay is approximately the density of cast Fine
Silver, not the same density as milled sheet. After firing…binder
is gone…metal remains. Good to go!
I really hope this helpful, even though you were ready to give up on
this thread,
This could be the best explanation…so now I can take the fired
rejected bead and put it through the roller and use portions of it as
enhancements? I don’t have to try to melt it further? Where did I
ever get the idea that I should put the things in the crucible and
fire to get liquid fine silver from the rejects? My experimenting
nature, I guess!
Interesting, and I will leave this discussion with a great big thank
you.
