Precious Metal Clays represent a dramatic development in the handling
of precious metals. PMC consists of microscopic particles of silver or
gold suspended in an organic binder to create a pliable material with a
consistency similar to modeling clay. PMC can be worked in the fingers
and with simple tools to create a vast range of forms and surfaces
unobtainable or laborious with traditional techniques.
When it is heated to a high temperature, the binder burns away and the
metal particles fuse to form solid metal that can be sanded, soldered,
colored and polished like conventional material. This booklet describes
some of the techniques devised for PMC and PMC+, and will guide you
through your first firing experience.
Precious Metal Clay is a patented material developed by Mitsubishi
Materials Corporation of Japan in the early 1990’s. The principle
ingredient in PMC is tiny metal particles only 20 microns in diameter.
As a point of reference, it would take as many as 25 of these particles
to make up a single grain of table salt. The rest of the material
consists of water and an organic (naturally occurring) binder. After
firing, both the water and binder have been completely removed, so PMC
may be hallmarked and will assay as .999 pure. Dried-out PMC or unwanted
fired objects can be refined just like conventional precious metal.
The firing process leaves a metal that is less dense than conventional
sheet or wire. This means that a piece of jewelry made of PMC is lighter
than the same piece made by fabrication or casting. Because it is less
dense, PMC is not recommended for applications that require high tensile
strength such as findings. PMC is available in two versions: standard
PMC, which provides the best modeling and greater shrinkage
characteristics; and PMC+, which is denser, has less shrinkage and
offers several firing options.
Three years after introducing PMC, Mitsubishi Materials Corporation
developed a second version, called PMC+. Both kinds of clay are worked
with the same tools, fired in the same kiln, and can be finished in
exactly the same way. Everything in this book applies equally to both
versions, with two exceptions: PMC+ has a different firing schedule, and
it shrinks less.
Three Kinds of PMC
Three years after introducing PMC, Mitsubishi Materials Corporation
developed a second version called PMC+. Both kinds of clay are worked
with the same tools, fired in the same kiln, and can be finished in
exactly the same way. Everything in this book applies equally to both
versions, with two exceptions: PMC+ has a different firing schedule, and
it shrinks less.
PMC+, like its older sibling, consists of silver particles and organic
binders. Because it has a higher percentage of metal, the binders and
water occupy less space. This means that when they burn out there is
less shrinkage. Like standard PMC, the shrinkage is evenly distributed
throughout the piece.
PMC+ fires much faster than standard PMC, making it perfect for short
and for users who want faster results. The material is denser than
standard PMC, so it is recommended for creating rings and for ..Standard
PMC and PMC+ can be used together and PMC+ can be fired for the two-hour
sequence used for standard PMC. PMC+ is available in lump form, as slip
in a syringe, and as paste slip in a jar. PMC+ offers three distinct
firing scenarios, outlined on page 9. When working with PMC+ alone,
you'll probably choose the fastest firing schedule. If you want to embed
sterling components into the PMC+, fire at the lower temperature of
1470°F (800°C).
PMC3 fires at an even
lower temperature (1290 F ) which not only allows implants such as glass,
but means alternative, low tech firing devices become possible.
(Torch Firing) Not every artist
will need all three versions. Some people find a preference and stick with
it, while others use different materials depending on the nature of their
work.
