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.
