How to Use Precious Metal Clay
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.
What Is It?
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.