With PMC, jewelry makers turn clay into silver or gold.

by Nina Cooper

Just a few years ago, the idea of turning clay into pure gold or silver would have sounded like the fantasy of a Medieval alchemist, but since the invention of Precious Metal Clay, better known as PMC, this seemingly magical transformation has become a routine event. In fact, the metal is present in the clay from the start, suspended in an organic binder that burns away when the material is fired in a kiln -- and when fired at the appropriate temperature for the correct length of time, an object fashioned from PMC will emerge from the kiln as solid metal.

PMC was developed by Mitsubishi Materials Corp. of Japan and introduced into the United States in 1996 through an exclusive distributor, Rio Grande Gems and Findings in Albuquerque, New Mexico. In the U.S., PMC is currently available in either fine silver or fine gold, that is, unalloyed. PMC versions of 18-karat gold and platinum exist, but are only marketed in Japan. Alloyed metals such as 18-karat gold require expensive oxygen-free kilns, which is one reason why the alloys are not sold in America yet.

During the firing process, the material shrinks by 30 to 50 percent as the organic binder burns away. McCreight uses coins to explain to students what they should expect. If you make a piece the size of a quarter, it will emerge roughly the size of a dime. Thin PMC shrinks more than thick PMC, which can create difficulties when constructing complex structures. Flat objects can be placed directly in the kiln, but other shapes should rest on a bed of alumina hydrate for support.

Mitsubishi insists that both the material and the firing process are completely non-toxic.

Those with a background working with clay are often the first to see the potential of PMC. Shelie Brooks uses PMC to create a collage of organic textures in her Fossils & Fragments brooches. Photo: Steve Gyurina.

BEHAVES LIKE CLAY. Aside from a kiln, very little in the way of materials is needed to work with PMC. Like other forms of clay, it responds well to hands and fingers. It can be rolled, coiled, pinched, pressed into molds, extruded (with some difficulty), and thrown on a potter's wheel. Because it retains surface patterns, an infinite variety of objects can be used to create texture. Some objects, like leaves, can be pressed into the clay and left there. They burn away when fired, leaving behind a detailed imprint.

One drawback to the material is its tendency to dry out quickly, so it should be stored in tightly sealed plastic. When working, McCreight recommends keeping most of the material covered in plastic and pinching off only the amount you plan to use immediately. Stiffening PMC can be rehydrated, but if it hardens completely it won't recover its original consistency. At this point, reducing the material to slurry for patching and joining is the best option.

Cost is another significant factor in the decision to work with PMC. Fine silver PMC runs two to three times the price of normal fine silver; in gold, the price is roughly double.

PMC silver is more porous and 20 percent lighter than regular silver. This difference has advantages and disadvantages. Large pieces are lighter and less expensive to produce -- a definite advantage. However, the lighter silver is weaker and less suitable for objects like clasps and chains that need to withstand pressure.

Because the material is porous, it is possible to make completely enclosed structures, such as beads, which is impossible in traditional casting. When working with PMC, you can fashion a bead around a core that later burns away, diffusing through the clay as it shrinks. Holes may be drilled after firing or worked into the design. On the other hand, because it is so porous, surfaces need to be burnished before soldering or the material will absorb the solder. Some artists have obtained interesting results by working enamel or potter's clay into the PMC. Implants of metal such as titanium, stainless steel, nickel, and fine silver work well, too. Gems that can withstand the heat (McCreight advises sticking to synthetics because of concern about natural inclusions not being sufficiently heat-resistant) are easily set by simply pressing them into the surface of the PMC before firing.

Some artists, including metalsmith Barbara Simon, have obtained interesting results by working enamel into the PMC before firing. Photo: Robert Diamante.

A pin by PMC artist and instructor Linda Kaye-Moses, using a scallop shell and coral for texturing. Photo: Evan Soldinger.

Speed is one of PMC's most attractive characteristics. Not only stone setting but all facets of construction are swifter with the clay than working with solid metal. Heidi Lowe, one of McCreight's students at the Maine College of Art in Portland gives an impressive account of her experience with the material. "I wasn't too crazy about PMC when I first used it, but it works very well for production because it is so fast. We have an annual holiday sale at the college. I made 50 heart pins with PMC in about 16 hours, and I sold every one of them." She credits good design and presentation for her success but acknowledges that she would not have had time to make so many pins if she had not used PMC, and she plans to continue working with it.

Chris Darway teaches PMC workshops up and down the East Coast as well as at the University of the Arts in Philadelphia and the New Jersey Center for the Visual Arts in Summit. He notes that metalsmiths seem to be resistant to the idea of PMC. "They often feel that they can get the same results using other techniques," he explains. Artists who work with enamel are the exception. Fine silver is ideal for enameling, and PMC offers the additional option of creating a cloisonne look by pushing in the surface of the clay to create metal walls between enamels rather than laying down wires.

For Darway, the biggest advantage of PMC is the ability to make hollow core beads with textures. He has experimented with many different core materials from Styrofoam to cheese "doodles" but prefers to use balls of potato bread dipped in wax. The wax burns away quicker than the bread, leaving room for the clay to shrink as it fuses. Darway also encourages students to experiment with negative space."For instance, if you mold PMC around an acorn, then cut it in half after firing, you find a perfect impression."

When pressed, Darway admits he is still working on ways to incorporate the material into his own production jewelry. "My designs tend to be mechanical, angular, and industrial looking, in contrast to the more organic feel of the PMC." To integrate the two, he is experimenting with molds and leather-hard filing. (Leather-hard PMC is obtained by partially firing a piece. In this state, the clay can be carved or filed and then fired again to complete the fusing process.)

NOVICES LOVE IT. People with no metal experience and those with a background in working with clay are often the most excited about PMC, Darway finds in his classes, because it offers instant access to the world of metal. Shellie Brooks of Cambridge, Massachusetts, certainly felt that way. She had a long history of working professionally with clay and more recently has been producing polymer jewelry.

Because PMC retains surface patterns, artists can create an endless variety of textures in the finished metal, as in this bracelet by Peggy Johnson. Photo: Robert Diamante.

During a PMC workshop with Fred Woell in 1996, Brooks realized that she had an ideal background for working with PMC. "I wanted to incorporate metal into my designs, and PMC let me work in the way I was used to expressing myself." Brooks creates elements from PMC, makes rubber molds of them, has the elements cast in silver, and then assembles them into earrings, brooches, and pendants. "I create a collage of textures. I use organic shapes, sometimes derived directly from nature. For instance, I may press a sea fan into polymer, fire it, and press the PMC into the negative space to make a raised imprint."

Brooks may cast 10 pieces of an original PMC element but she doesn't like to rework the surface of the PMC itself. "I like a fresh look. I will practice a gesture on new pieces of PMC until it comes naturally so that the final piece has a flow of energy to it." Some of her pieces include slabs of polymer with a separate surface design on the front and back. The polymer is inlaid into open bezels so that both patterns can be seen. From her introduction of the line at the American Craft Council show in Baltimore, customers have been intrigued by the process of forming Precious Metal Clay, and Brooks shares their fascination: "I am captivated by the transformative quality of the material."

It is advised that the gems used in PMC pieces be synthetic, like the rubies used in Barbara Simon's Easy Chair, as natural inclusions may not be sufficiently heat-resistant. Photo: Robert Diamante.

After working with metals for over 30 years, Barbara Simon of Cape Coral, Florida, began to work with glass a year and a half ago. When she decided to incorporate lampworked beads and metal, she found PMC useful. She needed a clasp for a strand of glass beads and made a catch from PMC. (As previously noted, a PMC clasp will have only about 80 percent the strength of a regular silver clasp.) Using a plain silver PMC base, Simon mixed blue enamel into PMC and used it to apply dots to the base in the same pattern that appears on the lampworked beads. In this manner, she was able to integrate the clasp into the overall design.

After a year of working with PMC, Simon is still experimenting. She enjoys mixing enamel powder into PMC or applying it to the surface of larger objects like bowls. For the bigger pieces, she finds it necessary to construct an internal network of support beams to overcome the material's tendency to slump when fired. She also tried to incorporate lampworking glass with the PMC, but the glass baked into the clay.

Nevertheless, she remains an advocate of the new material. "It solves certain aesthetic problems like spontaneity," she says. "In wax, the name of the game is texture. PMC gives the same but with an extra kick because you can really put your fingers into it."

Some artists, including metalsmith Barbara Simon, have obtained interesting results by working enamel into the PMC before firing. Photo: Robert Diamante.

In Japan, hobbyists are the primary PMC enthusiasts. In the United States, Mitsubishi has made a concerted effort to convert professional jewelers. Some of them have answered the call, but the attraction of creating silver and gold jewelry without extensive training or equipment is perhaps still greatest for novices.

Tapping into this potential market, Peter Solomon and Mary Edwards recently opened Precious Metal Arts, a studio in Santa Monica where people can take classes in PMC and make their own jewelry and artifacts. "We mostly get beginners in jewelry," Solomon explains. "We emphasize technique, starting with a basic clay class. Then people can move on to beads, hollow forms, box making, and candleholders. We also give six hours of free lab time for experimenting." After taking a class, anyone can drop in, buy a half-ounce of clay and work on their own. "We [the staff] eliminate the headaches by doing the firing and polishing, so clients can relax and enjoy working with the material."

The studio also teaches traditional metalsmithing and lost wax casting, but the clay studio takes up two thirds of the space. It is too soon to tell if the studio will have staying power, but given the success of do-it-yourself pottery studios, the pair might be on to something. Solomon, who taught for seven years at the Gemological Institute of America, is certainly optimistic.

"People really seem to enjoy seeing their work transformed into precious metal."

It's new, it's magical -- but will it last? PMC definitely has its enthusiasts, though other workshop leaders have noticed a waning of interest as the novelty factor fades. It may have limited appeal for seasoned metalsmiths but it definitely offers new options and opportunities to people who long to work in metal but don't have years to invest in training. In time, PMC will probably find its way into many interesting and innovative uses. After all, the experiment has just begun.