PMC expert Tim McCreight address kiln basics in this Q&A. Learn what you need to effectively fire your metal clay designs. Courtesy of the PMC Guild archives.
Q: What is a kiln and what kinds can be used to fire precious metal clay?
A: A kiln is an oven that's capable of achieving high heat—red hot or hotter. Any device that holds the required temperature for the required time will work for PMC. Those most commonly used are breadbox-sized electric kilns. Shapes differ, but all have the same components: an outer steel shell, a lining (usually soft fire brick), a coil of special wire that converts electricity to heat, and a switch that controls the flow of electricity into the wire.
Kilns like this are used for enameling, as burn-out furnaces for casting, and as potter's test kilns. Any kiln that will reach 900°C/1650°F and hold the heat for two hours is fine. Firing PMC will not damage or contaminate a kiln.
You will also need a heat-reading device called a pyrometer. These are often built into kilns, but are also available as add-on devices.
Q: Help! I bought some PMC several months ago and can't find anywhere to fire it, or even a kiln to buy. Can you give me a list of kilns that can fire PMC?
A: There are many kilns that will fire PMC. To fire PMC with consistently good results, choose a kiln with a switch to control the heat and a gauge to tell the temperature inside. A furnace like this is used by enamelists, jewelry casters, and lamp-workers, so it may be possible to borrow a kiln or to persuade a friend to help you with firing. PMC will not contaminate any kiln.
If you're ready to buy a kiln, let me suggest a couple. There are many good kilns on the market, but these are at the top of my recommendation list:
Rio PMC kilns: These kilns are my dream come true: they're made specifically to fire PMC. Both models are made of refractory foam, so they are much lighter than old-style kilns. What makes them special, though, is the electronic controller. This built-in device allows you to set the rate of heating, a maximum temperature, and a “cooking time.” This makes it possible to load the kiln, press the “on” button, and head for the beach!
Different sizes provide options for average users and “power users,” but note that the smaller unit is significantly smaller—the chamber is about the size of your fist. For the extra money, I'm glad I got the larger one.
Here's another good choice:
Neycraft 9" x 6.5" x 9" chamber, variable speed controller. This model has been available for several years and is sold by most jewelry supply companies in their casting section. It comes with a pyrometer and an infinite range dial. Because it does not have a controller, its necessary to monitor the firing manually. I've used many of these kilns and find them reliable and hard working.
Here's another option. All around the country, contemporary ceramic studios are starting to offer classes in PMC. These studios are drop-in centers where anyone with an interest can glaze unique designs onto ready-made pottery. Now, in addition to painting a mug, people will be able to make a pair of earrings. It's the latest thing—a way to get out and meet people and tap into creative energy at the same time. In addition to offering advice and a space to work, most of these shops will fire work made outside the studio as well. To find a shop near you, do a search online or check out your local yellow pages.