Courtesy of the PMC Guild archives! This Q & A session with Tim McCreight helps guide you in selecting the best core material for your metal clay designs. It also explains the burnishing process.
Q: I understand that I can wrap PMC around a core to make a hollow bead. What’s the best core material to use?
A: The ideal core material is inexpensive, will burn up completely and can be easily modeled to the desired shape. When burning, the material should not expand or generate a lot of smelly smoke.
I’ve tried many things, from cork to bread to paper. My favorite material is a commercial art product called paper clay, available under several brand names. This is a finely ground paper pulp sold in blocks at art supply stores. It is very easy to mold and burns out with relatively little smoke. Some brands contain plaster, which doesn’t burn away. This doesn’t create any problems in firing but will leave a residue that needs to be scraped away.
Though wax can be used for cores, it has some drawbacks. Wax makes a lot of smoke and will burst into flames if you introduce a flood of oxygen by opening the kiln door at a certain stage in the burning process. A coating of wax on papier maché cores helps sheets of PMC stick to the core, making modeling easier. If you use wax, keep the coating thin.
Q: I keep seeing the word ‘burnish’ in PMC instructions. Can you explain it?
A: Burnishing is the process of rubbing a soft material with a harder one to make it smooth and shiny. In working with PMC, burnishing compresses and smooths the particles of silver or gold. The result is dramatic: a matte white piece of jewelry fresh from the kiln instantly becomes brilliantly reflective.
Burnishing can be done with any hard, smooth object. Traditional jewelry tools are made of polished steel or agate. Because pure silver and gold are so soft, even hard plastic and dense wood tools can be used to burnish fired PMC work. A collection of tools of several sizes and shapes will be useful. Burnishers can be purchased at jewelry supply companies. Or use manicure tools, crochet hooks, and miscellaneous stainless steel implements such as nut picks, pickle forks, etc. Though not necessary, some people like to lubricate the burnishing action with soapy water.