Torch Firing Process
(With thanks to Tim McCreight & his article in Studio PMC)
Allow the work to dry overnight or drive off moisture with a hairdryer, or in a slow oven. Make sure it's completely dry or the work can explode! Torch firing is not recommended for large items and you need good ventilation as you'll be close to the clay when the binder is burning off.
2. Place the work on a soldering block or fire brick, which is in turn set on either a fireproof surface or something you don’t mind being singed (like a piece of plywood). If you are working on the kitchen counter and the piece rolls off the block you don’t want to scar the countertop.
3. Light the torch and hold it so the flame is nearly vertical with the tip of the cone about 3/4" away from the work. Within a minute, the piece will be enveloped in a soft flame as the binder burns away. The flame will soon go out by itself. Within another minute, the piece will start to glow red. Continue heating until this becomes a bright and luminous color. At this point, glance at a clock.
4. Hold this color as uniformly as possible for about 5-7minutes. When the time is up, turn off the torch and allow the piece to cool. If you're not sure it's fully cooled use tongs or tweezers to pick it up and (providing it's not stone set) quench it in water.
A suggestion - Melt some Silverclay on Purpose
Most standard handheld torches are rated at 2000F so they can melt silver clay, in an effort to avoid this it's worth doing this experiment so you know what to look for.
Pull off a pea-sized bit of your chosen silver clay (PMC or ACS), split it in half, and roll out two small rods. Follow the instructions above with one added step. Concentrate the flame on one of the rods in an effort to melt it. You’ll see a bright mercury-like skin form on the piece and the red color will become even brighter. The edges will start to curl and the metal will be drawn up into a ball.
Make a mental note of what you saw. This way you’ll know the signs of melting, and you can withdraw the torch in time before damaging a piece you care about. To complete the experiment, allow the other rod to cool and test it by bending, filing, burnishing, and polishing. This will confirm that, sure enough, torch firing really works!