Notes on Firing

Notes on Firing

October 12, 2022

I bisque- or biscuit-fire the work, usually to between cone 06 and cone 04 (in the range of 1830 to 1970 degrees Fahrenheit) to stabilize the clay before glazing. Sometimes I’ll do two bisque firings on a piece because I’ll first build and bisque a kind of chassis of the work, then add more components, and then bisque-fire again before glazing.

I glaze-fire usually to slightly in excess of cone 10 (around 2350 to 2400 degrees Fahrenheit depending on firing time). I sometimes do multiple glaze firings on a work, but this is rare because there’s so much going on with the layered glazes interacting with one another that I really don’t want to reactivate all that and undo things I’ve already done. So I’ve learned to try to work upfront with a kind of predictable volatility in terms of the interactions of the glazes. On very rare occasions, I might in a spot or two add bits of low-fire glaze to an already high-fired piece and refire to around cone 06.

Most of the recent works are fired in an oxidation kiln atmosphere (heat from well-oxygenated combustion) or a neutral kiln atmosphere (electric kiln, radiant heat). Occasionally I’ll fire with slightly under-oxygenated combustion for light reduction. The reasons for this are simple. I use both naturally formed oxides and manufactured colorants in my glazes. Reduction and oxidation get you different colors from various oxides, and reduction can dull the brilliance of the manufactured colorants. In my perfect world, I’d have the best of both worlds, but I like to keep my manufactured colorants bight, and on balance, I prefer what I get from the oxides in a non-reduction atmosphere over what I could get from reduction, so in the end, I usually go with oxidation or neutral.