Notes on Firing from Out of the Fire, a Potters Council Regional Conference in Duluth, Georgia August 10-11, 2007
Salt Kiln Firing Cycle
Turn on VERY LOW in the evening and fire on low overnight.
(This is necessary because I’m firing raw work. When I fire only bisqued work, the first fourteen hours of the firing can be compressed into about five.)
Gradual turn up until on full in the early morning.
My current salt kiln tends to fire in a neutral to slightly reducing atmosphere, so I don’t intentionally put it into reduction except for two brief 45 minute periods at cone 06, and at cone 4-5. (I get that reduction by adjusting the passive dampers in the chimney.)
After a period of re-oxidation, I start introducing salt at about cone 6-7, and try to have all of it in before cone 10 starts to bend. That process usually takes about three hours.
Then I do a late firing soak, trying to keep it firing for quite a while without getting any further cone movement -- ideally, I want cone 10 over but not flat and cone 11 up. My current kiln is still uneven front to back, so it actually fires with about a three cone spread.
I put in about 6 kilos of salt (or salt/soda mix) suspended in water and sprayed into the firebox area, not directly onto the pots.
Regular Cone Ten Reduction Firing Cycle
Low heat for about two hours (longer if the pots are very recently glazed)
Turn up for a steady rise until cone 010
60-90 minutes of heavy reduction – I reduce the oxygen by adjusting active and passive dampers, and making the gas/air mixture richer.
Keep the kiln in light reduction until end of firing -- ideally I want cone 9 flat, 10 going over and 11 still up.
Carbon Trap Shino Firing Cycle
Low heat for about two hours (longer if the pots are very recently glazed)
Turn up for a steady rise until cone 016
90 - 120 minutes of VERY heavy reduction – I reduce the oxygen by adjusting active and passive dampers, and making the gas/air mixture richer.
Keep the kiln in medium reduction until end of firing -- ideally I want cone 10 flat, and 11 half over.
Some thoughts on firing salt and reduction. When I set up my first studio in Virginia in 1973, I built a salt kiln. During most of my time as a potter I worked exclusively in salt. About six years ago, I had to convert my old salt kiln to reduction. (The bricks were deteriorating and I made that switch to prolong the kiln’s life.) Recently, I built a second kiln for salt, so now I have the option of both. That combination, plus the chance to put pots into my friend Kevin Crowe’s anagama/noborigama wood kiln means that in pottery terms, I live in the best of all possible worlds. I’ve enjoyed finding and developing reduction glazes – the expanded color range, the chance to learn new ways of decorating. But if I could only work in one firing style, it would still be salt. It doesn’t make economic or business sense, but I really love the warmth and texture of salt glazed pots!