Notes on Firing Cycles

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.)

Gradually turn up the heat until on full in the early morning. (I usually turn it up in three small increments at around 1:00, 3:00 and 5:00 AM.)

My current salt kiln tends to fire in a neutral to slightly reducing atmosphere, so I only intentionally put it into reduction during two brief 45 minute periods at cone 06, and at cone 4-5. (Reduction by adjusting the passive dampers in the chimney.)

After the second reduction at around cone 5, I reoxidize until about cone 6-7.  At that point, I start introducing salt and continue until it is all in, trying to have it done before cone 10 starts to bend. That process usually takes about three hours.

Salting is followed by 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 two cone spread.

I put in about 6 kilos of salt suspended in water and sprayed into the firebox area, not directly onto the pots.  My salt kiln has four stacks of 12′x24″ shelves.  It is a hardbrick car kiln, built by Donovan Palmquist of Master Kiln Builders.

Cone Ten Reduction Firing Cycle

Start on low heat for about two hours (longer if the pots are very recently glazed)

Turn up in two increments 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 018-016

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.

Further notes on Firing

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 seven 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.) After working just in stoneware for a while, 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, it would still be salt. It doesn’t make economic or business sense, but I love the warmth and texture of salt glazed pots!