Almost forty years on, I remain fascinated by the plastic nature of clay and its transformation into ceramic by heat. What started as a therapeutic antidote to academic research, and the challenge of learning to throw on a potter’s wheel, remains a crucial part of seeking a balance between head, heart and hands.
Throwing turned out to be just the start of an ongoing process of exploring this exacting and technical craft. I now choose to fire with wood, in a large kiln that I currently fire just once a year. The slow production cycle and unpredictable results require a level of detachment from concerns with efficiency, productivity or tight control. A lot can, and does, go wrong but it is the accidents, happy or otherwise, that often lead to new avenues to explore.
It is left to the flames, licking, flashing and depositing fly ash during the three-day firing to leave their mark and decorate the pot surfaces. Almost a day into the firing, when the temperature reaches about 1000 oC, the chimney struggles to pull in sufficient air for full and clean combustion each time the firebox is stoked with wood. The mysteries of this ‘reduction’ atmosphere bring out a rich palette of red through purple, orange and browns in the clay whilst carbon trapping gives greys and black and melting ash deposits fuse to form a glaze.
How best to stack the pots in the kiln, the firing schedule and the composition of the clay body are subject to ongoing (albeit slow) experimentation. To prevent the pots from fusing together with melted ash, the pots must all be separated from the kiln shelves, and from each other, with refractory wadding (made from fireclay, sand and sawdust) or with seashells. The stacking is a slow process, a three dimensional puzzle to maximise use of space in the kiln whilst leaving suitable paths for the flames to find a way through all parts, top, bottom, left and right from the firebox through to the chimney. Many pots are fired on their side. Bowls are often fired upside down, stacked on top of each other, to encourage the flames to lick across and flash the inside surfaces. Simple wood-ash or shino glazes are sometimes also used.
My current kiln was built in 2010 and is fired for three days and two nights with the support of an enthusiastic team of helpers. The top temperature of around 1340 oC is reached on the second day and is held for around 24 hours before the kiln is reduction cooled and sealed. The pots can be unloaded, cleaned and sorted a week or so later.