Wood has been used to fire kilns since the beginnings of pottery history, from prehistoric bonfire kilns used to fire cookware and storage vessels. Over the centuries wood firing kilns were improved and today they are more sophisticated.
Anagama is Japanese for ‘cave kiln’. In Japan in the fifth century, kilns were dug into a hillside. Kiln walls were reinforced with mud and grass. The kilns were fired slowly for many days, creating strong, durable pottery. Anagama kilns today have the same rounded cave shape.
My Anagama kiln is fired with soft wood off cuts from a fencing factory. The kiln is fired over a two day period, the pots being simply decorated with shino and woodash glazes. Towards the end of the firing salt is introduced to the back of the kiln chamber. This produces rich ‘orange peel’ textures on the wares. Pots are placed on seashells or wads of clay to prevent them fusing together; where they touch interesting scars are formed, giving each a unique character. I make a range of domestic and garden ware alongside his ‘one off’ pots which have been fired in the firebox of the kiln. These pots illustrate the almost destructive effects of fire and salt on clay.
In the initial stages of firing, pots have to be heated slowly to prevent cracking, which can occur from the release of moisture in the clay. The temperature of a wood kiln can be controlled by the size of the wood being burned. Large logs release heat slowly and are used at the start of the firing, while smaller bits of wood burn rapidly releasing heat quickly, ideal for use later in the firing.
It normally takes me three days to place the pots in the kiln, while packing the kiln I try to predict and control the path of the flame. The wood firing process is a lengthy and exhausting one for the potter. Over a period of two days and nights up to four tons of wood is stoked into the firebox. A top temperature of 1300°C is maintained for about eighteen hours. During this time salt is introduced and there is a constant ‘rustling’ of the firebox to stir up the ashes and send them melting onto the pots. Four days later the kiln is cool enough to unload and the pots can then tell their story.
Although the firing process is a time consuming one, the effects it creates are unique; no two pots will be the same. The way in which the kiln is packed will also influence the appearance of the work. Close packing reduces the contact between flame and pots and the amount of ash that glazes the surface. When fully burning the kilns are an impressive sight of flames, smoke and sparks.
