Firing kilns cannot be made of wood, or you will have to replace your kiln every time you fire a piece of pottery. However, wood is a great fuel to power firing kilns, offsetting the cost of electric and gas powered kilns. Though a wood-powered kiln will not reach the high temperatures necessary to completely transform earthenware into porcelain, a small wood kiln is ideal for hobby potters and occasional potters.
Purchase a small load of insulated, fire-safe brick. You will use the brick to make a small cube approximately 2-feet by 2-feet by 2-feet; mention this to the sales representative at the store in which you purchase the firebricks. Purchase a large 2-feet by 2-feet slab also made of insulated firebrick; this piece will serve as the lid of your small wood kiln.
Choose an outdoor location in which to place your kiln, a place in the middle of the yard, on high ground and several yards away from any buildings is ideal. You may place the kiln in an open barn or shed if you plan to be near the kiln at all times and during all hours in which the kiln is in use firing pieces of pottery.
Dig a hole where you will place the small wood kiln. The hole you dig should measure 2 and one-half feet wide by 2 and one-half feet long by 2-feet deep. Use a small level to make sure the bottom of the hole is close to level and as smooth as possible.
Mix a bag of concrete and pour into the hole, making a pad for the wood kiln that is approximately 6-inches thick. This pad will prevent the bricks from cracking and separating as the ground underneath settles. Allow the concrete to dry a day or two before continuing construction on the kiln.
Lay the bricks into the hole, creating a square bottom pad that measures approximately 2-feet by 2-feet. Once the pad is in place, begin building up the walls of the small wood burning kiln until all 4 walls are intact and measure approximately 2-feet tall. The walls should stick up out of the hole. Mortar is not necessary between the bricks, as the mortar does not allow the bricks to expand.
Place wood, sawdust, pottery pieces, and another small layer of sawdust and wood inside the kiln and sit the wood on fire. Slide the slab on top of the small kiln; the tiny crevices between bricks will allow enough air in to allow the fire to continue burning until all sawdust and wood is burnt up.