I utilize a down-draft, woodburning, salt glaze kiln. The chamber, approximately 58 cubic feet, has an interior wall of hard firebrick and an exterior wall of insulating brick. It has a sprung arch, constructed of hard arch brick, then layered with insulating brick and fiber. The fireboxes are directly beneath the chamber floor, and are two bricks thick.
Door stacked and ready to fire.
Wood Preparation
Wood is delivered in bundles from a local sawmill. I use strips, hardwood and pine, for firing the kiln.
Bundles of oak strips.
The strips are placed into a sawbuck and chain-sawed to accomodate the length of the fireboxes.
Ready to cut.
Chainsawing.
Once the wood has been cut, it is stacked and air dried before being used in a firing.
Stacked and waiting.
Loading the Kiln
Glazed pieces are set into the kiln. Care is taken to give adequate space between, allowing for the movement of flame and salt vapors. Pyrometric cones are strategically placed for viewing during the firing. This allows the gauging of temperature at selected degrees.
Starting to load the kiln.
Stacking complete.
Once loaded, the door is stacked shut. Peep holes are left to view the cones, as well as placement of a digital pyrometer probe. This allows for reading the rise and fall of temperature during the stoking of wood.
The door stacked.
Firing the Kiln
This kiln design has two fireboxes located underneath the chamber floor, on opposite sides, running perpendicular to the chimney. The flames enter into the kiln through the inlet flues, circulate in the chamber and pass down through the floor exit flues and out the chimney. Hence, the name "down-draft".
A small campfire is started in one firebox, below the grate; the other firebox is sealed off. Once sufficient embers have accumulated, the fire is moved to the top of the grate. The temperature is taken up gradually to 500 degrees F. Then, a fire is started in the opposite firebox. Alternate stoking is now continued through the rest of the firing.
Stoking the firebox.
View into the firebox.
Viewing the cones.
Salting
When peak temperature has been reached, approximately 2400 degrees F, it is time to salt the kiln. There are two salt ports, located front and back. 50 pounds of granular table salt is introduced into the kiln over a period of time. After each salting, the kiln has to brought back up to temperature. The entire salting cycle takes nearly two hours. During this time, rings of clay, known as salt rings, are pulled to check the build-up of the salt glaze. Once the salt glaze is sufficient, a final stoking is made. When the kiln atmosphere has cleared up, the fireboxes and chimney are sealed. The firing has finished, and the cool down begun.
Salting the kiln.
Pulling a ring.
Salt ring.
Unloading
It takes several days for the kiln to become cool enough to unload. Once the chamber temperature has dropped to around 300 degrees F, the door is unstacked. Its just like Christmas morning!
Ready to unload.
Temperature reached!
To read more about the designing and construction of my kiln...
Here