Downdraft gas kilns can be used to make beautiful pottery.
Ceramic kilns reach high temperatures and are used to cure clay, making it as hard as rock in some cases. They are available as electric or gas powered kilns. Traditional kilns used wood as fuel but all types are built using bricks that can withstand and contain the heat of the kiln. Simple gas kilns can be built in the shape of a box. Downdraft gas kilns have the advantage of channeling the flame through the pottery and back down to the floor of the kiln through the flu at the bottom. A simple kiln would be a top-loading kiln about 4 feet high with a lid made of refractory brick.
Instructions
1. Find a suitable area protected from rain to use as a kiln-site. Avoid building this kiln indoors because it may present a fire hazard. Prepare the ground by leveling a pad on which the kiln will be built. Scrape the ground and use the level to make sure it is completely level on all sides. Place the concrete blocks on the pad to create a solid base for the kiln. Cover the concrete blocks with a layer of ceramic insulation fiber to keep cool air from entering or hot air from exiting through the floor.
2. Mix your mortar with equal parts of cement, fire-clay and sand. Dry mix them first and then add water until it has a good consistency for brick work. Cover the cement block and fiber with a layer of
refractory bricks. Bond the sides with mortar until the floor is finished. Make sure to leave two openings for the burners in the floor at the back in both corners.
3. Build the chimney using the hollow refractory bricks. Cut away the hollow brick on one side to create the flu of the kiln. Create a big enough opening, about the size of two stacked normal sized bricks. Adjust the size of your flu by testing-firing the kiln at a later stage. Install the chimney at the back, between the two burner holes with the opening facing the inside of the kiln.
4. Build up the walls of the kiln with bricks, starting from both sides of the chimney. As you work your way up, leave two or three small openings at the front to use as peepholes for visually checking the kiln during firing. Create a slanted edge on the top row to make the flame curl inward as it shoots up from the floor towards the lid; this will make the kiln more efficient.
5. Use a level as you lay the bricks and only use a minimum amount of mortar. Build the walls until you've reached the desired height. Make sure that the top edge is completely level to create a tight seal with the lid.
6. Install the burners with valves and gas lines underneath the kiln on both sides at the back. Make the burners point upward into the kiln toward the lid. Place three bricks around the flu opening on the floor of the kiln. Leave space on the front corners for the flame to get through to the flu. Place a shelf on top of these bricks and install the lid to finish the kiln. The lid can be lifted on and off by hand or with a pulley system.
Tags: both sides, Build walls, completely level, concrete blocks, Downdraft kilns, flame through, floor kiln