How to Build an Underground Kiln
Underground kilns are an advantageous route for serious ceramic hobbyists to pursue. Over the centuries, kilns have been designed to use numerous types of heat sources, and their construction has become a true art form. Today electric kilns are more common and can be made specifically to suit the size of the hobbyist's particularly favored work. Utilizing fire bricks and an electrical heating coil, these kilns will be able to reach the necessary high temperatures for firing ceramics; however, they are not recommended for glass fusing.
Things You'll Need
- Measuring tape
- Pencil
- Paper
- Shovel
- Level
- Metal sheets
- Fire bricks
- Large paper/cardboard
- Masking tape
- Goggles
- Miter saw
- Brick-cutting saw blades
- Kiln coils
- Plastic sheeting
- High-heat mortar
- Putty knife
- Drill
- Drill bits
- Control box
Instructions
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1
Select an area of ground that will accommodate both the size and depth of the kiln. Measure the length, height, width and depth dimensions for the underground kiln with a measuring tape. Determine the depth based on how many ceramic pieces are to be fired at a time. Draw out a generalized sketch of the proposed kiln. Mark out the kiln's dimensions on the selected area of ground.
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2
Know the intended cubic foot measurement (length-by-width-by-height) of the kiln to determine the length and width of the metal sheet to sit snugly at the bottom. Determine the depth the kiln will be in the ground, noting that a deeply buried kiln will heat better. Dig and level the base to place the metal sheet inside the hole to form the bottom of the kiln.
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3
Trace the bricks on paper or cardboard in the pattern you choose, using trial and error placement. Take exact measurements for those bricks that will need to be cut down to fit. Label each brick's placement with a number or letter, using a small piece of masking tape on the brick itself.
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4
Don the proper safety equipment for using a miter saw to cut those bricks that require resizing to fit the pattern. Cut shallow grooves on those bricks where the heating coil will be placed. Decide if the lid of the kiln will be a metal sheet or more grooves and coils like the sides.
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5
Spread out plastic sheeting beside the kiln's location and bring out high-heat mortar. Use a putty knife to spread a thin, butterlike layer of mortar on the bricks, one by one, and place them in their designated location in the pattern, bottom to top. Wipe all miscellaneous droppings of mortar off quickly, since it hardens swiftly, and allow 24 hours to set.
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6
Place the heating coil in its designated grooves in the wall of the kiln, and if necessary, in the top of the kiln as well. Drill two holes in the kiln's side where the control box will attach externally, and place the wiring where it can be connected through to the coils. Connect the control box, and put the kiln lid in place.
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Tips & Warnings
The control box is one of the most complicated and important features of the kiln. Any serious kiln builder should thoroughly research the varied options for this device before actively constructing a kiln.
References
Resources
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