Design the Kiln

• 1). Select the location, shape and dimensions of the kiln. The location should have a non-flammable floor such as concrete in a basement and have enough room so the kiln is surrounded by a 1-foot clearance.
  
  The kiln can be round or rectangular. A round kiln gives more even heat and uses space better but it is more difficult to build. A good sized rectangular kiln would have an interior 18 inches square and 24 inches high. Such a kiln has a volume of 4.5 cubic feet and can be fed from a 30A breaker with a power of about 6,400 watts.
  
  
• 2). Calculate how many bricks you will need. Make a drawing of how to arrange the bricks. For a round kiln, you will have to cut the bricks at an angle so they form a circle. For the rectangular kiln in step 1, two 9-inch bricks per side with a 4-inch square corner will make up one layer of the inner wall. Eight layers of 3-inch thick bricks will make up the height. An additional layer of bricks around the outside will make the kiln more efficient, heat up more evenly and save power. Two layers of bricks should go on the floor and two layers will make up the cover. Make allowances for the fiberboard which will close the top of the kiln before you layer the bricks over it.
  
  
• 3). Calculate the power and length of the elements. The kiln should operate at 220 volts. To get the required power of about 6,400 watts, you can use eight elements of 800 watts. Fewer than four elements will make it difficult to control the heating when starting the kiln.
  
  The length of the elements will be slightly longer than the interior circumference of the kiln because the elements will go in grooves in the bricks. In the previous example, the inside circumference of the kiln is 18 inches times 4, or 72 inches. Since the elements will be in grooves about 1 inch deep, each side will have a groove 20 inches long, which means the total element length will be 80 inches.
  
  

Assemble the Kiln

• 1). Cut the bricks according to the design using a table saw. Cut the grooves for the elements by running the bricks for the interior wall across the table saw angled at 45 degrees and protruding from the table about 1 inch. Either make several cuts to get the groove thickness needed for the elements or attach several saw blades together to get the required thickness.
  
  
• 2). Place the beams parallel on the floor about 18 inches apart. The beams should have a length slightly longer than the outside wall or the diameter of the kiln. Place the aluminum plate on the beams. Assemble the bricks on the aluminum plate.
  
  If the kiln is round, the aluminum cladding must be thin enough to bend around the bricks. Tighten by placing steel straps around the kiln. For the rectangular kiln in the previous example, the aluminum cladding should be 1/4-inch panels. You can hold them in place by mounting angle irons along the panels and tightening with wire rope and turn buckles.
  
  
• 3). Insert the electric elements into the grooves. Drill two 1/8-inch holes about 2 inches apart through the walls of the kiln to allow each end of each element to penetrate the wall for the electrical connection. You can stretch the elements slightly if necessary. Make sure these holes are suitably located for connecting to the main power cables. Drill 1-inch holes through the aluminum where the element wires come out to prevent the wires from touching the aluminum. Insert insulated terminals into the holes and attach the ends of the elements. Drill peep holes where desired.
  
  

Connect the Electric Power

• 1). Run the power circuit(s) from the main board to the kiln. In our previous example, a 30A breaker in the main panel could feed the eight elements of the kiln. You could also use four 15A breakers. These will be 2-pole breakers since the voltage is 220 volts. The electrical arrangement is flexible but each circuit must be properly protected with a circuit breaker and the cable must be adequately sized.
  
  
• 2). Run the circuits to the kiln and, for each circuit, install a properly sized switch with a pilot light. For the previous example, four 15A switches could control the eight elements. Wire the elements so that a switch controls two elements which are not adjacent to promote even heating.
  
  Mount the switches on a wall near the kiln and run conduit down to where the elements are terminated on their insulators. Connect the power cables to give the desired control.
  
  
• 3). Check to make sure everything is operating according to the calculations. Use a multimeter to check voltages across each element and how much current each element is drawing. All elements should have 220 volts across the terminals and they should be drawing equal currents.
  
  When starting the kiln, switch on the elements over several hours, making sure that the switched on elements are evenly spaced. Place cones in the peep hole and check the timing and temperatures. The kiln should be able to exceed a cone 04 firing.