How to Run a Ceramic Kiln

Overview

Running a ceramic kiln means to fire a group of clay pieces that were either hand-built or thrown on the wheel. When the formed clay pieces are bone-dry it's time to load them into the kiln and bake them. Most clay pieces go through two firings. The first firing is called a bisque firing and the second a glaze firing. Today many ceramic kilns are run by a programmable digital monitoring device. But it's always good to learn how to fire your ceramic kiln manually so you thoroughly understand the firing process from start to finish.

Bisque Firing

Step 1

Make two identical cone packs. Roll some ceramic clay into a 3/4-inch diameter ball. Flatten it on the bottom by pressing it on a flat surface. Elongate it, and then take a fork and prick the clay with the prongs all over. This is done to make sure there is no air trapped in the clay. Take a cone--a hard, clay stick with three sides. One of the three edges is slightly flattened. Stick the cone into the pricked clay, leaning it at a 45-degree angle. Make the flattened edge the leading edge of the leaning cone. The cone used is rated for the temperature the kiln will fire the clay to. You will know the kiln has reached the right temperature for the clay when the cone bends over. You can see this through the peep hole of the kiln. Load the kiln with dry clay pieces.

Step 2

Set a cone pack in front of the lowest peep hole on a kiln shelf with the leaning cone facing to the right. Continue loading pieces into the kiln. Set the second cone pack on a kiln shelf in front of the top peephole in the kiln. Place a third cone in the kiln sitter--an electrical box mounted on the outside of the kiln that acts as a master switch. Lay the cone horizontally with the one flattened edge facing up across the two metal contact points of the kiln sitter. The top wire rod rests on the flattened edge of the cone. Push in the silver or red button on the kiln sitter. This opens up the electrical circuits to the kiln.

Step 3

Lower the lid of the kiln, but keep it cracked by putting a piece of firebrick or a 2-inch high kiln stilt--a hard clay spacer used between kiln shelves--between the lid and the top of the kiln wall. Turn all switches to Low on the electric kiln. Don't put any plugs in the peep holes.

Step 4

Plug the peepholes and close the lid of the kiln after an hour. Wait another hour and turn all the switches to Medium. After another hour, turn all switches to High.

Step 5

Start looking through the peepholes at the cone packs every half-hour to an hour after the kiln has been firing for seven hours. When the cones start slumping over, the kiln is getting close to reaching temperature. When the tip of a cone is bent over at least halfway, the kiln sitter should automatically trip the master switch or the kiln can manually be turned off. Cool the kiln for 12 to 16 hours before opening.

Glaze Firing

Step 1

Make two cone packs. This time the cones will be rated for a different temperature then the cones for a bisque firing. Read the label of the glazes to find out what cone temperature they must be fired to. Load the kiln with glazed pieces.

Step 2

Put a cone in the kiln sitter and press the silver or red button. Close the lid of the kiln completely. Turn all switches to Low. Leave the peepholes unplugged.

Step 3

Plug the peepholes after one hour. Turn all switches to Medium. Turn all switches to High after another hour has passed. After six, start checking the cone packs every half-hour to an hour.

Step 4

Watch for the cones to bend over. The kiln sitter will either trip the master switch, or you can turn off the kiln manually.

Tips and Warnings

  • When clay is being fired in a kiln, it gives off noxious gases. Be sure to vent the room the kiln is in. Never leave your electric kiln unattended. The kiln sitter could malfunction, and you could melt an entire kiln load of clay work. Worse, a fire can start if your kiln doesn't turn off when it should.

Things You'll Need

  • Electric kiln with kiln sitter
  • Formed clay pieces
  • Cones
  • Fork
  • Firebrick or kiln stilt

References

  • HotKilns: How To Fire a Manual Kiln
  • NMClay: How To Fire

Who Can Help

  • Clay-King: Orton Pyrometric Cones
Keywords: how to fire a kiln using a cone pack, how to fire an electric kiln, how to manually fire an electric kiln

About this Author

B. Ellen von Oostenburg became a full-time writer a decade ago. She has written features for local and state newspapers, as well as magazines, including Milwaukee Magazine, Wisconsin Trails and German Magazine. A graduate of the University of Wisconsin - Madison, von Oostenburg holds a Bachelor of Science Degree in fine art.

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