- 1). Establish the ideal firing temperature for your clay or glass pieces. The temperature varies according to the material you use, being higher for porcelain and lower for earthenware and glass. The temperature required dictates the cone level.
- 2). Choose the correct cones for the temperatures you require. Cones are single-use items that are numbered starting from the lowest kiln-firing temperature, which is around 1,080 degrees F, or the equivalent of cone 022, to the highest temperature around 2,350 degrees F, which corresponds to cone 10.
- 3). Load the kiln, and place three cones at the level of the peephole. Place one cone that is required by your load and two inferior cones. For instance, if you need to fire your ceramics to cone six, get cones four and five as well.
- 4). Insert the peephole plug and start the firing.
- 5). Check the kiln periodically. The cones are initially at an 8-degree angle and will start to bend, but the time required for them to bend depends on the type of kiln you use. The inferior cones will bend first.
- 6). Notice when the first cone starts to bend. It takes between 15 and 25 minutes for a cone to bend to a 90-degree angle once it starts to bend.
- 7). Shut off the kiln once the last cone is bent to a 90-degree angle. Allow the kiln to cool, ideally for 12 hours.
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