These ceramic cones are used to indicate the temperature in manual kilns, or kilns in general when you need to document that a desired temp has been reached within the kiln. Often used to test a kiln's actual temp, even if the kiln has a computerized temperature reading.
Orton makes cones from cone 022 up to cone 42. During firing, cones soften and melt as they are heated, and gravity causes them to bend. This bending indicates that the cone and the ware on that shelf have received a specific amount of heat, matching the formulated melting point of the materials in the cone. It usually takes 15 to 22 minutes for cones to bend fully once they begin melting.
Cone 06 and 6 are not the same, but 06 indicates a far lower temp than 6.
Cone numbers originally started at 1 and went to 20. Each higher cone number requires more heat (a higher temperature) to bend. As demand for cones grew, both lower and higher cones were developed. A zero was added in front of the number for cones maturing at lower temperatures, below the original cone 1. Thus cone 01 needs less heat than cone 1, and cone 020 needs less than cone 019. It is important not to mix up the lower maturing cones, whose numbers begin with zero, with the higher maturing cones.
When using cones in the Dawson Kiln-Sitter to control your kiln, place the cone for your desired target temperature between the claws of the cone holder inside your kiln. When the cone melts, the sensing rod will trip the plunger to shut off the kiln's power.
When using witness cones in your kiln, place cones on each shelf. It's common and recommended to use 3 cones on each shelf: one cone is the actual target temperature, one cone is one increment higher, and one lower. For a cone 04 firing, the trio of cones would be one each of 03-04-05. This combination will indicate how accurately your kiln reached the target temperature on each shelf of your kiln. Regularly using witness cones gives you the true measure of how accurately your kiln fires to the desired temperature. Leadfree glazes require consistent firings to the proper temperature to achieve proper clay/glaze fit and to meet food safety standards. Witness cones are a must for porcelain doll firings, too. Porcelain is unforgiving, and there is no margin for error.
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