(Pyrometric) cones have been used for around a hundred years as a way to control and monitor the firing of ceramic and pottery pieces. Pyrometric cones are used to measure heatwork during the firing process. They help determine if ware has reached maturity, if the kiln is operating properly, and if problems occur in a kiln during the firing process.

A cone is a slender pyramid or more recently bar of carefully controlled clay compositions that are developed to react repeatedly and consistently to varying degrees of heat. Their consistency has a range of about 50 degrees from one use to another. Cones are numbered so as to show how much heat they absorb before bending or ‘melting’. They bend when they begin to form glass from their composition melting. Cones can only be used once.

When originally developed by Orton, cones were numbered 1 through 20 with 20 being the hottest. When they developed cooler cones, they reversed the numbering by adding a zero in front of the number 01, 02, 03 etc. with cone 022 being the coolest. Cones currently range from coolest 022 to hottest 42. It is critical that when firing a kiln you be sure to check that instructions say cone 05 rather than 5, for example, in order to achieve success with the firing of your item. Firing an item at cone 5 that is supposed to be fired at cone 05 can only result in disaster.

To read the rest of this article, click here.

Tags: ceramic, cone, cones, firing, kiln, kiln firing, orton, orton cones, pottery, pyrometric, pyrometric cones

This entry was posted on Wednesday, February 25th, 2009 at 6:54 pm and is filed under About Ceramic Kilns and Firing. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.