What is a Pyrometric Cone?

What is a Pyrometric Cone?

Pyrometric Cones are small ceramic bars or cones that are created to melt at various temperatures. Pyrometric Cones assure users that their firing process is under control.

Cones measure heat work (the effect of time and temperature). When you want to fire a kiln to a certain temperature, you use a specific cone that will melt near that temperature. The pyrometric cone is placed near a peep-hole where the potter can see the progress of its melting. Pyrometric cones give you visual assurance that your firing process is consistent day after day after day.

Often, a potter will use a series of three cones of increasing melting point in a row. In this way, the potter can see the progress from cone to cone of the heat work inside the kiln.

Pyrometric cones are labeled with numbers that correspond to their melting points. The number labels can be confusing because some have a leading zero (Cone 010) and some do not (Cone 10). The leading zero can be thought of like a decimal point. The melting point of pyrometric cones with a leading zero actually decreases as the number increases (Cone 011 has a melting point around 1607 degrees Fahrenheit and Cone 010 has a melting point around 1657). The melting point of pyrometric cones without a leading zero increases as the number increases (Cone 11 has a melting point around 2345 degrees Fahrenheit and Cone 10 has a melting point around 2345). The melting points for each pyrometric cone can be seen in the complete Orton Cone Chart below.

Pyrometric cones come in a variety of shapes and sizes. Bar pyrometric cones are created in a uniform straight shape. This is for consistent placement in kiln-sitters. Kiln-sitters are devices used inside kilns that hold bar pyrometric cones. When the cone melts, the kiln-sitter automatically shuts off the kiln.

Regular pyrometric cones cannot stand upright by themselves. They are made to be placed in a pack of clay or a cone plaque to be supported.

Self-Standing or Self-Supporting Pyrometric cones are coned shaped and have extra material at the bottom so that they can stand upright by themselves on a kiln shelf.

Orton is the largest manufacturer of pyrometric cones. As a result, they set the standard of the heat temperature that each cone represents. The melting point of each pyrometric cone is shown in the Orton Pyrometric Cone Chart located here:

http://www.glazemixer.com/ortonconechart.htm

Good luck!

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Posted on 2007-03-29, By: GlazeMixer *

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