A pyrometric cone is a spike-shaped piece of chemically refined clay used to measure temperature in a kiln when firing pottery. Cones have carefully calibrated melting points, based on both temperature and the duration of temperature, indicated by their cone number. They are used to visually determine when a kiln has reached a desired temperature, by observing when a given cone in an observation port starts to droop. Additionally, some varieties can be arranged to mechanically trigger kiln controls when the temperature rises enough for them to deform.

The commercially produced pyrometric cone replaces the glaze cones used by European and American potters during historic periods. In this method, a glaze composition was evaporated to nearly the consistency of clay. It was then formed into cone shapes and set in a soft pad of clay. When placed near a viewing port in the kiln, the potter could see when the glaze reached its melting point. A similar concept among Asian potters was to produce draw rings, rings of clay dipped in glaze. They would be removed from the kiln by a metal rod and inspected for the melting point of the glaze.

Reference

• Hamer, Frank and Janet. The Potter's Dictionary of Materials and Techniques. A & C Black Publishers, Limited, London, England, Third Edition 1991. ISBN 0-8122-3112-0.

External links

• Description and use of pyrometric cones, with temperature table.