What Is A Pyrometric Cone And What Does It Have To Do With The Temperature Of A Pottery Kiln (With Video)


What Is A Pyrometric Cone And What Does It Have To Do With The Temperature Of A Pottery Kiln

Once a potter creates his pottery piece out of clay, the clay is set out to dry. After the drying process it will be placed into a kiln where it is hardened.

There are five general categories for which kiln temperatures are calculated.

  • Overglaze and China Painting : 1087-1465 degrees Fahrenheit
  • Glass Firing : 1382-1753 degrees Fahrenheit
  • Low Fire Ceramics : 1798-2109 degrees Fahrenheit
  • Mid Fire Ceramics : 2034-2295 degrees Fahrenheit
  • High Fire Ceramics : 2212-2371 degrees Fahrenheit

These temperature ranges are determined by small ceramic cones or bars called pyrometric cones that are designed to melt at various temperatures. Today’s modern kilns allow the temperature to be controlled, and these pyrometric cones are what control the temperature during the firing process.

When a potter is ready to fire a piece of pottery in a kiln they use a specific cone that will melt at approximately the same temperature that is needed to complete the process. The cones measure heat work, which is the effect of time and temperature. The cone is placed in the kiln so that the potter can watch the project’s progress, letting the potter know that temperature is consistent with his or her needs.

The pyrometric cone numbering system can be a bit baffling at first because of the leading zero, which can be thought of like a decimal point or a minus sign (-).

Imagine Cone Number 0 is 0 degrees Fahrenheit. Cone Number 01 could be construed at being -1 degrees, while Cone Number 1 would be +1 degrees. The cones that melt at lower temperatures have a leading zero, like 022 or 010. As the cone temperature rises the leading zero disappears and the numbers keep increasing.

Here are a few statements that may help with understanding the pyrometric cone numbering system:

  • Cone Number 022 is the cone with the lowest temperature.
  • Cone Number 14 is the cone with the highest temperature.
  • Cone Number 010 is colder than Cone Number 10.
  • Cone Number 10 is hotter than Cone Number 010.

Video: Understanding Pyrometric Cone Numbers For Kiln Sitters

November 25, 2013