Ceramic - Pottery Dictionary

by Susan Mussi

CONE (2) Pyrometric.

ca: CON (2) Piromètric

es: CONO (2) Pirométrico.

Pyrometric cones measure and control the heat in the kiln while firing and cut off the electricity when it reaches the correct temperature. There are two methods; the American Orton and English Harrison. They work in the same way but have two basic differences; one is their numbering in relation to heat and the other is their shape. Ortons are a slanted pyramid and Harrisons are straight and square.

There are two sizes, cones and mini-bars. Cones are larger and measure 63mm in length and mini-bars measure 25mm. They are delicate, can break easily are colored and numbered differently in relation to heat and are made up of minerals that reach a specified temperature.

They are placed in a kiln sitter between the sensing rod and the cone supports. When the kiln reaches the correct heat, which is a collapsing point, the cone bends and this automatically cut off the electricity, which turns off the kiln and finishes the firing.
In the following section there are three charts showing the different types of cones with their coding, make and temperatures in Centigrade and Fahrenheit.
KILN SITTER: a) Sensing tube, b) Sensing rod, c) Cone, d) Cone supports.