Why doesn’t my temperature indicator/controller reflect the behaviour of the Orton cones I placed in my firing?

Electronic temperature measurement is very accurate, but it only measures the temperature at one point in the kiln. Similarly it takes no account of the length of the firing or the effect of the kiln atmosphere on the ware. Pyrometric cones like those manufactured by Orton are subjected to the same firing conditions within the kiln as the ware, and therefore more accurately reflect the true firing.

See Orton’s website for more in-depth FAQ’s regarding the use of cones. For example, if a kiln is fired to 1250oC in 8 hours the result will be very different to the same kiln fired to the same temperature over 16 hours. This difference is known as ‘heat work’ which is effectively a combination of firing temperature, length of firing and kiln atmosphere conditions. Changes to any of these parameters will affect the fired appearance of the ware.