Pyrometric cones measure heat-work (the effect of time and temperature).
- Pyrometric cones are slender pyramids made from about 100 carefully controlled compositions.
- Each cone number is unique in measuring temperature within a small temperature range (less than 30°C).
- Cones measure the amount of heat absorbed.
- As the cone nears its maturing range, it softens and the tip begins to bend, drawn down by the influence of gravity.
While a single cone may be used on the shelf to “witness” the firing, it is common practice to use three different cones. A group consists of a Firing cone – the desired cone for the ware being produced, the Guide cone – one cone number cooler, and the Guard cone – one cone number hotter than the firing cone. These cones are set deep in the kiln, yet should be visible through a peephole.
When the Guide cone starts to bend, the ware is approaching maturity. The bending of the Firing cone indicates firing is at the correct point. If the Guard cone has bent, you have exceeded the best time-temperature relationship.
Guide Cone – one cone number cooler
Firing Cone – desired cone temperature
Guard Cone – one cone number hotter
Please Specify Cone # OCS____ in comments section in your final checkout.