Pyrometric cones gauge heatwork, which is the combination of heat and time, inside a kiln.
They work by contracting, or deforming, in the intense heat of the kiln.
The cones correspond to a specific cone number, and when the desired heat and temperature is reached, the cone tip will bend forward to the same level as the base.
For best results, have one cone higher and one lower in the kiln as well.
These plaques can be used up to cone 36.
These are made to hold standard-sized cones/