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.