The determination of the permanent variation of the linear dimensions of a sample of dense refractory material is made by measuring its dimensions before and after a heat treatment at a given temperature.

The thermal cycle (up to a maximum of 1700°C) and the firing atmosphere (oxidizing or inert), as well as the shape and size of the sample can be tailored according to the specific test requirements of the customer, or can follow the standards ASTM C113 or UNI 993-10.

In the case of insulating refractory materials, it is also possible to carry out a volumetric variation test (Reheat Change) according to ASTM C210.