Thermal resistance

As already noted when describing linear thermal expansion, a change in temperature is associated with a change in the size of the tile; and sudden or frequent temperature changes can cause quite serious consequences.

Let's imagine, for example, the tiled surface of a kitchen countertop on which a hot pan is placed. The surface of the tile heats up sharply and, as a result, expands, and the lower layers become colder and less expanded as they move away from it. In this state of thermal heterogeneity, the tile tends to deform and, being an inherently rigid material, can crack. External cladding or tile coverings in industrial premises are also susceptible to the effects of sudden temperature changes. Thus, in food industry enterprises, surfaces are often cleaned with a jet of steam whose temperature exceeds 100°C.

Thermal resistance is the ability of ceramic tiles to withstand without damage the stress caused by dimensional deformations due to sudden changes in temperature, especially if such changes are repeated frequently.

The test method is described in the EN ISO 10545-9 and consists of the following: the samples are subjected to 10 rapid temperature cycles from 15 °C to 145 °C. The maximum temperature is achieved by placing the samples in an oven for a minimum of 20 minutes, the minimum by completely immersing them in water at a temperature of 15°C. At the end of 10 cycles, samples are inspected for visible defects. If necessary, dyes are used to detect cracks.