Thermal expansion
Thermal expansion refers to the expansion that clays, clay bodys and glazes undergo when exposed to heat in the kiln. This phenomenon occurs because the increase in temperature causes increased vibration of the molecules, causing the materials to expand. During firing, this expansion is gradual, but in the cooling stage, the materials begin to contract. The correct understanding of thermal expansion is fundamental to avoid structural defects in ceramic pieces.
If the coefficient of thermal expansion of the glaze does not match that of the clay body, internal stresses occur in the part. These stresses can cause common problems such as cracking, spalling, or fracture. To avoid these problems, glazes and clays with compatible coefficients of expansion must be formulated. Proper choice of materials is especially critical in utility ceramics, where exposure to sudden temperature changes can cause thermal shocks that damage the part.Interesting Fact
Some industrial ceramics use materials with low thermal expansion, such as cordierite, to manufacture parts that are resistant to thermal shock. This property allows tableware, kilns and refractory plates to withstand sudden temperature changes without cracking or breaking.Helpful Tip
If you notice cracking or spalling on your pieces, check the compatibility of the coefficient of expansion between the glaze and the clay. You can adjust the glaze formula by adding oxides such as alumina or modifying the proportion of feldspars. Test small samples before final production to avoid losses in large batches of ceramics.
