Glaze adhesion is the ability of the glaze to bond firmly to the surface of the ceramic piece during firing. To achieve good adhesion, it is essential that the coefficient of thermal expansion of the glaze is slightly less than that of the clay body. This ensures that, during cooling, the glaze is compressed and does not crack.
If the glaze expands more than the piece, a phenomenon known as cracking can occur, where small cracks form on the surface. This type of defect can be aesthetic in certain styles, but is generally avoided, especially in functional tableware where it can compromise durability and food safety.
Interesting Fact
In raku ceramics, crackle is a desired effect, as it adds character to the piece and creates a unique aesthetic.
Helpful Tip
Always test small pieces before glazing a series of products. This will allow you to make sure that the coefficient of thermal expansion is compatible between the clay body and the glaze you are using.
