Cracked or crazed
Crazing is a decorative effect or defect characterized by the appearance of small cracks on the surface of the ceramic glaze. This phenomenon occurs due to differences in thermal expansion between the clay body and the glaze during firing or cooling. Variations in the density, thickness and composition of the glaze in relation to the underlying clay can generate internal stresses that result in the formation of fine, delicate cracks, creating a unique and attractive visual pattern.
Crazing can occur in an undesirable manner, compromising the structural integrity of the piece by weakening it and making it less suitable for holding liquids. However, in skilled hands, craquelure is an intentional technique that is deliberately pursued to create unique aesthetic effects. In particular, techniques such as raku, which originated in Japan, employ craquelure as a central element of their aesthetic, producing finishes with a rustic, organic character that highlights the dynamic interaction between the potter, fire and combustible materials.Interesting Fact
Artisans in Jingdezhen, known as the "Porcelain Capital" of China, perfected crackle techniques that allowed them to create intricate and attractive patterns that reflected mastery and attention to detail in ceramic production.Helpful Tip
If you want to avoid crackle on your functional parts, it is crucial to make sure that the coefficient of thermal expansion of the glaze is well matched to that of the clay body used. A good practice is to test fire different glaze formulations to find the combination that minimizes internal stresses during cooling. On the other hand, if you are looking for an intentional crackle effect, you can experiment with glazes specifically designed to crackle or adjust the density and application of the glaze to promote controlled cracking.
