Peeling Defect in Ceramics: Causes, Analysis & Prevention

Peeling Defect in Ceramics: Causes, Analysis & Prevention

Peeling is a defect in ceramic products where the glaze lifts or separates from the body of the product. This defect is also known as shivering. It is basically the opposite of crazing.

How Does Peeling Happen?

Peeling happens during the cooling stage after firing. As the ceramic product cools, both the glaze and the body contract. If the body shrinks more than the glaze, the glaze is left under compression. When this compression becomes too strong, the glaze separates or peels off from the surface of the body.

Root Cause: Thermal Expansion Mismatch

The root cause of peeling is a mismatch in the Coefficient of Thermal Expansion (CTE) between the glaze and the body. In peeling, the glaze has a lower CTE than the body. This means the glaze shrinks less than the body during cooling, creating a gap and causing separation between the two layers.

This is the opposite of crazing, where the glaze shrinks more than the body. In peeling, the body puts too much pressure on the glaze from underneath, and the glaze breaks away from the surface in small flakes or chips.

How to Prevent Peeling

To prevent peeling in ceramic products, the following steps should be taken:

• Adjust the glaze formula to increase its CTE so it better matches the body
• Use raw materials in the glaze that have higher thermal expansion properties
• Test the glaze and body combination before full production to check CTE compatibility
• Control the cooling rate in the kiln to reduce the stress on the glaze surface

Impact on Product Quality

Peeling leaves sharp edges and rough patches on the ceramic surface. This not only makes the product look bad but also makes it unsafe to use. Products with peeling defects are rejected in quality inspection as the glaze loss cannot be repaired after firing.