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Have you ever seen pottery with “crazing (or cracking)”? The beautiful crack patterns and unique atmosphere are one of the irresistible attractions for pottery lovers. This time, let’s explore this crazing.

Table of Contents
1.　What is Crazing?
2.　The Mechanism of Crazing
3.　The Charm
4.　Changes Over Time
5.　Summary

What is Crazing?

Crazing refers to the crack patterns in the glaze that occur when pottery is cooled. This is only a superficial crack caused by the difference in the shrinkage rate of the base and the glaze, and does not affect the strength of the pottery itself. In addition, technology has been developed to intentionally use crazing to decorate vessels. Crazing enhances the individuality and beauty of pottery, and although they may look similar at first glance, they are essentially different from crazes and scratches.

The Mechanism of Crazing

The basic principle of crazing is thermal expansion and its reaction. Materials have the property of expanding when heated and contracting when cooled. The pottery base and glaze also have this characteristic, but the shrinkage rate is different.
When the pottery comes out of the kiln, it is exposed to the outside air and the temperature drops rapidly. At this time, both the base and glaze shrink, but generally the glaze shrinks more than the clay. Because the base and glaze are in close contact, the pressure causes cracks to form on the surface of the glaze. This is crazing.

The Charm

Not all pottery will have crazing. The way crazing occurs varies depending on the type of clay and glaze. Also, even if the same clay, glaze, and pottery are fired in the same kiln, crazing may or may not occur depending on the position in the kiln and the subtle difference in temperature.
Crazing has a beauty that is born from the forces of nature that humans cannot control. Such natural changes and individuality are a charm that industrial products do not have. Some artists intentionally create crazing as one way of expressing pottery. Crazing can also occur naturally as the pottery is used, and this change over time is also one of the joys of pottery.

Changes Over Time

Crazling pottery can develop new patterns and colors as it is used. For example, the temperature of hot food or use in a dishwasher can cause the crazes to appear again, or moisture and oil can seep into the crazes and change the color. This change over time gives the impression that the pottery is carving out a shared story with the user, and the texture and attachment to the piece deepen. The changes in the crazes that occur depending on how it is used can be said to be the pottery’s growth process.

Summary

Crazing is a unique crack pattern that occurs due to the difference in the shrinkage rate of the pottery base and glaze. This pattern, which occurs when the glaze shrinks during cooling, is an element that enhances the beauty and individuality of the pottery. The way the crazes appear varies depending on the firing conditions and the environment in which it is used, so each piece has a unique expression. Crazing is one of the elements that increases the enjoyment of using pottery, and allows the user to feel the natural beauty that cannot be found in industrial products.

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