Do you sometime see cracks on the glaze of your Japanese pottery?

No, they are not defects. They are intended accidents. Those cracked patterns are called kan-nyuu (貫入) and it is actually a desirable feature of the pottery.

When glazed clay is fired, it expands. The high temperature melts the glaze and fuses it with the clay. When the pottery is cooled down, it shrinks...BUT, the rates of shrinkage of the clay and glaze are different. The glaze shrinks more than the clay and so during the cooling process, cracks are formed on the glaze surface. These crackle patterns are kan-nyuu.

No two kan-nyuu patterns are ever the same. This offers uniqueness in each piece of pottery.

Japanese people love kan-nyuu in their teacups and tea bowls. Tea seeps into the fine cracks, staining it bit by bit. The teacup is slowly changed with frequent use. Its character seems to grow together with its user. It is cherished like an old friend.

On the left, a new teacup. On the right, a well-used and well-loved teacup!

Check your favourite teacup...yes, the one you use everyday...the one that makes you feel that something is missing if it's not with you at the start of the day. Do you see kan-nyuu? :-)