Hagi ware is a traditional form of Japanese pottery made exclusively in Hagi, Yamaguchi Prefecture. It is derived from the styles of Korean potters who were brought to Hagi following the Japanese military invasion of Korea in the late sixteenth century. Hagi ware is famous in Japan as one of the three traditional types of pottery used in tea ceremonies, the other two are Raku and Karatsu ware.
Hagi ware is made from local clay that becomes a porous, red-brown stoneware when fired. Glaze is used to produce the distinct colors of Hagi ware, the most common of which is a milky white. The firing process is performed across several days using a long, multilevel kiln. After the pieces are fired the kiln is left closed for several days to cool. As the pieces inside the kiln cool, the glaze and clay contract at different speeds. During this process, the glaze often develops hairline fractures known as crazing.
The crazing of the glaze and the porousness of the clay cause the pottery to absorb tea during its use. This absorption will change the color of the piece over time, a process known as nanabake. Hagi ware is said to go through as many as seven different color changes as it is used, and pieces that have changed color in this way are highly prized. There are numerous styles and shapes of Hagi ware. Rather than being a static, unchanging craft, it is very much a living tradition.