Purple clay, known as Zi Sha, is a special type of clay with excellent transmission and preservation of heat. Teapots made from this material are designed to retain the aroma and flavors of tea brewed with them; therefore, it is best to brew only one particular type of tea in a Zi Sha pot, so that that pot absorbs the essence of the tea and brings it out in further sessions. These teapots became popular throughout China in the North Song Dynasty, and were traded to many other countries from there.
