Potters in Iran began to practice the luster technique in the middle of the twelfth century and reached their creative apogee in the first few decades of the thirteenth century. In the city of Kashan, located in central Iran, potters developed stonepaste, or fritware, a white composition made of ground quartz, ground glass, and a type of white clay that eliminated the need for an opaque white tin glaze. Fine rendering and elaborate designs characterize Persian lusterware.