On the contrary, it appeared over one thousand years ago during the Sung dynasty when it was known as chien yao or kemmoku. It was during this time that the two forms of crystal glaze were known as yao pien (dazzling changes) and yuti (oil spot).
結晶釉並不是今人所創，早在一千多年前的宋朝建窯（在今福建省），就已燒出「曜變」和「油滴」兩種結晶釉。