Large dish with ash glaze.

Ash glaze

Ash glazes (kaiyū) are ceramic glazes made from the ashes of plants, such as wood or straw. Traditionally, these are divided into three categories: pure wood ash, which is made from the bark of trees such as oak and chestnut and has a faintly blue hue; hearth ash, which contains impurities and has a faintly bluish-green hue; and straw ash, which produces a milky-white glaze.