Ash glaze

A Yunomi or tea cup with an ash glaze made from pine ash.

Ash glazes are types of high temperature glazes for stoneware pottery that include the ashes of trees, shrubs, plants or grasses within the glaze recipe.

Plant ashes are a complex mixture that reflect the nutritional requirements, and therefore composition, of the living plant. High in calcium and also incorporating other alkaline material, ash behaves as a flux, encouraging the glass forming oxide silica to melt at a temperature within the scope of a pottery kiln. Ash glazes often have a characteristic mottled or streaky texture, depending on the amount of ash incorporated.