salt glaze

In ceramics, a glaze having the texture of orange peel, formed on stoneware by throwing common salt into the kiln at the peak temperature. Sodium from the salt combines with silica in the clay to form a glassy coating of sodium silicate. The glaze may be colorless or may be colored various shades of brown (from iron oxide), blue (from cobalt oxide), or purple (from manganese oxide). Web resource here.

Nicholas Fox. Two-quart Jug. Salt-glazed stoneware. Ca. 1840.