Alkaline Glaze
(as it pertains to the Catawba Valley region of North Carolina).
Potters in the Catawba Valley region (Lincoln and Catawba counties) of North Carolina formulated an alkaline glaze type for use on their stoneware pottery. This glaze was compose of clay and wood ash, as well as one of two additional silica sources: iron slag, or glass.
The "cinder glaze" contained crushed iron slag, obtained from local smelting furnaces and rendered a deep glossy brown glaze with thick rivulets running down vertical surfaces.
The "glass glaze" utilized powdered glass made by crushing window panes and bottles. It's color was typically green and smoother in texture.
