An underglaze is a decorative technique used in pottery. Pigment is added to a wet, unfired piece of pottery which is then coated with glaze. The pigment fuses with the glaze when the piece is fired in a kiln, and appears to be under a layer of clear glaze. The opposite technique is overglazing, adding a layer of decoration on top of an already-fired layer of glaze.

Underglaze decoration is generally associated with the famous "blue and white" porcelain. In these cases the blue colour is achieved by using a cobalt pigment, fired at the correct temperature.

Porcelain | Pottery