Underglaze

An underglaze is a decorative technique used on some ceramic articles. Pigment is applied on either an unfired or biscuit fired article before being coated with glaze. The pigment fuses with the glaze when the piece is fired, either for the first time or during the glost fire, in a kiln. The reverse is overglazing, adding a layer of decoration on top of glaze, usually unfiired, before it is fired.

An example of underglaze decoration is the famous "blue and white" porcelain. In these cases the blue colour is derived from a cobalt pigment.