sentence: Colour comes from iron oxide, copper carbonate or cobalt carbonate.
sentences_before: Ceramic glaze raw materials generally include silica, which will be the main glass former. Various metal oxides, such as sodium, potassium and calcium, act as a flux to lower the melting temperature. Alumina, often derived from clay, stiffens the molten glaze to prevent it from running off the piece.
sentences_after: Tin oxide or zirconium oxide, are used to make the glaze opaque.
concept_name: colour
headings: Glaze
categories: Pottery