A substance that accelerates the drying of oil-based paints and varnishes. Dryers are sold as liquids and contain metallic salts of organic acids (i.e. metal soaps) which accelerate the oxidation of oil. Examples are cobalt linoleate, cobalt oleate and cobalt naphthenate. Salts of other heavy metals, such as manganese, cerium, lead, chromium, iron and zinc, can also be effective dryers. A prepared liquid dryer, or siccative, generally acts as a catalyst to speed the polymerisation and oxidation processes involved in the drying of oils and alkyds. Some pigments also act as dryers, such as lead oxide and manganese oxide. In recent years non-metallic dryers, such as orthophenathroline, are being used as replacement for the toxic heavy metal dryers. Synonyms: siccative; cobalt drier; drying agent. Trench (2000); Museum of Fine Arts, Boston (2000). [J. Cassar, R. de Angelis]