patina

patina , coating of carbonate of copper on articles of copper or bronze, formed after long exposure to a moist atmosphere or burial in the earth. Although commonly green, patina varies in color and consistency; it may be red, brown, black, blue, or gray, or it may be smooth, glossy, or crusty. It may be imitated by a number of oxidation processes. The term has been extended to include the film formed on metals, pottery, marble, and other materials by exposure and to the mellow surface acquired by furniture with time and waxing.

patina film produced by alteration of the surface of bronze, marble, etc. XVIII. — It. — L. patina dish; see PATEN.

patina. Incrustation, usually green, on the surface of a metal (typically bronze) object, caused by corrosion. Such discoloration occurs naturally with age through exposure to the atmosphere and can be accelerated or modified when an object is buried in the sea or soil, where various substances present will cause chemical reactions. Patination can produce an attractive, mellowing effect, and since the Renaissance bronze statues have often been artificially patinated, usually by treatment with acid. By extension, the term ‘patina’ can be applied to any form of surface discoloration or mellowing, for example dirty varnish on a painting.