Patina

Patina usually refers to the distinctive green or brown surface layer that forms on bronze and other metal sculpture. Natural patina arises from the slow oxidation of metal under the action of air, moisture and time: copper and bronze become coated with greenish or blue-green compounds, while other metals acquire brown, black or silvery tones. Such a layer not only changes the colour of the work but also to some extent protects the metal from further corrosion, giving the sculpture a sense of age and nobility. Besides forming naturally, patina is often applied artificially: sculptors and founders treat the surface of bronze with chemical solutions and heat to obtain the intended colour and texture — from deep green to warm brown or near-black. Patina thus becomes a deliberate artistic means, emphasising form and the play of light on the surface. In a broader figurative sense, the word "patina" describes the sheen of time on any old objects — tarnished metal, worn wood — as well as the aesthetic value of the marks of ageing. Conservators carefully distinguish valuable historic patina from harmful products of corrosion.