A film on the surface of bronze or similar metals, produced by oxidation over a long period; or a sheen on wooden furniture produced by age, wear, and polishing; or any such acquired change of a surface through age and exposure. On metal, patina is a coating of various chemical compounds such as oxides or carbonates formed on the surface during exposure to the elements (weathering). Patina also refers to accumulated changes in surface texture and color that result from normal use of an object such as a coin or a piece of furniture over time. Such naturally formed patinas have come to be greatly prized and are imitated by patineurs, who produce and apply the patinas. The chemical process by which a patina forms is called patination, and a work of art coated by a patina is said to be patinated. Tiffany Studios offered many varying patinas on their desk sets and lamp bases, including the green patina which simulated the effects of aging on copper and bronze by using green pigments.