Patina

patina (păt`ənə), 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.

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desert varnish

 or patina

Thin, dark red to black mineral coating (generally iron and manganese oxides and silica) deposited on pebbles and rocks on the surface of desert regions. As dew and soil moisture brought to the surface by capillary action evaporate, their dissolved minerals are deposited on the surface. Wind abrasion removes the softer salts and polishes the surface to a glossy finish. Both high evaporation rates and sufficient precipitation are necessary for desert varnish to form.

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patina¹

a film of oxide formed on the surface of a metal, esp the green oxidation of bronze or copper

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patina²

a broad shallow dish used in ancient Rome

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patina [′pat·ən·əorpə′tē·nə]

(geology)

A thin, colored film produced on a rock surface by weathering.

(metallurgy)

The greenish product, usually basic copper sulfate, formed on copper and copper-rich alloys as a result of prolonged atmospheric corrosion.

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patina, patination

1. A greenish brown crust which forms on bronze.

2. Any thin oxide film which forms on a metal; often multicolored.

3. A film, similar in color, which forms on a material other than metal.

4. Such effects artificially induced, or imitated.

5. A green coating on the surface of copper or copper alloys that have been exposed to the atmosphere for a long time.

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Patina 

a film ranging from green to cinnamon in color that forms on the surface of copper, bronze, and brass articles. A patina results from the natural corrosion of the metal or from patination—that is, heating or processing with oxidizing agents. A patina formed by the latter method is used to protect works of art and for decorative purposes. Roman artists were the first to recognize patina as a sign of beauty through aging. The term “patination” is also used to designate the process whereby articles not made from copper alloys, for example, plaster-of-paris sculptures, are tinted bronze.