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Figuratively, patina can refer to any fading, darkening, or other signs of age, which are felt to be natural or unavoidable (or both). The chemical process by which a patina forms or is deliberately induced is called patination, and a work of art coated by a patina is said to be patinated . Copper weather vane with verdigris patina.
Similar processes can be found on some ancient Egyptian copper sheets. [3] Another example of early chemical coloring of metals is the Nebra sky disk , which has a green patina and gold inlays. An early example of black colored iron is the famous Celtic spearhead found in the River Thames and dated between 200 and 50 BC.
Verdigris is a collective term for copper acetate, whose chemical varieties produce different hues. The technical literature is inconsistent in describing these variations. Some sources refer to "neutral verdigris" as copper (II) acetate monohydrate ( Cu (CH3CO2)2· (H2O)) and to "blue verdigris" as Cu (CH3CO2)2·CuO· (H2O)6. [ 18]
Cupronickel or copper–nickel (CuNi) is an alloy of copper with nickel, usually along with small quantities of other elements added for strength, such as iron and manganese. The copper content typically varies from 60 to 90 percent. ( Monel is a nickel–copper alloy that contains a minimum of 52 percent nickel.)
Shibuichi means "one-fourth" in Japanese, and indicates the standard formulation of one part silver to three parts copper, though this may vary considerably according to the desired effect. Several major variants of the alloy have specific names, as detailed below. In addition, the metal in general, and especially the paler shades, may be named ...
Bronzes. A bronze is an alloy of copper and other metals, most often tin, but also aluminium and silicon. Aluminium bronzes are alloys of copper and aluminium. The content of aluminium ranges mostly between 5% and 11%. Iron, nickel, manganese and silicon are sometimes added.
Unlike wear patina necessary in applications such as copper roofing, outdoor copper, bronze, and brass statues and fittings, chemical patina is considered a lot more uneven and undesirable [2]. Patina is the name given to tarnish on copper-based metals, while toning is a term for the type of tarnish which forms on coins.
Its name comes from the natural pigments that form a patina on copper, bronze, and brass as it ages. [2] The most famous example is the green patina that formed on the Statue of Liberty in New York Harbor. In the Middle Ages, the patina was made by attaching copper strips to a wooden block with acetic acid, then burying the sealed block in dung ...