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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.
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
Guanín objects made by the Taínos excavated in Cuba.. Guanín is an alloy of copper, gold and silver, similar to red gold, used in pre-Columbian central America. [1] The name guanín is taken from the language of the Taíno people, who prized it for its reddish color, brilliant shine, and unique smell, and associated it with both worldly and supernatural power.
The Statue of Liberty, showing advanced patination; verdigris is responsible for the statue's iconic green colour.. Verdigris (/ ˈ v ɜːr d ɪ ɡ r iː (s)/) [1] is a common name for any of a variety of somewhat toxic [2] [3] [4] copper salts of acetic acid, which range in colour from green to a bluish-green depending on their chemical composition.
Shakudō (赤銅) is a Japanese billon of gold and copper (typically 4–10% gold, 96–90% copper), one of the irogane class of colored metals, which can be treated to develop a black, or sometimes indigo, patina, resembling lacquer.
Kuro-shibuichi will develop a black patina which is different from the black patina of shakudo. It is a common misconception that both copper and silver oxides form, but in fact a detailed study has shown that only copper oxides are formed on the copper rich regions of the material's microstructure, while the silver rich regions are left ...
Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents, fungicides, and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c ...
Rokushō is used to treat a number of metals, including raw natural copper, which holds impurities, purified copper, and copper alloy mixes with two to five metals, to produce irogane metals, including: shakudō, an alloy of copper and gold, which becomes black to dark blue-violet; shibuichi, an alloy of fine silver and copper (in a higher percentage than sterling), which turns grey to misty ...