Bronze

Bronze is an alloy consisting primarily of copper and the addition of other metals (usually tin) and sometimes arsenic, phosphorus, aluminium, manganese, and silicon. These additions produces an alloy much harder than copper alone. The historical period where the archeological record contains many bronze artifacts is known as the Bronze Age.

There are many different bronze alloys, but typically modern bronze is 88% copper and 12%tin. Alpha bronzes consists of the alpha solid solution of tin in copper. Alpha bronzes alloys of 4–5% tin are used to make coins, springs, turbines and blades. Historical “bronzes” are highly variable in composition, as most metalworkers probably used whatever scrap was on hand; the metal of the 12th-century English Gloucester Candlestick is bronzes containing a mixture of copper, zinc, tin, lead, nickel, iron, antimony, arsenic with an unusually large amount of silver – between 22.5% in the base and 5.76% in the pan below the candle. The proportions of this mixture may suggest that the candlestick was made from a hoard of old coins. The Benin Bronzes are really brass, and the Romanesque Baptismal font at St Bartholomew’s Church, Liège is described as both bronzes and brass.

In the Bronze Age, two forms of bronzes were commonly used: “classic bronzes”, about 10% tin, was used in casting; and “mild bronzes”, about 6% tin, was hammered from ingots to make sheets. Bladed weapons were mostly cast from classic bronzes, while helmets and armor were hammered from mild bronzes.

Commercial bronzes (90% copper and 10% zinc) and architectural bronzes (57% copper, 3% lead, 40% zinc) are more properly regarded as brass alloys because they contain zinc as the main alloying ingredient. They are commonly used in architectural applications.

Bismuth bronzes is a bronzes alloy with a composition of 52% copper, 30% nickel, 12% zinc, 5% lead, and 1% bismuth. It is able to hold a good polish and so is sometimes used in light reflectors and mirrors.

Plastic bronzes is bronzes containing a significant quantity of lead which makes for improved plasticity possibly used by the ancient Greeks in their ship construction.

Other bronzes alloys include aluminium bronzes, phosphor bronzes, manganese bronzes, bell metal, arsenical bronzes, speculum metal and cymbal alloys.

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