Calamine brass
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Calamine brass is brass produced by a particular alloying technique using calamine, a zinc ore, rather than metallic zinc. Calamine brass was produced using proportions of two-sevenths fine copper, four-sevenths calamine, and one-seventh shruff (old plate brass). Calamine brass was the first type of brass produced, probably starting during the 1st millennium BC, and was not replaced in Europe by other brass manufactures until the 18th century (it is likely that Chinese and Indian brass manufacturers had developed more advanced techniques some centuries earlier).
Brass is an alloy of copper and zinc, and when it was first developed, methods for producing metallic zinc were unknown. Metallurgists wishing to produce brass thus used calamine (actually a mixture of the virtually indistinguishable zinc ores smithsonite and hemimorphite) as the zinc component of brass. The resulting brasses, produced by heating a mixture of copper and calamine to a high temperature for several hours (allowing zinc vapor to distill from the ores and permeate the metallic copper), contained a significant amount of slag material resulting from the non-zinc components of calamine. The use of ore rather than metallic zinc also made it difficult to accurately produce the desired final proportion of copper to zinc. This process is known as cementation.
The mineral calamine takes its name from La Calamine in Belgium. That area was the source of much of the medieval brass of northern Europe. Brass production was introduced to England in 1587 when several members of the Company of Mineral and Battery Works obtained a licence from the company (within whose monopoly it was) at built brass works at Isleworth. However a decade later the company obstructed the owners from mining calamine.
New brass works were built by Jacob Momma, a German immigrant in 1649 at Esher, probably using Swedish copper. After the passing of the Mines Royal Act in 1689, further works were built near Bristol, where brass production became a major industry in the 18th century. Later brass production sites in England included Cheadle and Birmingham.
Calamine brass was slowly phased out as zinc smelting techniques were developed in Europe, which produced metallic zinc more suitable for brass production than calamine. However, the conversion away from calamine brass manufacture was slow; a British patent was awarded to William Champion in 1738, but the alloying of metallic zinc and copper to produce brass was not patented until 1781 (by James Emerson), and calamine brass mills persisted in South Wales until as late as 1858. The slow diffusion of this technology was probably the result of economic factors.
[edit] References
- Alexander, W.O. "A Brief Review of the Development of the Copper, Zinc and Brass Industries in Great Britain from AD 1500 to 1900". Murex Review, 1:15, 1955.
- "A Short History of Baptist Mills Brass Works - Part One: The Early Years, 1700 - 1720". Retrieved August 3, 2005.
- R. F. Tylecote, A History of Metallurgy (2nd edn, 1991), 84.
- M. B. Donald, Elizabethan Monopolies (1961), 179-95.
- J. Day, 'Copper, Zinc and Brass Production' in J. Day & R. F. Tylecote (eds.), The Industrial Revolution in Metals (1991), 131-200.
