Product Code Database
Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, Engineering Designer 30(3): 6–9, May–July 2004 but copper typically has the larger proportion, generally copper and zinc. In use since prehistoric times, it is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.
Brass is similar to bronze, a copper alloy that contains tin instead of zinc. Machinery Handbook, New York, Industrial Press, Edition 24, p. 501 Both bronze and brass may include small proportions of a range of other Chemical element including arsenic, lead, phosphorus, aluminium, manganese and silicon. Historically, the distinction between the two alloys has been less consistent and clear, and increasingly museums use the more general term "copper alloy".
Brass has long been a popular material for its bright gold-like appearance and is still used for and door handle. It has also been widely used to make sculpture and utensils because of its low melting point, high workability (both with hand tools and with modern lathe and milling machines), durability, and electrical and thermal conductivity. Brasses with higher copper content are softer and more golden in colour; conversely those with less copper and thus more zinc are harder and more silvery in colour.
Brass is still commonly used in applications where corrosion resistance and low friction are required, such as padlock, , , bearings, ammunition casings, , plumbing, , , SCUBA regulators, and electrical plugs and sockets. It is used extensively for brass instrument such as horns and metallophone. The composition of brass makes it a favorable substitute for copper in costume jewelry and fashion jewelry, as it exhibits greater resistance to corrosion. Brass is not as hard as bronze and so is not suitable for most weapons and tools. Nor is it suitable for marine uses, because the zinc reacts with minerals in salt water, leaving porous copper behind; marine brass, with added tin, avoids this, as does bronze.
Brass is often used in situations in which it is important that sparks not be struck, such as in fittings and tools used near flammable or explosive materials.
Today, almost 90% of all brass alloys are recycled. Because brass is not Ferromagnetism, ferrous scrap can be separated from it by passing the scrap near a powerful magnet. Brass scrap is melted and recast into billets that are extruded into the desired form and size. The general softness of brass means that it can often be machined without the use of cutting fluid, though there are exceptions to this.
Aluminium makes brass stronger and more corrosion-resistant. Aluminium also causes a highly beneficial hard layer of aluminium oxide (Al2O3) to be formed on the surface that is thin, transparent, and self-healing. Tin has a similar effect and finds its use especially in seawater applications (naval brasses). Combinations of iron, aluminium, silicon, and manganese make brass wear- and Tear resistance. The addition of as little as 1% iron to a brass alloy will result in an alloy with a noticeable magnetic attraction.
Brass will corrosion in the presence of moisture, , , ammonia, and certain acids. This often happens when the copper reacts with sulfur to form a brown and eventually black surface layer of copper sulfide which, if regularly exposed to slightly acidic water such as urban rainwater, can then oxidize in air to form a patina of green-blue copper carbonate. Depending on how the patina layer was formed, it may protect the underlying brass from further damage.
Although copper and zinc have a large difference in electrical potential, the resulting brass alloy does not experience internalized galvanic corrosion because of the absence of a corrosive environment within the mixture. However, if brass is placed in contact with a more noble metal such as silver or gold in such an environment, the brass will corrode galvanically; conversely, if brass is in contact with a less noble metal such as zinc or iron, the less noble metal will corrode and the brass will be protected.
In October 1999, the California State Attorney General sued 13 key manufacturers and distributors over lead content. In laboratory tests, state researchers found the average brass key, new or old, exceeded the California Proposition 65 limits by an average factor of 19, assuming handling twice a day. News & Alerts – California Dept. of Justice – Office of the Attorney General. 12 October 1999. , In April 2001 manufacturers agreed to reduce lead content to 1.5%, or face a requirement to warn consumers about lead content. Keys plated with other metals are not affected by the settlement, and may continue to use brass alloys with a higher percentage of lead content. News & Alerts – California Dept. of Justice – Office of the Attorney General. 27 April 2001. San Francisco Superior Court, People v. Ilco Unican Corp., et al. (No. 307102) and Mateel Environmental Justice Foundation v. Ilco Unican Corp., et al. (No. 305765)
Also in California, lead-free materials must be used for "each component that comes into contact with the wetted surface of pipes and pipe fittings, plumbing fittings and fixtures". On 1 January 2010, the maximum amount of lead in "lead-free brass" in California was reduced from 4% to 0.25% lead. AB 1953 Assembly Bill – Bill Analysis . Info.sen.ca.gov. Retrieved on 9 December 2011. Requirements for Low Lead Plumbing Products in California , Fact Sheet, Department of Toxic Substances Control, State of California, February 2009
An example of DZR brass is the C352 brass, with about 30% zinc, 61–63% copper, 1.7–2.8% lead, and 0.02–0.15% arsenic. The lead and arsenic significantly suppress the zinc loss.
"Red brasses", a family of alloys with high copper proportion and generally less than 15% zinc, are more resistant to zinc loss. One of the metals called "red brass" is 85% copper, 5% tin, 5% lead, and 5% zinc. Copper alloy C23000, which is also known as "red brass", contains 84–86% copper, 0.05% each iron and lead, with the balance being zinc.
Another such material is gunmetal, from the family of red brasses. Gunmetal alloys contain roughly 88% copper, 8–10% tin, and 2–4% zinc. Lead can be added for ease of machining or for bearing alloys.
"Naval brass", for use in seawater, contains 40% zinc but also 1% tin. The tin addition suppresses zinc-leaching.
The NSF International requires brasses with more than 15% zinc, used in piping and plumbing fittings, to be dezincification-resistant.
Other may be constructed of brass or other metals, and indeed most modern student-model and are made of some variety of brass, usually a cupronickel alloy similar to nickel silver. Clarinets, especially low clarinets such as the contrabass and subcontrabass, are sometimes made of metal because of limited supplies of the dense, fine-grained tropical hardwoods traditionally preferred for smaller . For the same reason, some low clarinets, and feature a hybrid construction, with long, straight sections of wood, and curved joints, neck, and/or bell of metal. The use of metal also avoids the risks of exposing wooden instruments to changes in temperature or humidity, which can cause sudden cracking. Even though the and are classified as woodwind instruments, they are normally made of brass for similar reasons, and because their wide, conical bores and thin-walled bodies are more easily and efficiently made by forming sheet metal than by machining wood.
The keywork of most modern woodwinds, including wooden-bodied instruments, is also usually made of an alloy such as nickel silver. Such alloys are stiffer and more durable than the brass used to construct the instrument bodies, but still workable with simple hand tools—a boon to quick repairs. The mouthpieces of both brass instruments and, less commonly, woodwind instruments are often made of brass among other metals as well.
Next to the brass instruments, the most notable use of brass in music is in various percussion instruments, most notably , , and Tubular bells (large "church" are normally made of bronze). Small and "" are also commonly made of brass.
The harmonica is a free reed aerophone, also often made from brass. In Reed pipe of the reed family, brass strips (called tongues) are used as the reeds, which beat against the reed pipe (or beat "through" the shallot in the case of a "free" reed). Although not part of the brass section, are also sometimes made of brass. Some parts on electric guitars are also made from brass, especially inertia blocks on tremolo systems for its tonal properties, and for string nuts and saddles for both tonal properties and its low friction.
A large number of independent studies confirm this antimicrobial effect, even against antibiotic-resistant bacteria such as MRSA and VRSA. The mechanisms of antimicrobial action by copper and its alloys, including brass, are a subject of intense and ongoing investigation.
Other phases than α, β and γ are ε, a hexagonal intermetallic CuZn3, and η, a solid solution of copper in zinc.
Brass has sometimes historically been referred to as "yellow copper".
The compositions of these early "brass" objects are highly variable and most have zinc contents of between 5% and 15% wt which is lower than in brass produced by cementation.Craddock and Eckstein 2003 p. 217 These may be "natural alloys" manufactured by smelting zinc rich copper ores in redox conditions. Many have similar tin contents to contemporary bronze artefacts and it is possible that some copper-zinc alloys were accidental and perhaps not even distinguished from copper. However the large number of copper-zinc alloys now known suggests that at least some were deliberately manufactured and many have zinc contents of more than 12% wt which would have resulted in a distinctive golden colour.Thornton, C. P. and Ehlers, C. B. (2003) "Early Brass in the ancient Near East", in IAMS Newsletter 23 pp. 27–36
By the 8th–7th century BC cuneiform tablets mention the exploitation of the "copper of the mountains" and this may refer to "natural" brass.Bayley 1990, p. 8 "Oreikhalkon" (mountain copper), the Ancient Greek translation of this term, was later adapted to the Latin aurichalcum meaning "golden copper" which became the standard term for brass.Rehren and Martinon Torres 2008, p. 169 In the 4th century BC Plato knew orichalkos as rare and nearly as valuable as gold and Pliny describes how aurichalcum had come from Cyprus ore deposits which had been exhausted by the 1st century AD.Pliny the Elder Historia Naturalis XXXIV 2 X-ray fluorescence analysis of 39 orichalcum ingots recovered from a 2,600-year-old shipwreck off Sicily found them to be an alloy made with 75–80% copper, 15–20% zinc and small percentages of nickel, lead and iron.
By the first century BC brass was available in sufficient supply to use as in Phrygia and Bithynia, and after the Augustan currency reform of 23 BC it was also used to make Roman dupondius and Sestertius. The uniform use of brass for coinage and military equipment across the Roman world may indicate a degree of state involvement in the industry,Bayley 1990, p. 21 and brass even seems to have been deliberately boycotted by Jewish communities in Palestine because of its association with Roman authority.
Brass was produced by the cementation process where copper and zinc ore are heated together until zinc vapor is produced which reacts with the copper. There is good archaeological evidence for this process and used to produce brass by cementation have been found on Roman period sites including Xanten and Nidda in Germany, Lyon in FranceRehren and Martinon Torres 2008, pp. 170–71 and at a number of sites in Britain.Bayley 1990 They vary in size from tiny acorn sized to large like vessels but all have elevated levels of zinc on the interior and are lidded. They show no signs of slag or metal prills suggesting that zinc minerals were heated to produce zinc vapor which reacted with metallic copper in a solid state reaction. The fabric of these crucibles is porous, probably designed to prevent a buildup of pressure, and many have small holes in the lids which may be designed to release pressure or to add additional zinc minerals near the end of the process. Dioscorides mentioned that zinc minerals were used for both the working and finishing of brass, perhaps suggesting secondary additions.Craddock and Eckstein 2003, p. 224
Brass made during the early Roman period seems to have varied between 20% and 28% wt zinc. The high content of zinc in coinage and brass objects declined after the first century AD and it has been suggested that this reflects zinc loss during recycling and thus an interruption in the production of new brass. However it is now thought this was probably a deliberate change in composition and overall the use of brass increases over this period making up around 40% of all copper alloys used in the Roman world by the 4th century AD.Craddock 1978, p. 14
These places would remain important centres of brass making throughout the Middle Ages period,Day 1990, pp. 124–133 especially Dinant. Brass objects are still collectively known as dinanderie in French. The baptismal font at St Bartholomew's Church, Liège in modern Belgium (before 1117) is an outstanding masterpiece of Romanesque art brass casting, though also often described as bronze. The metal of the early 12th-century Gloucester Candlestick is unusual even by medieval standards in being a mixture of copper, zinc, tin, lead, nickel, iron, antimony and arsenic with an unusually large amount of silver, ranging from 22.5% in the base to 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, probably Late Roman.Noel Stratford, pp. 232, 245, in Zarnecki, George and others; English Romanesque Art, 1066–1200, 1984, Arts Council of Great Britain, Latten is a term for medieval alloys of uncertain and often variable composition often covering decorative borders and similar objects cut from sheet metal, whether of brass or bronze. Especially in Tibetan art, analysis of some objects shows very different compositions from different ends of a large piece. were typically made in brass in both the European and Islamic worlds.
The cementation process continued to be used but literary sources from both Europe and the Islamic world seem to describe variants of a higher temperature liquid process which took place in open-topped crucibles.Craddock and Eckstein 2003, pp. 224–25 Islamic cementation seems to have used zinc oxide known as tutiya or tutty rather than zinc ores for brass-making, resulting in a metal with lower iron impurities.Craddock et al. 1990, 78 A number of Islamic writers and the 13th century Italians Marco Polo describe how this was obtained by sublimation from zinc ores and Condensation onto clay or iron bars, archaeological examples of which have been identified at Hindu Kush in Iran.Craddock et al. 1990, pp. 73–76 It could then be used for brass making or medicinal purposes. In 10th century Yemen al-Hamdani described how spreading al-iglimiya, probably zinc oxide, onto the surface of molten copper produced tutiya vapor which then reacted with the metal.Craddock et al. 1990, p. 75 The 13th century Iranian writer al-Kashani describes a more complex process whereby tutiya was mixed with and gently roasted before being added to the surface of the molten metal. A temporary lid was added at this point presumably to minimize the escape of zinc vapor.Craddock et al. 1990, p. 76
In Europe a similar liquid process in open-topped crucibles took place which was probably less efficient than the Roman process and the use of the term tutty by Albertus Magnus in the 13th century suggests influence from Islamic technology.Rehren, T (1999) "The same... but different: A juxtaposition of Roman and Medieval brass making in Europe" in Young, S. M. M. (ed.) Metals in antiquity Oxford: Archaeopress pp. 252–257 The 12th century Germans monk Theophilus described how preheated crucibles were one sixth filled with powdered calamine and charcoal then topped up with copper and charcoal before being melted, stirred then filled again. The final product was casting, then again melted with calamine. It has been suggested that this second melting may have taken place at a lower temperature to allow more zinc to be absorbed.Craddock and Eckstein 2003, 226 Albertus Magnus noted that the "power" of both calamine and tutty could evaporate and described how the addition of powdered glass could create a film to bind it to the metal.Rehren and Martinon Torres 2008, pp. 176–178
German brass making crucibles are known from Dortmund dating to the 10th century AD and from Soest and Schwerte in Westphalia dating to around the 13th century confirm Theophilus' account, as they are open-topped, although ceramic discs from Soest may have served as loose lids which may have been used to reduce zinc evaporation, and have slag on the interior resulting from a liquid process.Rehren and Martinon Torres 2008, pp. 173–175
16th-century technical writers such as Biringuccio, Lazarus Ercker and Agricola described a variety of cementation brass making techniques and came closer to understanding the true nature of the process noting that copper became heavier as it changed to brass and that it became more golden as additional calamine was added.Martinon Torres and Rehren 2008, 181–82, de Ruette 1995 Zinc metal was also becoming more commonplace. By 1513 metallic zinc from India and China were arriving in London and pellets of zinc condensed in furnace flues at the Rammelsberg in Germany were exploited for cementation brass making from around 1550.de Ruette 1995, 198
Eventually it was discovered that metallic zinc could be with copper to make brass, a process known as speltering,Craddock and Eckstein 2003, 228 and by 1657 the German chemist Johann Glauber had recognized that calamine was "nothing else but unmeltable zinc" and that zinc was a "half ripe metal".de Ruette 1995, 198–9 However some earlier high zinc, low iron brasses such as the 1530 Wightman brass memorial plaque from England may have been made by alloying copper with zinc and include traces of cadmium similar to those found in some zinc ingots from China.
However, the cementation process was not abandoned, and as late as the early 19th century there are descriptions of solid-state cementation in a domed furnace at around 900–950 °C and lasting up to 10 hours.Craddock and Eckstein 2003, 226–27. The European brass industry continued to flourish into the post medieval period buoyed by innovations such as the 16th century introduction of water powered hammers for the production of wares such as pots.Day 1990, p. 131 By 1559 the Germany city of Aachen alone was capable of producing 300,000 centum weight of brass per year. After several false starts during the 16th and 17th centuries the brass industry was also established in England taking advantage of abundant supplies of cheap copper smelted in the new coal fired reverberatory furnace.Day 1991, pp. 135–144 In 1723 Bristol brass maker Nehemiah Champion patented the use of granulated copper, produced by pouring molten metal into cold water.Day 1990, p. 138 This increased the surface area of the copper helping it react and zinc contents of up to 33% wt were reported using this new technique.Craddock and Eckstein 2003, p. 227
In 1738 Nehemiah's son William Champion patented a technique for the first industrial scale distillation of metallic zinc known as distillation per descencum or "the English process".Day 1991, pp. 179–181 This local zinc was used in speltering and allowed greater control over the zinc content of brass and the production of high-zinc copper alloys which would have been difficult or impossible to produce using cementation, for use in expensive objects such as scientific instruments, , brass buttons and costume jewelry.Day 1991, p. 183 However Champion continued to use the cheaper calamine cementation method to produce lower-zinc brass and the archaeological remains of bee-hive shaped cementation furnaces have been identified at his works at Warmley. By the mid-to-late 18th century developments in cheaper zinc distillation such as John-Jaques Dony's horizontal furnaces in Belgium and the reduction of tariffs on zincDay 1991, pp. 186–189 as well as demand for corrosion-resistant high zinc alloys increased the popularity of speltering and as a result cementation was largely abandoned by the mid-19th century.Day 1991, pp. 192–93, Craddock and Eckstein 2003, p. 228
Season cracking
Brass is susceptible to stress corrosion cracking, especially from ammonia or substances containing or releasing ammonia. The problem is sometimes known as season cracking after it was first discovered in brass cartridges used for rifle ammunition during the 1920s in the British Indian Army. The problem was caused by high from cold forming of the cases during manufacture, together with chemical attack from traces of ammonia in the atmosphere. The cartridges were stored in stables and the ammonia concentration rose during the hot summer months, thus initiating brittle cracks. The problem was resolved by annealing the cases, and storing the cartridges elsewhere.
Types
Alpha brasses are malleable, can be worked cold, and are used in pressing, forging, or similar applications. They contain only one phase, with face-centred cubic crystal structure. With their high proportion of copper, these brasses have a more golden hue than others. The alpha phase is a substitution solid solution of zinc in copper. It is close in properties to copper, tough, strong, and somewhat difficult to machine. Best formability is with 32% of zinc. Corrosion-resistant red brasses, with 15% of zinc or less, belong here. Also called duplex brasses, these are suited for hot working. They contain both α and β' phases; the β'-phase is ordered body-centred cubic, with zinc atoms in the centre of the cubes, and is harder and stronger than α. Alpha-beta brasses are usually worked hot. The higher proportion of zinc means these brasses are brighter than alpha brasses. At 45% of zinc the alloy has the highest strength. Beta brasses can only be worked hot, and are harder, stronger, and suitable for casting. The high zinc-low copper content means these are some of the brightest and least-golden of the common brasses. There are also Ag-Zn and Au-Zn gamma brasses, Ag 30–50%, Au 41%. The gamma phase is a cubic-lattice intermetallic compound, Cu5Zn8. These are too brittle for general use. The term may also refer to certain types of nickel silver alloys as well as Cu-Zn-Sn alloys with high proportions (typically 40%+) of tin and/or zinc, as well as predominantly zinc casting alloys with copper additives. These have virtually no yellow colouring at all, and instead have a much more silvery appearance.
Brass alloys
Tin inhibits loss of zinc in many environments. Designed for use in marine service owing to its corrosion resistance, hardness and toughness. A characteristic application is to the protection of ships' bottoms, but more modern methods of cathodic protection have rendered its use less common. Its appearance resembles that of gold.Simons, E. N. (1970). A Dictionary of Alloys, Cornell University Aluminium improves corrosion resistance. It is used for heat exchanger and condenser tubes. Used for boiler fireboxes. Heat exchangers, plumbing requiring excellent corrosion resistance in water. An alloy of copper, zinc, and silicon which has an incredibly high tensile strength and is corrosion resistant. Doehler Die Casting Co. of Toledo, Ohio were known for the production of Brastil.Woldman’s Engineering Alloys, 9th Edition 1936, American Society for Metals, It was notably tested in 1932 on an M1911 pistol as it was cheaper than steel at the time as a cost-effective measure. Defined by California Assembly Bill AB 1953 contains "not more than 0.25 percent lead content". Prior upper limit was 4%. Good properties. Used for ammunition cases, plumbing, and hardware. Also called rivet brass. Cheap and standard for cold working. Dezincification resistant brass with a small percentage of arsenic. The proportions used make the material harder and suitable for valves and bearings. Also called 360 or C360 brass. High machinability. Softest type of brass commonly available. Gilding metal is typically used for ammunition bullet "jackets"; e.g., full metal jacket bullets. Almost red in colour. E.g. British Admiralty gunmetal. Has variations. Has a high tensile strength and is used for springs, , and . An alpha-beta brass with an addition of lead for improved machinability. Light golden colour, very ductile; used for flexible metal hoses and metal bellows. Used as cladding for United States golden dollar coins. Other manganese brass alloy compositions exist. Used as a lining on boats. Similar to admiralty brass. Also known as Tobin bronze, 464, or C464. Naval brass with added lead for machinability. Also known as 485, or C485. The outer ring of the bi-metallic one pound and two pound sterling coins and the one euro coin, plus the centre part of the two euro coin. Formerly used for the round one pound coin. Used in 10, 20, and 50 cents euro coins. Determined from 39 ingots recovered from an ancient shipwreck in Gela, Sicily. Invented in the early 18th century by Christopher Pinchbeck. Resembles gold to a point where people can buy the metal as budget gold "effect" jewelry. A type of alpha brass. Due to its yellow colour, it is used as an imitation of gold. National Pollutant Inventory – Copper and compounds fact sheet . Npi.gov.au. Retrieved on 9 December 2011. Also called Prince Rupert's metal, the alloy was named after Prince Rupert of the Rhine. Sometimes called "red brass" Sometimes called "red brass" Both an American term for the copper-zinc-tin alloy known as gunmetal, and an alloy which is considered both a brass and a bronze. Red brass is also an alternative name for copper alloy C23000, which is composed of 14–16% zinc, a minimum 0.05% iron and minimum 0.07% lead content, and the remainder copper. It may also refer to ounce metal (Cu 85.0, Zn 5.0, Pb 5.0, Sn 5.0). Often used in jewelry applications. Many variations. Used as an alternative for investment cast steel parts. Also called CW617N or CZ122 or OT58. It is not recommended for sea water use, being susceptible to dezincification. Print Layout 1 . (PDF) . Retrieved on 9 December 2011. An American term for 33% zinc brass.
History
Although forms of brass have been in use since prehistory,Thornton, C. P. (2007) "Of brass and bronze in prehistoric southwest Asia" in La Niece, S. Hook, D. and Craddock, P.T. (eds.) Metals and mines: Studies in archaeometallurgy London: Archetype Publications. its true nature as a copper-zinc alloy was not understood until the post-medieval period because the zinc vapor which reacted with copper to make brass was not recognized as a metal.de Ruette, M. (1995) "From Contrefei and Speauter to Zinc: The development of the understanding of the nature of zinc and brass in Post Medieval Europe" in Hook, D. R. and David Gaimster (eds). Trade and Discovery: The Scientific Study of Artefacts from Post Medieval Europe and Beyond. London: British Museum Occasional Papers 109 The King James Bible makes many references to "brass"Cruden's Complete Concordance p. 55 to translate "nechosheth" (bronze or copper) from Hebrew to English. The earliest brasses may have been natural alloys made by smelting zinc-rich copper .Craddock, P. T. and Eckstein, K (2003) "Production of Brass in Antiquity by Direct Reduction" in Craddock, P. T. and Lang, J. (eds.) Mining and Metal Production Through the Ages. London: British Museum, pp. 226–27 By the Ancient Rome period brass was being deliberately produced from metallic copper and zinc minerals using the cementation process, the product of which was calamine brass, and variations on this method continued until the mid-19th century.Rehren and Martinon Torres 2008, pp. 170–175 It was eventually replaced by , the direct alloying of copper and zinc metal which was introduced to Europe in the 16th century.
Early copper-zinc alloys
In West Asia and the Eastern Mediterranean early copper-zinc alloys are now known in small numbers from a number of 3rd millennium BC sites in the Aegean Sea, Iraq, the United Arab Emirates, Kalmykia, Turkmenistan and Georgia and from 2nd millennium BC sites in western India, Uzbekistan, Iran, Syria, Iraq and Canaan.Thornton 2007, pp. 189–201 Isolated examples of copper-zinc are known in China from the 1st century AD, long after bronze was widely used. The hilt of Sirohi sword (16-19th century CE) were made up of brass in India.
Roman world
During the later part of first millennium BC the use of brass spread across a wide geographical area from United Kingdom and Spain in the west to Iran, and India in the east.Craddock and Eckstein 2003, pp. 216–7 This seems to have been encouraged by exports and influence from the Middle East and eastern Mediterranean where deliberate production of brass from metallic copper and zinc ores had been introduced.Craddock and Eckstein 2003, p. 217 The 4th century BC writer Theopompus, quoted by Strabo, describes how heating earth from Andeira in Turkey produced "droplets of false silver", probably metallic zinc, which could be used to turn copper into oreichalkos.Bayley 1990, p. 9 In the 1st century BC the Greek Dioscorides seems to have recognized a link between zinc and brass describing how Cadmia (zinc oxide) was found on the walls of furnaces used to heat either zinc ore or copper and explaining that it can then be used to make brass.Craddock and Eckstein 2003, pp. 222–224. Bayley 1990, p. 10.
Medieval period
Little is known about the production of brass during the centuries immediately after the collapse of the Roman Empire. Disruption in the trade of tin for bronze from Western Europe may have contributed to the increasing popularity of brass in the east and by the 6th–7th centuries AD over 90% of copper alloy artefacts from Egypt were made of brass.Craddock, P. T., La Niece, S. C., and Hook, D. (1990). "Brass in the Medieval Islamic World". In Craddock, P. T. (ed.), 2000 Years of Zinc and Brass. London: British Museum, p. 73 However other alloys such as low tin bronze were also used and they vary depending on local cultural attitudes, the purpose of the metal and access to zinc, especially between the Islamic and Byzantine world. Conversely the use of true brass seems to have declined in Western Europe during this period in favor of and other mixed alloysBayley 1990, p. 22 but by about 1000 brass artefacts are found in graves in Scotland, brass was being used in the manufacture of coins in NorthumbriaGilmore, G. R. and Metcalf, D. M. (1980). "The alloy of the Northumbrian coinage in the mid-ninth century". In Metcalf, D. and Oddy, W. Metallurgy in Numismatics 1 pp. 83–98 and there is archaeological and historical evidence for the production of calamine brass in Germany and the Low Countries,Day 1990, pp. 123–150 areas rich in calamine ore.
Africa
Some of the most famous objects in African art are the lost wax castings of West Africa, mostly from what is now Nigeria, produced first by the Kingdom of Ife and then the Benin Empire. Though normally described as "bronzes", the Benin Bronzes, now mostly in the British Museum and other Western collections, and the large portrait heads such as the Bronze Head from Ife of "heavily leaded zinc-brass" and the Bronze Head of Queen Idia, both also British Museum, are better described as brass, though of variable compositions. "The Ife Head" on the British Museum collection database. Accessed 26 May 2014 Work in brass or bronze continued to be important in Benin art and other West African traditions such as Akan goldweights, where the metal was regarded as a more valuable material than in Europe.
Renaissance and post-medieval Europe
The Renaissance saw important changes to both the theory and practice of brassmaking in Europe. By the 15th century there is evidence for the renewed use of lidded cementation crucibles at Zwickau in Germany.Martinon Torres and Rehren 2002, pp. 95–111 These large crucibles were capable of producing c.20 kg of brass.Martinon Torres and Rehren 2002, pp. 105–06 There are traces of slag and pieces of metal on the interior. Their irregular composition suggests that this was a lower temperature, not entirely liquid, process.Martinon Torres and Rehren 2002, p. 103 The crucible lids had small holes which were blocked with clay plugs near the end of the process presumably to maximize zinc absorption in the final stages.Martinon Torres and Rehren 2002, p. 104 Triangular crucibles were then used to melt the brass for casting.Martinon Torres and Rehren 2002, p. 100
See also
Citations
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