Brass

Brass is an alloy made of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.Engineering Designer 30(3): 6–9, May–June 2004 It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.
By comparison, bronze is principally an alloy of copper and tin.Machinery Handbook, Industrial Press Inc, New York, Edition 24, p. 501 However, the common term "bronze" may also include , , , , and . The term is also applied to a variety of brasses, and the distinction is largely historical. Modern practice in museums and archaeology increasingly avoids both terms for historical objects in favour of the all-embracing "copper alloy".The British Museum collection database "scope note" on "copper alloy", "brass" and "bronze" reads, "The term copper alloy should be searched for full retrievals on objects made or bronze or brass. This is because bronze and brass have at times been used interchangeably in the old documentation, and copper alloy is the Broad Term of both. In addition, the public may refer to certain collections by their popular name, such as 'The Benin Bronzes' most of which are actually made of brass".British Museum, "Scope Note" for "copper alloy". Britishmuseum.org. Retrieved on 2014-05-26.
Brass is used for decoration for its bright gold-like appearance; for applications where low friction is required such as locks, gears, bearings, doorknobs, ammunition casings and valves; for plumbing and electrical applications; and extensively in brass musical instruments such as horns and bells where a combination of high workability (historically with hand tools) and durability is desired. It is also used in zippers. Brass is often used in situations in which it is important that sparks not be struck, such as in fittings and tools around explosive gases.OSH Answers: Non-sparking tools. Ccohs.ca (2011-06-02). Retrieved on 2011-12-09.
==Properties==
The malleability and traditionally attributed acoustic properties of brass have made it the metal of choice for musical instruments such as the trombone, tuba, trumpet, cornet, baritone horn, euphonium, tenor horn, and French horn which are collectively known as brass instruments. Even though the saxophone is classified as a woodwind instrument and the harmonica is a free reed aerophone, both are also often made from brass. In organ pipes of the reed family, brass strips (called tongues) are used as the reeds, which beat against the shallot (or beat "through" the shallot in the case of a "free" reed). Although not part of the brass section, snare drums are also sometimes made of brass.
Brass has higher malleability than bronze or zinc. The relatively low melting point of brass (900 to 940 °C, 1652 to 1724 °F, depending on composition) and its flow characteristics make it a relatively easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses. The density of brass is approximately .303 lb/cubic inch, 8.4 to 8.73 grams per cubic centimetre.
Today almost 90% of all brass alloys are recycled. Because brass is not ferromagnetic, it can be separated from ferrous scrap by passing the scrap near a powerful magnet. Brass scrap is collected and transported to the foundry where it is melted and recast into billets. Billets are heated and extruded into the desired form and size.
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 resistant.
==Lead content==
To enhance the machinability of brass, lead is often added in concentrations of around 2%. Since lead has a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules as it cools from casting. The pattern the globules form on the surface of the brass increases the available lead surface area which in turn affects the degree of leaching. In addition, cutting operations can smear the lead globules over the surface. These effects can lead to significant lead leaching from brasses of comparatively low lead content.
Silicon is an alternative to lead; however, when silicon is used in a brass alloy, the scrap must never be mixed with leaded brass scrap because of contamination and safety problems.Chase Brass & Copper Company, Inc. Chasebrass.com. Retrieved on 2011-12-09.
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, October 12, 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 higher percentage of lead content.News & Alerts – California Dept. of Justice – Office of the Attorney General, April 27, 2001San Francisco Superior Court, People v. Ilco Unican Corp., et a. (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 January 1, 2010, the maximum amount of lead in "lead-free brass" in California was reduced from 4% to 0.25% lead. The common practice of using pipes for electrical grounding is discouraged, as it accelerates lead corrosion.AB 1953 Assembly Bill – Bill Analysis. Info.sen.ca.gov. Retrieved on 2011-12-09.Requirements for Low Lead Plumbing Products in California, Fact Sheet, Department of Toxic Substances Control, State of California, February 2009
==Corrosion-resistant brass for harsh environments==
thumb|200px|Brass sampling cock with stainless steel handle. The so-called dezincification resistant (DZR or DR) brasses, sometimes referred to as CR (corrosion resistant) brasses, are used where there is a large corrosion risk and where normal brasses do not meet the standards. Applications with high water temperatures, chlorides present, or deviating water qualities (soft water) play a role. DZR-brass is excellent in water boiler systems. This brass alloy must be produced with great care, with special attention placed on a balanced composition and proper production temperatures and parameters to avoid long-term failures.
==Germicidal and antimicrobial applications==
The copper in brass makes brass germicidal. Depending upon the type and concentration of pathogens and the medium they are in, brass kills these microorganisms within a few minutes to hours of contact.
The bactericidal properties of brass have been observed for centuries and were confirmed in the laboratory in 1983. Subsequent experiments by research groups around the world reconfirmed the antimicrobial efficacy of brass, as well as copper and other copper alloys (see Antimicrobial copper-alloy touch surfaces). Extensive structural membrane damage to bacteria was noted after being exposed to copper.
In 2007, U.S. Department of Defense’s Telemedicine and Advanced Technology Research Center (TATRC) began to study the antimicrobial properties of copper alloys, including four brasses (C87610, C69300, C26000, C46400) in a multi-site clinical hospital trial conducted at the Memorial Sloan-Kettering Cancer Center (New York City), the Medical University of South Carolina, and the Ralph H. Johnson VA Medical Center (South Carolina). Commonly touched items, such as bed rails, over-the-bed tray tables, chair arms, nurse's call buttons, IV poles, etc. were retrofitted with antimicrobial copper alloys in certain patient rooms (i.e., the “coppered” rooms) in the Intensive Care Unit (ICU). Early results disclosed in 2011 indicate that the coppered rooms demonstrated a 97% reduction in surface pathogens versus the non-coppered rooms. This reduction is the same level achieved by “terminal” cleaning regimens conducted after patients vacate their rooms. Furthermore, of critical importance to health care professionals, the preliminary results indicated that patients in the coppered ICU rooms had a 40.4% lower risk of contracting a hospital acquired infection versus patients in non-coppered ICU rooms.TouchSurfaces Clinical Trials: Research Proves. Coppertouchsurfaces.org. Retrieved on 2011-12-09.World Health Organization’s 1st International Conference on Prevention and Infection Control (ICPIC) in Geneva, Switzerland on July 1st, 2011 The U.S. Department of Defense investigation contract, which is ongoing, will also evaluate the effectiveness of copper alloy touch surfaces to prevent the transfer of microbes to patients and the transfer of microbes from patients to touch surfaces, as well as the potential efficacy of copper-alloy based components to improve indoor air quality.
In the U.S., the Environmental Protection Agency regulates the registration of antimicrobial products. After extensive antimicrobial testing according to the Agency’s stringent test protocols, 355 copper alloys, including many brasses, were found to kill more than 99.9% of methicillin-resistant Staphylococcus aureus (MRSA), E. coli O157:H7, Pseudomonas aeruginosa, Staphylococcus aureus, Enterobacter aerogenes, and vancomycin-resistant Enterococci (VRE) within two hours of contact. Normal tarnishing was found not to impair antimicrobial effectiveness.
Antimicrobial tests have also revealed significant reductions of MRSA as well as two strains of epidemic MRSA (EMRSA-1 and EMRSA-16) on brass (C24000 with 80% Cu) at room temperature (22 °C) within three hours. Complete kills of the pathogens were observed within hours. These tests were performed under wet exposure conditions. The kill timeframes, while impressive, are nevertheless longer than for pure copper, where kill timeframes ranged between 45 to 90 minutes.
A novel assay that mimics dry bacterial exposure to touch surfaces was developed because this test method is thought to more closely replicate real world touch surface exposure conditions. In these conditions, copper alloy surfaces were found to kill several million Colony Forming Units of Escherichia coli within minutes. This observation, and the fact that kill timeframes shorten as the percentage of copper in an alloy increases, is proof that copper is the ingredient in brass and other copper alloys that kills the microbes.
The mechanisms of antimicrobial action by copper and its alloys, including brass, is a subject of intense and ongoing investigation. It is believed that the mechanisms are multifaceted and include the following: 1) Potassium or glutamate leakage through the outer membrane of bacteria; 2) Osmotic balance disturbances; 3) Binding to proteins that do not require or utilize copper; 4) Oxidative stress by hydrogen peroxide generation.
Research is being conducted at this time to determine whether brass, copper, and other copper alloys can help to reduce cross contamination in public facilities and reduce the incidence of nosocomial infections (hospital acquired infections) in healthcare facilities.
Also, owing to its antimicrobial/algaecidal properties that prevent biofouling, in conjunction with its strong structural and corrosion-resistant benefits for marine environments, brass alloy netting cages are currently being deployed in commercial-scale aquaculture operations in Asia, South America, and the USA.
==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 cartridge cases used for rifle ammunition during the 1920s in the British Indian Army. The problem was caused by high residual stresses 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.
==Brass types==
Class 	Copper (%)	Zinc (%)	Notes
Alpha brasses 	>65 	<35 	Alpha brasses are malleable, can be worked cold, and are used in pressing, forging, or similar applications. They contain only one phase, with face-centered cubic crystal structure.
Alpha-beta brasses	55–65 	35–45 	Also called duplex brasses. Suited for hot working. It contains both α and β' phase; the β'-phase is body-centered cubic and is harder and stronger than α. Alpha-beta brasses are usually worked hot.
Beta brasses 	50–55 	45–50 	Can only be worked hot, and are harder, stronger, and suitable for casting.
White brass 	<50 	>50 	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 additive.
 Brass alloys
Alloy name 	Copper (%)	Zinc (%)	Other 	Notes
Abyssinian gold 	90 	10 	 	
Admiralty brass 	69 	30 	1% tin 	Contains 1% tin to inhibit dezincification in many environments.
Aich's alloy 	60.66 	36.58 	1.02% tin, 1.74% iron 	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
Aluminum brass 	77.5 	20.5 	2% aluminum 	Aluminum improves corrosion resistance. It is used for heat exchanger and condenser tubes.
Arsenical brass 	 	 	arsenic, frequently aluminum	Used for boiler fireboxes.
Cartridge brass 	70 	30 	 	Good cold working properties. Used for ammunition cases.
Common brass 	 	37 	 	Also called rivet brass. Cheap and standard for cold working.
DZR brass 	 	 	arsenic 	Dezincification resistant brass with a small percentage of arsenic.
Gilding metal 	95 	5 	 	Softest type of brass commonly available. Gilding metal is typically used for ammunition bullet "jackets", e.g., full metal jacket bullets.
High brass 	65 	35 	 	Has a high tensile strength and is used for springs, screws, and rivets.
Leaded brass 	 	 	lead 	An alpha-beta brass with an addition of lead. It has excellent machinability.
Lead-free brass 	 	 	<0.25% lead 	Defined by California Assembly Bill AB 1953 contains "not more than 0.25 percent lead content".
Low brass 	80 	20 	 	Has a light golden color and excellent ductility; it is used for flexible metal hoses and metal bellows.
Manganese brass 	70 	29 	1.3% manganese 	Most notably used in making golden dollar coins in the United States.manganese brass: Definition from. Answers.com. Retrieved on 2011-12-09.
Muntz metal 	60 	40 	traces of iron 	Used as a lining on boats.
Naval brass 	59 	40 	1% tin 	Similar to admiralty brass.
Nickel brass 	70 	24.5 	5.5% nickel 	Used to make pound coins in the pound sterling currency. Also the main constituent of the bi-metallic One Euro coin and the centre part of the Two Euro coin.
Nordic gold 	89 	5 	5% aluminium, 1% tin 	Used in 10, 20, and 50 cents euro coins.
Prince's metal 	75 	25 	 	A type of alpha brass. Due to its yellow color, it is used as an imitation of gold.National Pollutant Inventory – Copper and compounds fact sheet. Npi.gov.au. Retrieved on 2011-12-09. Also called Prince Rupert's metal, the alloy was named after Prince Rupert of the Rhine.
Red brass, Rose brass 	85 	5 	5% tin, 5% lead 	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, 0.05% iron and lead, and the remainder copper. It may also refer to ounce metal, another copper-zinc-tin alloy.
Rich low brass, Tombac	 	5–20 	 	Often used in jewelry applications.
Silicon tombac 	80 	16 	4% silicon 	Used as an alternative for investment casted steel parts.
Tonval brass 	 	 	lead 	Also called CW617N or CZ122 or OT58. It is not recommended for seawater use, being susceptible to dezincification.Print Layout 1. (PDF) . Retrieved on 2011-12-09.
Yellow brass 	67 	33 	 	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. ISBN 1-904982-19-0 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 recognised 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 Gaimster, D.R.M (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 The Shakespearean English form of the word 'brass' can mean any bronze alloy, or copper, rather than the strict modern definition of brass. The earliest brasses may have been natural alloys made by smelting zinc-rich copper ores.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. 226–7 By the Roman period brass was being deliberately produced from metallic copper and zinc minerals using the cementation process and variations on this method continued until the mid-19th century.Rehren and Martinon Torres 2008, pp. 170–5 It was eventually replaced by speltering, 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 third millennium BC sites in the Aegean, Iraq, the United Arab Emirates, Kalmykia, Turkmenistan and Georgia and from 2nd Millennium BC sites in West India, Uzbekistan, Iran, Syria, Iraq and Israel.Thornton 2007, pp. 189–201 However, isolated examples of copper-zinc alloys are known in China from as early as the 5th Millennium BC.
The compositions of these early "brass" objects are very 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 color.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 Assyrian 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 Cypriot 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 percent copper, 15-20 percent zinc and small percentages of nickel, lead and iron.
===Brass making in the Roman World===
During the later part of first millennium BC the use of brass spread across a wide geographical area from Britain 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 recognised a link between zinc minerals 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. 222–4. Bayley 1990, p. 10.
By the first century BC brass was available in sufficient supply to use as coinage in Phrygia and Bithynia, and after the Augustan currency reform of 23 BC it was also used to make Roman dupondii and sestertii. 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 crucibles 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. 170–1 and at a number of sites in Britain.Bayley 1990 They vary in size from tiny acorn sized to large amphorae 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% to 28% wt zinc.Craddock and Eckstein 2003, 224 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.Caley 1964 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
===Brass making in the 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 favour of gunmetals and other mixed alloysBayley 1990, p. 22 but by about 1000 brass artefacts are found in Scandinavian 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 brass in GermanyRehren 1999 and The Low Countries,Day 1990, pp. 123–150 areas rich in calamine ore.
These places would remain important centres of brass making throughout the medieval period,Day 1990, pp. 124–33 especially Dinant. Brass objects are still collectively known as dinanterie in French. The baptismal font at St Bartholomew's Church, Liège in modern Belgium (before 1117) is an outstanding masterpiece of Romanesque 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 , , , , , , and with an unusually large amount of - 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, probably Late Roman.Noel Stratford, pp. 232, 245, in Zarnecki, George and others; English Romanesque Art, 1066–1200, 1984, Arts Council of Great Britain, ISBN 0728703866 Latten is a term for decorative borders and similar objects cut from sheet metal, whether of brass or bronze. Aquamaniles 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 places in open-topped crucibles.Craddock and Eckstein 2003, pp. 224–5 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 Italian Marco Polo describe how this was obtained by sublimation from zinc ores and condensed onto clay or iron bars, archaeological examples of which have been identified at Kush in Iran.Craddock et al. 1990, pp. 73–6 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 raisins and gently roasted before being added to the surface of the molten metal. A temporary lid was added at this point presumably to minimise 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. 252–7 The 12th century German 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 cast, 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. 176–8 
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. 173–5
===Brass in Africa===
thumb|250px|12th century "Bronze Head from Ife", actually of "heavily leaded zinc-brass"
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 Bronze plaques, now mostly in the British Museum and other Western collections, and the large portrait heads such as the Ife Head 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.
===Brass making in 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. 105–6 There are traces of slag and pieces of metal on the interior. Their irregular composition suggesting 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 maximise 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
16th-century technical writers such as Biringuccio, 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, 181–2, de Ruette 1995 Zinc metal was also becoming more commonplace By 1513 metallic zinc ingots 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 alloyed with copper to make brass; a process known as spelteringCraddock and Eckstein 2003, 228 and by 1657 the German chemist Johann Glauber had recognised 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 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, 226–7. 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 battery wares.Day 1990, p. 131 By 1559 the Germany city of Aachen alone was capable of producing 300,000 cwt 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. 135–44 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. 179–81 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, clocks, brass buttons and costume jewellery.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. 186–9 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. 192–3, Craddock and Eckstein 2003, p. 228
==See also==
*Tombac
*Brass bed
*Brass rubbing
*Bronze and brass ornamental work
*List of copper alloys
==References==
==Bibliography==
*Bayley, J. (1990) "The Production of Brass in Antiquity with Particular Reference to Roman Britain" in Craddock, P.T. (ed.) 2000 Years of Zinc and Brass London: British Museum
*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
*Day, J. (1990) "Brass and Zinc in Europe from the Middle Ages until the 19th century" in Craddock, P.T. (ed.) 2000 Years of Zinc and Brass London: British Museum
*Day, J (1991) "Copper, Zinc and Brass Production" in Day, J and Tylecote, R.F (eds) The Industrial Revolution in Metals London: The Institute of Metals
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*Rehren, T. and Martinon Torres, M. (2008) "Naturam ars imitate: European brassmaking between craft and science" in Martinon-Torres, M and Rehren, T. (eds) Archaeology, History and Science Integrating Approaches to Ancient Material: Left Coast Press
==External links==
*Brass.org
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