Although forms of brass have been in use since
prehistory, 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. The
King James Bible makes many references to "brass" to translate "nechosheth" (bronze or copper) from Hebrew to English. The earliest brasses may have been natural alloys made by
smelting zinc-rich copper
ores. By the
Roman 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. 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 3rd millennium BC sites in the
Aegean,
Iraq, the
United Arab Emirates,
Kalmykia,
Turkmenistan and
Georgia and from 2nd millennium BC sites in
western India,
Uzbekistan,
Iran,
Syria, Iraq and
Canaan. Isolated examples of copper-zinc
alloys are known in
China from the 1st century AD, long after bronze was widely used. 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. 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. "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. In the 4th century BC
Plato knew
orichalkos as rare and nearly as valuable as gold
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.
Roman world in brass with copper inlay,
Walters Art Museum,
Baltimore, Maryland, US During the later part of first millennium BC the use of brass spread across a wide geographical area from
Britain and
Spain 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. 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. In the 1st century BC the Greek
Dioscorides seems to have recognized 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. By the first century BC brass was available in sufficient supply to use as
coinage in
Phrygia and
Bithynia, and at a number of sites in Britain. 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. Brass made during the early Roman period seems to have varied between 20% and 28% wt zinc.
Medieval period '' on the 12th-century
baptismal font at St Bartholomew's Church, Liège 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. 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. but by about 1000 brass artefacts are found in
Scandinavian graves in
Scotland, and there is archaeological and historical evidence for the production of
calamine brass in Germany areas rich in
calamine ore. These places would remain important centres of brass making throughout the
Middle Ages period, 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 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.
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.
Aquamaniles were typically made in brass in both the European and Islamic worlds. from
Lower Saxony, Germany, c. 1250 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. 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. 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. 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. 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 minimize the escape of zinc vapor. 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. 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. 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. 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.
Africa ", 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 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. 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
Manilla (money) bracelets were also used as a means of exchange, across
West Africa, into the 20th century.
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. These large crucibles were capable of producing c.20 kg of brass. 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. 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. Triangular crucibles were then used to melt the brass for
casting. 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. 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. Eventually it was discovered that metallic zinc could be
alloyed with copper to make brass, a process known as speltering, 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". 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. 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. By 1559 the Germany city of
Aachen alone was capable of producing 300,000
cwt of brass per year. In 1723
Bristol brass maker Nehemiah Champion patented the use of
granulated copper, produced by pouring molten metal into cold water. 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. 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". However Champion continued to use the cheaper calamine cementation method to produce lower-zinc brass 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. The hilt of
Sirohi swords (16-19th century CE) were made up of
brass in
India. ==See also==