Editing Brass (section)

===Roman world===
[[File:Iranian - Ewer - Walters 54457 - Profile.jpg|thumb|upright|7th-century Persian [[ewer]] 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 [[United Kingdom|Britain]]<ref>{{cite journal |last1=Craddock |first1=P. T. |last2=Cowell |first2=M. |last3=Stead |first3=I. |year=2004 |title=Britain's first brass |journal=Antiquaries Journal |doi=10.1017/S000358150004587X |volume=84 |pages=339–46|s2cid=163717910 }}</ref> and [[Spain]]<ref name=r13/> in the west to [[Iran]], and [[India]] in the east.<ref>Craddock and Eckstein 2003, pp. 216–7</ref> 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.<ref>Craddock and Eckstein 2003, p. 217</ref> The 4th century BC writer [[Theopompus]], quoted by [[Strabo]], describes how heating earth from [[Astyra (Aeolis)|Andeira]] in [[Turkey]] produced "droplets of false silver", probably metallic zinc, which could be used to turn copper into oreichalkos.<ref>Bayley 1990, p. 9</ref> In the 1st century BC the Greek [[Dioscorides]] seems to have recognized a link between zinc [[mineral]]s and brass describing how [[Cadmia]] ([[zinc oxide]]) was found on the walls of [[Metallurgical furnace|furnace]]s used to heat either zinc ore or copper and explaining that it can then be used to make brass.<ref>Craddock and Eckstein 2003, pp. 222–224. Bayley 1990, p. 10.</ref>

By the first century BC brass was available in sufficient supply to use as [[coin]]age in [[Phrygia]] and [[Bithynia]],<ref name=r14/> and after the Augustan [[currency reform]] of 23 BC it was also used to make Roman ''[[dupondius|dupondii]]'' and ''[[Sestertius|sestertii]]''.<ref name=r15/> The uniform use of brass for coinage and military equipment across the [[Roman world]] may indicate a degree of state involvement in the industry,<ref>Bayley 1990, p. 21</ref><ref name=r16/> and brass even seems to have been deliberately boycotted by [[Jewish]] communities in Palestine because of its association with Roman authority.<ref name=r17/>
 
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 [[crucible]]s used to produce brass by cementation have been found on [[Roman period]] sites including [[Xanten]]<ref name=r18/> and [[Nidda, Hesse|Nidda]]<ref name=r19/> in [[Germany]], [[Lyon]] in [[France]]<ref name="ReferenceA">Rehren and Martinon Torres 2008, pp. 170–71</ref> and at a number of sites in Britain.<ref>Bayley 1990</ref> They vary in size from tiny acorn sized to large [[amphora]]e like vessels but all have elevated levels of zinc on the interior and are lidded.<ref name="ReferenceA"/> 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<ref name="ReferenceA"/> 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.<ref name = ce2003p224>Craddock and Eckstein 2003, p. 224</ref>

Brass made during the early Roman period seems to have varied between 20% and 28% wt zinc.<ref name = ce2003p224/> 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.<ref name = r15/> However it is now thought this was probably a deliberate change in composition<ref name=r21/> 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.<ref>Craddock 1978, p. 14</ref>