Editing Smelting (section)

==History==
Of the [[metals of antiquity|seven metals known in antiquity]], only [[gold]] regularly occurs in nature as a [[native metal]]. The others – [[copper]], [[lead]], [[silver]], [[tin]], [[iron]], and [[mercury (element)|mercury]] – occur primarily as minerals, although [[native copper]] is occasionally found in commercially significant quantities. These minerals are primarily [[carbonate]]s, [[sulfide]]s, or [[oxide]]s of the metal, mixed with other components such as [[silica]] and [[alumina]]. [[Roasting (metallurgy)|Roasting]] the carbonate and sulfide minerals in the air converts them to oxides. The oxides, in turn, are smelted into the metal. Carbon monoxide was (and is) the reducing agent of choice for smelting. It is easily produced during the heating process, and as a gas comes into intimate contact with the ore.

In the [[Old World]], humans learned to smelt metals in [[Prehistory|prehistoric]] times, more than 8000 years ago. The discovery and use of the "useful" metals – copper and bronze at first, then iron a few millennia later – had an enormous impact on human society. The impact was so pervasive that scholars traditionally divide ancient history into [[Stone Age]], [[Bronze Age]], and [[Iron Age]].

In the [[Americas]], pre-[[Inca]] civilizations of the central [[Andes]] in Peru had mastered the smelting of copper and silver at least six centuries before the first Europeans arrived in the 16th century, while never mastering the smelting of metals such as iron for use with weapon craft.<ref name="sciencedaily.com">{{cite web|url=https://www.sciencedaily.com/releases/2007/04/070423100437.htm|title=releases/2007/04/070423100437|publisher=sciencedaily.com|access-date=26 August 2015|url-status=live|archive-url=https://web.archive.org/web/20150909222002/https://www.sciencedaily.com/releases/2007/04/070423100437.htm|archive-date=9 September 2015}}</ref>

===Copper and bronze===
{{see also|Copper extraction}}
[[File:Tiangong Kaiwu Tripod Casting.jpg|thumb|Casting bronze ding-tripods, from the Chinese ''Tiangong Kaiwu'' encyclopedia of [[Song Yingxing]], published in 1637]]
Copper was the first metal to be smelted.<ref>{{cite web |last1=McGeough |first1=Joseph |title=Early metals and smelting |url=https://www.britannica.com/technology/hand-tool/Early-metals-and-smelting |website=Brittanica }}</ref> How the discovery came about is debated. Campfires are about 200&nbsp;°C short of the temperature needed, so some propose that the first smelting of copper may have occurred in pottery [[kiln]]s.<ref>{{cite book|title=The Prehistory of Metallurgy in the British Isles|author=Tylecote, R. F.|date=1986|publisher=The Institute of Metals|publication-place=London|pages=16–17}}</ref> (The development of copper smelting in the Andes, which is believed to have occurred independently of the [[Old World]], may have occurred in the same way.<ref name="sciencedaily.com"/>)

The earliest current evidence of copper smelting, dating from between 5500&nbsp;BC and 5000&nbsp;BC, has been found in [[Pločnik]] and Belovode, Serbia.<ref name="stonepages">{{cite web|url=http://www.stonepages.com/news/archives/002557.html|title=Stone Pages Archaeo News: Ancient metal workshop found in Serbia|publisher=stonepages.com|access-date=26 August 2015|url-status=live|archive-url=https://web.archive.org/web/20150924110730/http://www.stonepages.com/news/archives/002557.html|archive-date=24 September 2015}}</ref><ref name="archaeologydaily">{{cite web|url=http://www.archaeologydaily.com/news/201006274431/Belovode-site-in-Serbia-may-have-hosted-first-copper-makers.html|title=201006274431 &#124; Belovode site in Serbia may have hosted first copper makers|publisher=archaeologydaily.com|access-date=26 August 2015|url-status=dead|archive-url=https://web.archive.org/web/20120229205002/http://www.archaeologydaily.com/news/201006274431/Belovode-site-in-Serbia-may-have-hosted-first-copper-makers.html|archive-date=29 February 2012}}</ref> A mace head found in Turkey and dated to 5000&nbsp;BC, once thought to be the oldest evidence, now appears to be hammered, native copper.<ref name="google">{{cite book|title=Ancient Turkey|author1=Sagona, A.G.|author2=Zimansky, P.E.|date=2009|publisher=Routledge|isbn=9780415481236|url=https://books.google.com/books?id=QHAlOAAACAAJ|url-status=live|archive-url=https://web.archive.org/web/20160306062734/https://books.google.co.uk/books?id=QHAlOAAACAAJ|archive-date=6 March 2016}}</ref>

Combining copper with tin or [[arsenic]] in the right proportions produces [[bronze]], an [[alloy]] that is significantly harder than copper. The first [[Arsenical bronze|copper/arsenic bronzes]] date from 4200&nbsp;BC from [[Asia Minor]]. The Inca bronze alloys were also of this type. Arsenic is often an impurity in copper ores, so the discovery could have been made by accident. Eventually, arsenic-bearing minerals were intentionally added during smelting.{{citation needed|date=May 2009}}

Copper–tin bronzes, harder and more durable, were developed around 3500&nbsp;BC, also in Asia Minor.<ref>{{Cite web|title=History of Bronze Infographic {{!}} About {{!}} Website {{!}} Makin Metal Powders (UK)|url=http://www.makin-metals.com/about/history-of-bronze-infographic/#:~:text=Around%203500%20BC%20the%20first,used%20to%20build%20campfire%20rings.|access-date=2021-02-23|website=www.makin-metals.com|archive-date=8 November 2020|archive-url=https://web.archive.org/web/20201108125933/http://www.makin-metals.com/about/history-of-bronze-infographic/#:~:text=Around%203500%20BC%20the%20first,used%20to%20build%20campfire%20rings.|url-status=dead}}</ref>

How smiths learned to produce copper/tin bronzes is unknown. The first such bronzes may have been a lucky accident from tin-contaminated copper ores. However, by 2000&nbsp;BC, people were mining tin on purpose to produce bronze—which is remarkable as tin is a semi-rare metal, and even a rich [[cassiterite]] ore only has 5% tin.{{citation needed|date=July 2017}}

The discovery of copper and bronze manufacture had a significant impact on the history of the [[Old World]]. Metals were hard enough to make weapons that were heavier, stronger, and more resistant to impact damage than wood, bone, or stone equivalents. For several millennia, bronze was the material of choice for weapons such as [[sword]]s, [[dagger]]s, [[battle axe]]s, and [[spear]] and [[arrow]] points, as well as protective gear such as [[shield]]s, [[helmet]]s, [[greave]]s (metal shin guards), and other [[body armor]]. Bronze also supplanted stone, wood, and organic materials in tools and household utensils—such as [[chisel]]s, [[saw]]s, [[adze]]s, [[Nail (fastener)|nail]]s, [[blade shears]], [[knife|knives]], [[sewing needle]]s and [[pin]]s, [[Jug (container)|jug]]s, [[cooking pot]]s and [[cauldron]]s, [[mirror]]s, and [[horse harness]]es.{{Citation needed|date=May 2009}} Tin and copper also contributed to the establishment of trade networks that spanned large areas of Europe and Asia and had a major effect on the distribution of wealth among individuals and nations.{{citation needed|date=May 2009}}

===Tin and lead===
The earliest known [[Casting|cast]] lead beads were thought to be in the [[Çatalhöyük]] site in [[Anatolia]] ([[Turkey]]), and dated from about 6500&nbsp;BC.<ref>{{Cite journal |last1=Gale |first1=N.H. |last2=Stos-Gale |first2=Z.A. |date=1981 |title=Ancient Egyptian Silver |url=https://journals.sagepub.com/doi/abs/10.1177/030751338106700110 |journal=The Journal of Egyptian Archaeology |volume=67 |issue=1 |pages=103–115 |doi=10.1177/030751338106700110 |s2cid=192397529 |via=Sage Journals}}</ref> However, recent research has discovered that this was not lead, but rather cerussite and galena, minerals rich in, but distinct from, lead.<ref>{{Cite journal |last1=Radivojević |first1=Miljana |last2=Rehren |first2=Thilo |last3=Farid |first3=Shahina |last4=Pernicka |first4=Ernst |last5=Camurcuoğlu |first5=Duygu |date=2017-10-01 |title=Repealing the Çatalhöyük extractive metallurgy: The green, the fire and the 'slag' |url=https://www.sciencedirect.com/science/article/abs/pii/S0305440317301024 |journal=Journal of Archaeological Science |volume=86 |pages=101–122 |doi=10.1016/j.jas.2017.07.001 |bibcode=2017JArSc..86..101R |issn=0305-4403}}</ref>

Since the discovery happened several millennia before the invention of writing, there is no written record of how it was made. However, tin and lead can be smelted by placing the ores in a wood fire, leaving the possibility that the discovery may have occurred by accident.{{Citation needed|date=August 2023}} Recent scholarship however has called this find into question.<ref>{{Cite journal |last1=Radivojević |first1=Miljana |last2=Rehren |first2=Thilo |last3=Farid |first3=Shahina |last4=Pernicka |first4=Ernst |last5=Camurcuoğlu |first5=Duygu |date=2017 |title=Repealing the Çatalhöyük extractive metallurgy: The green, the fire and the 'slag' |journal=Journal of Archaeological Science |volume=86 |pages=101–122 |doi=10.1016/j.jas.2017.07.001|bibcode=2017JArSc..86..101R |url=https://discovery.ucl.ac.uk/id/eprint/1571679/ }}</ref>

Lead is a common metal, but its discovery had relatively little impact in the ancient world. It is too soft to use for structural elements or weapons, though its high density relative to other metals makes it ideal for [[sling (weapon)|sling]] projectiles. However, since it was easy to cast and shape, workers in the classical world of [[Ancient Greece]] and [[Ancient Rome]] used it extensively to pipe and store water. They also used it as a [[Mortar (masonry)|mortar]] in stone buildings.<ref>{{Cite news|last=Browne|first=Malcolm W.|date=1997-12-09|title=Ice Cap Shows Ancient Mines Polluted the Globe (Published 1997)|language=en-US|work=The New York Times|url=https://www.nytimes.com/1997/12/09/science/ice-cap-shows-ancient-mines-polluted-the-globe.html|access-date=2021-02-23|issn=0362-4331}}</ref><ref>{{Cite journal|last1=Loveluck|first1=Christopher P.|last2=McCormick|first2=Michael|last3=Spaulding|first3=Nicole E.|last4=Clifford|first4=Heather|last5=Handley|first5=Michael J.|last6=Hartman|first6=Laura|last7=Hoffmann|first7=Helene|last8=Korotkikh|first8=Elena V.|last9=Kurbatov|first9=Andrei V.|last10=More|first10=Alexander F.|last11=Sneed|first11=Sharon B.|date=December 2018|title=Alpine ice-core evidence for the transformation of the European monetary system, AD 640–670|journal=Antiquity|language=en|volume=92|issue=366|pages=1571–1585|doi=10.15184/aqy.2018.110|issn=0003-598X|doi-access=free}}</ref>

Tin was much less common than lead, is only marginally harder, and had even less impact by itself.

===Early iron smelting{{anchor|early_iron_smelting_anchor}}===
{{Main|Ferrous metallurgy}}

The earliest evidence for iron-making is a small number of iron fragments with the appropriate amounts of carbon admixture found in the Proto-Hittite layers at [[Kaman-Kalehöyük]] and dated to 2200–2000&nbsp;BC.<ref>{{cite journal |last=Akanuma |first=Hideo |title=The significance of Early Bronze Age iron objects from Kaman-Kalehöyük, Turkey |journal=Anatolian Archaeological Studies |volume=17 |pages=313–320 |year=2008 |url=http://www.jiaa-kaman.org/pdfs/aas_17/AAS_17_Akanuma_H_pp_313_320.pdf |publisher=Japanese Institute of Anatolian Archaeology |place=Tokyo |archive-date=26 March 2023 |access-date=19 March 2018 |archive-url=https://web.archive.org/web/20230326030515/http://www.jiaa-kaman.org/pdfs/aas_17/AAS_17_Akanuma_H_pp_313_320.pdf |url-status=dead }}</ref> Souckova-Siegolová (2001) shows that iron implements were made in Central Anatolia in very limited quantities around 1800 BC and were in general use by elites, though not by commoners, during the [[Hittites#New Kingdom|New Hittite Empire]] (~1400–1200 BC).<ref>{{cite journal |last=Souckova-Siegolová |first=J. |title=Treatment and usage of iron in the Hittite empire in the 2nd millennium BC |journal=Mediterranean Archaeology |volume=14 |pages=189–93 |year=2001}}.</ref>

Archaeologists have found indications of iron working in [[Ancient Egypt]], somewhere between the [[Third Intermediate Period]] and [[Twenty-third dynasty of Egypt|23rd Dynasty]] (ca. 1100–750&nbsp;BC). Significantly though, they have found no evidence of iron ore smelting in any (pre-modern) period. In addition, very early instances of [[carbon steel]] were in production around 2000 years ago (around [[1st century|the first-century]].) in northwest [[Tanzania]], based on complex preheating principles. These discoveries are significant for the history of metallurgy.<ref>Peter Schmidt, Donald H. Avery. [http://www.sciencemag.org/cgi/content/abstract/201/4361/1085 Complex Iron Smelting and Prehistoric Culture in Tanzania] {{webarchive|url=https://web.archive.org/web/20100409173608/http://www.sciencemag.org/cgi/content/abstract/201/4361/1085 |date=9 April 2010 }}, Science 22 September 1978: Vol. 201. no. 4361, pp. 1085–1089</ref>

Most early processes in Europe and Africa involved smelting iron ore in a [[bloomery]], where the temperature is kept low enough so that the iron does not melt. This produces a spongy mass of iron called a bloom, which then must be consolidated with a hammer to produce [[wrought iron]]. Some of the earliest evidence to date for the bloomery smelting of iron is found at [[Tell Hammeh]], Jordan, [[Radiocarbon dating|radiocarbon-dated]] to {{Circa|930 BC}}.<ref>{{Cite book |last1=Veldhuijzen |first1=Xander |url=https://www.worldcat.org/oclc/174131337 |title=Metals and Mines: Studies in Archaeometallurgy |last2=Rehren |first2=Thilo |publisher=Archetype, British Museum |year=2007 |isbn=978-1904982197 |editor-last=La Niece |editor-first=Susan |pages=189–201 |language=en |chapter=Slags and the city: early iron production at Tell Hammeh |oclc=174131337 |editor-last2=Hook |editor-first2=Duncan |editor-last3=Craddock |editor-first3=Paul |chapter-url=https://www.researchgate.net/publication/269100440}}</ref>

===Later iron smelting===
{{Main|Blast furnace}}
From the medieval period, an indirect process began to replace the direct reduction in bloomeries. This used a [[blast furnace]] to make [[pig iron]], which then had to undergo a further process to make forgeable bar iron. Processes for the second stage include fining in a [[finery forge]]. In the [[13th century]]  during the [[High Middle Ages]] the blast furnace was introduced by China who had been using it since as early as 200 b.c during the [[Qin dynasty]]. [https://www.britannica.com/summary/blast-furnace#:~:text=Blast%20furnaces%20were%20used%20in,century%2C%20replacing%20the%20bloomery%20process. blast furnace summary | Britannica] [[Puddling (metallurgy)|Puddling]] was also introduced in the [[Industrial Revolution]].

Both processes are now obsolete, and wrought iron is now rarely made. Instead, mild steel is produced from a [[Bessemer converter]] or by other means including smelting reduction processes such as the [[Corex Process]].