Archaeometallurgy
The Archaeometallurgy is a research discipline of Archaeometry , which deals with the metallurgy of archaeological finds from the prehistory concerned to modern times.
Originally, the main focus was on the reconstruction of the introduction of new metallic materials, such as copper , bronze and iron , as a rough breakdown of cultural developments ( Copper Age , Bronze Age , Iron Age ), and the development of relevant manufacturing and processing methods. The latter is part of the history of technology . It was only later that it became clear that the developments are not only of a descriptive character, but are an integral part of general cultural history and are embedded in cultural traditions and must be seen in their historical and socio-economic context. Today it is generally accepted that technology is a central part of culture and that both influence one another; accordingly there are different theoretical models and analysis methods in anthropology that are also and especially relevant for archaeometallurgy.
The main fields of activity of archaeometallurgy are the origin analysis of objects (e.g. lead isotope analysis and trace element analysis ) and the reconstruction of first exchange of goods, later trade, prehistoric materials science including the reconstruction of manufacturing processes, and the cultural significance of metals and the associated processes in their societies. The reconstruction extractive processes such as degradation of finding and archaeological relevant ores , their smelting and processing of the metals form the mining archeology , which serves as a field science a combination of geological and archaeological methods. Studies on the typology and distribution of metal objects provide important information, an area that is heavily based on classical methods of archaeological find processing. The instrumental examination of production waste and finished products forms a further focus, often with a strong engineering influence, which seamlessly transitions into restoration research . The investigation of coins and jewelry represent further specialties within archaeometallurgy.
Methods
Archaeometallurgy is a classically interdisciplinary field of research that draws its methods from three main sources:
- Archeology for field work and finding processing,
- Mineralogy and chemistry for the study of ores, slags, technical ceramics and other materials, and
- Metallurgy for the study of metal objects and the reconstruction of high temperature extractive processes.
In archeology, metals and metallurgical residues initially appear in the same way as other materials and can be processed accordingly. Specific methods, on the other hand, should always be used when leaving 'normal' excavation sites and examining old mines or slag heaps . The surveying of old mine workings makes special demands not only because of the often extreme physical conditions, but also because of the three-dimensional character of the mine workings and the limited lines of sight, which often make normal surveying methods impossible. Slag heaps are often found in isolated regions and require the management of extreme amounts of finds. Both ancient mining and slag heaps can be problematic to date if the normal archaeological methods of dating such as stratigraphy or ceramic typology are inapplicable. Physical dating methods are irreplaceable here.
The focus of the laboratory procedures is the metallographic examination of all finds with the light microscope or reflected light microscope (see metallography ), the determination of mechanical parameters such as hardness and ductility of the metals on a micro-scale, as well as analytical methods for chemical composition, such as B. the scanning electron microscope (SEM), atomic absorption spectrometry (AAS) or inductively coupled plasma spectrometry (ICP). Optical and electron microscopy, the latter mostly coupled with energy-dispersive X-ray spectroscopy (EDX or EDS) or wavelength-dispersive X-ray spectroscopy (WDX or WDS) for chemical analysis in the micro range, are among the most widely used methods for examining archaeometallurgical samples.
Geographical and temporal developments
The production of metals was believed to have been developed independently in several places. The oldest traces can be found in West Asia ( Iran / Turkey ), where metal processing goes back over 10,000 years . The beginnings of metallurgy in the Balkans and the Iberian Peninsula are only a little more recent .
South America has a completely independent metallurgy that is younger but also goes back several thousand years. From the 1st century onwards there was a parallel development in the Mochica culture, which settled in the area of the Pacific coast of northern Peru . On a narrow, but around 600 km long strip in the coastal desert, the Mochica operated high-yield irrigation farming with guano fertilization . The pottery was highly developed, as well as the metal processing. In addition to gold and silver, the Mochica also processed copper and made copper alloys, especially Tumbago . Their method of gilding copper is also technologically remarkable.
The same can be assumed for Africa and East Asia . In addition to independent development, it can also be argued for a spread of metallurgy through diffusion for all areas except South America, which could be traced back to the core area in West Asia .
For Eurasia, a sequence is generally assumed that begins with the cold processing of solid metals ( gold and copper ) and does not yet require any “metallurgical” knowledge. This phase can last several millennia before the smelting of copper ore and the smelting and pouring of metal occur roughly at the same time. According to this scheme, pure copper is then replaced for a more or less long period of time by arsenic-containing copper, which has improved properties compared to pure copper. The color is lighter and the product is less prone to corrosion; ( Patina ) the melting point is lower, which makes it easier to process, and the metal itself is harder, which improves tool properties. It is believed that the arsenic content stems from the smelting of arsenic-containing ores that were deliberately or accidentally exploited. It is difficult to control the alloy composition and can only be done afterwards by estimating the metal color. The use of arsenic bronze is (relatively) short-lived; it will soon be completely replaced by tin bronze in many areas (in many places around 2000 BC). Tin bronze, typically with five to twelve percent by weight tin, is made by alloying metallic tin and copper, which facilitates the production of relatively well-defined alloys.
Even later (in Western Asia and Europe around 1800 to 800 BC ) iron appeared as an artificially produced metal that, due to its much higher smelting temperature (approx. 1,250 ° C), required a completely new method of processing: forging instead of casting . The next big step is the introduction of indirect iron smelting, which produces cast iron . The beginnings are in Europe around 1200 AD. Initially unintentionally, the cast iron was often referred to as pig iron by the smelters of the time , because it could not be forged.
The times given are only to be seen as a rough guide, cultural differences are sometimes quite considerable and cannot be approximated here. In China, for example, cast iron technology is apparently around 500 BC. . Chr fully developed, while very little evidence available in Africa on a copper metallurgy before the introduction of the iron.
Central Europe is an example of the much more detailed structure that is possible for individual areas today. The beginnings of copper metallurgy take place here in several phases and are considered part of the secondary products revolution :
- Phase 1: 4300 - 3800 v. Chr.
(Early Neolithic Age - Schussenried Culture , Early Michelsberg Culture , Hornstaader Group ):
- - only a few copper finds
- - imports
- - Southeast and East Central European area
- - no processing traces
- Phase 2: 3800-3380 BC Chr.
(late Neolithic - Altheimer group , Pfyner culture , late Michelsberg culture):
- - Formation of a north alpine circle of shapes
- - Oxide copper ores from Eastern Alpine and Slovak deposits
- - Crucible
- Phase 3: 3380-2750 BC Chr.
(early End Neolithic - Horgen culture , Goldberg III facies ):
- - drastic decrease in copper finds and shape impoverishment
- - Eastern cultural references
- - Oxide copper ores from Eastern Alpine and Slovak deposits
- - Beginning of copper production in western Switzerland?
- Phase 4: 2750-2200 BC Chr.
(Late Neolithic Age - Cord Ceramics , Bell Beaker Culture ):
- - increasing copper finds (grave finds, southwest Germany is an exception)
- - extensive cultural references
- - Oxide copper ores from Eastern Alpine and Slovak deposits
- - Copper extraction in western Switzerland
- - No processing documents
- - Gold Jewellery
Early copper extraction
After and adjacent to the picking up of solid copper , the actual metallurgical recovery of copper begins with the smelting of oxidic ores such as malachite Cu2 [(OH) 2 | CO3]. To do this, the ore is mixed with charcoal in a reaction vessel ( crucible or small furnace). Burning the charcoal generates heat of 1000 ° C to 1200 ° C and carbon monoxide. From a temperature of 230 ° C, malachite reacts to form copper (II) oxide, among other things. This is reduced by the carbon monoxide. The finished copper flows to the bottom of the reaction vessel and can be removed after cooling. Sulphidic copper ore is processed in another, and probably later used, process. To do this, slag formation is necessary in order to separate the secondary components (mostly iron sulfide / iron oxide and silica as gangue ) from the copper. The sulfur also has to be removed from the ore to enable reduction. Typical temperatures for copper smelting are around 1100 to 1200 ° C, enough to melt both the slag and the metal. The use of furnaces instead of crucibles allows much larger amounts of metal to be extracted; accordingly, smelting in the crucible is usually linked to the beginning of copper extraction. Later crucibles were used almost exclusively for casting.
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Early iron extraction
The smelting of iron ore into iron is historically divided into two processes:
- The "direct process" or " race (fire) process", which was first documented around 1800 BC, from the beginning. By the Hittites - through the Middle Ages , the Renaissance to the industrial revolution, and was the dominant method of iron extraction
- the “indirect” or “ blast furnace process”, in which liquid pig iron is produced, which in a second step has to be further processed into forgeable steel before it can be used.
The racing process differs from the extraction of other metals in that the iron produced is initially present as a porous iron sponge (hist. Luppets) and not as a liquid metal.
The - in the glowing state - semi-solid in the reduction process of iron had recovered to separate from the adhering slag by the forging first manually compressed and repeated by re-heating in the forge for cleaning forged be. This process is also known as fermentation .
The extremely important invention of steel , which was produced from soft iron by hardening - and is still used today - was achieved through quenching and tempering around 1400 BC. According to historical knowledge, also the Hittites. This heralded the long transition from bronze to "iron".
History of science
The scientific investigation of archaeological metal finds goes back to the 18th century. Since then, chemists, mineralogists, metallurgists and mining engineers have repeatedly been active in this field, mostly using the methods and issues of their parent disciplines and only occasionally in collaboration with archaeologists. This early phase of archaeometallurgy is characterized by the lack of continuity and specific scientific methods or communication channels. Archaeometallurgy has only been institutionalized since the second half of the 20th century and has not yet been completed.
The term “archaeometallurgy” probably goes back to Beno Rothenberg , who was co-founder of the Institute for Archaeo-Metallurgical Studies (IAMS) in London in 1972/73 . Other institutes that are specifically dedicated to archaeometallurgy beyond the interests of a single scientist have existed since the 1970s in Beijing at the University of Science and Technology and in Harvard at the Massachusetts Institute of Technology , and since 1990 in Bochum at the German Mining Department -Museum (DBM). Various research departments in large museums, such as B. at the British Museum in London, the Prussian Cultural Heritage Foundation in Berlin, the Smithsonian Institution in Washington or the Metropolitan Museum of Art in New York, also have many years of experience in the field of archaeometallurgy, but without making this a formal focus of their work .
The anchoring of archaeometallurgy in university teaching is also not very advanced. While several universities in Great Britain have special chairs, working groups and teaching programs in archeometallurgy (e.g. Bradford, Sheffield, London and Oxford) and other universities teach archeometallurgy as part of archeology (Liverpool, Nottingham, Cambridge etc.), there are in Germany only one special chair for archaeometry with a focus on archaeometallurgy (within archeology in Tübingen) as well as several minor subject offers at other universities (e.g. Bochum in cooperation with the DBM, Münster). The situation is similar in Switzerland, with a chair for archaeometry / archaeometallurgy in Friborg (within the geosciences) and several working groups at regional museums.
The institutionalization of archaeometallurgy is reflected in the appearance of specific journals ( Historical Metallurgy , published since 1966 by the Historical Metallurgy Society founded in London in 1962, as well as the Metal Museum Bulletin, published by the Metal Museum in Japan (19xx to 2004), the iams journal , published by IAMS in London, and Metalla , published since 1996 by the German Mining Museum in Bochum).
See also
literature
- Irenäus Matuschik: The new material - metal. ALManach 2. Stuttgart, 1997
- Christian Strahm: The beginnings of metallurgy in Central Europe. Helv. Arch. 25 (97), 1995, 2-39
- Paul T. Craddock: Early Metal Mining and Production , Edinburgh, 1995
Individual evidence
- ↑ Barbara S. Ottaway : Prehistoric Archaeometallurgy. Espelkamp, Leidorf, ISBN 3924734046
- ↑ Otto Johannsen: History of the iron. 3rd edition, Verlag Stahleisen, Düsseldorf, 1953, p. 44.
- ↑ Friedrich Cornelius : Geistesgeschichte der Frühzeit , Volume 1, Verlag Brill-Archive, 1960, p. 132.