Corinthian ore

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Corinthian ore (Corinthium aes), including the Japanese alloy Shakudō

Corinthian ore , Latin names aes Corinthium , more often Corinthium aes , is an alloy that was often used in antiquity , but its production and use can already be proven in ancient Egypt . The alloy, the name of which changed depending on the time and place, is copper-based with admixtures of the precious metals gold and silver . In addition to these main components, ancient sources cite additives of up to 5% of lead, tin, arsenic or iron. Thanks to improved separation processes and substitutes with the same material properties, it is now possible to dispense with the use of toxic admixtures. Corinthian ore was mainly used for the manufacture of luxury items and statues . The most famous centers for production were located in the Greco-Roman epoch on Aegina and Delos and of course in the eponymous city of Corinth .

Admixtures

Admixtures either resulted from the incorrect separation or were intended, both to change the material properties, including the formation of patina, and to change the colors and optical properties of gold, such as bronze and brass , but also silver, such as arsenic bronze , and cuprum album called to imitate. The lowering of the material costs by reducing the quantitative proportion of the expensive precious metals in the alloy could also be a reason. The replacement of the poisonous admixtures while maintaining the desired properties begins as early as the 18th and 19th centuries. The replacement of arsenic by a copper-zinc-nickel alloy can be dated to the tender for Germany in 1823 by the Association for the Promotion of Industry.

Impurities

In the specialist literature toxic additives such as arsenic and lead are mentioned. These are not necessarily the intended alloy components of Corinthium Aes, but arise during the smelting metallurgical extraction of copper and, depending on the current state of metallurgical knowledge and technology, could not be completely separated. The basic procedural principle was still uniform, only the efficiency differed.

The extracted copper ore consists, for. B. with copper antimony shine, made of copper with admixtures of antimony, arsenic , lead, iron and sulfur . Attempts are made to purify the molten raw copper, which had 90-96% Cu content, by blowing in air and adding slag-forming additives. Elements such as antimony, arsenic, lead and zinc volatilize as oxides or form iron, cobalt, nickel and tin oxide slags. This slag in turn can be separated from the cooking copper.

Intended additions

Intentional admixture could be given in order to change or improve basic metal properties. The change in strength, flexibility, sliding properties and machinability can be cited as an example for the improvement of a material property, with the addition of lead in particular can increase hot brittleness. As a pure change, one can apply the creation of a new color tone. Arsenic, meaning the golden-yellow arsenic mineral auripigment, derives its name from the ancient Persian al-zarnik , which means "gold-colored". It occurs as a normal impurity in copper and was also added intentionally because of its color. The silvery-white arsenic bronzes, also golden-reddish when heated several times, form a clear contrast to the golden-yellow tin bronzes.

Quite a few admixtures have both functions. In the past centuries , lead was a possible admixture due to its ease of manufacture and processing, but also due to its corrosion resistance and high density .

Historical development and delimitation

Anch -Kreuz replica of Corinthium aes with glyphs

Mediterranean area

The production and use of the "black gold of antiquity" can be traced back to Egyptian black bronze, the Egyptian name of which can be reproduced with HMTY-KM. A more detailed metallurgical consideration, even if not nearly as extensive as later with Alessandra R. Giumlia-Mair, as well as the use of the HMTY-KM can be found as early as 1966 in the article “On the Meaning of [black copper / bronze]”; the bracketed area of ​​the article contains the corresponding hieroglyphs in the original article . From the 1990s on, Giumlia-Mair also used the designations HSMN-KM or NMTI-KM, but abandoned this after 1993 in favor of the already mentioned HMTY-KM. HMTI-KM was only used briefly, although Giumlia-Mair did not specify in later publications whether this variant was written e.g. B. was based on the misinterpretation of the group writing of a cartridge . HMTY-KM is pronounced as ['hɛmp.tʰi kʰæːm]. The meaning of the hieroglyphs, which can be seen in the adjacent picture, can be stated as follows: The ideogram with the meaning of copper, brass and, in general, an object made of copper or bronze. Including the hieroglyph for black. Separated by the three strokes of the plural marker from the phonetic km, u. a. with the meanings of copper grain and copper ore. Two of the best-known preserved figures made of Egyptian black bronze are the depiction of Harpocrates from the 18th dynasty, in which the continuous bronze figure was supplemented with golden hair applications, and a woman statue from the late period in which gold inlays were incorporated into the bronze of the body.

Corinthium aes coin from 2017, material and patination by Markus Eckardt

The high point of production in the Mediterranean, to which the alloy owes its name, which is still in use today, was in Corinth in terms of space and in the Greco-Roman era. The Greek name was Κορινθιακό χάλκινο, Korinthiako chialkino, or χάλκινο for short. The Greek name was a substance, but above all quality information. The Mycenaean name κυανός, kyanos, on the other hand, clearly refers to a certain color property of the patina, which was already known in Egypt, but which was increasingly implemented in the Mycenaean environment. Both in Mycenaean Greek and Classical Greek , the German translations for the term κυανός “cornflower” or “blue”. And in fact, it is not wrong to choose “cornflower blue” as the translation variant in this specific case, since treatment with weak copper salt solutions gives the patina a complementary color spectrum from deep violet to blue. The Latin names Corinthium aes and Aes Corinthium, however, are pure place references. The Latin noun aes can be translated into German as “ore”, “copper” or “bronze”, Corinthius / -a / -um is an adjective and simply means “Corinthian”. So you get "Corinthian bronze" as a possible translation variant.

Asia

Very similar copper alloys were also used in Syria, Persia, India and China, which can be proven through very different documents in the form of traditions and artifacts. The Japanese Irogane alloys, including the Japanese red copper Shakudō , are probably independent lines of development, even if a basic exchange of knowledge cannot be ruled out. Both the slightly different composition of the alloy components and the significantly different patina thickness speak in favor of the thesis of independent lines of development. This is approx. 1 µ for Shakudō, whereas it is almost 20 µ for the non-Japanese alloys.

Others

The previously mentioned are to be separated from other copper alloys of similar composition, such as. As the Mesoamerican tumbaga because in this copper-gold alloy clearly the lower melting temperature and greater hardness shall be recognized as targets, how on the subsequent removal of copper oxide - patina may tighten.

Experimental research work

The exact details of ancient, mostly Roman sources about the composition of Corinthium Aes, which describe it as a mixture of copper, silver and gold, have long been doubted by experts. There was no point in adding precious metals to achieve a black patina. Instead, the thesis was put forward that the translators were mistaken or misinterpreted. At the same time, black-colored metal inlays on antique objects were wrongly classified as niello . In 1993, the archaeometallurgist Alessandra R. Giumlia-Mair from the University of Udine and Paul T. Craddock from the British Museum published a first comparative volume based on analysis data of various alloys of copper, silver, gold and other metals that have a stable, dark patina . The authors try to show that there was a comprehensible travel route for this (pre-) ancient forging technique and that it spanned a period of at least 3,500 years. Later practical experiments aimed to produce different Corinthium aes variants based on ancient and modern sources. The most detailed recipe was provided by the 2nd century manuscript of the alchemist Zosimos von Panopolis , now in the University of Cambridge , which was translated into French by Marcellin Berthelot in 1893 . Giumlia-Mair and Craddock were able to conclusively prove the theory of the assumed connection between the various black gold alloys from Egypt, Palestine, Mycenae, the Roman Empire and more recent ones from some countries in Asia with the same or similar alloy compositions and properties through a comparative analysis in 1996.

Corinthium instead of Shakudō

In the following years, Giumlia-Mair shifted the focus of her work increasingly to the field of Japanese Irogane metals, with a focus on the Shakudō alloys, which they consider to be similar to, and even related, to Corinthium Aes. The basis of her thesis is the proven trade relations and the transfer of knowledge between Asia and Europe. She establishes the connection between the metals in the later emergence of the Japanese Irogane metals, which, as with the Kanjis , is determined by a Japanese Take over Chinese knowledge about Korea . The collective term "Irogane metals" means the "colored metals", i.e. the colored alloys that were traditionally used in Japanese forging technology. The term is made up of the Kanjis 色, pronounced iro with the meaning color and 金, pronounced kane / gane with the meanings metal, money, assets. 色 の 金, iro no gane, is a colored metal or colored property, which refers quite well to the various bronze alloys as well as to the precious metal-containing alloys Shakudō and Shibuichi. Shakudō, 赤銅, is often translated as red copper in German, which can lead to irritation, as the alloy, like Corinthium Aes, was valued primarily for its black color. A resolution of this apparent, conceptual contradiction is quickly achieved. If you designate the alloy using the Japanese numerical identifier for colors, you get 赤銅 色, i.e. shakudōiro, with the meanings bronze-colored and black-brown. It can thus be said that 赤銅 can be translated into German with both “red copper” and “black brown copper”.

The results of their own research as well as of cooperation projects in the field of experimental archeology were among others. a. Presented at a conference in Matsue in 1998 . The basic functionality of the procedure could be verified and thus the correctness of many of the ancient sources could be confirmed. Further results from the field of experimental archeology included the areas of processability and patinability of black copper alloys with changing additives and different patination baths. A modern branch has emerged from the use of new alloys, such as B. the German Mujodogane, in the field of Japanese forging technology. Due to the existing similarities of Shakudō with the various Corinthium Aes alloys, the step of using these non-Japanese alloys with Mokume-Gane was obvious.

The experimental research work is in all its facets in the tradition of the historical Corinthium production, as this has been subject to significant variations over the centuries and in the different production locations, as metal analyzes have shown.

Coloring, patination

The standard patina of Corinthium aes has an aubergine-black color in its classic form. The patina , which is always reproduced through skin contact, is the alloy's interesting property for gold and silversmiths. This means that there is no scarring of the jewelry, which is understood to mean the formation of clearly visible scratches in the metal. The patina is re-formed by oxidation of the copper alloy with atmospheric oxygen and sweat .

Abrasion with darkening of the corresponding skin area

The newly formed patina can lead to a darkening of the skin contact point of the wearer due to abrasion. This can be prevented by internal elements made of a different metal.

Since 2001, the German goldsmith M. Lehr has shown how to achieve the same patinability despite a reduction in the precious metal content . Another focus was the German goldsmith Markus Eckardt, whose work since 2012 has focused on the full development of the patina and its preservation after completion. The background and trigger for the work were the full development of patina despite the interior elements, the special coloring intention and the contrast function. Since the end of the 1990s Eckardt had primarily been producing replicas of Roman finds from Corinthium Aes, but the later use of interior elements made of other metals to avoid abrasion led to problems with the full development of the patina. The pure intention to color, in turn, requires the possibility of a full development of an ultimately even deep black patina with a slight sheen, which only changes into the normal patina formation cycle in the event of scarring and otherwise ideally retains its full development.

New lines of development in the field of copper alloy coloring should come as no surprise. As the German Copper Institute explained in its 1961 edition “Copper”, dyeing is “a very complex technology that has not yet been achieved by chemical progress. Coloring copper, like no other surface treatment process, requires great craftsmanship, combined with long practical experience. "

Modern development

Corinthium with diamonds and gold. Focus: contrast of the patina

Corinthium aes has experienced a renaissance as an alloy since 2003 in Germany due to its increased use in the mokume-gane technique, which originally came from Japan, as well as damask production for the jewelry sector.

The reason for this is the lower price than palladium , white gold and gold , which was additionally fueled by the possibility of precious metal reduction in the alloy composition, especially at the time of rising precious metal prices.

Corinthium aes coin from 2017, material and the typical dark black patina by Markus Eckardt

Otherwise, the good workability and the interesting color change, which ranges from copper-colored to dark brown to deep black and the absence of scarring, speak for the use of Corinthium aes. The Corinthian ore does not belong to the classic Japanese Mokume Gane Damascus materials and is used by the hallmark u. a. clearly separated from the Japanese Shakudō . The difference can only be seen optically after the patina has developed; the red gold Shakudō achieves a maximum of a rich, deep brown color, while Corinthium aes forms an aubergine-black patina. This trend started by a number of Mokume Gane artists since 2000.

In the course of this use, the desire for a stronger contrast function, away from the classic aubergine-black to a deep black patina, can be located.

gallery

  • Corinthium aes

  • Replica of a woman's ring from a Roman excavation from Corinthium aes

  • Men's ring replica with partially developed patina

  • Corinthium aes bangle replica with clearly developing patina

  • Inside of the ring with stamping

  • Corinthium Aes ring with brilliant inlay, focus is strong contrast of the alloy

  • Corinthium aes bowl with deep black patina

literature

  • Berthelot, Marcellin: Histoire Des Sciences La Chimie Au Moyen Age V2 (1893), Rubens Duval (transl.), Whitefish (MT) 2009.
  • Giumlia-Mair, Alessandra R. et al .: The black gold of the alchemists - Corinthium Aes, Darmstadt 1993.
  • von Bibra, Ernst : The bronzes and copper alloys of the ancient peoples. Erlangen 1869

swell

  1. ↑ Carl Bischoff: The copper and its alloys, with special consideration of their application in technology, Berlin 1865, p. 40 et passim.
  2. ↑ See Ioannes Alexandrides (Pseudo-Democritus): Physica et Mystica, Chrysopoeia 1880.
  3. ↑ a b c d Cf. Corrosion patina or voluntary patina? Contribution of non-destructive analyzes to the surface study of copper based archaeological objects. Retrieved December 8, 2014 .
  4. ↑ Cf. Alessandra Giumlia-Mair, Péter Gaboda, u. a .: Two statuettes with HMTY KM in the fine arts museum Budapest, In: Metals and Societies, Studies in honor of Barbara S. Ottaway, TL Kienlin (Universitätsforschungen zur prehistorischen Aräologie, 169), B. Roberts (Ed.), Bonn 2009, pp. 433-442.
  5. ^ John D. Cooney: On the Meaning of [black copper / bronze], Zeitschrift für ägyptische Sprache und Altertumskunde 93, Berlin 1966, pp. 43-48.
  6. ↑ PT Craddock and AR Giumlia-Mair: HSMN KM Corinthium aes Shakudo: Blackpainted bronze in the ancient world, In: Metal Plating & Patination. Cultural, technical & historical developments (Chapter 9), London 1993.
  7. ↑ a b c cf. Alessandra R. Giumlia-Mair u. Paul T. Craddock: The black gold of the alchemists - Corinthium Aes, Darmstadt 1993.
  8. ↑ Alternatively: The helmet made of Corinthian bronze is referred to as Χάλκινο κορινθιακό κράνος, and αργυρό και χάλκινο also indicates silver and bronze as metal / material information. Κορινθιακό adapted with reference to χάλκινο. χαλκος κορινθιακος, Chalkos korinthiakos, Corinthian copper, but Κορινθιακό χάλκινο Corinthian bronze, in the sense of Corinthian bronze as a quality feature of the product.
  9. ↑ Cf. Freiherrn von Bibra, Ernst: The bronzes and copper alloys of the ancient and oldest peoples with consideration for those of the modern age, Erlangen 1869, p. 208 ep
  10. ^ Cf. Elizabeth P. Benson: The art of Precolumbian gold: the Jan Mitchell collection, Boston 1985.
  11. ↑ a b so: Pliny Secundus d. Ä .: Naturkunde / Naturalis Historiae, Metallurgie, Roderick König (Hg./Übers.) u. a., Munich / Zurich 1989. And: Marcellin Berthelot: Histoire Des Sciences La Chimie Au Moyen Age V2 (1893), Rubens Duval (transl.), Whitefish (MT) 2009.
  12. ↑ See www.archaeometallurgie.de, as of January 31, 2008
  13. ↑ Cf. Alessandra Giumlia-Mair: Black Copper is not Niello, London 1997 (11), p. 35f.
  14. ↑ Cf. Zosimos von Panopolos: on the production and coloring of Corinthian bronze or black metal, Cambridge manuscript Mm 6, 29.
  15. ↑ Further reading: Marcellin Berthelot: La Chimie au Moyen Âge II, Paris 1893, p. 223. See also: Digitized edition Berthelot: La Chimie au Moyen Âge. Retrieved December 7, 2014 .
  16. ↑ Cf. A. Giumlia-Mair: Das Krokodil and Amenemhat III from el-Faiyum - Hmti km - copies from the Middle Kingdom, In: Antike Welt 27, 4 (1996), pp. 257-267; ibid. Section Crocodile by El Fayum in the Egyptian collection in Munich.
  17. ↑ See AR Giumlia-Mair u. PT Craddock: Irogane alloys in classical antiquity (Bulletin of the Metals Museum), Sendai 1994, pp. 3-17. And: AR Giumlia-Mair: Early instances of Shakudo-type alloys in the West (Bulletin of the Metals Museum), Sendai 1997, pp. 3-15.
  18. ↑ Silvia Miklin-Kniefacz: Shakudo and Shibuichi, Insights into Japanese Goldsmithing, In: Metal Conservation, Metal Restoration, History, Method and Practice, (Martina Griesser-Stermscheg and Gabriela Krist eds.), Vienna a. a. 2009, 129-138, p. 129.
  19. ↑ Cf. A. Giumlia-Mair & M. Lehr:. Patina Ting Black Bronzes: Texts and tests, Proceedings of the 4th International Conference on the Beginning of the Use on Metals and Alloys (BUMA IV), Sendai 1998th
  20. ↑ Cf. A. Giumlia-Mair & M. Lehr: Experimental reproduction of artificially patinated alloys identified in ancient egyptian, palestinian, mycenean and roman objects, Eindhoven 2003.
  21. ↑ See Mujodogane. Archived from the original on August 23, 2014 ; Retrieved December 25, 2014 . u. State award for design, silver alloy "Mujodogane", recognition of product design. Retrieved December 25, 2014 .
  22. ↑ Cf. Andreas Neumann: Mokume Gane-Damast as an example of Japanese lines of development (Astarte-Verlag), In: Open Abstract- u. Collection of essays from the All Asian Society 2000–2007, Wadgassen 2008, p. 21.
  23. ↑ a b c Cf. Corinthium aes. The black gold of antiquity - the soul of a night full of magic. Retrieved December 8, 2014 .
  24. ↑ a b cf. A. Giumlia-Mair u. M. Lehr: Production of Corinthium Aes, Goldschmiedezeitung 1/2000, pp. 104-107.
  25. ↑ a b See examples for permanent patina in Corinthium aes, Markus Eckardt. Retrieved December 7, 2014 .
  26. ↑ See: Deutsches Kupferinstitut Berufsverband eV: Kupfer, Düsseldorf 1982.