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II. La fabrique du noir

Selenium-based black bronze treatment, as compared to other patination technologies of ancient and historic black bronzes

Traitement au sélénium des bronzes noirs, comparé à d’autres techniques de patine des bronzes noirs antiques et historiques
Jennifer L. Mass, Aaron Shugar, Adam C. Finnefrock, Satoko Tanimoto, Margaret Little, Renée Stein et Ellen Archie
p. 64-74

Résumés

Dès l’Antiquité, en Méditerranée et en Extrême-Orient, des métallurgistes ont utilisé des patines noires sur de petits bronzes de prestige. Les indices textuels peuvent se révéler ambigus, mais la composition de ces bronzes a fait l’objet d’études et de caractérisations approfondies au cours des dernières décennies. Les analyses élémentaires et moléculaires des bronzes noirs produits durant des millénaires dans différentes cultures mettent en évidence, outre les techniques antiques, la présence fréquente de patines au sélénium, que nous avons identifiées comme étant de la sélénite de cuivre dihydrate. On a longtemps considéré que les formulations de patine au sélénium furent utilisées en Europe au xixsiècle en réaction aux alliages patinés noirs (tels que le shakudō et le shibuichi) importés du Japon à partir de la restauration de Meiji. Mais la littérature technique européenne du xixsiècle ne confirme pas ce point de vue, de sorte que les techniques de patine au sélénium sont restées méconnues. Nous étudions ici le foisonnement des techniques à base de sélénium au début du xxsiècle, ainsi que la validité des hypothèses concernant leurs origines dans les formulations de patine.

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Texte intégral

Ancient and historic black bronzes – an overview of textual and scientific findings

  • 1 Giumlia-Mair, 2020, p. 11.
  • 2 Barbour, Glinsman, 2015, p. 23.

1This paper provides a brief review of the scientific study of black patinas on ancient and historic bronzes and then focuses on the presence and origins of black selenium patinas on bronze antiquities, research initiated by our identification of selenium on ancient Greek and Egyptian diminutive bronzes (fig. 1-3). Bronze antiquities from diverse cultures and time periods often have rich black patinas that range in color from pure black to blacks with deep blue and violet overtones (fig. 4)1. These beautiful patinas were desirable in Antiquity and remain so to the present day. However, the particular fascination with black bronze antiquities after the late 18th to 19th century excavations at Herculaneum (and the recreation of these patinas on reproductions) raises questions about when the extant black patinas we observe today were originally applied (fig. 5). Our identification of selenium in black bronze patinas across cultures and time periods (something many other conservators and scientists have also observed) suggests that these selenium-based patinas are not ancient in origin. As a result, selenium-based patinas have often been dismissed as a “faker’s trick” and their origin has received little attention beyond a possible connection to the selenium-based toners used by 19th century photographers2. Here we provide an abbreviated history of black bronze patinas, a summary of the scientific study of their origins, and the results of our investigation into the origins of the black selenium-based patina, shown below to be due to copper selenite dihydrate. This research was inspired by our discovery of selenium patination on Egyptian objects from the Barnes Foundation and Greek Hellenistic bronzes in the Michael C. Carlos Museum at Emory University.

Fig. 1. Fulcrum attachment cast in the form of a wild mule, 1st c. BCE, Hellenistic Greek, bronze with silver inlay, Atlanta, The Michael C. Carlos Museum of Emory University (inv. 2003.011.004)

Fig. 1. Fulcrum attachment cast in the form of a wild mule, 1st c. BCE, Hellenistic Greek, bronze with silver inlay, Atlanta, The Michael C. Carlos Museum of Emory University (inv. 2003.011.004)

The impetus for this research was the identification of the original patina for this diminutive bronze, i.e. was this in fact a black bronze.

MCCM, CC-BY-NC-SA 4.0.

Fig. 2. Fulcrum attachment cast in the form of a wild mule, 1st c. BCE, Hellenistic Greek, bronze, silver, copper, Atlanta, The Michael C. Carlos Museum of Emory University (inv. 2003.011.003)

Fig. 2. Fulcrum attachment cast in the form of a wild mule, 1st c. BCE, Hellenistic Greek, bronze, silver, copper, Atlanta, The Michael C. Carlos Museum of Emory University (inv. 2003.011.003)

MCCM, CC-BY-NC-SA 4.0.

Fig. 3. Unidentified artist, statuette of the Apis Bull, 664-30 BCE, bronze, Philadelphia, The Barnes Foundation (inv. A75)

Fig. 3. Unidentified artist, statuette of the Apis Bull, 664-30 BCE, bronze, Philadelphia, The Barnes Foundation (inv. A75)

© The Barnes Foundation.

Fig. 4. Ishiguro Masayoshi (1774-ca. 1862), sword tsuba, 19th century, shakudō, gold, shibuichi and copper, New York, Metropolitan Museum of Art (inv. 48.63.5a). Note the blue-violet hue of the patina

Fig. 4. Ishiguro Masayoshi (1774-ca. 1862), sword tsuba, 19th century, shakudō, gold, shibuichi and copper, New York, Metropolitan Museum of Art (inv. 48.63.5a). Note the blue-violet hue of the patina

Rogers Fund, 1948, Metropolitan Museum of Art, Open Access.

Fig. 5. Mercury in Repose, bronze, Villa of the Papyri, Herculaneum, Napoli, Museo Archeologico Nazionale (inv. 5625)

Fig. 5. Mercury in Repose, bronze, Villa of the Papyri, Herculaneum, Napoli, Museo Archeologico Nazionale (inv. 5625)

© M.-L. Nguyen/CC-BY 2.5.

  • 3 Craddock, Giumlia-Mair, 1993, p. 102.
  • 4 Mohamed, Darweesh, 2012, p. 182-184.
  • 5 Aucouturier et al., 2010; Craddock, Giumlia-Mair, 1993, p. 102; Benzonelli et al., 2017.
  • 6 Mathis, 2005.
  • 7 Mohamed, Darweesh, 2012, p. 181, 190.

2We will broadly define ancient and historic bronzes here as typically either a binary alloy of copper and tin or a ternary one prepared with the addition of lead. Black-hued bronzes were prized by a diversity of cultures in Antiquity, including the Greeks, Romans, and Egyptians. There has been extensive interest and research on the black patinas of Egyptian and Roman copper alloys, beginning in the mid-19th century as discussed by Craddock and Giumlia-Mair3 (fig. 6). While a comprehensive overview of the history of black bronze technologies is beyond the scope of this paper, a few key examples are provided below. We note here that these objects tend to be diminutive and have a contrasting gold or electrum inlay, and the patinas are largely understood to be the result of oxidation of bronzes with minor amounts of gold and that there appears to be more than one cause for these surfaces4. Multiple authors have identified cuprite (Cu2O) as the major phase on the black surfaces, often in the presence of black tenorite (CuO)5. An in-depth PIXE and RBS study of the surface oxidation phenomena has been carried out by Mathis6. Other black materials identified in ancient black patinas include copper sulfides such as digenite, Cu9S57.

Fig. 6. Sphinx of Siamon, 21st Dynasty, bronze with silver or electrum inlay, Paris, musée du Louvre, département des Antiquités égyptiennes (inv. E 3914)

Fig. 6. Sphinx of Siamon, 21st Dynasty, bronze with silver or electrum inlay, Paris, musée du Louvre, département des Antiquités égyptiennes (inv. E 3914)

An example of a diminutive bronze that compositionally aligns with hmty-km.

© Musée du Louvre/Christian Décamps.

  • 8 Benzonelli et al., 2017.
  • 9 Benzonelli et al., 2017.
  • 10 Mathis et al., 2009.
  • 11 Oguchi, 1983.
  • 12 Pliny (the Elder), 1857, 46, 128.

3One additional component of the Egyptian hmty-km cuprite-based black surface may be gold nanoparticles, but these have yet to be identified in analysis of ancient objects8. Recently, Benzonelli et al. have proposed a network of cuprite with dispersed gold nanoparticles as the microstructure comprising ancient bluish black patinas, and these nanoparticles have been observed in the authors’ modern reproductions9. Other features of Egyptian black bronzes are relatively thick patinas (greater than 10 μm10). Copper sulfate or copper sulfide have both been suggested as reagents for the desired hmty-km patina, similar to the use of copper salts in the Japanese black shakudō alloy (see below11). The presence of copper sulfide in another Egyptian black patina could suggest the use of egg yolk, a material used to blacken silver in ancient Egypt12.

  • 13 Aucouturier et al., 2010.
  • 14 Oguchi, 1983.

4Black ancient Egyptian and Roman patinas were found by previous researchers to have gold contents up to 6.7 wt% and silver contents up to 3 wt%, and while the major crystalline phase in the black patinas was cuprite (Cu2O)13. XRD data for gold and/or silver were also identified. Ag2O, also a black compound, was further suggested by the data. Cultural heritage scientists have thus not reached a consensus about the technology behind the black patinas of Antiquity. Furthermore, the restoration and conservation treatment histories of antiquities in the 19th and 20th centuries complicates our investigation of these ancient technologies. One impetus for the application of black patinas to antiquities repatinated during the 19th century is the West’s admiration for Japanese black copper alloys following the opening of trade with Japan in 1853. The Japanese shakudō alloy is a Cu-Au alloy containing 0.5-4 wt% gold, and the black patinas are created by placing the alloy in a boiling solution of copper salts (including copper acetate) to produce a thin cuprite layer (Cu2O)14.

  • 15 Giumlia-Mair, 2013, p. 100.
  • 16 Buccolieri et al., 2015.
  • 17 Buccolieri et al., 2015, p. 106.

5Black bronzes from the ancient Greek and Roman periods include Mycenaean lead-tin alloys that have been found to contain traces of gold and silver15. The black patinas of the famous Riace bronzes (5th c. BCE, recovered from the Ionian Sea) contain both tin oxide (cassiterite, SnO2) and copper sulfide (Cu2S) as well as Mg and Fe compounds16. These are considered to be artificial patinas and suggest the use of a copper sulfide-based patina in Antiquity. This conclusion is based on sulfur compositions higher than 10 wt% in numerous locations on the sculpture’s surface, with one location containing 12.5 wt% sulfur17.

  • 18 Fucito, 2013, p. 137-139.
  • 19 Hughes, Rowe, 1991, p. 14.
  • 20 Mathis et al., 2007; Hunter, 2001; Giumla-Mair, 2001.

6Restorers carried out artificial patination of archaeological bronzes in the 19th and 20th centuries after natural or ancient patinas had been removed. This work conformed with nineteenth-century perceptions (and misperceptions) of how antiquities should appear, and as a response to the fashions of the time. For example, in the 19th century, one could order reproductions of Greek and Roman bronzes with their patinas specified, including a “Herculaneum black” patina18. The black patinas of the Herculaneum bronzes may, however, have been the result of a misunderstanding of their ancient appearance. Pliny the Elder describes the oiling of Roman bronzes to produce a golden shine. The carbonization of this oil-based coating on Herculaneum bronzes due to their anoxic burial environment would produce a black sooty surface similar to the carbonization of other organic matter from this site. Philostratus mentions a black bronze in his writing that he calls aes nigrum19. Similarly, the Greek alchemist Zosimos of Panopolis (end of the 3rd c. to beginning of the 4th c. BCE) writes of recipes for producing dark patinas on bronzes20.

7The scientific study of ancient black bronzes continues, with selenium frequently being identified in these surfaces.

Scientific study of two Hellenistic Greek black bronze fulcra and one Late period Egyptian Apis Bull statuette

8The two Hellenistic Greek bronze objects responsible for initiating this research (fig. 1-2) date to the 1st century BCE and are a fulcrum attachment cast in the form of a wild mule (Carlos Museum, object number 2003.011.004) and a fulcrum in the form of a mule’s head (Carlos Museum, object number 2003.011.003). Both were examined to identify the presence and nature of any artificial patination applied to the objects, specifically to determine if the current black and grey patinas could have been original to these works or if they were a later application for aesthetic purposes, as discussed above. This question became of particular interest when selenium was found during X-ray fluorescence (XRF) examination of both the surfaces of one of the fulcra (2003.011.004) and a diminutive bronze Apis Bull from the Barnes Foundation (Barnes Foundation, A75) (fig. 3), suggesting the use of what must be a nineteenth- or twentieth-century patination process.

Instrumental methodology

  • Fourier transform infrared spectroscopy (FTIR): A size 11 steel blade scalpel was used to remove small (millimeter sized) samples for molecular analysis by FTIR. Samples were mounted on a diamond half-cell support for transmission mode. Data were acquired and analyzed with a Thermo Scientific Nicolet iN-10 FTIR microscope controlled by OMNIC Picta software. A total of 128 scans were collected over a spectral range of 4000-650 cm-1 with a spectral resolution of 4 cm-1. A number of public and commercial databases were used for identification. Multicomponent spectral deconvolutions and sample identifications were performed with OMNIC Specta software.

  • X-ray fluorescence (XRF): Qualitative energy-dispersive X-ray fluorescence spectroscopy was carried out using a Bruker Tracer III-SD handheld XRF with a rhodium X-ray tube and a silicon drift detector. The analysis conditions were a tube voltage of 40 kV and 13 µA, no filter, and data collection time of 60 seconds real time.

Results

9Molecular analysis of the MCM 2003.011.004 fulcrum by FTIR revealed the presence of copper selenite dihydrate, the compound responsible for the black color of the selenium patination treatments. To our knowledge, this is the first identification of the black phase that is formed when selenous (or “selenious”) acid is used to patinate or repatinate an ancient bronze. While selenium was present in the XRF data for the Apis Bull (fig. 3), only bitumen, verdigris, and Prussian blue could be identified in the black region of its patina, suggesting a potentially long and intricate restoration history. This finding, from a microgram sample of green patina removed from behind the plume of the head for fulcrum 2003.011.004, also contained malachite [CuCO3.Cu(OH)2], chrysocolla (CuSiO3.nH2O), and beeswax. Malachite can be part of a natural passivating patina on ancient bronzes, but it can also be applied as a pigment to make an attractive surface, or even scraped off of an ancient bronze surface and then reapplied after electrolytic reduction. The finding copper of selenite dihydrate, however, strongly suggests the black patina on this fulcrum is not original. The only other indication of a later treatment of this bronze is a beeswax coating (which could be applied for corrosion protection or as a medium for a malachite application as discussed above). However, the presence of chrysocolla, a blue/green copper silicate pigment, further suggests the application of an artificial patina to this region of the object. To our knowledge a full characterization of the compounds formed when selenous acid is applied to a copper alloy has not been investigated, but this is an important area for further research.

Evidence for nineteenth-century selenium-based bronze patination recipes

  • 21 Hammer, 1903, p. 372.
  • 22 Michel, 1931; Hiorns, 1892 and 1903; Buchner, 1901 and 1910; Lacombe, 1887.

10One of the most commonly observed features of ancient and historic black bronze patinas is the presence of selenium. Notably, the presence of selenium-based black patinas on ancient and historic bronzes are observed on objects across cultures and spanning broad periods of time. Black selenium patinas have been identified on Japanese, Chinese, Pre-Colombian, Native American, Roman, and Hellenistic bronzes, predominately by X-ray fluorescence. Based on this broad range in time and location, and the fact that selenium was not discovered until 1817, selenium patination appears to have been a restoration treatment21. Restorers may have used selenium to repair a damaged original black patina, or to create a black patina in line with the current fashion of the day. The latter possibility has led to a conventional wisdom among conservators and scientists that selenium-based patinations were nineteenth-century treatments intended to imitate dark patinas imported from Japan or prepared by the master patineurs at work in Paris in this period. A review of French, German and English chemical patination literature from the 19th century, however, does not reveal any selenium-based recipes22.

  • 23 Michel, 1931.

11One important compilation of French black patina recipes from the turn of the 20th century is La Coloration des Métaux by Jacques Michel (1931)23. Instructions for the dark patination of copper and its alloys in this volume include oxidation, sulfidation, and the use of antimony, arsenic, or platinum-based reagents. Michel further notes that nitrates, sulfates, and carbonates can be used to produce dark-hued surfaces. One 1904 recipe from this volume for a Patine noire du cuivre suggests “immersing the object in a strongly diluted copper (II) sulfate solution, allowing the object to dry, and then placing it in a hot dilute solution of sodium hyposulfite”. A recipe from Bellet’s Meilleures recettes for a Patine noire du cuivre is as follows: “The pieces to be blackened are first coated with tallow and exposed to the flame of a resin torch...”, a method analogous to the Herculaneum patina hypothesis above. A 1905 recipe suggests for its Patine noire du cuivre immersing the copper object for thirty minutes in a solution of antimony chloride dissolved in alcohol and hydrochloric acid.

  • 24 Hiorns, 1903, p. 156, 157, 159, 161, 163, and 164 respectively.
  • 25 Buchner, 1901 and 1910.
  • 26 Lacombe, 1887.

12The 1911 edition of La Nature provides instructions for “glossy black patinas with metallic highlights”: “A gray black with reflections formed from a deposit of antimony can be obtained on brass by applying to well-cleaned metal surfaces a solution of 10 grams of antimony chloride (antimony butter)…in hydrochloric acid...” Another recipe collected by Michel Coloration en noir du bronze ou du cuivre calls for white arsenic (As2O3) and potassium cyanide in place of antimony. Our archival research further included Metal Colouring and Bronzing, by A. H. Hiorns (1892 and 1903 editions24), Die Metallfärbung und deren Ausführung mit besonderer Berücksichtigung der chemischen Metallfärbung by Georg Buchner (1901 and 1910 editions25), and Nouveau manuel complet du bronzage des métaux et du plâtre by M. S. Lacombe (1887)26. The 1903 Hiorns edition has recipes for dark brown to black colors on copper that use ammonium sulfide, potassium sulfide, mercury salts, sodium or potassium sulfantimonate, arsenic salts, copper nitrate with potassium sulfide, and barium sulfide. No selenium-based recipes appear in this volume nor in the Buchner or Lacombe volumes. In fact, to date we have found no evidence of selenium-based patination recipes in the nineteenth-century literature.

Evidence for selenium-based patinas in the 20th century

  • 27 Malherbe, 1904, p. 23603-23604.
  • 28 Malherbe, 1904, p. 23603.

13The first documented information in English that we can find for selenium’s use as a patination reagent occurs early in the 20th century. There is a selenium-based patination recipe reprinted from Malherbe in a 1904 Scientific American27. Cupric selenite and nitric acid mixtures are first introduced here as a steel bluing or blackening recipe, as reprinted from La Chronique industrielle, “Direct Coloration of Iron and Steel by Cupric Selenite” by M. Paul Malherbe. He notes: “[iron] immersed in a solution of cupric selenite, acidulated with a few drops of nitric acid, it precipitates these two metals on its surface in the form of a dull black deposit, but slightly adherent… If rubbed with a cloth, this deposit turns a blue black or brilliant black…28” Malherbe then describes the production of a “brilliant black coloration” of iron and steel using selenous acid, cupric sulfate, water, and nitric acid. Crucially, the patina color depends on the immersion time, and “the metal can be colored in succession yellow, rose, purple, violet, blue” before it turns black. This sequence of coloration suggests that the bluish hue of these beautiful black patinas is in fact a thin film interference effect. However, when the patina gets thick enough, the black of the copper selenite dihydrate appears.

  • 29 He provides two recipes for the “coloration of copper and brass with cupric selenite”, both of whic (...)

14Malherbe then notes that copper and brass can be similarly colored with cupric selenite by the immersion of the metal in an aqueous copper sulfate solution acidified with nitric acid and selenous acid. This is the first textual reference for the selenium patination of copper and one of its alloys that we have identified. Malherbe goes on to state “the following colors are obtained, according to the time of immersion: yellow, orange, rose, purple, violet, and blue, which is the last color that can be obtained”. This suggests that his reagents are depleted prior to the production of a patina thick enough to appear black29. Malherbe does not discuss the use of copper selenite as bronze patination in this publication, which with its different composition may not have an identical response to the brass described above. We must emphasize here that the use of a technology typically predates its patent filing, and so copper selenite dihydrate may well have been employed as a black patina for copper and one or more of its alloys in a limited scale prior to 1904. Malherbe adds one final note that without acidification of the solution the patina will be fugitive and spotty.

  • 30 Fuller, 1942.
  • 31 Scroxton, 1950.

15A patent for a selenium-based patina is not filed with the United States Patent Office until 1941 (US patent number 2303350, Metal Coating, submitted by William A. Fuller, San Jose, California30). This patent is focused on a different metal substrate rather than an iron, steel, or copper alloy – aluminum in this instance. The invention described is meant to provide a “permanent and uniformly black surface” to aluminum-containing alloys. Significantly Fuller notes “it is another object of the invention to provide a coating… to produce… optical black, oxidized, and antique finishes”. Fuller prepared his patina with a dilute aqueous solution of a “selenium compound which produces a selenous acid, and a soluble halogen salt of copper”. In 1948, Wright G. Scroxton filed a closely related patent for bluing metals (Application November 4, 1948, Bluing Metals, patent number 2527232)31. His recipe uses copper selenite dihydrate to produce a blue color on ferrous metal gun barrels with an aqueous solution of copper chloride, selenous acid, Aerosol OS (a wetting agent), and an unspecified blue colorant. This copper selenite dihydrate technology has been used from the early 1950s to the present as a “cold bluing” formulation for gun bluing, a decorative and passivating surface patina used on firearms.

  • 32 Born, 1990.

16Selenium patination may have originally been carried out to darken ancient copper alloys that had their patinas stripped during the electrolytic reduction treatments that were popular from the 1880s to the 1930s. Electrolytic refining was published by Friedrich Rathgen in 1889 and again by Colin Fink in the 1930s and has since been described as “catastrophic” to the surface aesthetics of ancient objects, suggesting a strong desire to repatinate them32.

Selenium as an artists’ material in the 19th and 20th centuries

17Selenous acid was first commercially available, and hence available to artists and restorers, in the 1860s even though there is no documented evidence of patination recipes or handbooks that use it until 190433. How then might selenium-based formulations for metal patinas have entered into the patineur’s toolkit? One possible answer is through the availability of selenium-based pigments for glasses, ceramics, and plastics. In 1892, a United States patent for a selenium-based glass colorant is filed by Bohemian glass chemist Franz Welz of Austria-Hungary – Manufacture of Rose or Orange Stained Glass (US patent number 479689)34. This patent indicates that selenium was likely already in use as a red colorant for glasses this date. By ca. 1894, Kopp glassworks in Pittsburgh expanded upon Welz’s technology to invent the selenium-based red glass that would be used in the United States for traffic lights35. By 1916, the English firm Johnson Matthey & Company, Ltd. was advertising selenium to glassmakers in the glass trade periodical National Glass Budget, demonstrating its ready commercial availability for artists (fig. 7)36. However, we have yet to discover documentation of a specific artist experimenting with both selenium-colored pyrotechnologies and selenium-based patination recipes.

Fig. 7. Advertisement for selenium reagents for glassmakers from the National Glass Budget trade journal, 1916

Fig. 7. Advertisement for selenium reagents for glassmakers from the National Glass Budget trade journal, 1916
  • 37 Barbour, Glinsman, 2015, p. 23.
  • 38 Barbour, Glinsman, 2015, p. 23.
  • 39 Mengele, 1933.
  • 40 Barbour, Glinsman, 2015, p. 27.

18A perhaps more promising route for the introduction of selenium to the patineur’s palette is through photographic toning. Barbour and Glinsman in their 2015 publication on Rodin’s bronze patinas discuss the great Parisian patineur Jean-François Germain Limet (1855-1941, fig. 8), who worked at the turn of the 20th century as both a patineur and photographer of Rodin’s sculptures37. In Limet, we therefore have a potential connection between experimentation in photographic toners and in bronze patinas. Barbour and Glinsman go on to note Limet’s complaints to Rodin about preparing an aesthetically acceptable and enduring black patina, which likely led to his experimentation with formulations that could produce black hues. Limet notes “that black is not varied enough, or the metal does not lend itself to that color38”. As a photographer, Limet may well have been knowledgeable about selenium toners in photography (although the patent for the use of selenium-based toners in photography was not filed until 1930 in Germany and 1931 in the United States39). This patent describes the use of selenous acid-based toning baths containing citric acid for the production of a sepia-toned silver photographs, while making it clear that several types of selenium-based toning baths were already in use. While Barbour and Glinsman note that “Limet not only created colorful patinas that embraced contemporaneous aesthetics but did so in a manner that borrowed from his concurrent profession as a photographer40”, they identify selenium in the patina of Rodin’s The Walking Man’s (likely 1903 cast) base and feet only, but not on the sculpture’s black right thigh. This raises two possible interpretations of The Walking Man data, the first that the selenium-based toner is an experimental formulation by Limet, and the second that the selenium is part of a later repair of a region vulnerable to surface abrasion rather than original to Limet’s work. Further research into Limet’s purchases from Poulenc Frères, a chemical and art supply store, may help to resolve this question. In the meantime, as a photographer and patineur, Limet remains a compelling link between the two selenium-based artists’ techniques.

Fig. 8. Jean-François Germain Limet (1855-1941) working in his Paris studio, 1938

Fig. 8. Jean-François Germain Limet (1855-1941) working in his Paris studio, 1938

Photo by Malvina Hoffmann, Sculpture Inside Out, George Allen and Unwin Ltd, 1939, London. © M. Hoffmann.

Conclusions

19The initial impetus for this work was our identification of a selenium patina on a Greek bronze fulcrum from the Michael C. Carlos Museum of Emory University and a Ptolemaic Egyptian bronze statuette from the Barnes Foundation. Similar to our colleagues’ experiences, these observations took place after we had repeatedly identified selenium-based patinas on bronzes over a broad range of cultures and time periods. We used FTIR to identify the Carlos bronze black patina as copper selenite dihydrate. This provided the motivation to investigate selenium patination’s origins: as a restoration practice, a faker’s trick, or a response to the European admiration of black Japanese patinated metals such as shakudō or shibuichi. Our study of English, German, and French patination literature from the 19th and early 20th centuries reveals that while these Japanese technologies were greatly admired, they were not the impetus for the Western use of selenium-based patinas. Our investigation of the use of selenium colorants in other artists’ media do not reveal a connection with selenium- colored red glasses, but instead, as noted by Barbour and Glinsman, a potential connection involving an artist who worked in both photographic toners and bronze patination. This will be a rich area for further research and experimentation. It also, in conjunction with the patent literature, points to selenium patination likely being an early twentieth-century technology or a very late nineteenth-century one. As noted above, the first English mention we have identified for selenium-based black patinas dates to 1904, and for selenium-based photographic toners to 1930. Here, for the first time, we have explored the time frame, origins, and chemistry for the selenium patination of copper alloys in cultural heritage collections. The next steps for our research will involve experimental reproduction, interviews of mid-twentieth century restorers, and further investigation into the practices of Limet. While we now understand more about when and how these patinas were used, who used them and for what purposes (restoration or deceit) remains to be discovered.

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Bibliographie

Aucouturier M. et al., 2010, “Intentional patina of metal archaeological artefacts: non-destructive investigation of Egyptian and Roman museum treasures”, Corrosion Engineering, Science and Technology, 45, 5, p. 314-321.

Barbour D. S., Glinsman L. D., 2015, “Auguste Rodin’s lifetime bronze sculptures in the Simpson Collection”, in Barbour D. S., Gifford E. M. (ed.), Facture: Conservation Science Art History, Volume 2: Art in Context, National Gallery of Art, Washington D.C., p. 54-81.

Benzonelli A., Freestone I. C., Martinon-Torres M., 2017, “A better shade of black: effects of manufacturing parameters on the development of ancient black bronzes”, Archaeometry, 59, 6, p. 1034-1049.

Born H., 1990, “Patinated and painted bronzes: Exotic technique or ancient tradition?”, in True M., Podany J. (ed.), Small bronze sculpture from the Ancient World. Symposium (Malibu, The J. Paul Getty Museum, 16-19 March 1989), Getty Publications, Los Angeles, p. 179-196.

Brown B. F., Burnett H. C., Chase W. T., Goodway M., Kruger J., Pourbaix M., 1977, Corrosion and Metal Artifacts – A dialogue between conservators and archaeologists and corrosion scientists, U.S. Department of Commerce, National Bureau of Standards, Washington D.C., p. 208-209.

Buccolieri et al., 2015, “Portable EDXRF investigation of the patinas on the Riace Bronzes”, Nuclear Instruments and Methods in Physics Research B, 343, p. 101-109.

Buchner G., ed. 1901 and ed. 1910, Die Metallfärbung und deren Ausführung mit besonderer Berücksichtigung der chemischen Metallfärbung, Verlag von M. Krayn, Berlin.

Craddock P., Giumlia-Mair A. R. G., 1993, “Hsmn-Km, Corinthian bronze, shakudo: black patinated bronze in the ancient world”, in La Niece S., Craddock P. (ed.), Metal Plating and Patination, Butterworth Heinemann, Oxford, p. 101-127.

Fucito L., 2013, “Methods and materials used for patination at the Fonderia Chiurazzi”, in Risser E., Saunders D. (ed.), The Restoration of Ancient Bronzes: Naples and beyond, Getty Publications, Los Angeles, p. 137-142.

Fuller W. A., 1941, US Patent 2303350, Metal Coating. Application filed April 14, 1941, Application granted Dec. 1, 1942.

Giumla-Mair A. R. G., 2001, “Zosimos the alchemist-manuscript 6.29, Cambridge, metallurgical Interpretation”, in I Bronzi Antichi, Atti del XV Congresso Internazionale (Università di Udine, 22-26 May 2001), p. 317-323.

Giumlia-Mair A. R. G., 2013, “Development of artificial black patina on Mycenaean metal finds”, Surface Engineering, 29, 2, p. 98-106.

Giumlia-Mair A. R. G., 2020, “Plating and surface treatments on ancient metalwork”, Advances in Archaeomaterials, 1, p. 7-11.

Hammer W. J., 1903, “The properties and applications of selenium”, Transcript of a lecture delivered at a meeting of the American Institute of Electrical Engineers and the American Electrochemical Society (New York, April 17th, 1903), p. 372-393.

Hiorns A. H., ed. 1892 and ed. 1903, Metal Colouring and Bronzing, MacMillan and Company, London.

Hughes R., Rowe M., 1991, The colouring, bronzing and patination of metals, Watson-Guptill Publications/Whitney Library of Design, New York.

Hunter E. C. D., 2001, “Beautiful black bronzes: ‘Zosimos’ treatises in Cam. Mm 6.29”, in I Bronzi Antichi, Atti del XV Congresso Internazionale (Università di Udine, 22-26 May 2001), p. 655-660.

Lacombe M. S., 1887, Nouveau manuel complet du bronzage des métaux et du plâtre, Librairie encyclopédique de Roret, Paris.

Malherbe M. P., 1904, “Coloring of Metals”, Scientific American Supplement, 57.

Mangou H., Ioannou P. V., 2000, “Studies of the Late Bronze Age copper-based ingots found in Greece”, Annual of the British School at Athens, 95, p. 207-217.

Mathis F. et al., 2007, “Corrosion patina or voluntary patina? Contribution of non-destructive analyses to the surface study of copper based archaeological objects”, in Dillmann P., Beranger G., Piccardo P., Matthiessen H. (ed.), Corrosion of Metallic Heritage Artifacts, Woodhead Publishing Ltd., p. 219-238.

Mathis F. et al., 2009, “Hmty-Km (black copper) and the Egyptian bronzes’ collection of the Musée du Louvre”, Journal of Cultural Heritage, 10, p. 63-72.

Michel J., 1931, La Coloration des Métaux, Bronzage, Patinage, Oxydation, Marbrage, Irisation, Nielle, J. C. Godefroy, Paris.

Mengele H., 1931, US Patent 1899972, Process for Toning Silver Pictures, Application filed June 4, 1931, Patent granted, 1933.

Mohamed W., Darweesh S., 2012, “Ancient Egyptian black-patinated copper alloys”, Archaeometry, 54, p. 175-192.

Oguchi H., 1983, “Japanese Shakudo: its history, properties and production from gold-containing alloys”, Gold Bulletin, 16, p. 125-132.

Pliny (the Elder), 1857, The Natural History of Pliny, Book XXXIII (trans. J. Bostock, H. T. Riley), Henry G. Bohn, London.

Rehren Th., Northover J. P., 1991, “Selenium and tellurium in ancient copper ingots”, in Pernicka E., Wagner G. A. (dir.), Archaeometry 90’, Birkhäuser Verlag, Basel, p. 221-228.

Scroxton W. G., 1948, US Patent 2527232, Bluing Metals, Application filed November 4, 1948, Application granted October 24, 1950.

Welz F., 1892, US Patent 479689, Manufacture of Rose or Orange Stained Glass, Application filed January 11, 1892.

Unpublished document

Mathis F., 2005, Croissance et propriétés des couches d’oxydation et des patines à la surface d’alliages cuivreux d’intérêt archéologique ou artistique. Thèse de doctorat en sciences des matériaux – Métallurgie, Université Paris Sud – Paris XI [HAL ID: tel-00011255, version 1].

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Notes

1 Giumlia-Mair, 2020, p. 11.

2 Barbour, Glinsman, 2015, p. 23.

3 Craddock, Giumlia-Mair, 1993, p. 102.

4 Mohamed, Darweesh, 2012, p. 182-184.

5 Aucouturier et al., 2010; Craddock, Giumlia-Mair, 1993, p. 102; Benzonelli et al., 2017.

6 Mathis, 2005.

7 Mohamed, Darweesh, 2012, p. 181, 190.

8 Benzonelli et al., 2017.

9 Benzonelli et al., 2017.

10 Mathis et al., 2009.

11 Oguchi, 1983.

12 Pliny (the Elder), 1857, 46, 128.

13 Aucouturier et al., 2010.

14 Oguchi, 1983.

15 Giumlia-Mair, 2013, p. 100.

16 Buccolieri et al., 2015.

17 Buccolieri et al., 2015, p. 106.

18 Fucito, 2013, p. 137-139.

19 Hughes, Rowe, 1991, p. 14.

20 Mathis et al., 2007; Hunter, 2001; Giumla-Mair, 2001.

21 Hammer, 1903, p. 372.

22 Michel, 1931; Hiorns, 1892 and 1903; Buchner, 1901 and 1910; Lacombe, 1887.

23 Michel, 1931.

24 Hiorns, 1903, p. 156, 157, 159, 161, 163, and 164 respectively.

25 Buchner, 1901 and 1910.

26 Lacombe, 1887.

27 Malherbe, 1904, p. 23603-23604.

28 Malherbe, 1904, p. 23603.

29 He provides two recipes for the “coloration of copper and brass with cupric selenite”, both of which contain aqueous solutions selenous acid, copper sulfate, and nitric acid.

30 Fuller, 1942.

31 Scroxton, 1950.

32 Born, 1990.

33 Malherbe, 1904, p. 23603-23604.

34 Welz, 1892.

35 [https://www.koppglass.com/custom-solutions/glass-portfolio/colored-glass].

36 National Glass Budget, Weekly Review of the American Glass Industry, 1916.

37 Barbour, Glinsman, 2015, p. 23.

38 Barbour, Glinsman, 2015, p. 23.

39 Mengele, 1933.

40 Barbour, Glinsman, 2015, p. 27.

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Table des illustrations

Titre Fig. 1. Fulcrum attachment cast in the form of a wild mule, 1st c. BCE, Hellenistic Greek, bronze with silver inlay, Atlanta, The Michael C. Carlos Museum of Emory University (inv. 2003.011.004)
Légende The impetus for this research was the identification of the original patina for this diminutive bronze, i.e. was this in fact a black bronze.
Crédits MCCM, CC-BY-NC-SA 4.0.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-1.jpg
Fichier image/jpeg, 576k
Titre Fig. 2. Fulcrum attachment cast in the form of a wild mule, 1st c. BCE, Hellenistic Greek, bronze, silver, copper, Atlanta, The Michael C. Carlos Museum of Emory University (inv. 2003.011.003)
Crédits MCCM, CC-BY-NC-SA 4.0.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-2.jpg
Fichier image/jpeg, 500k
Titre Fig. 3. Unidentified artist, statuette of the Apis Bull, 664-30 BCE, bronze, Philadelphia, The Barnes Foundation (inv. A75)
Crédits © The Barnes Foundation.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-3.jpg
Fichier image/jpeg, 360k
Titre Fig. 4. Ishiguro Masayoshi (1774-ca. 1862), sword tsuba, 19th century, shakudō, gold, shibuichi and copper, New York, Metropolitan Museum of Art (inv. 48.63.5a). Note the blue-violet hue of the patina
Crédits Rogers Fund, 1948, Metropolitan Museum of Art, Open Access.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-4.jpg
Fichier image/jpeg, 384k
Titre Fig. 5. Mercury in Repose, bronze, Villa of the Papyri, Herculaneum, Napoli, Museo Archeologico Nazionale (inv. 5625)
Crédits © M.-L. Nguyen/CC-BY 2.5.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-5.jpg
Fichier image/jpeg, 852k
Titre Fig. 6. Sphinx of Siamon, 21st Dynasty, bronze with silver or electrum inlay, Paris, musée du Louvre, département des Antiquités égyptiennes (inv. E 3914)
Légende An example of a diminutive bronze that compositionally aligns with hmty-km.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-6.jpg
Fichier image/jpeg, 376k
Titre Fig. 7. Advertisement for selenium reagents for glassmakers from the National Glass Budget trade journal, 1916
URL http://journals.openedition.org/techne/docannexe/image/17341/img-7.jpg
Fichier image/jpeg, 64k
Titre Fig. 8. Jean-François Germain Limet (1855-1941) working in his Paris studio, 1938
Crédits Photo by Malvina Hoffmann, Sculpture Inside Out, George Allen and Unwin Ltd, 1939, London. © M. Hoffmann.
URL http://journals.openedition.org/techne/docannexe/image/17341/img-8.jpg
Fichier image/jpeg, 1,3M
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Pour citer cet article

Référence papier

Jennifer L. Mass, Aaron Shugar, Adam C. Finnefrock, Satoko Tanimoto, Margaret Little, Renée Stein et Ellen Archie, « Selenium-based black bronze treatment, as compared to other patination technologies of ancient and historic black bronzes »Technè, 55 | 2023, 64-74.

Référence électronique

Jennifer L. Mass, Aaron Shugar, Adam C. Finnefrock, Satoko Tanimoto, Margaret Little, Renée Stein et Ellen Archie, « Selenium-based black bronze treatment, as compared to other patination technologies of ancient and historic black bronzes »Technè [En ligne], 55 | 2023, mis en ligne le 16 novembre 2024, consulté le 15 février 2025. URL : http://journals.openedition.org/techne/17341 ; DOI : https://doi.org/10.4000/techne.17341

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Auteurs

Jennifer L. Mass

Professor of Cultural Heritage Science, Bard Graduate Center, President, Scientific Analysis of Fine Art, LLC, New York (jennifer.mass[at]bgc.bard.edu) (jen[at]scienceforfineart.com).

Aaron Shugar

Bader Chair in Art Conservation, Department of Art History and Art Conservation, Queen’s University, Kingston – University of Toronto, Department of Anthropology, Toronto (Ontario), Canada (shugar[at]queen.su.ca).

Adam C. Finnefrock

Vice President, Scientific Analysis of Fine Art, LLC, New York (adam[at]scienceforfineart.com).

Satoko Tanimoto

Senior Scientist, Scientific Analysis of Fine Art, LLC, New York (satoko[at]scienceforfineart.com).

Margaret Little

Senior Conservator of Objects, The Barnes Foundation, Philadelphia (mlittle[at]barnesfoundation.org).

Renée Stein

Chief Conservator, Michael C. Carlos Museum, Emory University, Atlanta (rastein[at]emory.edu).

Ellen Archie

Emory University, Atlanta (earchie[at]emory.edu).

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Le texte seul est utilisable sous licence CC BY-NC-ND 4.0. Les autres éléments (illustrations, fichiers annexes importés) sont « Tous droits réservés », sauf mention contraire.

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