Engineering:Chemical coloring of metals

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Short description: Process of changing the color of metal surfaces with different chemical solutions


See also: Engineering:Patina
Henry Moore, Family Group (1950), patinated bronze
Bull Head Attachment, about 700-600 BCE, Urartian, northwest Iran, bronze – Cleveland Museum of Art, early example of metal coloring

File:Metallocromie di Nobili inv.3881 IF 38021.tif

File:Cetko pvd 2624.jpg
PVD colored stainless steel tray

The chemical coloring of metals involve processes that change the color of metal surfaces with different chemical solutions. These processes can be categorized into four types:

  • Electroplating – coating the metal surface with another metal using electrolysis.
  • Patination – chemically reacting the metal surface to form a colored oxide or salt.[1]
  • Anodizing – electrolytic passivation process used to increase the thickness of the natural oxide layer, producing a porous surface that can accept organic or inorganic dyes easily. In the case of titanium, niobium, and stainless steel, the color formed depends on the thickness of the oxide (which is determined by the anodizing voltage).
  • Physical vapor deposition (PVD) – coating the surface with a thin film of vaporized material. This is the best method for coloring stainless steel, for the color produced is much more durable than those via other processes.[2]

Chemically coloring a metal is distinct from simply coating it via a method such as gilding or mercury silvering, since chemical coloring involves a chemical reaction, whereas simple coating does not.

Modern possibilities of using laser to patinate copper and of using microscopic fungi to patinate copper and iron are also being researched.[3][4]

History

The process of chemically coloring metal is as old as metalworking technology. Some of the earliest-known examples of colored metal objects are about 5,000 years old. They are bronze casts with some silver-colored parts, which originate from the Anatolian region.[5] Similar processes can be found on some ancient Egyptian copper sheets.[6] Another example of early chemical coloring of metals is the Nebra sky disc, which has a green patina and gold inlays. An early example of black colored iron is a Celtic spearhead found in the River Thames dated between 200 and 50 BC.[7][8]

Pliny the Elder mentioned liver of sulfur and the distinction between naturally occurring and artificial patina in the first century CE. Another ancient document about the chemical coloring of metals is the Leyden papyrus X (3rd century CE).[9] Zosimos of Panopolis, a Greek-Egyptian alchemist who lived in the late 3rd and early 4th centuries is attributed with some of the oldest written recipes for chemical coloring of metals.[7]


At the time of the Renaissance, the most significant documents were the Treatise on Goldsmithing and the Treatise on Sculpture by Italian mannerist, sculptor, and goldsmith Benvenuto Cellini.[10] Patination is briefly mentioned by Italian painter and writer Giorgio Vasari and by Pomponius Gauricus in his work De Sculptura in 1504. André Felibien mentions techniques for patination of bronze sculptures in his work Principes in 1699.[11]

The beginning of modern science-based chemical or electrochemical coloring of metals is marked by Leopoldo Nobili's (1784–1835) discovery of Nobilis colored rings in 1826.[12] Leonhard Elsner, Alexander Watt, Antoine César Becquerel (1788–1878) and Rudolf Christian Böttger (1806–1881) are also important people in the early history of electrochemical coloring of metals. George Richards Elkington (1801–1865) patented a process for electroplating silver and gold in 1840,[13] which was further refined by J.E. Stareck in 1937.[14][15] In the 19th century, the first manuals dedicated exclusively to the chemical coloring of metals were published.[16]

In 1868, Puscher reported on the application of multicolored or lustre patina based on sodium thiosulphate and lead acetate for the first time (contemporary recipes for this patina use copper compounds instead of lead).[17][18]

Great progress was made in the industrial application of chemical coloring of metals in the early 20th century. 1904 saw the first use of selenium-based black and multicolor patinas for steel, copper and brass. Around 1905, the first patents for black nickel (German patents DRP 183972 and DRP 201663) and black oxide (circa 1915–1922, German patents DRP 292603, DRP 357198, DRP 368548) were made.[19] Between 1923 and 1928, the first UK patents relating to oxidized aluminium were published,[20][21] and black chromium was developed in 1929 (German patent GP 607, 420).{{Citation needed|date=April 2026} After the Second World War, there was a growing interest in green patinated copper sheets, which were intended primarily for architectural use.[22][23][24] Technologies for anodic oxidation of titanium,[25] and later niobium and tantalum, have evolved since the mid-1960s. Technology for coloring stainless steel via anodic oxidation was developed in 1957.[26]

Now, the possibilities of using bacterial cultures in the patination of copper and iron are being investigated, and laser-induced staining of copper and its alloys, niobium, titanium, stainless steel, and chromium plated objects, are being tested.[27][28][29]

Uses

Examples

Silver (Ag)

Copper (Cu)

  • Green: Objects are coated with a solution of 250 grams of ammonium carbonate / 250 grams of ammonium chloride / 1 litre of water, each layer is dried for 24 hours. If the amount of chlorides decreases, the color will be more bluish-green, if carbonate decreases, more yellow.[31]
  • Black: Items are submerged in a 2.5% solution of sodium polysulfide 2.5%.[32]
  • Brown: Items are boiled in at least 3-day-old water solution of 12% copper sulfate.[33]
File:Cetko zelena Cu.jpg
Green patina on copper, test plate

Iron (Fe)

See also: Chemistry:Black oxide
  • Black: Object is coated in linseed oil and heated to 300–400 °C. This process can be used many metals, excepting those with low melting points (e.g., lead, tin).[34]
  • Brown: Item is coated in a 5% aqueous solution of ferric chloride and later abraded.[34]

Titanium (Ti)

Stainless Steel

File:Blackened steel.jpg
Blackened steel test plate, oiled with linseed oil and then heated to 300 - 400 C

Other Metals

  • Gray for tin or pewter: Object is immersed in 20% aqueous solution of ferric chloride.[41]
  • Gray-black for zinc: Object is immersed in 20% aqueous solution of ferric chloride.[41]
  • Black for aluminum: Object is immersed in a boiling solution of 20 g/L ammonium molybdate and 5 g/L of sodium thiosulfate.[42]

Lustre colours

Various colors on titanium (anodic oxidation)
anodized stainless steel test plate (molybdate based solution - can be used on pewter too)

See also

References

  1. ↑ Fishlock, David: Metal Colouring, Teddington 1962., p.8
  2. ↑ "Exploring PVD Stainless Steel: The Future of Durable and Stylish Coatings - SteelPRO Group". 27 September 2024. https://steelprogroup.com/stainless-steel/pvd/. 
  3. ↑ B.A. Dajnowski, J. Marczak, A. Sarzyński, M. Strzelec, J.L. Mass, A. Lins, S.I. Shah, R. Murray, T.P. Beebe Jr., Z. Voras Creating Laser Patinas on Copper Alloys: Origins of Colors and Their Implications on Copper Alloys, METAL 2016, New Delhi 2017. Conference Proceedings, p.153–160
  4. ↑ E. Joseph, A. Simon, S. Prati, M. Wörle, D. Job, R. Mazzeo. Development of an analytical procedure for evaluation of the protective behaviour of innovative fungal patinas on archaeological and artistic metal artefacts. Analytical and Bioanalytical Chemistry 2011, 399 (9), 2899-2907. (Paper in forefront and cover image)
  5. ↑ LaNiece, Susan; Craddock, Paul : Metal Plating and Patination: Cultural, Technical and Historical Developments, Boston 1993., p.6
  6. ↑ Hughes, R.; Rowe, M. The Colouring, Bronzing and Patination of Metals, London, 1982, page 10
  7. ↑ 7.0 7.1 Giumlia-Mair, Alessandra (1 December 2020). "Plating and Surface Treatments on Ancient Metalwork". Advances in Archaeomaterials 1 (1): 1–26. doi:10.1016/j.aia.2020.10.001. 
  8. ↑ "Spear-head | British Museum". The British Museum. https://www.britishmuseum.org/collection/object/H_1938-0504-1. 
  9. ↑ Jensen, William B., ed (2008). The Leyden and Stockholm Papyri: Greco-Egyptian Chemical Documents From the Early 4th Century AD. Cincinnati, Ohio: Oesper Collections in the History of Chemistry, University of Cincinnati. http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Books/Leyden%20&%20Stockholm%20Papyri.pdf. 
  10. ↑ Cellini, Benvenuto (1857). I trattati dell'oreficeria e della scultura. National Library of Naples. Firenze : Felice Le Monnier. http://archive.org/details/bub_gb_Gsh2BJGzZLEC. 
  11. ↑ Dent Weil, Phoebe. "Patina From the Historical-Artistic Point of View". https://www.northernlightstudio.com/#/patina. 
  12. ↑ L. Nobili: Sui colori in generale ed in particolare sopra una nuova scala cromatica dedotta dalla metallocromia ad uso delle scienze e delle arti, Antologia, 39, 117, 1830 e su Bibl. Univ. 15, 337, 1830; e 16, 35, 1830
  13. ↑ Gane, Jo (2023). "Photography and electroplate in 1840s Birmingham". doi:10.15180/232014. https://journal.sciencemuseum.ac.uk/article/photography-and-electroplate-in-1840s-birmingham/#abstract. 
  14. ↑ Fishlock, David : Metal Colouring, Teddington 1962., page 126
  15. ↑ , Jesse E."Decorating metals" US patent 2081121A, published 1937-05-18, issued 1937-05-18, assigned to Kansas City Testing Laboratory
  16. ↑ Fink, F. (02) Auteur du texte; Debonliez, G. Auteur du texte (1870) (in EN). Manuels-Roret. Nouveau manuel complet du bronzage des métaux et du plâtre... suivi de la peinture et du vernissage des métaux et du bois, par MM. G. Debonliez et F. Fink. Ouvrages enrichis de nouveaux procédés relatifs au bronzage, à la peinture et au vernissage, traduits... et publiés par M. F. Malepeyre, d'après M. le Dr E. Winckler et autres praticiens. https://gallica.bnf.fr/ark:/12148/bpt6k6218907f. 
  17. ↑ Puscher, C. (1868). "Ueber ein neues und billiges verfahren, ohne anwendung von farben verschiedene metalle (wie gold, silber, kupfer, argentan, messing, tombak, eisen, zink) mit prachtvollen lüsterfarben zu überziehen" (in de). Polytechnischen Journal 190 (3): 421-423. https://books.google.com/books?id=Tww1AAAAMAAJ&pg=PA421&source=gbs_toc_r&cad=2#v=onepage&q&f=false. 
  18. ↑ Fishlock, David : Metal Colouring, Teddington 1962., p.219
  19. ↑ Malherbe M. P., 1904, “Coloring of Metals”, Scientific American Supplement, 57.
  20. ↑ "An improved process for providing a resistant coating upon the surfaces of aluminium or aluminium alloys" GB patent 290901A, published 1928-05-24
  21. ↑ "Improved process of protecting surfaces of aluminium of aluminium alloys" GB patent 223994A, published 1924-11-03
  22. ↑ , Clarence E. & George L. Craig"Production of an adherent patina upon copper or its alloys" US patent 1974140A, published 1933-06-24, issued 1934-09-18, assigned to Battelle Memorial Institute, Inc.
  23. ↑ , K.E. Matthson & O. Holm Rolf"Method for applying green patina to objects, preferably made from copper or copper alloys" CA patent 734897A, published 1966-05-24, issued 1966-05-24, assigned to Svenska Metallverken AB
  24. ↑ , Tsutomu & Kazuo Toda"Formation of patina on copper or copper alloy surface by electrolysis" JP patent S53142935A, published 1977-05-20, issued 1978-12-13, assigned to Mitsubishi Metal Corp.
  25. ↑ "The use of titanium in silversmithing and jewellery – a short history". http://www.reflectionandrefraction.co.uk/history.html. 
  26. ↑ , Roy C. & Jack M. Beigay"Coloring stainless steel" US patent 2957812A, published 1960-10-25, assigned to Allegheny Ludlum Steel Corp.
  27. ↑ "Biological patinA for arcHaeological and Artistic Metal ArtefactS (BAHAMAS)". 2012-05-31. https://www.up2europe.eu/european/projects/biological-patina-for-archaeological-and-artistic-metal-artefacts_8707.html. 
  28. ↑ Dajnowski, Bartosz; Mass, Jennifer L.; Marczak, Jan; Sarzynski, Antoni; Strzelec, Marek; Lins, Andrew; Shah, Syed Ismat; Murray, Roy et al. (2016). "Creating Laser Patinas: Origins of Colors and their Implications on Copper Alloys". Proceedings of the Interim Meeting of the ICOM-CC Metals Working Group, September 26-30, 2016, New Delhi India. ISBN 978-92-9012-418-4. https://www.icom-cc-publications-online.org/4907/Creating-Laser-Patinas--Origins-of-Colors-and-their-Implications-on-Copper-Alloys. 
  29. ↑ Andreeva, Ya M.; Luong, V.C.; Lutoshina, D.S.; Medvedev, O.S.; Mikhailovskii, V. Yu.; Moskvin, M.K.; Odintsova, G.V.; Romanov, V.V. et al. (2019). "Laser coloration of metals in visual art and design". Optical Materials Express 9 (3): 1310-1319. https://doi.org/10.1364/OME.9.001310. 
  30. ↑ Fishlock, David : Metal Colouring, Teddington 1962.
  31. ↑ Deutsches Kupfer Institut: Chemische Färbungen von Kupfer und Kupferlegierungen, Berlin 1974., p.19
  32. ↑ Deutsches Kupfer Institut: Chemische Färbungen von Kupfer und Kupferlegierungen, Berlin 1974., p.33
  33. ↑ Deutsches Kupfer Institut: Chemische Färbungen von Kupfer und Kupferlegierungen, Berlin 1974., p.38
  34. ↑ 34.0 34.1 Angier, R.H.: Firearm Blueing and Browning, Onslow County 1936.
  35. ↑ Untracht, O.: Jewelry concepts and technology, New York 1980.
  36. ↑ Bobrikova, I.G.; Selivanov, V.N.: Tehnologii elektrohimicheskoi i himichskoi hudozhestvenno dekorativnoi obrabotki metalov i ih splavov, Novocherkask 2009., p. 87
  37. ↑ "Method for production of stainless steel with colour mirrorlike surface". https://patents.google.com/patent/CN1118022A/en. 
  38. ↑ Alliott, George (2020). The electrochemical colouring of austenitic stainless steel in sodium molybdate and other environmentally benign solutions (thesis). Loughborough University. doi:10.26174/thesis.lboro.12530660.v1.
  39. ↑ "A kind of coloring liquid painted for stainless steel electrochemical and colorize method". https://patents.google.com/patent/CN103114320B/en. 
  40. ↑ "Stainless steel galvano-chemistry bepainting technique". https://patents.google.com/patent/CN101173367B/en. 
  41. ↑ 41.0 41.1 Buchner, G.: Die Metallfärbung und deren Ausführung, Berlin 1891.
  42. ↑ Krause, H.: Metallfärbung, Berlin 1922., p.152
  43. ↑ Hughes, R., Rowe, M.: The Colouring, Bronzing and Patination of Metals, London 1992.
  44. ↑ US patent 9,163,312 B2.
  45. ↑ USSR patent 815081

Literature

Hiorns, A. (1907). Metal Colouring and Bronzing. London: Macmillan and Co.. OCLC 3757279. https://archive.org/details/metalcolouringa00hiorgoog. 

Kaup, W. J. (1914). Metal Coloring and Finishing. New York City: Industrial Press. https://archive.org/details/metalcoloringfin00kauprich. 

Field, S. (1925). The Chemical Coloring of Metals and Allied Processes. London: Chapman & Hall, Ltd.. OCLC 2922065. https://archive.org/details/chemicalcoloring00fiel. 

Fishlock, D. (1962). Metal Colouring. Teddington: R. Draper. OCLC 3982659. 

Hughes, R.; Rowe, M. (1991). The Colouring, Bronzing and Patination of Metals (3rd ed.). London: Thames and Hudson. ISBN 9780500015018. OCLC 24734412. 

LaNiece, S.; Craddock, P. (1993). Metal Plating and Patination: Cultural, Technical and Historical Developments. Oxford: Butterworth-Heinemann. ISBN 9780750616119. OCLC 27336439. 

Young, R.D. (2000). Contemporary Patination (5th ed.). Escondido: Sculpt-Nouveau. ISBN 9780960374410. 

Kipper, P. (2003). Pátinas for Silicon Bronze (2nd ed.). Loveland: Path Publications. ISBN 9780964726901. OCLC 930605479. 

Sugimori, E. (2004). Japanese Patinas. Portland: Brynmorgen Press. ISBN 9781929565115. OCLC 62859653. 

Runfola, M. (2014). Patina : 300+ Coloration Effects for Jewelers & Metalsmiths. Loveland: Interveave Press. ISBN 9781620331392. OCLC 871436497. 

  • Lewton Brain, C.: Patinas for small studios (pdf-file), 1985
  • Budija, G.: Collection of formulas for the chemical, electrochemical and heat colouring of metals, the cyanide free immersion plating and electroplating (pdf file), Zagreb 2025



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