Chemicals and pigments have been used to synthetically induce a thin, uniform patina on a metal surfaces. Bronze, in particular, was often patinated to accentuate the red colors or to simulate aged surfaces. As early as the third millenium BCE, Anatolian metalwork used arsenic and antimony salts on bronze to give a silvery tone. Many patination techniques use heat to form an oxidation layer on the surface of the metal. For example, annealing copper can produce, red, brown, and black oxides.
In the recipes given by Proctor (1905), new bronze items were polished, cleaned with benzine, then plated in a cyanide bath typically containing copper cyanide, sodium carbonate, sodium bisulfite, and copper carbonate. The pieces were rinsed then dipped in an acid bath containing copper sulfate in sulfuric acid. This produced a thin soft, red copper deposit on the surface of the piece. From this point, several color options were available:
- a red to dark brown color was obtained by dipping the piece quickly in a potassium sulfide bath, followed by washing, buffing and varnishing with a clear lacquer.
- a black surface with dark green recesses (Egyptian green or ancient verde) was obtained by dipping the piece in a turpentine solution containing zinc white, chrome green, lampblack, and chrome yellow, followed by washing, drying and varnishing with a black lacquer.
- a whitish, green variegated surface (Roman bronze) was obtained by dipping the piece in a turpentine solution of zinc white, light chrome green and copal, followed by washing, drying, buffing and varnishing with a dilute lacquer.
Synonyms and Related Terms
bronzing; Egyptian green; ancient verde; Roman bronze; patine artificielle (Fr.); künstliche Patina (Deut.); synthetisch Patina; pátina, artificial (Port.)
° C. Proctor, "The Modern Way of Producing Verde Antique, Roman Bronze and Patinas on the Soft Metal Alloys by the Aid of Pigments" reprinted in Conservation & Technology, 2/85 from The Metal Industry, January 1905. ° R. Hughes, M.Rowe, The Colouring, Bronzing and Patination of Metal, Crafts Council, London, 1982.
Sources Checked for Data in Record
- External source or communication Comment: C. Proctor, "The Modern Way of Producing Verde Antique, Roman Bronze and Patinas on the soft Metal Alloys by the Aid of Pigments" reprinted in Conservation & Technology 2/85 from The Metal Industry, January 1905
- The Dictionary of Art, Grove's Dictionaries Inc., New York, 1996 Comment: 'Metals'