Verdigris

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This article is about copper(II) acetate, used as a pigment. For other uses, see Verdigris (disambiguation).
Verdigris
 
CIELChuv (L, C, h)
(67, 45, 187°)
Source[1]
ISCC–NBS descriptorBrilliant bluish green
B: Normalized to [0–255] (byte)
The Statue of Liberty, showing advanced patination; verdigris is responsible for the statue's iconic green colour.

Verdigris

polychromatic sculptures, and illumination of maps.[10]: 414–423 [11] However, due to its instability, its popularity declined as other green pigments became readily available.[9]: 171  The instability of its appearance stems from its hydration level and basicity, which changes as the pigment interacts with other materials over time.[12]
: 637 

History

Etymology

The name verdigris comes from the Middle English vertegrez, from the Old French verte grez. According to one view, it comes from vert d'aigre,[13] "green [made by action] of vinegar". The modern French writing of this word is vert-de-gris ("green of grey"), sounding like the older name verdet gris ("grey greenish"), itself a deformation of verte grez. It was used as a pigment in paintings and other art objects (as green color), mostly imported from Greece, and hence it is more usually given another etymology as vert-de-Grèce ("green of Greece").[14][15]

Production

Copper(II) acetate is prepared by treatment of

WWI.[9]
: 179–182 

Chemical composition

An example of naturally occurring "blue verdigris" on a memorial at the base of Annapurna in Nepal
Verdigris in Prague Underground

Verdigris is a collective term for copper acetate, whose chemical varieties produce different hues. The technical literature is inconsistent in describing these variations. Some sources refer to "neutral verdigris" as

monohydrate (Cu(CH3CO2)2·(H2O)) and to "blue verdigris" as Cu(CH3CO2)2·CuO·(H2O)6.[18] Other sources describe the main copper salt in natural verdigris as Cu4SO4(OH)6 (brochantite).[19] Still other sources describe it as basic copper carbonate (Cu2CO3(OH)2),[20] or as Cu(CH3CO2)2·(Cu(OH)2)n where n varies from 0 to 3.[21] In marine environments, the main copper salt is tribasic copper chloride (Cu2(OH)3Cl).[19][20]

Overall, variations of verdigris can be divided into two groups: basic verdigris and neutral verdigris.[6]: 132  The difference in colour depends on the hydration level and degrees of basicity.[12]: 637   

Toxicity

Main article: Copper toxicity

Verdigris, which was once used as a medicine[7][8] and pharmaceutical preparation

better source needed] Symptoms of toxicity include nausea, anemia and death, although widespread acquired immunity has been documented, as occurred with female workers in Montpellier.[22]
Nontoxic substitutes have been developed for some applications, such as art pigments.

Uses

Verdigris on The Spirit of Detroit

Verdigris is a naturally occurring protective layer on metals such as copper, brass, and bronze. In addition to be a desirable artistic effect, it has been used primarily as a pigment and now-outdated medicinal preparations.

Pigment

Verdigris has been used as a pigment since antiquity, including in paintings in Rome and Pompeii. The use of verdigris continued into the

Emerald Green and viridian became more popular.[6]
: 132 

Stability

The art pigment verdigris is subject to colour change. The changes are most pronounced during the first month of exposure to air. The changes also depend on the type of

Botticelli's The Mystical Nativity, from 1500, the blue-green costumes of the angels have darkened to a dark green colour.[24]

Verdigris pigment is lightfast in oil paint, as numerous examples of 15th-century paintings show. However, its lightfastness and air resistance are very low in other media. Copper resinate, made from verdigris by boiling it in a resin, is not lightfast, even in oil paint. In the presence of light and air, green copper resinate becomes stable brown copper oxide.[14] The browning mechanism is attributed to the transient formation of Cu(I) in the pigment and oil system. The reduction of Cu(II) into Cu(I) due to the release of a carboxylate, causes changes in the optical properties of pigment. Furthermore, linseed oil induces the transformation of the copper acetate bimetallic structure, and forms monomeric series. Dioxygen that reacts with partially decarboxylated dimers to form a peroxy-Cu dimer complex is responsible for the darkening of the pigment.[12]: 635–638 

In previous literature on painting, verdigris has been described as unstable when combined with other pigments which leads to further deterioration. Due to the fickle nature of the pigment, it required special preparation of paint, carefully layered application, and immediate sealing with varnish to avoid rapid discoloration (but not in the case of oil paint).[14] However, further scientific research suggests that the difficulties are less extreme than previously described. The pigment nonetheless has the ability to degrade cellulosic materials, such as paper.[6]: 137  In terms of identification and reproduction, modern technology and reproducible synthesis procedures have been developed to be used for museums and collections to identify distinct verdigris phases in historical artworks.[23]: 14857  Certain components of historical verdigris pigments, copper(II) acetates, are partially irreproducible based on the given historical recipes.[23]: 14847 

  • One of the earliest uses of verdigris as a pigment in painting; Last Supper (1306) by Giotto Di Bondone
    One of the earliest uses of verdigris as a pigment in painting; Last Supper (1306) by Giotto Di Bondone
  • Raphael used verdigris for the green coat of Saint John, the left angel's frock, and other accents, in The Mond Crucifixion
    Raphael used verdigris for the green coat of Saint John, the left angel's frock, and other accents, in The Mond Crucifixion
  • The Verdigris of the angels' costumes in Nativita Mistica by Botticelli darkened from bluish green to foliage green.
    The Verdigris of the angels' costumes in Nativita Mistica by
    Botticelli
    darkened from bluish green to foliage green.

Medicine

Verdigris has also been used in medicine,

pharmaceutical preparations[10]: 414  in the 18th century to treat canker sores.[9]
: 176 

See also

References

  1. ^ "Its pronunciation in English is still unsettled" (Fowler's Dictionary of Modern English Usage (4 ed.) edited by: Jeremy Butterfield). The pronunciation /-ɡriːs/ is the first one given by Merriam-Webster's dictionary, but /-ɡriː/ is first in the Oxford Dictionary of English (3 ed.) (2015).
  2. ^ a b "Verdigris". Merriam-Webster.com Dictionary.
  3. ^ a b Karmakar, Rabindra N. (2015). Forensic medicine and toxicology: theory, oral & practical. Academic Publishers.
  4. ^ a b Anant, Jagdish Kumar, S. R. Inchulkar, and Sangeeta Bhagat (2018). "An overview of copper toxicity relevance to public health." EJPMR 5, no. 11 : 236.
  5. ^
    ISSN 0140-6736
    .
  6. ^ a b c d e f g h H. Kühn, Verdigris and Copper Resinate, in Artists' Pigments. A Handbook of Their History and Characteristics, Vol. 2: A. Roy (Ed.) Oxford University Press 1993, p. 131 – 158
  7. ^ a b c d "Medical Uses of Copper in Antiquity". Copper Development Association. Retrieved 8 June 2014.
  8. ^ a b c d Paris, John Ayrton (1831). Pharmacologia. New York: W. E. Dean. The rust of the spear of Telephus, mentioned in Homer as a cure for the wounds which that weapon inflicted, was probably Verdegris, and led to the discovery of its use as a surgical application
  9. ^
    S2CID 112614238
    .
  10. ^
    ISSN 0361-2317
    .
  11. ^ Verdigris, ColourLex
  12. ^
    S2CID 253847558
    .
  13. ^ Dauthenay, Henri (1905). Répertoire de couleurs pour aider à la détermination des couleurs des fleurs, des feuillages et des fruits. Vol. 2. Paris: Librairie horticole. p. 240. RC2.
  14. ^
    OCLC 936144129
    .
  15. ^ The Concise Oxford Dictionary of English Etymology, edited by T. F. Hoad (1996), and Merriam-Webster's dictionary give only this second etymology.
  16. ^
    doi:10.1021/ed200096e
    .
  17. ^ Darnton, Robert. "A Bourgeois Puts His World in Order" in The Great Cat Massacre --and other Episodes in French Cultural History. New York: Vintage Books, 1985. p. 114.
  18. ISBN 3527306730
    .
  19. ^
    ISSN 0010-938X
    .
  20. ^ a b Sharp, D. W. A: Penguin Dictionary of Chemistry, page 419. Penguin Books, 1990 (2nd edition)
  21. doi:10.1179/sic.1970.15.1.002
    .
  22. ^ Women and the Verdigris Industry in Montpellier, European Women and Preindustrial Craft. Project MUSE, Indiana University Press, 1995
  23. ^
    PMID 29043336
    .
  24. ISBN 978-1-85709-442-8
    .

External links

Look up verdigris in Wiktionary, the free dictionary.
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