Indigo

MFA Acc. #: 49.414

Description

A natural dark blue dye obtained from Indigofera tinctoria plants native to India, Java, Peru, and other tropical areas. The use of indigo was first mentioned in Indian manuscripts in the 4th century BCE. It was exported to Europe in Roman times but did not become plentiful until sea routes opened up in the 17th century. The natural material is collected as a precipitate from a fermented solution of the plant. The coloring component, indigotin, is extracted as a colorless glycoside, but turns blue with oxidation. Synthetic indigo was first produced in 1880 by Adolf von Baeyer. Made from anthranilic acid, the synthetic colorant is chemically identical to natural indigo and has almost entirely replaced the natural dyestuff. Indigo is a fine, intense powder which may be used directly as a pigment in oil, tempera, or watercolor media. The exposed pigment can fade rapidly in strong sunlight. Indigo is still used to dye jeans, where its fading and uneven coloring have become favorable characteristics.

Synonyms and Related Terms

2,2'-biindolinyliden-3,3'-dion; Indigofera tinctoria; Natural Blue 1; CI 75780 (natural); Vat Blue 1; CI 73000 (synthetic); Pigment Blue 66; indigotin; indicum (Pliny); indigo (Esp. Fr., Dan., Ned., Port., Sven.); Indigo (Deut.); anil (Esp.); Indiko (Gr.); indaco (It.); aneel; anile; ai (Jap.); rams (Tibetan); blue ynde; blue inde; anneil; India blue; intense blue; rock indigo; stone blue; indigo carmine; intense blue; indico; indicoe; indego; nil

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Other Properties

Soluble in nitrobenzene, phenol, chloroform, glacial acetic acid. Insoluble in water, ethanol, acetone, ethyl acetate, pinene.

Absorption max = 599 (in xylene).

ISO R105 Lightfastness Classification = 3-4

Microscopically, indigo has fine, translucent dark blue, rounded particles that are weakly birefringent and appear red under Chelsea filter.

Composition	C16H10N2O2
CAS	482-89-3
Melting Point	390-392
Molecular Weight	mol. wt. = 262.26
Refractive Index	>1.662

Hazards and Safety

Discolored by reducing agents and bleaches.
Fisher Scientific: MSDS

Additional Information

­° H.Schweppe, "Indigo and Woad", Artists Pigments, Volume 3, E. West FitzHugh (ed.), Oxford University Press: Oxford, 1997.
° Pigments Through the Ages: Indigo

Comparisons

Characteristics of Common Blue Pigmentstion

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Authority

• Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Siddall, Pigment Compendium, Vol. 1 and II, Elsevier Butterworth-Heinemann, Oxford, 2004

• The Dictionary of Art, Grove's Dictionaries Inc., New York, 1996. comments: 'Pigment'

• Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)

• Palmy Weigle, Ancient Dyes for Modern Weavers, Watson-Guptill Publications, New York, 1974

• Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982

• Ward Bucher (ed.), Dictionary of Building Preservation, John Wiley & Sons, Inc., New York City, 1996

• The Merck Index, 10th edition, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 1983. comments: entry 4977

• A.Scharff, 'Synthetic dyestuffs for textiles and their fastness to washing', ICOM-CC Preprints Lyon, Getty Conservation Institute, Los Angeles, 1999

• Hermann Kuhn, Conservation and Restoration of Works of Art and Antiquities, Butterworths, London, 1986

• Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980

• R.Feller, M.Curran, C.Bailie, 'Identification of Traditional Organic Colorants Employed in Japanese Prints and Determination of their Rates of Fading', Japanese Woodblock Prints, Allen Memorial Art Museum, Oberlin College, Oberlin, 1984

• F. Crace-Calvert, Dyeing and Calico Printing, Palmer & Howe, London, 1876

• Webster's Encyclopedic Unabridged Dictionary of the English Language, Random House, Grammercy Book, New York, 1997

• Encyclopedia Britannica, http://www.britannica.com. comments: "indigo" Encyclopædia Britannica from Encyclopædia Britannica Premium Service. [Accessed May 6, 2004].

• Colour Index International online at www.colour-index.org

• Book and Paper Group, Paper Conservation Catalog, AIC, 1984, 1989

• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000

• Pigments Through the Ages: http://webexhibits.org/pigments/indiv/history/indigo.html