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1.  Overview     2. History of use     3. Making the pigment     4. Technical details

About the chemical structure:          Chemical name: 2,2'-Biindolinyliden-3,3'-dion Formula: 3D model: grey = carbon, red = oxygen, white = hydrogen, blue = nitrogen Crystal system: rhombic Refractive index: n/a

A swatch of Indigo paint:

How can you identify Indigo?          Chemical identification: n/a Spectra: Raman spectra (pdf file download; at University of Florence, Italy) MS spectra (at: Integrated Spectral Data Base System for Organic Compounds, Japan) IR spectra (at: Integrated Spectral Data Base System for Organic Compounds, Japan)   Usage and handling:          Permanence: Toxicity: very poor MSDS (at Fisher Scientific)   Literature:             Seefelder, M., Indigo - Kultur, Wissenschaft und Technik, Ecomed Verlag, Landsberg 1994 Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 3: E.W. Fitzhugh (Ed.) Oxford University Press 1997, p.81-107. Indigo (at Pigmentlexikon by Th. Seilnacht)

Other blues         (intro) - Azurite - Cerulean Blue - cobalt blue - Egyptian blue - Indigo       Prussian blue - smalt - Ultramarine