Indigo: Ukiyo-e colorant

Indigo 藍 (ai): 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. In Japan, indigo was introduced from China in the 6th century CE. The dye is obtained from an indigo plant native to Asia, Persicaria tinctoria (蓼藍 tadeai). The colorant can also be extracted from indigo dyed cloth or fibers according to Hokusai's illustrated treatise, Ehon saishikitsū (画本彩色通). Indian indigo began to be imported around the end of the Edo period (1603–1868).

Indigo and dayflower are the two blues used in Japanese woodblock prints until Prussian blue enters the palette in the 1830s. Indigo appears most frequently from the 1740s onwards as a color mixed with orpiment to produce a variety of greens. As a single colorant, it appears as a comparatively dull blue color. Due to its poor tinting strength, a relatively large amount needs to be used during printing in order to obtain a good saturation of this color. Its texture is somewhat coarse which makes it difficult to execute graduated hues from dark to light.

Indigo and orpiment are mixed or overprinted to create a green. This mixture is the most commonly seen combination to create a green.

For additional information see: Indigo, Uemura Dye Archive: Indigo 272, 274, 275, Persicaria tinctoria (Kew)

Examples of Indigo in Ukiyo-e Prints

Pt 6: Printed Katsushika Hokusai, 11.19657

Pt 7: Printed Utagawa Kunisada, 11.15216

Pt 9: Printed Keisai Eisen, 11.25669

Pt 1: Printed Keisai Eisen, 11.17878

Analysis

Fiber optic reflectance spectroscopy (FORS) can easily identify the three blues: dayflower, indigo, and Prussian blue.

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  FORS spectrum of Dayflower reference
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  FORS spectrum of Indigo reference
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  FORS spectrum of Prussian blue reference

Images of Indigo

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  Persicaria tinctoria, by Tokushima Prefectural Souvenir and Tourism Plaza

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  Indigofera tinctoria

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  Indigo sticks, by Takeo City Library

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  Indigo piece (Indigofera tinctoria)

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  Indigo powder (Indigofera tinctoria)

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  Sukumo indigo (Persicaria tinctoria)

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  Paper dyed with indigo

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  Paper dyed with indigo at 50x

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  Indigo blue at 500x

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  Printed Indigo

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  Printed Indigo

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  Indigo paste, by National Museum of Natural History

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  Indigo (audio), by Harvard Art Museums

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  Ai-Tokushima:The story of Japan blue (video), by Tokushima prefecture channel

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  Awa indigo and its production method (video), by jrtservice623

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  Indigo Building (video), by Yamatokoriyama City Tourism Association

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  Indigo dye extraction (video), by kmaexports

List of Prints

Below is a list of prints where indigo was detected.