Indigo: The Story of Blue Gold

Indigo is a deep blue dye extracted from the leaves of a wide range of vegetation. It was not solely a dye, however it has additionally been used as a pigment since historic instances. For hundreds of years, Indigo was a invaluable commodity that was traded throughout the globe, incomes it the identify ‘Blue Gold’. This text seems to be on the historical past of Indigo and its function in artwork, from Mayan artefacts to Seventeenth-century European oil portray.

Indigo: The Story of Blue Gold

What’s Indigo?

The overwhelming majority of blue pigments all through historical past have been constructed from minerals, like pure Ultramarine Blue and Azurite, or from metal-containing compounds like Cobalt or Prussian Blue. Indigo stands aside as a result of it’s derived from vegetation. There are greater than 300 totally different vegetation that produce Indigo dye, however a few of the most necessary have been Indigofera tinctoria (native to the Indian subcontinent), Persicaria tinctoria (discovered predominantly in East Asia), and Indigofera suffruticosa (a species that grows in Central and South America).

Indigo plant (Indigofera tinctoria L.): flowering stem with separate flower and fruit segments, c. 1750
J.J. or J.E. Haid, after Georg Dionysius Ehret
Colored engraving
Wellcome Assortment

Chemically, the blue-producing compound we all know as Indigo is named Indigotin. Nevertheless, Indigo-producing vegetation don’t truly comprise indigotin. As an alternative, they comprise a chemical precursor referred to as indican. To extract the indican, the leaves are steeped in water and fermented. The fermentation course of breaks down the indican into indoxyl and glucose. The combination is then oxygenated by whisked it, which prompts molecules of indoxyl to mix to make indigotin. Indigotin is insoluble in water and sinks to the underside of the answer the place it may be dried out and pressed into truffles.

Dry Indigo pigment

Indigo as a Dye

The earliest recognized proof of Indigo dyeing is a chunk of material present in Peru which is over 6000 years previous. Using Indigo additionally goes again to historic instances in India and West Africa, the place the indigo plant Indigofera tinctoria, is definitely cultivated. In Europe, blue dyes had been produced for 1000’s of years utilizing woad (Isatis tinctoria), a plant that’s native to the steppes and deserts of Asia however is straightforward to develop in colder climates. Woad accommodates the identical blue compounds as Indigo however produces a weaker, much less lightfast color. Indian Indigo, extracted from Indigofera tinctoria, was recognized to supply a superior color. Actually, the phrase ‘Indigo’ comes from the Greek indikon, which means ‘from India’. Indigo and Indigo-dyed textiles from India have been necessary commodities traded alongside the Silk Street through the Center Ages.

When bigger portions of Indian Indigo started to enter the European market within the sixteenth century, it introduced a risk to the native commerce in woad. Guilds in England, France, and Germany imposed harsh sanctions (generally even the dying penalty) on the import of ‘satan’ Indigo. Within the Seventeenth century, these rules have been relaxed, and because the demand for blue textiles grew, the European import of Indigo accelerated on a never-before-seen scale.

The Colonial Historical past of Indigo

From the sixteenth century, Indigo vegetation have been cultivated throughout European colonies in North and Central America. Like different colonial money crops, slave labour was used to maximise yield and revenue. Plantation homeowners additionally trusted the experience of enslaved Africans, particularly these from West Africa the place Indigo had been cultivated and processed for hundreds of years. The life expectancy of enslaved labourers at Indigo plantations was simply 5 to seven years.

An indigo plantation within the Caribbean islands, with black employees and a white overseer, 1683
Sébastien Le Clerc
Engraving
Wellcome Assortment

The North American Indigo business collapsed through the Revolutionary Warfare, however the British have been already trying to the east. Indigo had been cultivated and used for dyeing in India for 1000’s of years, however over the 18th and nineteenth centuries, contract farmers in Bengal have been coerced by the East India Firm into rising Indigo for the British as a substitute of meals crops. The farmers have been provided financial advances, however it was not sufficient to cowl the whole means of planting and harvesting, and the farmers have been paid far under market worth for his or her crop. After they couldn’t pay again the mortgage, they have been provided one other advance to develop extra Indigo, and so cycles of debt adopted generations of farmers who couldn’t get out of the exploitative contracts. These situations led to the Indigo Revolt of 1859, when farmers in a single Bengali district went on strike. This led to the Indigo Act of 1860, after which farmers might not be compelled to develop the crop.

Indigo Vats, 1850s
Captain R. B. Hill
Albumen silver print, 19.1 x 24.8 cm | 7 1/2 x 9 3/4 in
The Metropolitan Museum of Artwork

Within the ultimate years of the nineteenth century, an artificial model of Indigo was launched. From then on, the dye may very well be produced from aniline (derived from coal tar) totally in a manufacturing unit setting, at a fraction of the price of the pure product. Whereas this marked the fast decline of the pure Indigo business, it was additionally an enormous step in direction of dismantling techniques that had, for hundreds of years, exploited generations of individuals to satisfy the European demand for blue dye. Immediately, greater than 5000 tonnes of artificial Indigo is produced yearly, and most of it’s used within the manufacturing of denims and different denim clothes. Pure Indigo remains to be cultivated and used for dyeing and portray, however it’s on a a lot smaller, extra sustainable scale than it as soon as was. An instance is Lutea, a paintmaking firm primarily based in Belgium who domesticate Indigo for his or her plant-based pigments and watercolours.

Schmincke Horadam Indigofera watercolour

The Historical past of Indigo in Portray

Pure Indigo is produced in truffles of pressed powder. When these truffles are floor up, the powder can be utilized as a portray pigment. Whereas natural pigments constructed from dyes have typically poor lightfastness, Indigo doesn’t fade as readily.

The historical past of portray with Indigo may be very historic. In India, Indigo was used as a pigment on paper and in murals since no less than 2000 BC. Evidently the Historic Greeks and Romans largely reserved Indian Indigo as a pigment, and used woad for dyeing.

Fragmentary Leaf from an Ashtasahasrika Prajnaparamita Sutra, twelfth century
Unidentified Artist, Kashmiri
Gold, lapis lazuli, cinnabar, indigo, and orpiment pigments and black ink on paper, 8.5 × 7.5 cm | 3 3/8 × 2 15/16 in
The Metropolitan Museum of Artwork

Whereas Indigo was referred to as ‘Blue Gold’, it has additionally been mixed with actual gold to create luxurious manuscripts and scrolls. The well-known ‘Blue Qu’ran’, which is written in gold lettering on Indigo-dyed paper, is taken into account to be one of many most interesting examples of Islamic calligraphy. Luxurious Buddhist scrolls produced in Japan, China, and Korea have been illuminated with gold and silver, richly contrasted in opposition to a background of darkish blue Indigo-dyed paper.

Nice Knowledge Sutra (Daihannya-kyō), c. 1175
One of many Chūsonji Sutras (Chūsonji-kyō)
Handscroll; gold and silver on indigo-dyed paper, 25.4 x 18.1 cm | 10 x 7 1/8 in
The Metropolitan Museum of Artwork

Indigo was the colouring agent in Maya Blue, a pigment utilized by pre-Columbian civilisations in Central America. They found a course of of mixing Indigo with palygorskite clay, probably utilizing warmth, which embedded the Indigo deep inside the needle-like microstructure of the clay. The ensuing pigment is extraordinarily lightfast and chemically secure, a lot in order that it has survived centuries on objects and partitions. It additionally seems that it was utilized in ritual practices. The method for making Maya Blue was misplaced after the Spanish colonisation, and for a very long time its chemistry and why it’s so everlasting baffled the archaeologists and scientists who examined it. It’s only lately that now we have began to know extra in regards to the pigment and the function that it performed in pre-Columbian societies.

Crocodile whistle and rattle, 700–800
Maya
Ceramic, pigment, 5.1 x 8.5 x 18.7 cm | H. 2 x W. 3 3/8 x D. 7 3/8 in
The Metropolitan Museum of Artwork

Over the Seventeenth century, giant portions of Indigo have been shipped to Holland by the Dutch East India Firm, so it’s unsurprising that it was used steadily in Northern European oil portray. As a result of it’s a deep, clear pigment it was notably helpful as a glazing color for blue material – which itself would have been dyed with Indigo.

The Disillusioned Medea, c. 1640
Paulus Bor
Oil on canvas, 155.6 x 112.4 cm | 61 1/4 x 44 1/4 in
The Metropolitan Museum of Artwork

In addition to in portray, Indigo was additionally utilized by European artists in drawing. There are examples courting from the fifteenth century by which the pigment has been used to tone paper in preparation for silverpoint or ink drawings. Within the under drawing on paper by Peter Paul Rubens, it has been utilized as a wash so as to add tone and dimension.

The Backyard of Love (left portion), c. 1633–35
Peter Paul Rubens
Pen, brown ink, brush and gray-green wash over traces of black chalk, touched with indigo, inexperienced, yellowish, and white paint, 46.3 x 70.5 cm | 18 1/4 x 27 3/4 in
The Metropolitan Museum of Artwork

Indigo remained a invaluable commodity till the start of the twentieth century. Nevertheless, it fell out of favour within the artist palette within the 18th century when Prussian Blue was launched. Prussian Blue is a equally deep, moody blue, however was cheaper to supply and far stronger in color.

Indigo Paints within the Fashionable Artist’s Palette

Indigo is a standard color present in paint ranges right this moment. A small quantity are made with real Indigo, which is good for artists who wish to discover the qualities of the true factor. Paints labelled with the pigment index quantity PB66 are made utilizing artificial Indigo, whereas these labelled as NB1 are made with pure Indigo.

From left: Lutea Indigo watercolour (no pigment index given) and Schmincke Horadam Indigofera watercolour (NB1)

Real Indigo is a fantastic color. It’s nearly black in masstone, however washes out to a tender, muted sky blue. It’s simple to see why the colourful and punchy Prussian Blue got here to exchange Indigo, however taking a look at them side-by-side the older pigment has a greyish character that makes it notably enigmatic.

The overwhelming majority of paints which are referred to as Indigo will not be made with the real pigment, however are composed of various blue and black pigments which recreate the unique color. Though real Indigo has fairly good lightfastness in comparison with different natural plant-derived pigments, it nonetheless falls in need of excessive trendy requirements, so these Indigo hues be certain that the color will final. Nevertheless, as you may see from the examples under, they fluctuate significantly in hue.

From left: Jackson’s Indigo Hue watercolour (PBk7 PB15:1 PB60), Daniel Smith Indigo watercolour (PB60, PBk6), and Jackson’s Indigo Skilled oil paint (PB15:3, PBk7, PV19)

Indigo is a rare reminder of how historic pigments and dyes have formed cultures and histories, however it is crucial to not overlook that the color has been produced at an unlimited human price. Immediately, most individuals encounter a model of Indigo that’s faraway from the historic pure product – whether or not that’s artificial Indigo used to dye our clothes or the ‘Indigo’ paints made with mixtures of blue and black pigments. Nevertheless, the truth that it’s nonetheless so current in our on a regular basis lives is a testomony to the enduring energy of color.