[This essay was also published on Medium where it was featured by editors as an ‘Editor’s Pick’ on the main page https://medium.com/@emswam/indian-yellow-science-unlocks-the-mystery-of-a-fabled-pigment-cd1320ac5077 ]

 

Ragini Sohavi, wife of Raga Megh. Source Credit: Francesca Galloway https://www.francescagalloway.com/m/exhibitions/28/works/

Seemingly, 2019 was the year museums in the US discovered the Ragamala paintings in their vaults. Across the country, from San Diego to DC, museums of art and Asian history held exhibitions to showcase this extraordinary genre of art that flourished, in India, between the fifteenth and the eighteenth centuries. Ragamala paintings are designed as miniatures and as illustrations of portfolios. They are often framed in the ambience of courtly gardens and employ gouache on paper to produce a luminescent and tapestried ornamentation of color.

The distinctive quality of this style is that each painting is an artistic interpretation of a poetic verse-couplet; which is itself written as a eulogy for music. There are many verses composed in this vein; mostly in Sanskrit, although Telugu is not uncommon. A Ragamala painting centers thematically on the imagery and metaphors of a specific verse-couplet. That verse is scribed in a panel on the top (the panel is missing in some paintings) and the art is positioned underneath. The painting is not a literal interpretation of the words. It instead attempts to do what music does — create a mood; preferably one that matches the music and it does this by deploying the imagination in form, circumstance and color. Each work is thus, a combined experience of three major art-forms — music, painting and poetry. The architecture of a Ragamala locates the inner spaces of life and living within the outdoors; in both a physical and a metaphysical sense. This conceptual arrangement allows the artist an explosive range of expression in structure, landscape, color and sentiment.

If one knows the music and can read the poetry; the melding of word, song and color provokes a synesthetic mesmerism. But that sort of knowledge is arduously cultivated by a few. Mindful of that, considerate curators strove to recreate the experience with lecture-demonstrations of music and poetry alongside the art on display. Even without these aids; the Ragamala paintings are visually hypnotizing in themselves for both the color of the pigments and the exquisite aesthete of their composition.

All colors of the Ragamala have natural origins and each is extracted and utilized for its striking allure. But of them all, there is one — a special stand out — that effortlessly snares the gaze. It seems to hold, in easy harmony, the yellow of turmeric, the gold of the Sun, the yellowish-orange of mangoes and the orangish-yellow of marigolds; swirling and blending their hues with the luminosity of a desert sunlight. For all its heady lure, this pigment has a simple name — ‘Indian yellow’.

In our current time, and like most naturally occurring pigments, Indian-yellow has been synthesized and its synthetic form is widely available. However, unlike them, its origin is shrouded in mystery. Worse, what little is known of its provenance is unverifiable, since it went out of production in the early decades of the twentieth century, with no documentation of its source and/or extraction process. Indian yellow simply vanished from sight. All that is left are a few remnant balls of pigment in museum collections and a story whose details are so fantastic, it has long been decried as a fabrication¹. Now, after decades of perplexity, the fog is finally clearing as advances in chemistry laboriously seal the gaps of history.

 

 

From the Forbes Collection at the Sackler museum, Harvard University; Cambridge, MA. Source Credit: The Paris Review https://www.theparisreview.org/blog/2018/07/12/the-harvard-color-detectives/

 

 

Ragini Madhumadhavi of Bhairav. The San Diego Museum of Art. Source Credit: Personal copy of “Music As Art’ https://www.amazon.com/dp/0300215479/ref=cm_sw_r_tw_dp_U_x_T0H7Eb96CCJ4C

The origin-story

Following the lead of Lavoisier and Boyle, the science of chemistry exploded, in the nineteenth century, with the discovery of more than fifty elements and the creation of the Periodic Table. In the heady spirit of the age, the compositional analysis of natural pigments was adopted early as a subject of research with the intent of creating long lasting synthetic versions. Until this time, dyes and pigments had only three known sources — plant, animal and mineral. The pioneering breakthrough of the structure of benzene (Kekule) and the parallel discovery of benzene, aniline and other aromatic hydrocarbons in coal tar (Hofmann), paved the road to unearthing the chemical formulae of natural pigments. Synthesis, in the lab, was merely a step away.

From coal tar, came the first synthetic. It dyed silk in a homogeneous, fade-resistant purple stain and was named ‘Mauvein’; its color, Mauve. The same source (coal tar) then produced aniline red and aniline blue in quick succession. The fourth in line and the first discovery of the principle compound of a natural pigment, was Alizarin. The pigment was Madder — the deep red of a plant root used, since ancient times, as a fabric and carpet dye. Madder’s Alizarin opened the doors to the analysis and subsequent synthesis of the pigments in roses, cotton, peonies, geraniums, snapdragons and a host of fruit and flower yielding plants and trees.

Evidently, the world of pigment-chemistry was closely tied to the world of naturalists. It is not surprising then, that JD Hooker — the celebrated botanist and plant cataloger — is central to the story of Indian-yellow. From its very inception, chemistry was a fiercely competitive science, with individuals and nations vying to exploit its immense commercial potential. Hooker had spent many years in India, painstakingly cataloging its plants into the voluminous ‘Flora Indica’, and was familiar with the lay of the land. In 1882, when he was the director of the Kew Gardens, he was approached by German scientists to assist in tracing the source of Indian yellow which was, until then, only known as a commodity that shipped from the markets of Calcutta to London. Curiously, the British (who were great chroniclers) had not published a record of India’s pigments; not even of its fabled yellow which was already much in use by their artists. The most celebrated of them was JW Turner, whose prolific use of Indian yellow came to it being called, Turner yellow; for a while.

 

 

Teignmouth; Joseph W. Turner, 1812. Oil on canvas. Source credit: Tate Gallery https://www.tate.org.uk/art/artworks/turner-teignmouth-t03882

Until the creation of synthetic dyes, there were few sources of yellow apart from Indian yellow. Orpiment and Realgar (mineral sources) contained arsenic and were toxic; Gamboge (plant source — resin of Garcinia) was toxic (if not equally) with an erratic supply and Persian yellow (plant source — sitgmata of saffron flowers) was a better green (in combination with other pigments) than yellow¹. Comparatively, Indian yellow was not toxic and produced a brilliantly luminescent, lasting color that made it the preferred yellow of many artists.

[Van Gogh’s ‘Starry Nights’ and Vermeer’s ‘Woman Holding a Balance’ are two works in which its use is documented.]

 

 

The Starry Night. Vincent van Gogh, 1889 MOMA, NYC. Source credit: https://www.moma.org/learn/moma_learning/vincent-van-gogh-the-starry-night-1889/

 

 

Woman Holding a Balance. Johannes Vermeer, 1664. National Gallery of Art, Smithsonian, DC. https://www.nga.gov/collection/art-object-page.1236.html

Tracing the source of Indian yellow therefore became critical to its synthesis. Hooker dutifully corresponded with officials in Calcutta who then assigned the job to TN Mukherji, a cataloger of products for exhibitions. Mukherji traveled to the town of Munger in Bihar (Monghyr in British usage) and returned to file a report that he personally attested: the balls of yellow were the filtered residue of a prolonged boiling of cow-urine and sand. He added that this particular cow-urine had an unusual tint due to a modified bovine diet that was composed exclusively of fresh and dried mango leaves with a dash of turmeric. Indian yellow was thus deemed to be animal in origin (Hooker had suggested it was a plant pigment due to preliminary studies that hinted at an absence of nitrogen).

Mukherji added details on the physical condition of the cows. They were stunted in appearance, sickly and malnourished due to the force-feeding of bitter mango leaves and the denial of a normal bovine diet. This considerable torment was worsened by the added affliction of a severe form of urinary retention. The cows were unable to voluntarily pass urine and needed the assistance of human manual compression to void. This dietarily-induced ailment perversely suited the makers of Indian yellow, since they now had direct control over the output of the pigmented urine.

The distressing nature of these revelations did not go unnoticed. Soon after, the production of Indian yellow was banned by the British under the provisions of the Prevention of Cruelty to Animals Act that was passed by the Government of India in 1890. (Note: given the climate and the history of the British in India, it is not implausible that there were commercial reasons behind the ban; however, such motives do not figure in the written record).

This then was determined to be the origin of Indian yellow which led to the abrupt closure of its production and commercial sale. But the story had an individual and uncorroborated record. That, along with its sudden disappearance, continued to intrigue art historians. The people who made Indian yellow faded into history along with the dye. A couple of generations later, there was no public memory left; either of them or of the trade. There was no way to confirm the story except through the back stories of its chemistry. And to do that, scientists started with the question: are Indian yellow’s compound pigments plant-based or animal-based?

 

 

Raja Mandhata; Raga Nimal. Source credit: The Freer Museum of Art at the Smithsonian http://ragamalaexhibit.com/raja-mandhata/

The Chemistry of Indian yellow

Mukherji shipped his report to Hooker along with a package. It contained: a ball of Indian yellow from the markets of Calcutta, a ball of Indian yellow from Munger (Monghyr), mineral yellow imported from London, a bottle of urine from a cow that was the pigment-source in Munger, an earthen pot used for boiling the mixture, a sack-like burlap which was used to filter the boiled solution and a clump of mango leaves². Upon receiving the package, Hooker sent a portion of the Monghyr ball to the German chemist who first requested the sample — Professor Graebe. Graebe conducted a detailed chemical analysis and determined the pigment to be a mixture of euxanthic acid (51%) and undescribed volatile substances (42%)³. He also noted that euxanthic acid — a combination of glucuronic acid and euxanthone — was always a salt (usually of magnesium). Euxanthic acid is rarely found in plants⁴ and so, the focus shifted to its components.

Glucuronic acid is what is called a sugar-acid. It is naturally present in all cells and is produced by the biochemical processing of glucose through oxidation. Its function is as an effective conjugator (binding substance) of toxins, drugs and intermediaries in metabolic reactions. A substance or compound that binds with glucuronic acid becomes a glucuronide which is water soluble and can be safely excreted from the body. So, euxanthic acid is the same as euxanthone glucuronide (euxanthone + glucuronic acid = euxanthic acid aka euxanthone glucuronide).

Glucuronic acid is present in both plants and animals and its presence, in the Monghyr ball, revealed little. On the other hand, both xanthone and euxanthone are biologically active compounds found naturally in many plant families⁵. One such plant is the Indian mango — Mangifera indica — whose leaves, fruit, bark and seed are all rich in xanthone and its derivatives. Here, at long last, was the connection to both mangoes (xanthones) and a possible animal source (glucuronide). Mukherji’s story appeared to be bona fide. The matter was laid to rest in an uneasy credulity and looked headed for an eternal repose. Thankfully, that was not to be.

 

 

Ragini Vasanti. From the royal house of Mandi, now housed at the Metropolitan Museum, New York. Source credit: https://www.metmuseum.org/art/collection/search/73149

The Key was in the Kew

The chemical exploration of Indian yellow’s global excursions were painstakingly researched by two scientist conservationists — Ploeger and Shugar². Despite writing this paleo-history; they found themselves, at the end of the exercise, still lumped with the nagging company of an unanswered riddle — what happened to the rest of Mukherji’s package? With the shrewd reasoning that the discovery of the package would itself lend more heft to the tale, they set out on its trail, bolstered by the tantalizing prospect of new chemical discoveries and, perhaps even, a final closure.

Mukherji’s correspondence with Hooker was during the latter’s years as director of the Kew gardens. Unsurprisingly, the trail ended in the crypts of the Economy Botany Collection at Kew; where, sitting on a shelf, and waiting to be discovered, was an obscure and long forgotten package that arrived in 1883 from Calcutta, with labels and contents intact! Armed with the requisite permissions, and with three elsewhere-archived control samples of Indian-yellow, Plueger and Shugar set to work.

 

 

Source credit: https://doi.org/10.1016/j.dyepig.2018.08.014

The seven contents of Mukherji’s package and the three acquired samples were each individually subject to a battery of analytic techniques that included induced-fluorescence, microscopy, spectroscopy and mass-spectrometry⁶. The results of this multianalytic examination were both banal and exhilarating. Expectedly; all the samples, the pot, and the cloth, contained euxanthic acid, glucuronic acid and their derivatives. But the samples also revealed the presence of a long-hidden and previously unexamined compound — hippuric acid. This finding was exhilarating not just for itself but for its implications in Indian yellow’s history.

Hippuric acid is a common ruminant metabolite, found in the urine of many bovines and ungulates. Additionally, its concentration in urine rises when animals are fed a diet rich in polyphenols. Mango leaves are very rich in polyphenols⁷. The end of the tunnel had been breached. Hippuric acid was the missing piece in the mystery of Indian yellow. It connected the disparate fragments of Mukherji’s story — the cows, mango leaves, bovine urine and the manufacturing process — into a composite whole. His report now had a sheen of authenticity and it was time for the yellow fog around Indian miniatures to slip out of the frame⁸.

 

 

Ragaputra Harsha, Kangra, Pahari. Source: personal copy of the book ‘Ragachitra’: Deccani Ragamala paintings’

The ends of the circle might have closed on the origins of Indian yellow but it was an invention, not a discovery and that leaves us with one curious and as yet unanswered detail: is this the first historical record of a manufactured pigment? Our fascination with color and pigments is as old as the trees. From ancient times, and across civilizations and cultures, we have harnessed the color of the natural world to enliven the bland monochrome of the human body with body art, seed jewelry, flowers and color dyes. For all these purposes, we mobilized pigments that were already naturally present in the colors of flowers, leaves, barks, roots and minerals; extracted and used them either as single color or as blended chemical recipes⁹ (Table 1). But Indian yellow is neither; it is a manufactured invention. How it was discovered boggles the mind; but it might be the first instance of human manufacturing of pigment.

I read Victoria Finlay’s excellent book on color — ‘Color: A Natural History of the Palette’ — some many years back; but with this new thought, I scoured her book again. In ten chapters, each dedicated to one color, she holds the reader captivated with stories of the myriad hues that populate our geography and vegetation; of the varied strivings of humans around the globe to extract the colors of the earth. Indian yellow does not escape her attention. (In the chapter titled ‘Yellow’, she records with great hilarity her failed mission of tracking Mukherji’s journey through Calcutta and Munger. Too much time had elapsed and she was unable to confirm the veracity of his report. I have appended a section of her account here).

 

 

 

 

Both pictures are pages from ‘Color’ by Victoria Finlay; pp 234–235 and describe her search for Indian yellow

Re-reading ‘Color’, I once more traveled the rainbow lore of red, ochre, brown, white, yellow, black, purple, orange and blue — all extracted pigments; alchemized even — but was unable to track another story like that of Indian yellow. There are records of animals being killed for pigment — cochineal red and Tyrean purple are two such — but Indian yellow uses the body of an animal, like a machine, to manufacture a pigment from a natural source. The animal is not killed but repurposed for human use. Whether this is the first or the only story of pigment manufacturing, before the era of synthetic production, I do not yet know. But it is likely that this extraordinary account of malefic ingenuity holds still more hidden intrigues.

It is no longer possible to look at the spellbinding yellow luminescence in a Vermeer, in Mughal miniatures or the Ragamalas, without a twinge of sadness for the gentle creatures that endured great suffering just so creatures of another species could construct beauty. A stoic might reconcile himself with the thought that the very act of creation is fraught with ruthlessness and suffering. But the creation in nature, and that some ascribe to God, is a consciously accepted struggle imbued with a biological purpose of feeding and survival. That struggle cannot account for the premeditated brutality that we inflict on our fellow creatures for no lofty goals with redeeming absolutions but for extraordinarily petty and perverse utilitarian ends. This mystery — that of the extremes of human nature — will forever be unsolvable; the extreme magnanimity and the extreme brutality that we are equally capable of. That sentiment is gloriously capped by Thomas Carlyle in ‘The French Revolution’; sections of which I learnt from my beloved father who is fond of quoting it, in chapter and verse, both for the genius of its language and for the cautionary tale it tells:

“There are depths in man that go the length of lowest hell as there are that reach highest Heaven; for are not both Heaven and Hell made out of him, made by him, everlasting miracle and mystery as he is”

 

 

Raga Megh; From the Claudio Moscatelli collection. Source credit: https://www.christies.com/lotfinder/Lot/an-illustration-to-a-ragamala-series-shankara-6072543-details.aspx

Table 1: Pigments of the Ragamala

 

 

Pigment list compiled by the author. Pic credit: author’s own of an exhibit at the ‘Hidden Vaults’ 2019 exhibition at the San Diego Museum of Art

References and bibliography

1. Finlay, V. (2002). Colour (pp 239–240). Hodder and Stoughton
2. R. Ploeger, A. Shugar, The story of Indian yellow — excreting a solution, Journal of Cultural Heritage (2016), http://dx.doi.org/10.1016/j.culher.2016.12.001
3. Magnesium and Calcium (in almost equal proportions), Silica, Aluminium and water made up the rest. Ibid pp 9–10
4. Naturally occurring forms of euxanthic acid are rare and then only in the plant family called the Gentians.
5. Xanthone (a precursor compound of euxanthone) is prolific in plants and fungi. Euxanthone too has a wide distribution across plant families but is especially numerous in two families — Clusiaceae and Fabaceae.
6. R.Ploeger, A. Shugar, G.D. Smith and V.J. Chen, Late 19th century accounts of Indian yellow: The analysis of samples from the Royal Botanic Gardens, Kew Dyes and Pigments 160 (2019) 418–431 https://doi.org/10.1016/j.dyepig.2018.08.014
7. Polyphenols are a naturally occurring (now also synthesized) class of plant compounds, structurally composed of multiple phenol rings, that have value as pigments and as nutriceutical antioxidants. Common polyphenols in mango leaves are: mangiferrin, anthocyanins, kaempferol and quercetin amongst others. If combined with curcumin, they turn a rich yellow color. This method of yellow pigment production is put to good use by Indonesia’s Batik industry. https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1541-4337.2008.00047.x
8. The coming together of ‘fog’ and ‘yellow’ in the same sentence immediately brought TS Eliot’s Prufrock to my mind and I could not resist the great man’s magnetic pull https://www.poetryfoundation.org/poetrymagazine/poems/44212/the-love-song-of-j-alfred-prufrock
9. Blue is a good example of these recipes. Three geographically disparate civilizations invented, sui generis, different recipes for blue. Chinese Blue, Egyptian Blue and Mayan Blue are three versions of the color that existed in ancient times, not as natural pigments but as ingenious recipe-combinations of plant and mineral pigments. (Detailed in Table 1)

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