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Tuesday, February 1, 2011

Indian Yellow

Photo courtesy of Windsor & Newton
Balls of Indian Yellow on display
at Windsor & Newton's museum.
Photo © Winsor & Newton

Indian Yellow is a pigment of legend and mystery. Also known as C.I. Natural Yellow 20, Gaugoli, Giallo Indiano, Peori, euxanthic acid, Purree and Purée of India. It has long been claimed to be the made from the urine of cows (or camels according to W. Schmidt, 1855) that were cruelly force fed Mango leaves.
Due to the color and urine like smell, Indian Yellow had long been rumored to be made from urine of cattle or camels, but the true nature of the pigment was a not really known. The process of making it was kept a secret and there was apparently only one main source for the color, manufactured by an "Englishman in Calcutta".
Then, in 1883, a letter was received at the Society of Arts in London. In that letter, from a Mr. T.N. Mukharji, the process for making Indian Yellow was stated by Mr. Mukharji to be the urine of cows fed Mango leaves. Mr. Mukharji claimed to have studied the process in Monghyr, north-east Bihar, India. Mr. Mukharji further described how the urine of the cows was collected in buckets placed under the cows, it was then cooled (uh?cooled and heated?) and concentrated over a fire. The liquid was then filtered through a cloth and the sediment collected into balls, and then dried over a fire and in the sun. The European importers would wash and purify the balls, separating greenish and yellow phases.
A legend was born, and through repeated telling, it seems to have been accepted as fact, for it has been reiterated in countless books and writings, even by respected authors, ever sense that time. It has continued on so far as to claim it was illegalized in the late 1800's or early 1900's, on the bases of being cruel to animals.

There was always some doubt cast as to the truth of the of this myth. As early as 1839, J.F.L. Merimee, in his book "The Art of Painting in Oil and Fresco," gives a more plausible source for Indian yellow as follows:
"For many years past the English traders have furnished us (in France) with a brilliant yellow lake, which is more lasting than the greater number of this class. I have been informed by a learned naturalist, who traveled in that country (Bengal), that this color is manufactured in Calcutta by an Englishman (mmm?, do we know somebody from Calcutta?), who keeps the process quite a secret; but the traveler has found out that the coloring matter is extracted from a tree, or large shrub, called memecylon tinctorium*(see more info on memecylon tinctorium below), the leaves of which are employed by the natives in their yellow dyes. From a smell like cows' urine, which exhales from this color, it is probable that this material is employed in extracting the tint of the memecylon."

In 1844, chemist Dr. John Stenhouse, PH.D examined the origin of Indian yellow in an article published in the November 1844 edition of the Philosophical Magazine, Examination of a yellow substance from India called Purree, from which the pigment called Indian Yellow is manufactured. Dr. Stenhouse carried out a complete chemical analysis and found the principal coloring matter to be magnesium salts of a chemical he preliminarily named purreic acid (now called euxanthic acid). He found no traces of ammonia or nitrogen (which would be found if it have been made from urine) and concluded it was in fact of vegetable origin, and that it was "highly probable that the purree of commerce is the juice of some tree or plant, which, after it has been expressed, has been saturated with magnesia and boiled down to its present consistence"

In her 2004 book 'Color: A Natural History of the Palette', Victoria Finlay attempted to verify whether Indian yellow was really made from cow urine. Apparently the only printed source mentioning this practice she was able to find was a single letter written by a Mr. T.N. Mukharji of Calcutta (mmm? Calcutta, sound familiar?), who claimed to have seen the color being made. Aside from this letter, there seems to be no other written sources from the time period mentioning the making of Indian yellow. Finlay also searched for legal records for the supposed banning of Indian yellow production in the India Library in London and the National Library in Calcutta, and found none. She visited the town in India mentioned in Mukharji's letter as the only source of the color, but found absolutely no trace of evidence that the color had ever been produced there. None of the locals she spoke with had ever heard of the practice.


Even if the story of how Indian Yellow was produced, has some truth, which is doubtful, mango leaves were probably not force fed to cattle, or cruel at all.
In the 2005 'Species Profiles for Pacific Island Agroforestry' a publication made to educate extension agents, farmers, ranchers and landowners about growing native and traditional trees, it is stated "Mangos grow well in pastures, although cattle will graze off lower leaves. It is necessary to fence off young trees for the first 3–4 years to protect them from livestock.", In other words the Mango leaves need to be protected from the cattle, because the cattle love them!
There have also been numerous studies of the food value of mango leaves and in most cases have been found to have little ill effects. In the article 'Feeding Value of Mango Leaf (Mangifera indica) for Growing Rabbits' in the Journal of Animal and Veterinary Advances, 2006,Vol.5, Iss.10,Pgs 800-804 it was concluded that "Mango leaf meal can be fed to weaner rabbits up to 50% level without any adverse effect on performance variables."
In Indonesia and the Philippines, young mango leaves are cooked and eaten by people! (reference 'Uses of Mango Leaves,Seeds and Bark' at www.mdidea.com)

Chemically the principle coloring matter Indian yellow is magnesium euxanthate a magnesium salt of euxanthic acid. It is a brilliant deep and luminescent reddish yellow pigment that fluoresces in "yellow green" spectrum. Considering the above information on the origin of Indian yellow, it is quite possible to conclude that it did not come from cows urine at all, and is most likely magnesium euxanthate extracted from some plant source and possibly precipitated onto a calcium or magnesium carbonate base. Another possibly is euxanthic acid extracted from mango leaves or other plant (euxanthic acid is a  glycoside of the mango pigment euxanthone, also isolated from the roots of the herb Polygala caudata, and other plants), and then treated with magnesium carbonate to precipitate the magnesium euxanthate (see  Hand-book of chemistry, Volume 17, By Leopold Gmelin, Henry Watts, 1866).

In "The Chemistry Of Paints And Painting", by Arthur H. Church (see the Free Art Books Page), there is a recipe for a yellow pigment using euxanthic acid by Church: "A fine yellow pigment may be prepared from the euxanthic acid, which is the characteristic constituent of Indian yellow, by throwing it down in combination with the two bases - alumina and magnesia. The following directions may be followed: Dissolve 1 part of pure euxanthic acid in just sufficient dilute ammonia. Pour the solution into a liquid prepared by dissolving 45 parts of potash-alum, 15 parts Epsom salts, and 6 parts salammoniac in 250 parts of water. Now cautiously add dilute ammonia to the mixture, stirring all the time, and avoiding any excess of ammonia. The precipitated pigment is to be thoroughly washed, and then pressed, dried, and ground." Although no ammonia was found in the samples of real Indian Yellow by Dr. Stenhouse's analysis in 1844, It should be noted that made with excess ammonia, or before being washed, the finished substance using the recipe above may well look and smell like dried p---.

Making a Pseudo Indian Yellow Oil Paint:

It seems that for some reason, a lot of interesting pigments are available in watercolor but not in oils, even when the pigment is known to be compatible with the oil medium. I've been thinking about trying to convert  a watercolor into an oil color for some time now and decided to give it a try.
I happened to have the Daniel Smith watercolor "Indian Yellow" with magnesium euxanthate (PY108) in my watercolor paint collection. That paint for all intents and purposes could be called a genuine "Indian Yellow" as it is most likely chemically similar or possibly almost identical to the known samples of the genuine article. It is a very nice transparent bright reddish yellow, that does look like it could have been made of p--,   Yep, you guessed it.--- Luckily, it doesn't have the smell.

At this time, Daniel Smith is the only manufacturer of artists paints that carries a paint with magnesium euxanthate as the only pigment. I wish they had it in oil paint too, but so far, they only make it in watercolor.
Because I have been unable to find a magnesium euxanthate oil color and at the moment couldn't afford to get the pigment from Kremer Pigments or a chemical supply house, I decided to try an experiment converting the Daniel Smith Indian Yellow watercolor to an oil paint.
Although I don't know all the ingredients to D. S. watercolors, it is safe to say they are probably mostly pigment in a gum arabic solution (see below for my thoughts on the pigment load of the Daniel Smith watercolors). Considering all the possible additives, they would most likely would have added some glycerin to help in re-wetting, and probably also have a very small amounts of stabilizers, dextrose or honey, maybe small amounts of a wetting agent or flow improver (such as ox gall) and a preservative. Most of the additive substances, in normal use (added in very small amounts), should have little or no real adverse effects on an oil paint film that I'm aware of.

I began by simply taking a little less than a teaspoon of paint from the tube of Daniel Smith Indian Yellow and mixed in about 3 parts of calcium carbonate to extend it (I figured this would also dilute any additives that might be present), while mixing in some water to thoroughly wet, and dye, the pigment onto the calcium. That amount of calcium only lightened the color slightly. I could have used Aluminum Hydroxide (would have been more transparent) as an extender, but I wanted to stay within the chemical make up of the genuine pigment and calcium is found in the original. After allowing that mixture to thoroughly dry for a day, I pulverized the dried mass and ground it down, with mortar and pestle, into a very fine powder.

Grinding the dried mixture (water,  Daniel Smith Indian Yellow and calcium carbonate), with a mortar and pestle
Daniel Smith Indian Yellow watercolor mixed with calcium and changed into a dry powdered Pigment

I added a little linseed oil (walnut oil is clearer and would be an interesting alternative), and then a touch of  Dorland's Wax Medium to act as a stabilizer and give it a "buttery" quality (Gamblin's "Cold Wax Medium" would work just as well, or better, in this application). I then mixed up a paste using a palette knife. I got out my trusty old Glass Muller and proceeded to mull the dull out of it. I kept grinding the paint until I was satisfied with the smoothness and "buttery" quality, about 15 minutes all together.


Roughly mixed with linseed oil before grinding the paint
After grinding the paint for about 15 min.

With the calcium carbonate I had added, I was able to get about 15 ml "Indian Yellow" oil paint from a short teaspoon (about 3-4 ml) of the Daniel Smith watercolor. I made a "draw down" test and am very pleased with the color and handling of this paint. I am really surprised at it's tinting strength and brightness, considering that I diluted it by almost 3 to1 with the calcium carbonate. This really attests to the exceptional pigment load of Daniel Smith watercolors. Chemically this pigment may be very close to the genuine and certainly has a similar color to the actual pigment samples that Windsor & Newton have. For comparison, I have it shown next to a draw down of Sennelier Indian yellow PY153 straight from the tube and also with a tint mixed with 50% titanium white.. ummmm........vvverry inter-reeeeesting...

My DS Psuedo Indian Yellow Oil color,
CI Pigment yellow 108, made from Daniel Smith watercolor "Indian Yellow"
Sennelier Indian Yellow
PY153
Photo courtesy of Windsor & Newton
Balls of Indian Yellow on display
at Windsor & Newton's museum.
Photo © Winsor & Newton
  Update 3/5/2011: The paint seems to be taking a long time to dry. The straight color took about 4 days to dry, and the thicker areas mixed with white are still wet 8 days later. This may be do to the additives in the that were in the water color paint or just a property of the pigment. The paint that was mixed with 50% titanium white (an old tube of Alexander titanium white) long drying time may be do to the brand used. Poppy oil is often used in white paints to avoid yellowing and takes longer to dry than linseed oil.
 Update 3/9/2011: The paint is still not dried, the glycerin or other additives in the original watercolor paint must be inhibiting the drying process somehow. I should have washed the original watercolor by mixing it with water and letting the pigment settle out. That would have removed all water soluble additives. Earlier I had thought the paint without white was dry, but when I checked it again the thick areas were still wet. I'll have to try adding a drier to speed things up.
 Update 3/12/2011: The paint is finally dry to the touch and seems to have made a firm but elastic film. I may try making some more and, this time, removing the watercolor gum and additives by washing. Although it took 7 days to thoroughly dry, I am pleased with the final paint color and consistency.

* "Memecylon tinctorium; a cold infusion of its leaves gives a yellow colour. It is used for dyeing cotton cloths and grass mats. It also forms an ingredient of the dyes obtained from sappan wood and myrobalans, and it is likewise used with the chay-root, Hedyotis umbellata, as a red dye." Description from The cyclopædia of India and of eastern and southern Asia ..., Volume 1, By Edward Balfour.
"The leaves of Memecylon tinctorium and M. edule, Roxb. are used in dying, and afford under proper management a very delicate yellow lake, but I have not heard whether the color is permanent. The berries of most of them are pulpy and have an astringent sweetish taste." from Illustrations of Indian botany: or figures illustrative of each of the ..., By Robert Wight.

 References:
* Agroforestry.org, (2005) Species Profiles for Pacific Island Agroforestry
* Church, Arthur Herbert (1901 ) The Chemistry of Paints and Painting, Published by Seeley (see my Free Art Books Page)
* Eastaugh, Nicholas (2004). Pigment Compendium: A Dictionary of Historical Pigments. Butterworth-Heinemann. ISBN 0750657499.
* Feller, Robert L., ed., Artists Pigments : a Handbook of their History and Characteristics, Vol. 1, National Gallery of Art, Washington, D.C., 1986.
* Finlay, Victoria (2003). Color: A Natural History of the Palette. Random House. ISBN 0812971426. (Kindle Edition $9.35)
* Journal of Animal and Veterinary Advances, 2006,Vol.5, Iss.10,Pgs 800-804, Feeding Value of Mango Leaf (Mangifera indica) for Growing Rabbits
* mdidea.com, 2011, Uses of Mango Leaves,Seeds and Bark'
* Merimee, M.J.F.L. (8/5/2009). The Art of Painting in Oil and Fresco. Kessinger Publishing. ISBN 9781437141160. Stenhouse (Kindle Edition 99 cents), also see my Free Art Books Page
* Stenhouse, John (November 1844). Examination of a yellow substance from India called Purree, from which the pigment called Indian Yellow is manufactured, The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science: 321–325.
* Watts, Leopold Gmelin, Henry, 1866 Hand-book of chemistry, Volume 17 pg.530
* Weber, F.W. Artists' Pigments: Their Chemical and Physical Properties. New York: D. Van Nostrand Company, 1923.
* wikipedia.org : Indian Yellow

3 comments:

Karen Affleck said...

Very interesting post. I had been toying with the idea of trying to make oil paint from watercolours, because I have tons of them. Your experience doing it makes me think it is possible at least.

sunsikell said...

Great post. My inquiries have led you in the same direction as yours. I've been planning for a while to attempt the creation of historic Indian yellow from mango leaves and magnesium carbonate, but have been stymied by the California law forbidding the import of mango leaves. I have also planned an informational post about Indian yellow, but you've done a much more thorough job than I would have done. - L. Lawrence.

Michal Peichl said...

VERY INTRIGUING!! I am a paper conservator by trade and there is a yellow color, very common in the 17th, 18th and early 19th century, that is most likely Indian Yellow. The strange thing is, that it does not behave as a pigment, but rather a dye. Would you happen to know whether the original Indian Yellow becomes soluble in Ethanol or Acetone?


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