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Gum Arabic

These pinks pinks and no-pinks are.

I’ve taken a break from making more pigments to transform some of those pigments into watercolors—tiny, almost gemlike nuggets ready to be mixed with water and applied to paper.  I like to keep noodling around with things until I understand them—what Michael Ondaatje calls thinkering—and I’ve been thinkering pretty hard about pigments lately.  But as a teacher, I also know it’s important to have milestones, or “summative assessments,” or maybe just exams, since having a test makes the whole process fall into place.  So I set this week as a chance to follow some recipes for watercolor binder—the stuff, in Robert Dossie’s words, that makes water “fit” for carrying insoluble colors.  I have painted a little still life, what in the age was called a “miniature.”  It is called “These Pinks Pinks and No-Pinks Are,” and the artist’s note would explain that this little potted dianthus is painted entirely from eighteenth-century pinks derived from woad, buckthorn, brazilwood, coffee, and madder.  So: one botanical, made from five others, Frankenstein-like.

James Gillray’s compact reduction of sugar to human bondage: “Barbarities in the West Indias,” 1797. Used under license from the National Portrait Gallery (click to link).

Thinkering forces encounters with the kinds of things that don’t turn up in our normal histories. Those things aren’t casual in a real sense; they are made that way by how we do history, or, by how history is done.  You can know a casual commodity because it can be mentioned, unironically, in a list of commodities preceded by the word “also.”  (This point is raised in an essay by Jutta Wimmler.)  So, in 1688, the year Aphra Behn published Oroonoko, Surinam was exporting 7 million pounds of sugar annually, “and also” tobacco, exotic lumber, indigo, various gums and resins, Amerindian objects, and so on (i.e. Goslinga, 268).  Sugar earns its place before the “also” by being the most visible commodity in the “triangular” trading regime which plundered Africa for slave labor to produce a commodity in the West Indies that was consumed in England.  It’s hard to imagine any development in the eighteenth century more important to understand than chattel slavery, since the differences it installs have hardened up into our modern categories of black and white, global north and global south, and so on.  And sugar: the taste for sweetness was both cause and effect of that plundering, a new aesthetics sense which empire was constructed to satisfy (i.e. Mintz’s magisterial Sweetness and Power).  Faced, therefore, by the systematized violation of nature and human rights that was slavery, or, looked at differently the asymmetrical systems of labor and resource extraction that was sugar, everything else takes up its place after the “also.”  Those things are made casual.

Gum Arabic, a modern name for various exudates of west African flora. (Detail of image by Simon A. Eugster, CC BY-SA 3.0. click to link)

One such casualty of history is the general category of polysaccharide glycoprotein “gums” exuded from some trees and shrubs native to western Africa.  I say this carefully, because this chemical stuff has gone by many names—indeed has been chopped and changed in many categories, has even been changed through selective cultivation— in the almost 300 years since the motley emblem was made.  These gums are non-toxic and tasteless; they dissolve in water; and they change the viscosity of whatever they are a part of.  Ground up, they become impalpable.  Tasteless, odorless, invisible in water and impalpable to the touch: this is exactly the kind of thing that could be overlooked.  But exactly because of these nearly magical qualities, because it can thicken a solution without changing any of its other properties, gums have wound up in everyday materials as diverse as adhesives and cosmetics, foods and drinks, candies and pills.  They also turn up in more recherche things, like “pan” watercolors, where it is important to be able manage the phase transition between solid and liquid, and back again, as part of what it means to paint.

Made casual in a different way: one of the “natural flavors” in Coca-Cola is gum Arabic. (click for more)

But, though the stuff is sticky, the categories are slippery.  They are what we might call a product of historical ontology.  The very category “gum Arabic,” which is one way of naming some of this stuff, is a claim about what is real in the world, and that claim depends on a certain historical set of conditions, which, today, include a whole apparatus of harvesting and marketing, food regulations and laboratory regulation—even climate change in northern Africa and the political-economic conditions on the ground.  For instance, in trade publications, distinctions are made between grades of gum, based on their visual appearance and their capacity to refract light; in ecological literature, distinctions are made based on the genus, species, and even subspecies of tree from which the gum is extracted.  And that is not even to broach things like the recent rebranding of “gum arabic” as “acacia gum,” owing to a fear that Western consumers would somehow associate these gums with Islamic terrorism—as if Western consumers shop by acquainting themselves with chemical processes and deliberately occulted reagents, anyways.  “Gum Arabic” is not one thing, gathered from one tree; it is a surprisingly wide range of things, different to different people, gathered not only from one species, but from many different species in a whole family of trees and shrubs.  This helps account, as well, for the bewildering range of names that stick to the institution of west-African gums: gum Senegal, Acacia gum, Indian gum, Hashab, Talha, food additive E414, and so on.

The chemist and apothecary William Lewis knew the difference between gums Arabic and Senegal. Engraving by Pierre-Charles Canot, in “Commercium Philosophico-Technicum,” 1763. Image from Wellcome Collection.

None of this would be a problem, except when it meets the test of manual practice.  Finding our way to the right results means meddling with the right materials, and those materials can be difficult to recover.  Eighteenth-century watercolor binders made use of two things in precise ratios, and those things don’t exist anymore—not because the things couldn’t be had as things, more or less, but because our sense of the world has changed, and the names we have do different work, or, slice up the world differently.  These two things were called gum Arabic and gum Senegal.  The materials, like the differences the names encode, were historically real.  They had different prices and different qualities.  Studies were done to determine their different affordances.  But what they were is not known.  It is tempting to think that their gum Arabic is our gum Arabic, and gum Senegal something else that needs to be found out.  It is also tempting to think that they were making a distinction without a difference, and were simply naming the same thing, shipped through different routes or packaged differently.  But the problem appears instead to be that chemists felt and manipulated a distinction between materials that has simply been lost, to be replaced by a different category with different boundaries and outlines.

My solution (a chemical joke?) is to respect the craft knowledge that goes with harvesting and initial sorting, as a thing with its own repertoire and acquired discipline, outside of the regime of print.  Meeting the difference halfway means substituting the two extant trade categories of gum Arabic—Hashab and Talha—for the eighteenth-century distinction Arabic and Senegal.  Respecting the acquired knowledge of generations of harvesters and wagonners and merchants feels like it is in the spirit of the motley emblem, I mean to make the invisible manifest.  And it seems likely to me that the earliest distinctions between gums, the distinctions made by hands in the field and at the tale were probably reflected somehow when the things made it to the apothecary’s counter or the colourman’s workshop, so there’s something to be said for respecting that continuity, too.  So: for “gum Arabic,” I use hashab; for “gum Senegal,” Talha.  For what it’s worth, I can’t tell the difference, once they’re ground to powder.  But people have been sorting gums for generations upon generations, and they can.

Some of the lakes, pinks and mineral pigments prepared as pan watercolors at the motley lab.

Below, I include a recipe for an eighteenth-century watercolor binder.  Modern binders generally contain three ingredients: gum Arabic, glycerol, and honey.  Glycerol is a historically recent innovation; it helps manage the transition between solid and liquid, making it easier to work up a useable paint from the solid stored in a pan.  But I can say from experience that it is not strictly necessary, and my paints are perfectly useable without it.  Honey is also a recent addition; it is a humectant, which means that it helps retain moisture, and is also not strictly necessary for binding pigments to paper.  But no-one in the eighteenth-century thought to use honey as a humectant additive.  Since honey is basically sugar-water with a few impurities, I suspect our preference is partly the result of historical associations, of the associations of organic honey with some sort of artisanal virtue.  So, too, in the moment of the motley emblem.  There, in some gum waters, but not all, artists added refined sugar, half as much as the combined weights of gums.  It was double-refined sugar, in the eighteenth century, which was the desirable commodity– and not homely honey.  And so, we might say, in the history of miniature painting, it is sugar which is casual; a watercolor binder is gum Arabic, gum Senegal, “and also” sugar.

Here’s the method from Robert Dossie’s 1758 Handmaid to the Arts:

Take three quarters of an ounce of gum Arabic and a quarter of an ounce of gum Senegal; powder them, and then tie them up in a linen rag; leaving so much unfilled room in the bag as to admit its being flattened by the pressure of the hand.  Having squeezed the bag till it be flat, put it into a quart of hot water; and there let it continue, moving it sometimes about, and stirring the water for about twenty-four hours; the gums will then be dissolved, and the bag must be taken out.  The fluid being divided into two parts, to one half of it add a quarter of an ounce of white sugar-candy powdered, and keep the other in its pure state.  By this means, a strong and weak gum water, each proper for their particular purposes, will be obtained.