”To produce the Tyrian hue the wool is soaked in the juice of the pelagiæ [snail] while the mixture is in an uncooked and raw state; after which its tint is changed by being dipped in the juice of the buccinum [snail]. It is considered of the best quality when it has exactly the color of clotted blood”
-Pliny the Elder

Forbes Pigment Collection - Harvard Art Museums

Color is a fundamental element of human existence, both giving us illumination and interest in art and differentiating the poisonous and dangerous in nature. Throughout history, pigments of rare and brilliant colors have been incredibly desirable and their trade a valuable proposition. The Dutch Masters of the Renaissance emphasized blue in their paintings precisely because ultramarine prepared from lapis lazuli was rare and expensive (making it an artistic statement to paint blue peasant clothing), and patronized artists of earlier eras would grind other gemstones for their pigments to add status to their clients. Byzantine rulers were “born to the purple” [1] and indeed Tyrian purple was the color of kings: the only ones who could hope to afford a dye produced from the secretions of a small gland in the body of a carnivorous snail crushed by the millions to dye a single robe.

Color Perceived

Natural vs. simulated butterfly (UV) vision – Dr. Klaus Schmitt

The human eye senses color through the interaction of light with sensors in the retina called cones. Humans have three types of cones, tuned to different colors of light; other creatures might have as few as one or as many as four or even five! White light is not “a mix of all colors” as you may have learned, but all photoreceptors in the eye being stimulated equally. The photon energy levels that can be detected by the eye are called visible light, which is somewhat self-centered of us, as many other creatures see higher- or lower-energy photons. Many birds, fish, and insects see well in the high-energy ultraviolet, while snakes sense lower-energy infrared (though through pit organs, not through eyes). Color, then, is dependent on the biochemical framework for photon sensing, and the spectrum of red to purple is not the end of color as perceived by those not like us. This opens up rich potential for sight with other senses, but for today we will stay in the (humanly) visible.

Color as Craft

Colorants may be incorporated by the artisan as dyes, pigments, or, in the case of pyrotechnics, as flammable chemicals. The first two form what are known as subtractive colors; what is observed is the reflected light remaining after the pigment absorbs or “subtracts” the other colors in white light. Pyrotechnics are a form of additive color: the light you see is actually generated by the excited atomic states of the compounds involved.

Dye

Wool dyed with woad, indigo, madder, weld, cochineal, and mixtures - Pamela Saunders

Dyes are coloring compounds that are either liquids, or that may be dissolved in liquid, bound by chemical reaction to dyed material for long-lasting color. Most historical dyes were made from plants: the leaves, roots, barks, and even wood of trees. Many dyes are improved by mordants, which chemically modify, or fix, the dye on the dyed fibers. A common practice to develop rare colors or deeper saturation of the same color is called bottoming, in which the material is dyed and then dyed again. Masters of the art of dying textiles were well treated- the economy of even simple black cloth was of significant importance to the community. [1]

Pigment

Pigments are solid and insoluble materials, affixed to a surface with a binder. Most colored ancient inks, such as those used in illuminated manuscripts, are pigments in gum or resin binder, including carbon for black, cinnabar for vermillion, and orpiment for yellow. [2] Many dyes may be incorporated on a neutrally colored mordant such as alum, which fixes the color, and the dyed mordant may then be used as a pigment. Most paints are pigments with a binder such as egg tempera, beeswax encaustic, or drying oils like linseed.

Flame

FIRE-WORKES and ILLUMINATIONS on the River Thames, 1749

Coloring flame and smoke has sparked festivities and signaled armies ever since gunpowder was discovered, and the composition of black powder hasn’t changed much in a millennia: charcoal, saltpeter, and sulfur in the right proportions will fire cannon, burst shells, and lift rockets. Techniques and chemicals for coloring have been refined over time, but the available options are limited by physics because the light emitted from a flame is determined only by the chemical species involved and the temperature reached in combustion.

Crafting the Rainbow

Red

Madder Root raw dye and dyed wool (different mordants left-right: alum, tin, iron)

Red is a common color both for pigments and for dyes, but the deepest, brightest crimsons are still prized (and are marked targets for deviancy by adulteration, as cinnabar was often cut with red lead or even powdered brick!). Cinnabar (mercury sulfide) is one of the oldest red pigments, having colored everything from noblewoman’s makeup in Rome to Mayan tombs to Chinese lacquer. Red ochre and red lead are produced by roasting iron and lead ores, and realgar (arsenic sulfide) rounds out the ancient red pigments. Ochre, the least desirable, is the only one non-toxic.

Moving on to dyes, kermes was extracted from an insect that grew on oak trees around the Mediterranean. Kermes was eventually replaced by the new world cochineal, also an insect, grown on cactus. The madder plant was grown around the Mediterranean and its root used for vat dying, and other plant sources of the same dye chemical were used elsewhere. Madder was often fixed on alum as the quintessential red lake pigment, and could have its red color adjusted towards purple by the addition of metal salts. Another use of metal salts, such as lithium chloride from desert dry lake beds, is as a source of red flame in pyrotechnics. The brighter, redder colors are obtained from strontium salts such as the sulfate mineral celestine.

Orange

Orange is a rare color in both pigments and dyes. With the right treatment, henna is a plant-based option for orange, and a few other plants will work even if they tend more towards yellow or brown. More generally, orange was achieved by mixing finely ground red and yellow pigments, or by bottoming a yellow dye with red. The color is never as bright as it would be with a true orange, but these are chemical compounds of cadmium or chrome that were not available until the industrial age. Orange is an easy color to achieve in flame, though, as powdered charcoal or iron will add orange sparks and calcium compounds like gypsum will glow orange.

Yellow

Yellow is another common color. Weld and buckthorn have a long history as dyes in Europe, while saffron and turmeric stood in Asia. The Americas used butternut and oak bark to the same effect. Yellow pigments are relatively common as well, with orpiment (arsenic sesquisulfide) common in the East and yellow ochre, a hydrated iron oxide, common everywhere. Various other sulfides associated with mining are yellow, and lead and tin oxides may be heated together in the furnace to produce the lead-tin yellow famous in the Renaissance. Flame yellows are common as well; all sodium salts burn yellow, so even sea salt will color the flame.

Green

Chinese buckthorn is one of the very few natural sources of green dye, although as with the other rare colors it can be created by bottoming a yellow with a blue. The forest green of Robin Hood’s merry band would have been dyed first with woad and then with weld. Green pigments are common and generally involve copper: either ores such as malachite (copper carbonate hydroxide) or compounds prepared from copper such as verdigris (copper acetate). Green flames are almost exclusively colored by barium salts such as barite (barium sulfate), which might be obtained from desert evaporate deposits (along with gypsum).

Blue

Indigo dye – Technical University of Dresden

Blue is the last of the common dye colors, with indigo taken from its namesake plant in Asia and woad providing the same chemical in Europe and on the British Isles, where it has a long and sometimes magical history among the native tribes. [3] Along with weld and madder, woad rounds out the traditional primary dyes of Europe. Woad and indigo are unusual in that the dye goes on clear yellow-green and turns blue during drying as the dye chemical is oxidized by the air, which can make achieving the desired color saturation tricky at best.

Blue pigments were rare and expensive, at least outside of Ancient Egypt, where what was certainly one of the first synthetic pigments was made by packing copper, lime, and sand together and heating it. (Everyone else had to pay for imported lapis lazuli gemstones to grind into ultramarine.) Blue flames contain copper and are easy to produce, though achieving a bright and brilliant blue is a mark of a distinguished artisan.

Purple

Purple Dye Murex – Flickr

Purple is the rarest dye of antiquity. It was produced from the Murex whelks, a family of small carnivorous snails native to the Mediterranean. The Phoenicians learned how to raise them in captivity and built an empire on their expense: at perhaps several million shells to a pound of dye, purple was at times more precious than gold. [4] The Phoenicians found other purple dyes as well, including one derived from lichens on the rocky shores of Crete and the Canary and Cape Verde islands in the Atlantic Ocean, but these were apparently only seen as fit for dying a base color to redye with the prized Tyrian purple. [5]

Purple pigments were also almost unknown until the discovery of chromium-based compounds in the industrial age. The best one could hope for was color-shifting a red madder lake pigment towards purple with the right mordant, or redying blue with red otherwise. Similarly, purple flames are a combination of strontium and copper, or red and blue, with pure purple only developed in the modern era.

White

No dye can color a garment white, although a few chemicals can bleach the existing color away. White pigments are comparatively common, including chalk, lead oxide and carbonate, gypsum, White light flames are typically produced by fine metal particles such as aluminum and titanium that were unavailable to the ancients. Antimony sulfide is one of the few minerals that will do the job, but must be mixed with a strong oxidizer like the chlorates that have been synthesized only recently. Many seasoned fireworks veterans have lit an M-80 firecracker: these are fueled by antimony sulfide, aluminum powder, and potassium perchlorate.

Black

Black dyes are frequently based on plant tannins modified with iron, as in iron gall ink made from oak galls. Walnut husks are another good source of tannin, as are mangrove leaves and the logwood tree. Black pigments are almost exclusively based on burnt material, such as soot from burning oil or pitch, or char from burning bone or even ivory. Soot has extremely fine particles by nature, and the chars can be ground fine before dispersing them in a binder. In dye or pigment, achieving a true deep black is a rare talent and one that will dearly reward the artisan who is able to bring it to market.

Peacocks and Penguins

Color brightens the drab world, informs patterns of thinking, and conveys status and wealth. Conversely, color might be rejected as a symbol of the excesses of the rich and powerful, stripped from outward appearance and reserved only for holy works and manuscripts. Even in the black there is work for the dye vat and the herbalist, and those who ply their trade well will leave their mark upon the world as they fill it with their chosen colors.

Further reading

[1] J. Schneider, “Peacocks and Penguins: The Political Economy of European Cloth and Colors,” American Ethnologist 5(3) (1978) Link

[2] R. Nöller and O. Hahn, “Illuminated Manuscripts from Turfan Tracing Silk Road Glamour by Analyzing Pigments,” STAR: Science & Technology of Archaeological Research 1(2) (2015) Link

[3] G. Carr, Woad, Tattooing and Identity in later Iron Age and early Roman Britain,” Oxford Journal of Archaeology 24(3) (2005)

[4] C.P. McCord, “The Lowly Whelk and the Lofty Royal Purple Dye,” Archives of Environmental Health 18(3) (1969)

[5] Pliny the Elder, “The Natural History,” John Bostock, Ed. 26.66 Link

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