KRESS

HISTORICAL MATERIALS/TECHNIQUES

ORGANIC PIGMENTS

What is a Pigment?

Paint is composed of at least three components, a pigment, a binder, and a diluent. Pigments are colored particles that are insoluble in their binders. The earliest pigments were simply ground colored earths and soot. In the ancient world, natural organic colorants were discovered and emplyed while relatively simple compounds, like lead white, were synthesized. Many new pigments were created during the Industrial Revolution and organic pigment synthesis began in the nineteenth century. More modern pigments are now produced through sophisticated chemical processes and engineering. With a timeline of discovery or creation, popularity and usage, pigments can be identified and help to date a work of art or cultural artifact, especially if the pigment was manufactured only recently.

What are Organic Pigments?

Organic pigments are labeled “organic” because they are primarily composed of the element carbon. With the exception of carbon black, most early organic pigments were derived from natural dyes extracted from plants and animals; and require some form of processing. Dyes may be soluble in their binders, so dyes were usually struck onto an inorganic substrate, often aluminum hydroxide, to create an insoluble particle. Organic pigments can be quite brilliant in color but may not be lightfast and may fade over time. Fading was especially characteristic of early organic pigments.

The term “lake” pigment is also used to describe organic pigments made by striking an organic dye onto an inorganic substrate. The name lake comes from “lac” or shellac which was the source of a highly prized organic red lake.

Historic Use of Organic Pigments

Carbon blacks from burnt wood have been identified in ancient cave paintings. In antiquity, Tyrian purple was derived from Mediterranean snails, and other organic colorants were obtained from bark, plants, and insects. Pigments were made from kermes and Polish cochineal insects native to Europe. These were largely supplanted by colorants made from North American cochineal insects after they were first imported in the early sixteenth century. Indigo pigments from indigo and European woad were popular as more affordable alternatives to the costly mineral blues. Indigo colorants became less important after the synthesis of Prussian blue in the eighteenth century. Tarry materials such as asphaltum or bitumen have been used periodically in Western painting, but coal tars dry poorly and generally cause significant problems when used in oil paint. One of the most interesting organic pigments is Indian yellow, which was created by collecting the urine of cows that were fed only mango leaves. The super-charged urine was then boiled to precipitate the pigment. Cows so treated did not live very long, and the creation of Indian yellow was outlawed in the early twentieth century. Organic synthesis which began in the nineteenth century allowed for the creation of hundreds of new dyes. Most of these were not stable to light and rapidly faded. New lightfast organic pigments were synthesized in the twentieth century.

References

Berrie, Barbara, ed. Artists’ Pigments: A Handbook of their History and Characteristics, Vol. 4. Washington, DC: National Gallery of Art, 2007.

Eastaugh, Nicholas, Valentine Walsh, Tracey Chaplin, and Ruth Siddall. Pigment Compendium: A Dictionary of Historical Pigments. Oxford, GB: Elsevier Butterworth-Heinemann, 2004.

Eastaugh, Nicholas, Valentine Walsh, Tracey Chaplin, and Ruth Siddall. 2004. Pigment Compendium: Optical Microscopy of Historical Pigments. Oxford, GB: Elsevier Butterworth-Heinemann, 2004.

Feller, Robert L. ed. Artists’ Pigments: A Handbook of their History and Characteristics, Vol. 1. Washington, DC: The National Gallery of Art, 1986.

Fitzhugh, Elizabeth F., ed. Artists’ pigments: A Handbook of their History and Characteristics, Vol. 3. Washington, DC: The National Gallery of Art, 1997.

Graaff, Judith H., and Wima G. Th. Roelofs. The Colorful Past:: Origins, Chemistry, and identification of Natural Dyestuffs. London: Archetype Publications, 2004.

Kirsh, Andrea, and Rustin S. Levenson, Seeing Through Paintings, 101-106. New Haven: Yale University Press, 2000.

Roy, Ashok, ed. Artists’ Pigments: A Handbook of their History and Characteristics, Vol. 2. Washington, DC: The National Gallery of Art, 1993.