Paint-Making in Prehistory

At least 4,000 years ago, prehistoric people living in the lower Pecos River region of southwest Texas and northern Mexico began painting elaborate murals under cliff overhangs and in rock shelters. Some of these paintings are over 100 feet in length and 30 feet in height. The palette used by the artists to create these murals included a wide range of earth colors, including reds, yellows, oranges, browns, and black. What did these ancient artists use to make paint that was so durable that it has lasted 4,000 years? Using experimental archeology, Drs. Carolyn Boyd and Phil Dering have begun the process of trying to rediscover the ingredients in the Pecos River Style paintings.

Radiocarbon ages for the Pecos River Style rock art, which is the oldest and most abundant art style in the region, range from approximately 3000 to 4200 years ago. Many of these ancient murals extend hundreds of feet in length.

In 1982, Mike Zolensky identified the “pigments” used to produce the earth colors represented in the Pecos River Style pictographs. The term pigment refers to a colored substance that, when suspended in a liquid medium or “binder”, becomes paint. Pigments can be derived from either organic or inorganic substances. The inorganic pigments that are derived from minerals, ores, and sedimentary deposits are referred to as earth colors. The principal color-producing agent in most earth colors is an iron oxide mineral. The mineral pigments used to create the earth colors used by the archaic artists of the Lower Pecos include hematite (red), limonite (yellow), and manganese oxide (black). All of these minerals can be found within the lower Pecos River region. The preparation of earth pigments, although simple, is time consuming when using primitive tools. The prehistoric artists ground the mineral pigment to a very fine powder using a grinding stone.

The next important ingredient in producing paint is the “binder.” A binder is the liquid in paints that holds particles of pigment together and fastens them to the support (in this case the support is the shelter wall). Chemistry professor, Dr. Marvin Rowe, and his students at Texas A&M, determined that the binder used in the paint was of an organic nature, however; they still did not know what kind of organic binder was used. In an attempt to answer this question, artist and archeologist Dr. Carolyn Boyd, began the process of trying to rediscover the binder used 4000 years ago through experimental archeology.

Native Americans are reported to have used a variety of substances as binders in making paint, including blood, egg whites, sap from plants, animal fat and even urine. As an artist well experienced in mural painting both indoors and outdoors, Boyd knew that the binder required to produce fluid continuous lines in an arid environment needed to be a slow drying substance. This eliminated such possible binders as blood, urine and egg whites. The binder also should be close to colorless when used to make such colors as yellows and whites, which again rules out blood. Quantity was also a consideration. The amount of binder required to produce some of the pictographs would be sizeable. Given these considerations, she determined that animal fat seemed the most likely source. In considering the fauna available 4000 years ago, deer would have been an excellent source of fat. Dr. Boyd communicated with Dr. Jerry Cook, a wildlife ecologist at Texas A&M, and was informed that the highest source of fat on a deer is contained within the bone marrow, especially in the long bones of the tibia and humerus. Using a hammerstone and granite anvil, Boyd broke the long bones and extracted the marrow. The color of the marrow ranged from virtually colorless in the tibia and radius, to red in the humerus and femur. She noted that the quantity and color of the marrow varied according to age, season, and health of the deer. The finely ground mineral pigments and the deer bone marrow blended easily, however, the consistency was too thick to be used for painting. A “thinner” was required to achieve the necessary fluidity.

Water could not serve as the thinner due to its immiscibility or inability to mix with fat. Boyd needed a third ingredient that would act as an emulsifying agent to allow the water and the fat to be dispersed one into the other. She asked Dr. Phil Dering, a botanist and archeologist at Texas A&M, if there was a plant that could provide the needed emulsifier. He informed her that yucca, also known as soap plant, contains an ingredient known as saponin. Saponins are molecules that act like a detergent and are composed of a steroid attached to a sugar molecule. In aqueous solutions, saponins have an ability to foam, thereby acting as an emulsifier. In reviewing the ethnographic literature, she found that yucca was not only used by various Native American groups as a detergent, but as a binder in paint as well.

The roots of the yucca contain the most saponin. After removing the woody bark, Boyd pounded the roots enough to break them open and allowed them to soak in small amount water over night. The next day the roots were pounded into a pulpy mass and squeezed to render a soapy liquid.

The yucca juice, combined with the water added in the processing of the yucca, served as an excellent emulsifier-thinner. The liquid mixed well with the fat and pigment, creating a silky, fluid paint. The consistency of the paint could be adjusted with varying quantities of yucca juice. The proportions needed of each ingredient varied depending on which mineral pigment was used, the quality of fat, and the concentration of yucca juice.

The final product produced intense earth colors. The paint was highly fluid and as easy to work with as commercial oil paints. The deer bone marrow served as an excellent binder when used in combination with the yucca juice as the emulsifier-thinner. Although we do not know for certain that this combination of ingredients was the formula used by the ancient artists, we do know that the formula works and the resources to create the paint would have been readily available to the artists 4000 years ago in the lower Pecos River region of Texas.