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Recent research using electron microscopes has revealed insights into how North American hunter-gatherers created the ochre paint used in their pre-historic rock art at Babine Lake, British Columbia. The findings are surprising, showing that advanced technology was being used to create the red paint that has persisted on the walls of rock for thousands of years.
In a paper published last November in Scientific Reports, a journal of Nature, a team of researchers from the University of Missouri described how they investigated pigments of ochre paint to understand how it’s created. This may be used to influence the engineering of future thermo-stable paints.
Revealing How Ancient Paint was Created and Its Impact on Today’s Practices
Ochre is known for its use in creating the bright red paint used by global ancient civilizations to create rock art in the form of pictographs. Although its use has been discovered at numerous global sites of historic interest, little is known about how it was produced.
Most research into ochre pairings has focused on decoding its meaning, but understanding how hunter-gatherer societies made this paint is important for gaining a deeper understanding of the societies that used it. For example, it gives an insight into their knowledge, creativity, and intelligence. These ancient techniques could also help to inform modern scientists on how to create products for today’s world.
Ochre is special as it is one of the few materials that was used continually for over 200,000 years. For centuries civilizations were producing this material, but until now, there have been few studies to understand what processes these ancient people undertook to create this important material. The Missouri-based team set out to unlock the secrets of ochre paint.
Electron Microscopy Uncovers Paint Creation Process
The scientists collected samples of the ochre paint and studied how single grains of it were impacted by temperature changes under an electron microscope. They were then able to determine that the hunter-gathers at Babine Lake had purposefully harvested and heated the iron-oxidizing bacteria found in the lake, known as Leptothrix ochracea, to turn it from brownish to a vibrant red. By observing the ochre under the electron microscope they were able to determine that the individuals at the lake had heated the bacteria to temperatures between 750 °C and 850 °C.
This was the first study of the ochre paint used at Babine Lake, and it revealed that the settlement who lived there were using techniques to harvest and heat the iron-rich bacteria to create this paint.
Making Ochre Was More Complicated than May be Assumed
While previous civilizations may be envisaged crushing up red rocks to create the pigment in red paint, the true process is far more complicated. It involved several scientific methods, which required higher-level cognition, insight, and skill. The researchers concluded that the process of making ochre paint could not have been stumbled on by mistake, it was an intentional process, designed with a goal in mind. This is important for gaining a deeper understanding of the people who lived in these times.
Humans were engaging with this bacterium and had an understanding of its properties, which allowed them to devise the method of heating it to produce red paint. The hunter-gatherers also had to understand the nature of the bacteria, which led to them to harvesting the iron mats where the bacteria was located, to be heated and enhanced in color before being produced into paint.
Researchers also believe the heat treatment process served to increase color fastness and degradation resistance of the paint, ensuring it would stand the test of time. These processes show that these societies were capable of innovating specialized technologies.
Past Practices Inspire Future Products
Modern engineers are tasked with developing highly thermo-stable paints for use in the industries of aerospace and manufacturing. However, while much time and money have been spent pursuing this goal, little success has emerged. This research may enable modern scientists to develop thermo-stable paints, using inspiration from the past.
References and Further Reading
- Henshilwood, C., d'Errico, F., van Niekerk, K., Coquinot, Y., Jacobs, Z., Lauritzen, S., Menu, M. and Garcia-Moreno, R. (2011). A 100,000-Year-Old Ochre-Processing Workshop at Blombos Cave, South Africa. Science, 334(6053), pp.219-222. https://science.sciencemag.org/content/334/6053/219
- MacDonald, B., Stalla, D., He, X., Rahemtulla, F., Emerson, D., Dube, P., Maschmann, M., Klesner, C. and White, T. (2019). Hunter-Gatherers Harvested and Heated Microbial Biogenic Iron Oxides to Produce Rock Art Pigment. Scientific Reports, 9(1). https://www.nature.com/articles/s41598-019-53564-w#citeas