Artists have been painting with ochre, a naturally occurring pigment, for hundreds of thousands of years. Their masterpieces range from prehistoric, ochre-pigmented images on cave walls to paintings on canvasses and other artwork from medieval times and onward. Ochre pronounced OAK-er is clay pigmented by hematite, a reddish mineral that contains oxidized iron, which is iron that's been mixed with oxygen, said Paul Pettitt, a professor of paleolithic archaeology at Durham University in the United Kingdom.
Because ochre is a mineral, it doesn't wash away or decay, allowing it to persist through the ages. Ochre occurs naturally in rocks and soil — essentially in any environment where iron minerals have pooled and formed, Pettitt said.
In its more eroded form, ochre can be found in certain soils and then sieved out. People who pick up ochre will notice that it stains their hands a "nice red or yellow color," Pettitt noted. Once collected, ochre can easily be grated against a coarse piece of stone or ground by a mortar and pestle and then turned into a powder. Then, this powder can be mixed with a liquid, such as water, saliva or egg whites, and turned into pigmented paint.
Ochre can also be used as a crayon. The earliest evidence of ancient humans using ochre dates to the Paleolithic, about , years ago, at a Homo erectus site called GnJh in Kenya. There, archaeologists found about 70 pieces of ochre weighing about 11 lbs. Ochre can be used raw yellowish , or roasted for a deeper brown-red color from loss of water of hydration. Produces a quick-drying oil paint.
Artificial variety of pigment Synthetic red Iron oxide pigments were first made in a laboratory setting by the 18th century. This pigments were given the name Mars Red. These pigments contained all the properties of their counterparts, i. Natural Iron Oxide Pigments. Olorgesailie, Kenya: Researchers recently discovered two pieces of ochre, intentionally shaped by humans, that were at least , years old.
Northern Cape, South Africa: Ochre fragments from a cluster of sites suggest the material was being collected as early as , years ago, though some researchers dispute the dates.
Twin Rivers, Zambia: Pieces of ochre up to , years old include a quartzite cobble stained with ochre that may be the earliest known ochre-processing tool. Porc-Epic, Ethiopia: The largest collection of ochre pieces ever found, weighing nearly 90 pounds in total, includes a variety of tools to process and use the material 40, years ago. Rose Cottage Cave, South Africa: Researchers have pieced together a story of ochre collection and processing that spans more than 60, years, from 30, to 96, years ago.
Madjedbebe, Australia: Various ochre pieces, found among thousands of stone tools, helped researchers establish in that humans were in Australia 65, years ago — 20, years earlier than researchers thought. But some archaeologists have begun to challenge the idea that ochre was primarily symbolic for early humans.
Instead, they believe ochre had a number of functional applications, some of which traditional societies, particularly in Africa and Australia, still employ. In the arid environment of southern Ethiopia, for example, the Hamar people use ochre to clean their hair.
And in South Africa, Hodgskiss says, ochre is widely used as sunscreen. The archaeological record suggests ochre had some other practical uses, turning up on tools and weapons. Experimental archaeologists, who seek to understand how our ancestors used different materials by replicating the processes involved, concluded that ochre was mixed with other substances to create a hafting adhesive used to attach, for example, a stone arrow point to its wooden shaft. Riaan Rifkin, an archaeologist at the University of Pretoria in South Africa, has been one of the leading proponents of a new, functional interpretation of ochre in the story of human evolution.
For nearly a decade, his experiments, along with those of colleagues, have pointed to prehistoric use of the material not just as a sunscreen and adhesive but also an insect repellent and leather preservative. This was an amazing adaptive advantage. He suspects ochre sunscreen evolved about the same time humans began using ostrich eggshells as containers for water and other provisions, about 65, years ago.
Not everyone in the field is as enthusiastic about a functional interpretation of ochre. I think the initial attraction was the color. The awareness of its other uses came gradually, over time. And humans appear to have adapted those uses to their needs. One of the obstacles to resolving how and why the rocks were used is in their very nature.
Whatever the application was is gone. The vast majority of ochre used is no longer part of the archaeological record. The remnants archaeologists are left with can still be impressive. The material was excavated in the s, but in Rosso and her team performed a high-tech analysis on the pieces, which are about 40, years old. Some modern artists mix Ocher with other acrylic paints in the same painting presenting a beautiful contrast of both earthy and bright colors. Anything naturally occurring including sand, ash or charcoal may be mixed into the white or other colors to make a different color.
Because of its use and value it was often traded between tribes of various regional areas expanding the color palette of trading tribes. Different Ochers have been found several hundreds of kilometers from its source which demonstrates it commercial use and desirability.
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