We are all familiar with the stunning sceneries on various cave walls, or ceilings, or buildings painted during historical times. From Africa to Europe, from Middle East to far Asia and Central America, people seemed to have used the same paint for thousands of years-ochre.
But what is ochre and why was so popular?
On short-ochre is a pigment obtained from clay minerals which contain iron (Fe) oxides or manganese oxides.
Clay minerals are found in nature in various chemical compositions depending on the geological conditions in which they formed and they vary across the planet and geological time. So the ochre from Sahara will be totally different from the one in Great Britain for example.
These pigmented clays vary in color from yellow to red (for iron based ones) and from brown shades to black for manganese ones. There are also purple, blue, green clays but these colors seemed to be underappreciated by our ancestors but they are spectacular.
Red beds in Grand Canyon, Arizona (blogspot.com)
Variegated clays in Peru (photo from handluggageonly.co.uk)
Limonite is the iron oxide (Fe3+) that gives the yellow color and it's the most frequent in rocks. It forms in volcanic environments, swamps (as we saw some posts ago), lateritic soils, marine sediments, weathering surfaces, but most abundant is in laterites (closer to tropics) and volcanic areas.
Red colour comes from another iron oxide-hematite (Fe2+) which is also very abundant in rocks. In comparison with limonite which is hidratated (contains water), hematite is not thus is easier to prepare and use. Removing water from rocks can be quite a pain in the ass and I can tell you from personal experience :))) but if you are lucky to be in a dry environment the exposure to elements will do it for you. Brown shades are possible thanks to goethite, another iron oxide and brown-black by manganese oxides.
Red powder obtained from Miocene clays, Bulgaria
Before art, people were using various types of clays as repellent against insects or sun protection (in warm zones), wound treatments, camouflage or in religious/symbolistic purpose. The type of clay used depends on its geographical accessibility and geological background. I am keep saying clay minerals because this is the natural product. Ochre itself it's a human-made product, based again on the local conditions.
How to prepare ochre
As I said, ochre is a secondary product. In order to prepare it, clay was collected from an available outcrop (a place where the rock or soil is exposed) and dried over fire, in the oven, or directly in the sun. Using heat allows controlling the final pigment shade since burning is oxidizing the material, thus the iron inside, intensifying the color. The rock was then grinded until it became powder and mixed with a lipid source. Lipids could be of both animal or vegetal origin. If they hunted something or had some animals sacrificed, best fat would of been collected, melted and mixed with the powder. The mixture could of been used after that in various purposes. Various oils could replace the animal fat and maybe even make things more appealing since it wasn't that stinky...Vegetal ingredients also made the composition structure easier to spread and thus easier to use. Later on, antiques learned to blend other pigments inside the recepy and even create a plenuria of new other colors based on natural pigments. We see them in temples, palaces, tombs or private buildings, especially in the Mediterranean area.
We don't know exactly what led the people to paint the first rocks, but probably they had the same desire like us nowadays to snapshot the beauty of the nature surrounding them or bring in the world personal feelings. They have found a way to expres the extraordinary and the ordinary in their lives giving us a glimpse in the past. First there were clumsy abstract drawings like in South Africa (Blombos cave-75ky), then bone painting and hand prints (first as a funerary practice) in Great Britain (Paviland, Wales-33ky) and Southern France (Pech merle-25ky) then the masterpieces from Lascaux (France~17ky) and Altamira (Spain~16.5ky), Algeria (Tassili n'Ajjer) or Egypt (Cave of swimmers). Ochre was used on every continent (except Antarctica, of course :p) until modern times and it was part of history since it was discover. Almost an intimate connection I would say.
People swimming in Western Desert (Egypt) before Sahara's aridisation (weeklyhubris.com)
I was just a sausage of few years old when I saw the first time the paintings from Sahara. It was a summer Saturday and the entire family was gathered in the front of tv to see the only program dedicated to natural sciences and history-Teleenciclopedia, running on the only available tv channel. The country was still struggeling to recover from communism and we lived in the countryside, so technical resources were extremely limited. I was staring at the vivid paintings with people swimming in a lake today extinct, telling a story of a wet Sahara. They looked so happy and peaceful and I promised myself that one day I will visit them. That day hasn't come yet but it's still in the top of my bucket list.
How is it in practice?
In order to show you how it can be done in real life, I will prepare some samples that I have from Bulgaria, collected when I started my PhD. The samples are taken from the coast area in between Bolata (to N) and Balcik (to S). They are Miocene (~10 million years) and the reddish ones come from bauxites (clay minerals formed on limestone alteration areas, rick in hematite), while the whitish ones are normal marine clays.
Because I work in a cool lab I preferred to freeze-dry the samples. You can do it in the classical way in the oven. The result will be better because the oxidation resulted from burning the rock will enlighten the colour. After drying the samples, I grinded them using a mortar and pistil until I obtained a fine powder and stored them in separate vials.
Sampling and preparing clays in the lab.
Since I work in a biomarker lab, getting lipids inside is sacrilege so I got the samples home. In order to prepare the actual pigment you need a source of lipids (fat) and it can be of animal or vegetal origin. During prehistory, people were using animal fat, but the Egyptians and romans preferred oils because the paint was easier to handle and probably less stinky. I have only olive oil, so I used that one. For a cleaner work environment I poured some olive oil in a cup and I used a spoon to transfer it in the vials with powder. To get a good balance for your paint, I advice to add as much oil as you have sample (so 50% powder, 50% oil). After adding the oil, mix it thoroughly util you get a homogenous paste and repeat if you have different clays.
Preparing the ochre paint by adding olive oil
After you prepared the pigment, grab a stone (mandatory cleaned before). During prehistory people were living in caves or rock shelters. This mean that they were using as canvas mostly limestones and sandstones. They are great since they have high porosity and permeability and absorb the fluid very fast. This allows the pigment to penetrate the rock and it will preserve the painting for a long period. If you have acces to limestones or sandstones it's perfect. You can also try directly on the wall. It will have the same effect. For the moment, I have only some hercynian schists from Taunus Mountains (these rocks formed >400 million years ago during the collision between Laurrusia and Gondwana, 2 paleo continents. The collision between them formed a series of mountain ranges that were eroded in time until they don't look as mountains anymore. They are almost flat now). Schists are not great for using natural pigments on them, but they are nice since they can be shaped easily into slabs (due to their schistuosity, preference to breaking on planes).
Attempt of painting
Once you have everything ready, just leave your imagination wild... Everything can be painted, real or imaginary. The first image that popped into my brain was a tiny baby goat jumping around. A bit stylized here for the sake of art or my lack of talent:)). Obviously my cat Edra do not approve and offers herself as muse :P. What can I ask for more?