One of the oldest pigments ever used by humans is Ochre. It comes in a variety of shades; everything from yellow to green and red. Today I'm going to talk a bit about the history of ochre in general and a bit about what makes burnt ochre different than regular ochre.
The earliest known use of the pigment ochre is from about 285,000--for you history buffs that was during the time of the Homo erectus. A site in Kenya (called GnJh-03 incase you wanted to look into it) yielded a cache of ochre equalling around 11 pounds in a variety of sizes. Its clear that it was being mined and saved for use although for what scientists aren't quite sure.
It was prominently used by neanderthals to paint the interiors of their shelters. There are two different preserved sites from this time period (around 250,000 years ago) one in the Netherlands (Maastricht Belvédère) and one in Spain (Benzu).
Art created during the middle stone age (10,000-8,000 BCE) featured ochre pigment prominently and scientist Carlos Duarte (2014) has argued that there seems to be some evidence that the first human tattoos were created using red ochre during this time period.
Chemically, ochre is comprised of iron oxide and sometimes calcined iron oxide with a variety of hydrated iron oxide and manganese. Other minerals can also be present depending upon the mine site. Interestingly enough this simple foundation of iron oxide creates a multitude of pigments that most people don't even know are technically an ochre! Bloodstone, Burnt Hematite, Burnt Sienna, Sienna, Mummy Brown (modern version) Hematite Violet....all are technically ochres! Its the secondary elements and proportions that make the astounding variety of pigments. At my last count there are 47 different unique artist pigments made with ochre!
Today I'm going to talk a little bit about burnt ochre. In all likelihood this was the first modification that early humans made to ochre mined out of the earth. When its exposed to heat the pigment dehydrates and transforms from a bright yellow into a brown toned color. Ochre in general tends to be a very dry pigment--quick to dry down and cures quickly when made into paint. But its been my experience that this is even more true for burnt ochre. It can also get very dry and crack in the pan when in watercolor form. Don't panic if this happens to you--a small amount of glycerine can help to offset the drying if it really bothers you.
Burnt Ochre that is made from natural pigments and not its man-made counterpart looks very different in the pan or tube than it does on the paper. My students are often shocked at just how much yellower it paints up. This is why its important to look carefully at both the swatch and if possible the chemical composition of your paint if you're buying online. Synthetic burnt ochre (and I mean the those that simulate the color NOT the kind made with man-made iron oxide) has a different look to it, even if the color matches. Its also important to note that the opacity of burnt ochre can change depending upon where the pigment is sourced from--because there can be impurities that make it more opaque. Chemically yellow ochre is: FeO(OH), it is extremely stable and has strong lightfast qualities.
Here is what it looks like painted up:
Its important to note that burnt ochre has become a color in its own right (and not just a reference to paint made with the chemical formula) and the name is often used indiscriminately regardless of what pigments are actually in it. For example I've seen leather that is colored "burnt ochre" but is not actually dyed with ochre! Even within the realm of real burnt ochre there is a wide color array so its important to see a swatch of it painted whenever possible; even knowing the chemical formula you won't be able to tell you how it looks when painted with. Like with so many things in color theory, don't expect all things with the same name to present the same or paint the same!
I hope you enjoyed reading a bit about this amazing pigment and the next time you load up your brush with burnt ochre you can think about the fact that you are using the same pigment that our ancestors did over 200,000 years ago!