They say that the reason barns were painted red has everything to do with stars. Stars are the forge that create all the heavy elements like metals and it just so happens that iron (Fe) is one of the most abundant minerals in earths crust (and blood). Just to connect the dots... iron oxide is red (rust); however, I have my suspicions that barn paint may have been red lead... I haven’t researched it and I know about lead white paint, but not much about red lead paint other than it’s pretty much banned.
As an aside, red lead was a good rust inhibitor for steel and was ubiquitous in the construction industry when I started at age 13, and it was phased out and outlawed for most applications in my lifetime by 1978, along with other nasties like leaded gasoline. Red lead is lead oxide and I will spare you chemical formulas.
Surprisingly, lead white is rather popular in traditional oil painting, and probably goes back to Greek and Roman antiquity if not earlier (Egyptians maybe). It’s amazing how it’s made... a couple of ways like the stack process involving horse manure and terra cotta jars and forms lead carbonates. This really is not a blog post about chemistry, per se, so your safe. It’s not really about lead white, either. There is one thing I want to say about lead white though, and it’s true for red lead, as well... Lead tetraoxide/calcium plumbate... there I looked it up. Lead white forms a strong bond and tough film, is flexible, but it also forms soaps or salts that can damage paintings (after 300 years). That and lead paint is toxic, kids ate it and got lead poisoning and artists need to handle it carefully but because of risk of ingestion mostly. Don’t lick the paint brush bristles to make your point.
Lots of paints are made from toxic minerals... lead, lead white, red lead, lead-tin yellow, or lead chromate (chrome yellow) are just a few. There is cobalt, cadmium, and other heavy metals, chromium. In years gone by arsenic. Strides are being made to move away from toxic paints like cadmium free and lead free alternatives. Aside from cow pee and insect bodies or plants and chemistry, most paint is made from naturally occurring minerals (not plant based, inorganic) with long chemical formulas esoteric chemical or mineral names. Rocks and dirt, basically. Most of the browns and purples come from iron or manganese containing minerals... the ochres and siennas. There are every color family of ochres, red, yellow, orange, blue, green and even purple, not just browns. The yellow and brown ochres and siennas are considered dark yellows. Originally, blue oil paint was made from ground sapphires... then later ground lapis lazuli, but the Egyptians had learned to synthesize cerulean blue (Egyptian blue) but after Rome fell the recipe was forgotten.
In the late 19th century, chemistry improvements and the invention of paint tubes resulted in all kinds of vibrant new colors like synthetic paints. Oil paints come in two flavors, organic and inorganic. The organic colors (plant based) can be synthesized... the phthalocyanines, quinacidrones, dioxazines, pyrroles, and napthanols (and these are their color names). The inorganic pigments are basically and generally still just ground rocks or minerals, even if they could be synthesized. I’m pretty sure most contain metals though although maybe not all... carbon black or bone black, although that contains calcium, an alkaline earth metal. But it’s not one of the heavy metals associated with toxicity. Everything in moderation, right?
Which brings me to today, where we have current trends towards eco friendly, non toxic oil paints. Naturally occurring minerals in yellows, oranges, greens, blues, purples, browns and blacks. I recently purchased some reds and purples that were harvested from mine tailings. There are some serious pigment practitioners out there collecting rocks and dirts. Some make organic colors and dyes like indigo. I know some make inks from walnuts or coffee grounds. There are measures in paint materials... toxicity, opacity, and light fastness that matter.
There is an even newer innovation that mimics nature. Carbon Nano-tubes like Vanta black or black 2.0 that absorb 99% of all light that strikes it. Now there are even innovations in blues and greens utilizing the technology of butterfly wings that reflect the frequency of light that we see using layers of clear molecules like scales while passing the rest of the spectrum through the translucent aggregate of materials. They have not come out in tube paints, yet.