Forty Thousand Years of Black, and Only Seventy of Them Petroleum

Humans have been making black colorants from plants for longer than we have had agriculture, writing, or cities. The fossil fuel era is the short and strange chapter in that story.

By Jane Palmer, CEO, Nature Coatings

Somewhere in southwestern France, on a limestone wall in the dark, there is a bison drawn in charcoal. It is roughly thirty thousand years old. Whoever made it burned wood, let it char, picked up what was left, and drew. That is the entire process. It is the oldest continuously used pigment technology on earth, and it has never really stopped working.

I think about that bison more than you might expect for someone who runs a modern pigment company. Because the thing that strikes me is not how primitive it was. It is how correct it was. Char plant material, capture the carbon, make black. Forty thousand years later, that is still the only fundamental way anyone makes a true black pigment.

For most of recorded history, the answer to that question was whatever grew nearby. Vine black came from charred grapevines and stems and produced a beautiful cool, bluish black that Renaissance painters prized. Lamp black was soot, collected from oil lamps burning in low oxygen, and it is old enough to appear in Egyptian tomb painting, on Greek pottery, in Roman wall decoration. In Han dynasty China, finely prepared lamp black bound with animal glue became the inkstick, which then carried two thousand years of calligraphy, painting, and scholarship. Chinese ink dates to the twenty-third century BCE, originally just charcoal powder mixed with water.

Bone black came from burnt bones and gave a warmer, browner black. Ivory black, ground from actual ivory, was the richest of all of them and priced accordingly. Charcoal was the cheap workhorse, gritty and difficult to handle but everywhere. A sixteenth century painter had a genuine palette of blacks to choose among, each with its own temperature and undertone, all of them made from something that had recently been alive.

Black also carried more cultural weight than almost any other color, and the weight kept changing. In Egypt it belonged to Anubis and the afterlife. In medieval Europe it signaled sin in a hell scene and humility on a monk. Then in fourteenth century Italy and Burgundy it became the color of power and sobriety, the shade the wealthy wore to be taken seriously, and it has never entirely lost that association. Four thousand years of symbolic reinvention, and the material underneath was always the same: charred organic matter.

Then, in the span of a single human lifetime, the feedstock changed and almost nobody noticed.

The industrial revolution created enormous demand for black, and the twentieth century answered it with the furnace process. The chemistry is not conceptually different from what happened on that cave wall. You still burn a carbon-rich material with and collect what remains. But the material fed into those furnaces was no longer vines or bones or wood. It was petroleum: aromatic oils, coal tar distillates, the heavy leftover fractions of refining. Feedstock is sprayed into a brick-lined chamber running above 1,400 degrees Celsius, pyrolyzed, quenched with water, and filtered out as powder.

It worked extraordinarily well and it scaled almost without limit, which is why it took over completely. The overwhelming majority of it went into tires and industrial rubber, where carbon black is a structural reinforcing filler rather than a color. But the same furnaces also supplied the ink, the coatings, the plastics, the textiles, and the cosmetics. Petroleum became the default answer to a question humans had been answering with plants since before we had agriculture.

The problem is what comes along with the feedstock. Burning heavy petroleum fractions produces polycyclic aromatic hydrocarbons, some of which international health agencies classify as carcinogens. It produces particles at the nanoscale. It carries residual volatiles. None of that was true of vine black. It is a property of the source, not of the color, and it arrived as a package deal that the industries buying black had no realistic way to decline.

That is the part worth sitting with. For four hundred centuries, black was a plant product. For roughly the last seventy years, it has been a fossil fuel product. We tend to treat the current arrangement as the natural state of things, the baseline that any alternative has to argue against. Historically, it is the anomaly. It is a brief detour that happened to coincide with the period when industrial chemistry got very good at using petroleum for everything.

Which is roughly the thought I had, years ago, standing in a factory watching black ink move through a mixing tank and understanding for the first time where it came from. The path forward was not to invent something unprecedented. It was to go back to the feedstock humans had used all along and apply modern process engineering to it. Wood waste, already generated in enormous volume by sawmills and construction and mostly burned or landfilled, turns out to be an excellent feedstock. 

Converted in a closed loop, with no added chemicals, on renewable electricity, we called the pigment we created BioBlack. It produces a black that is carbon negative, and free of the PAHs and nanoparticles that came bundled with petroleum. It’s a modern material that does not burn the wood like they did in the old days.

The chemistry of what we make would be entirely recognizable to whoever drew that bison. Char plant material, capture the carbon, make black. What has changed is the precision: consistent particle structure, controlled jetness and tint strength, verified through third-party life cycle assessment, certified through chain of custody back to the forest. The oldest pigment technology on earth, run with instruments.

So when someone describes bio-based black as a novel material, I understand the reflex, but the history runs the other way. Petroleum black is the novelty. Wood is what we always used. We are not asking industries to try something unproven. We are asking them to come back to a forty thousand year old idea, now that it finally performs.