This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
- Vegan, but not edible. [Photo by the author]
A surprising amount of art can be made by tools that have been burnt in a fire. Willow or vine charcoals are made from charred willow or vine branches. Verona Brown is the ancient pigment Terre Verte after being exposed to high heat. And there are paints made from burnt bone and ivory.
One of my former jobs was managing an art supply store. About a decade ago, I was helping a muralist pick out some economic, but decent paints for a large commission. She was going to need huge amounts of black, and the cheapest, low-grade fine art acrylic paint we had was labeled Bone Black. Bone Black is quite dark, and doesn't tend to brown at the edges or turn blue over time. Perfect for a large mural.
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But hold up - the muralist was vegan.
Understandably, she wasn't comfortable using a pigment made from bone. Bone Black is actually the relatively new pigment made from carbonized animal bones that replaced Ivory Black, made from, yup: ivory. Because oil painters tend to be a traditional, wary-of-change group, you can often find the name Ivory Black still on tubes of what might actually be made from Bone Black. The obvious alternative, Vine Black, made from charred plants, wasn't available in the line of paints suitable in the mass quantities of acrylic paint needed for the mural.
So what to do?
Knowing that formulas for paint often change without the descriptive names changing, I hunted around and found the supplier's number. I called them up, and customer service didn't know for sure if animal bones were used in making their bone black. They put me through to their chemist, an affable guy, quite happy to share their process.
I outlined the problem: we needed a vegan black.
No worries, he told me. They don't use animal bones in their product: the densities and impurities make it too inconsistent. "We use acetylene," he said, "like the soot you get when you hold a lighter under a pane of glass."
The paint chemist went on to assure me that was an oversimplification, after I joked that that process sounded like it must take a while. I thanked him, and said good-bye.
These days, to make acetylene black, "Acetylene black is produced in refractory chambers in the absence of air by the decomposition of acetylene gas preheated to 800° C (1,500° F). It is used in applications requiring high electrical conductivity, such as dry cells."¹ This is the same black carbon found in things such as batteries, and even rocket booster insulation and satellite shielding.²
And the best thing? It's vegan.
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carbon black. (2014). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/94868/carbon-black
Acetylene Black. Soltex Inc. Retrieved from http://www.soltexinc.com/pdf/Acetylene%20Black%20Overview.pdf
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All fine art paints are pigment particles bound in a sticky medium: vegetable oil (oils), gum arabic (watercolour), wax (encaustic), plaster (fresco) or acrylic polymer (acrylic).
This is the 5th post in the Pinch of Pigmentseries.