The Blackest Black

Color is a prismatic subject, if we can strain an adjective to its limits.

Are black and white colors? Open your box of crayons; white and black will likely nestle in the neat rows. So, they’re colors, right?

In physical optics, however, black and white are not treated as colors. Check a human’s visible light spectrum – ROYGBIV – and you won’t find white or black. When photons are involved, white arises when all wavelengths mix, while black appears when no visible light presents. Black holes are named not because a cosmic artist stroked them with dark paint but because light cannot escape them.

The discrepancy comes from the nature of the media. Visible light is additive; pigments, such as those used by painters or crayon-toting toddlers, are subtractive. In other words, if different wavelengths (colors) of visible light hit each other, they combine. Put them all together and white light materializes; take them all away and one gets black. Subtractive is harder to visualize, to stretch a verb to its limits. When an object seems to be a color to humans, that object is reflecting that color’s wavelengths and absorbing others. Put a transparent yellow filter over a white background and your eyes will see reflected yellow light. If we add several filters, your stack begins to absorb more and more wavelengths. Add enough of the proper colors and the visible wavelengths might all be soaked, resulting in your eyes seeing black.

Additive light combines to form white light - image rendered by DemonD
Color filters begin to form black - photo by Zátonyi Sándor

Why do light and pigments present differently in the universe? To answer this question, I’ll have to point you to a different newsletter.

Whatever the reason, to human eyes, two methods to craft black technically exist. Either mix all the colors to keep your eyes from seeing all the wavelengths or completely remove all light. It’s relatively difficult to remove all light from the world. The sun, the moon, the stars, and human light pollution conspire to keep true darkness in check. If you want to, you know, actually see an object, then making it black by removing light is not going to work. (Aside: if our eyes show us an object is black because no light hits it, but, should light hit said object, it would be another color, is the object black or its “natural” color? To answer this, I’ll once again need to refer you to another authority)

So, we’ve resorted to creating black through pigments.

Through centuries of experimentation, humans developed black paint that absorbs 97.5% of visible light. That’s some good engineering!

While 97.5% is pretty nice, scientists see 2.5% in improvements ready to be made.

In the early 2000s, the United Kingdom’s National Physical Laboratory made a breakthrough in black technology. They developed a nickel-phosphorous alloy that could be spread on a surface. When exposed to acid, the alloy produced a super black coating. They aptly named this substance “super black.” The magic of this material comes from microscopic craters that were etched on the surface of the alloy by the acid. These cavities would cause less light to be reflected, especially from certain angles. Super black gobbled light 10 to 20 times better than the best traditional paint, upping the percentage of total light absorbed to 99.9%!

That figure is rather close to 100%. Normal engineers might say, “close enough!” Mathematicians and physicists would remind them that 99.9% does not have enough trailing 9s to equal 100. When it comes to totality, rounding is no good! Of course, the researchers pushed onward.

In 2009, a company called Surrey NanoSystems concocted a new black, though they did not publicly reveal this substance until 2014. Called Vantablack, this “paint” truly seems like voodoo. VANTA stands for vertically aligned nanotube arrays. Like super black before it, the makers of Vantablack understood that the darkest blacks would not come simply from mixing pigments. Instead, the wizardry would require veritable light bending. The substance is composed of carbon nanotubes, essentially miniature forests in coating form. When light enters the carbon forests, it bounces around from tube to tube. The light continues to bounce until it is absorbed and released as heat.

Vantablack captures 99.965% of visible light. It is so effective that it seems to warp human visual perception. This statement is not hyperbole. Vanta is so black that objects coated with it appear to humans as flattened, two-dimensional holes. They look like photoshopped FBI or NSA redactions.

Vantablack on wrinkled aluminum foil - photo by SurreyNanoSystems
Vantablack on more foil - photo by Surrey NanoSystems
Vantablack on two identical busts - photo by Surrey NanoSystems
A new type of black hole - photo by Surrey NanoSystems
Vantablack on a BMW - photo by Surrey NanoSystems

Surrey and Vantablack caused a furor after its release when they announced that British-Indian artist Anish Kapoor procured exclusive artistic rights to use the coating. Kapoor released an installation at Lisson Gallery in New York featuring the dark arts. Should anyone have a monopoly on a color? How much was the privilege worth?

Fortunately, Surrey did not intend to limit Vantablack to only the creative world. This substance has a vast number of scientific implications. From reducing extraneous light in telescopes to improving the capture of cameras, the potential boon for astronomy is manifest. More terrestrial applications exist, too, from cinemas to solar cells.

Anish Kapoor's installation at Lisson Gallery - photo from Lisson Gallery

As incredible as this innovation is, as close to perfect as its light absorption quality is, Vantablack is already a former champion.

In 2019, scientists at MIT unveiled a new material that reflects one-tenth the light of Vantablack, raising the absorption bar to 99.995%. In an ironic trick, as part of an art installation, they tested the creation on a multi-million-dollar diamond. Diamonds, of course, are composed of carbon. So, a coating of carbon nanotubes renders an expensive lattice of shiny carbon invisible. The dualities of the universe never cease to amaze.

In a power move, the MIT researchers do not seem to have named their material or color. It not only lacks reflective light, it lacks nomenclature.

Until recently, blacknesses of this level have been relegated to the realms of the theoretical. We know black holes exist, but we cannot exactly see them. We hypothesize craters of eternal darkness – spots that never see light thanks to quirks in planetary geography – but we’ve never visited one. Though super black, Vantablack, and MIT’s black are not complete absorbers, they might effectively be close to our limits for creating such a simulation.

As our ability to craft technology of greater and greater sophistication continues, the title for blackest black is likely unsettled. Someday soon, a new blackest black will push closer to 100%.

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