As of 2017, what was the darkest substance ever made?

Vantablack is not a paint, pigment, or fabric dye, but a coating of “Vertically Aligned NanoTube Arrays” made of pure carbon. When first produced in 2014 at the UK National Physics Laboratory, the then-nameless material absorbed 99.965% of visible, infrared, and ultraviolet light. Surrey NanoSystems (SNS), the United Kingdom firm that named and developed the substance, claims that no existing spectrometer can detect normal light reflected from it.

A nanotube is a group of carbon molecules arranged in a cylinder. The size of each of the nanotubes in Vantablack is 20 nanometers. A nanometer is one billionth of a meter. In the original process, the nanotubes were grown onto a surface, in a “forest” of particles. Around a million of them are needed to cover a 1 square cm area.

Photons of light that enter this forest get trapped there, in the gaps among the tubes. Only a high-powered laser light hitting the coated surface registers anything at all on a spectrometer, and those reading are extremely minimal. Most photons are absorbed and dissipate as heat.

The process of creating the nanotubes requires heat in the range of 400 degrees Celsius (752 degrees Fahrenheit). But SNS has developed a spray-on version of Vantablack, so the substance can be applied at lower temperatures. It traps 99.8% of light.