How Black is Black?

As noted in a number of British journals in early February, including New Scientist (February 6, 2003)—reports brought to our attention by SGHT contributor J. Gordon Holt—scientists at the UK's National Physical Laboratory (NPL) have developed a new super-black coating that is said to reflect less the 0.35% of the light that strikes it, an absorption efficiency about seven times better than black paint. The coating can be put on materials ranging from metals to ceramics.

In case you're wondering about painting the walls of your home theater room with it, however, producing the video equivalent of an audio anechoic chamber, you can only do so by immersing your walls in a solution of nickel sulphate and sodium hypophosphite for five hours, then etching it with nitric acid. The black, pitted, nickel and phosphorus coating that results cannot be made into a paint.

If the process proves to be relatively workable and affordable, however, the possible video equipment applications are intriguing. Lenses, all the way from the camera to the projector, could profit from reduced internal reflections. Most exciting, however, is the potential for increased contrast in digital projectors. A DLP projector, for example, has to redirect the light from its bulb away from the lens in order to reproduce black. The better the redirected light is absorbed within the case, the darker the black—and the more detail in the information just above black that's no longer being washed-out by stray light.

Nothing in the articles suggests how practical it may be too use this material in such an application (the most frequently mentioned uses are in space technology). But several artists have expressed interest in using the material, suggesting that widespread use in fields with limited budgets may not be wishful thinking.

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