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Super black is a surface treatment developed at the National Physical Laboratory (NPL) in the United Kingdom. It absorbs approximately 99.6% of visible light at normal incidence, while conventional black paint absorbs about 97.5%. At other angles of incidence, super black is even more effective: at an angle of 45°, it absorbs 99.9% of light.
Vantablack S-VIS, a sprayable paint that uses randomly aligned carbon nanotubes and very high levels of absorption from ultraviolet to the terahertz spectrum, has been exclusively licensed to Anish Kapoor's studio for artistic use. [31] The manufacturer claims that Vantablack is subject to export controls by the UK.
These coatings are useful in situations where high transmission through a surface is unimportant or undesirable, but low reflectivity is required. They can produce very low reflectance with few layers, and can often be produced more cheaply, or at greater scale, than standard non-absorbing AR coatings. (See, for example, US Patent 5,091,244.)
Although ordinary black paint has high solar absorption, it also has high thermal emissivity, and thus it is not a selective surface. Typical values for a selective surface might be 0.90 solar absorption and 0.10 thermal emissivity, but can range from 0.8/0.3 for paints on metal to 0.96/0.05 for commercial surfaces.
SRI measures the roof's ability to reject solar heat, defined such that a standard black (reflectance 0.05, emittance 0.90) is 0 and a standard white (reflectance 0.80, emittance 0.90) is 100. [44] A perfect SRI is approximately 122, the value for a perfect mirror, which absorbs no sunlight and has very low emissivity.
For example, white paint absorbs very little visible light. However, at an infrared wavelength of 10×10 −6 metre, paint absorbs light very well, and has a high emissivity. Similarly, pure water absorbs very little visible light, but water is nonetheless a strong infrared absorber and has a correspondingly high emissivity.
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634 S High St, Columbus, OH · Directions · (614) 221-1845