All substances emit thermal radiation (at temperatures above absolute zero). Nevertheless, for any specific temperature and wavelength the total emitted thermal radiation is determined by the emissivity of the substances surface.

Emissivity of materials is defined as the ratio of the energy radiated from a substance’s surface to the energy radiated from an ideal emitter (black body emission / black body radiation) under the same conditions. It is a value between 0 for an ideal reflector and 100% for an ideal emitter.

The surface emissivity can be altered by applying the appropriate coating, for example high emissivity black paint, black anodized or ultimately Acktar vacuum deposited black coatings (pvd thin film) that reach the nearly ideal infrared emitter with the value of 98.5%.

The Blackest material with highest emissivity in the industry with a coating thickness of just 5 microns.

Emissivity of materials over wavelength range
Wavelength range 3-10 microns 3-30 microns
Emissivity Measuring Instrument Bruker – FTIR Devices and Services Emissometer
Coating Type
Ultra Black >98 >93
Fractal Black >97 >88
Vacuum Black >95 >85
Magic Black >93 >75
Coated Foils
Metal Velvet >98.5 >90
Spectral Black >97 >85
Scatter Black™ >97.5 >92