What material has the most uniform reflectance spectra, including visible, IR, and UV?
A material with the chemical name polytetrafluoroethylene (PTFE) that also goes by trade names of Halon and Spectralon is recognized as a very good and uniform (nonselective) reflector through the visible spectrum and into the ultraviolet and infrared wavelengths as well. It is sometimes mixed with carbon black to make a good, nonselective gray. As an example, Labsphere produces a selection of their Spectralon standards at various gray levels. They could provide more information on the reflectance properties outside the visible wavelengths.
