Hi, I am currently doing a scientific project that requires a grey standard that extends into the UV range. What be the cheapest option? as spectralon is expensive.
You can also mix Black 3.0 (super-black) paint with barium sulphate and water to make your own grey standard with moderately good UV-vis-IR range reflectance (from about 1 to 30% reflectance). The coating is very delicate, but is very diffuse when sprayed on in multiple thin coats. Like all grey standards, reflectance does vary slightly spectrally, and you’ll need to measure this yourself.
See here: http://www.empiricalimaging.com/knowledge-base/make-your-own-colour-grey-standard/ for a range of options. Barium sulphate or simple plumbers tape are great!