This looks like good stuff for the interior of mirror boxes
Protostar Telescope Making & Upgrading (http://www.fpi-protostar.com/flock.htm)

if you search on "telescope flocking" you will find other alternatives too

but it is not as good as nanotube black :-) which isnt a product yet I think
Nanotubes yield the blackest black › News in Science (ABC Science) (http://www.abc.net.au/science/articles/2008/01/16/2139711.htm)

Peter Murphy