Bob Atkins , Oct 06, 2008; 01:58 a.m.
Probably black velvet, though the way to make the black background black is by choosing the correct lighting and exposure to make it black. If it comes out grey, you're overexposing it. Try some negative exposure compensation.
Don't forget that an exposure meter wants to try to make everything a mid grey tone, so if you have a lot of black background in your shot, the camera will indeed try to make it grey.