We are kitting out our studio with a track and black drapes. I have two choices, Black Wool Serge or Black Velour. The serge is cheaper and the manufacturers say that is what they usually use in studios. However, a cinematographer has told me that velour is 'blacker'. I put this to the manufacturer and they told me that though serge is indeed more like a charcoal colour, it has no sheen, whereas velour does.
Velour is crazy black. If you had the subject four feet from the backdrop, you could have the sun visit your studio and the Velour would stay black. I have never been able to light Velour where it gives off any gradations. It is possible to hit the Velour from the side and there will be a kind of sheen, but, you will see it and be able to adjust the light to less of an angle.
If you backdrop is going to be far from the subject (you have a big studio) I don