"At first glance, these paintings may appear solid black. However, prolonged contemplation reveals the slow build-up of the surface through multiple layers and the close attention Rothko paid to gradations in tone and texture. Rather than annihilating colour and light, the Black-Form paintings appear almost luminous as their surfaces absorb and reflect light. The paintings invite the viewer to look more closely, introducing an element of duration and physical self-awareness into the process of perception."...hmmmm
Very good Mr Mendham... very good.
I'd like to take credit, but it's from the TATE's site: http://www.tate.org.uk/modern/exhibitions/markrothko/roomguide/room6.shtm