Bitumen paint is made to repair a leaking roof. It is dreadful stuff to work with, sticky, stinking and as black as can be. It is like the dregs of a barrel of crude oil, but when dried on a painting it can be a sublime, rich, and deep black. Pure black like Japanese lacquer, but with a velvety softness. Here a vivid red is enhansed by the black bitumen next to it, and the traces of colour in the lower panel.