A Treatise on Painting/Chapter 266
Chap. CCLXVI.—How to detach Figures from the Ground.
All solid bodies will appear to have a greater relief, and to come more out of the canvass, on a ground of an undetermined colour, with the greatest variety of lights and shades against the confines of such bodies (as will be demonstrated in its place), provided a proper diminution of lights in the white tints, and of darkness in the shades, be judiciously observed.