COLOURS IN REGARD TO LIGHT AND SHADOW.
Chap. CCXLIX.—Of the Light proper for painting Flesh Colour from Nature.
Your window must be open to the sky, and the walls painted of a reddish colour. The summertime is the best, when the clouds conceal the sun, or else your walls on the south side of the room must be so high, as that the sun-beams cannot strike on the opposite side, in order that the reflexion of those beams may not destroy the shadows.