“[In Leone Battista] Alberti’s Della Pittura . . . the treatment of light and colour is discussed. For Alberti . . . white and black serve the all-important purpose of creating the impression of relief. To achieve this purpose, we learn, the painter must always balance the whites against darks. He suggests in fact that the painter should proceed in a gradual process of adjustment, always adding a little white here and a little black there and watch the form acquiring relief. . . .

Modifying a remark Vitruvius makes about minium, he says that he wishes white pigments were as expensive to buy as the most precious jewels, for then painters would use them sparingly. . . . He knows—and he may have been the first to know this—that the painter’s gamut of relationships can never match the range of light intensities that can occur in nature. He must scale them down. The painter must remember—he writes—never to paint any surface so white that it could not be whiter still. Even if you dressed your figures in the most shining white you would have to stop short very far from utmost whiteness. For the painter will find that he has nothing but white with which to render the extreme lustre of the most polished sword and nothing but black to show the utter darkness of night. The power of a correct juxtaposition of black and white can be seen where vessels appear to be of silver, gold or glass and seem to shine, though they are only painted.”

—E.H. Gombrich, Light, Form and Texture in Fifteenth-cenury Painting, first published in the Journal of the Royal Society of Arts CXII, October 1964.