Note 15 — EASTLAKE'S HISTORY OF OIL-PAINTING.[13]
Reading edition
"The mediæval painters were so accustomed to this appearance in varnishes, and considered it so indispensable, that they even supplied the tint when it did not exist. Thus Cardanus observes that when white of eggs was used as a varnish, it was customary to tinge it with red lead."—Eastlake, p. 270.