Although Titian's works seem to many to have been created without much effort, this is far from the truth and those who think so are deceiving themselves. In fact, it is clear that Titian retouched his pictures, going over them with his colours several times, so that he must obviously have taken great pains. The method he used is judicious, beautiful, and astonishing, for it makes pictures appear alive and painted with great art, but it conceals the labour that has gone into them.

Giorgio Vasari in "Titian of Cadore", in Lives of the Artists as translated by George Bull (1987), Vol. I p. 458.