Grisaille was originated in Renaissance times and was used intensively in the Baroque. It is a technique for the large multiple figure compositions with no prior preparations or very little. The artist was sketching directly on the canvas with thin layers of paint - washes. Few colors were used and basically fast drying ones. With these washes it was possible to create the whole composition without making the canvas over-loaded with paint. Corrections were easy to do and all changes were done on the canvas. Then underpainting was used for final colors to be as sound as possible. None of the direct painters can come close to the quality of the colors of the indirect method.
Sargent was not a direct painter because he was going over and over, sometimes more than 40 times. The direct method is basically Impressionistic that never has the quality of color that we see in Old Masters indirect approaches. I call direct painting "Rooster approach" that can do cockle-doodle-do as soon as it opens its eyes in the morning - very natural and sweet but the method won't work for the conductor of some opera by Wagner.
