Now that the local colors and forms are in place, I can begin to deepen the shadows with dark glazes and lighten the light areas with scumbles. Here I’ll show you the process with the green cloth. For the cool shadows cast by my warm light, I mix ultramarine blue with a little raw umber and alizarin crimson. I mix a bit of glaze medium into my mixture, which makes it more transparent and liquid. I apply the glaze with a soft sable brush, feathering out the edges. I wipe and blot the excess glaze off of the painting with a cotton pad, leaving a transparent layer. Often this first layer isn’t dark enough. That’s fine. I can always let it dry and add another layer. I actually prefer to do this, as it’s easy to add more, but impossible to take away. Also, I find that many layers add interest, as the glazes are always slightly different and you can see one through another. You can see in the bottom of the image how the underlayer of green shows in places through the dark glaze. This gives the look of a luminous shadow.
For the light areas, I add scumbles, which are dryish coatings of thick, opaque, light colored paint, lightly dragged over the dried underlayer, usually with the flat side of a stiffer, ox-hair brush. The paint catches only on the top fibers of the canvas, resulting in a a speckly, pebbled surface, that beautifully mimics the look of light bouncing off of the fabric. Scumbled colors always have a cool quality, so for a warm light, as on the right, I have to use a much yellower paint than you would first imagine. The scumbles on the left side are depicting cool light coming in through the window, so the coolish bluel color looks fine there.