Toning a canvas
For fast, one day paintings a toned canvas can be a real treat. I find that toned canvases work best if the toned color is dry on the canvas before I begin my painting. Therefore, I prefer to tone my canvases with a thin layer of acrylic because it drys so quickly and I don't have to worry about breathing in all of the fumes from the Terp. You can tone a canvas with oil color, but allow it to dry for at least a week before you intend to paint on it.
A toned canvas is simply a canvas that has a thin (watery) layer of a single color all over it. I like to tone several canvases at a time, and give myself multiple color options.
Toning allows the artist to leave canvas showing without having little white dots from the canvas texture.