Some artists do it and some don't. Toning the canvas that is.
- You may simply not like the stark white surface when starting or find it distracting.
- It can help unify a painting, especially in the early stages before all the areas are covered.
- You may like some of the toned color peaking through.
- A toned canvas may make it easier to paint some subjects. (I regularly tone a canvas when I am painting a tree that has fine branches, leaving some to show through.)
- You want to set a mood.
- The white canvas is cold in color. That may distort some colors for you. They may appear warm next to the white until the canvas is completely covered.
- You may have more spontaneity with a toned canvas.
- The brightness of white may give a glare when painting outdoors.
- Some artists feel that with a toned canvas they can't record accurate color when putting paint to canvas.
- The whole canvas is covered in different background colors with the blockin. So, why bother with toning.
- You may lose some spontaneity with toning.
- With transparent paints, the white of the canvas can make the colors more vibrant and glowing.
- Some artists like some of the white canvas peaking through.
- You have the choice of several different think washes of colors over different parts of the painting.