I’m using burnt sienna and lead white for the underpainting. I use these colors for two reasons. One is that they have a low oil content. In oil painting, there is a fundamental rule to always paint fat over lean. In other words, to only use oily pigments in the top layers of a painting, and less oily ones in the bottom layers. If you break this rule, the paint films won’t be stable, and the paint layers could crack over time. The second reason is that I use a lot of warm, earthy colors in my work. Because bits of the underpainting show through in the finished painting, I want its color to be a harmonious one.
Here, I’ve premixed 9 values. The darkest value, #9, which is pure burnt sienna with no white added, is my darkest value. This is much lighter than the darkest value in the finished painting, which is a pure black. I always make my underpainting lighter in value than the finished work will be. I find that painting over dark values can dull the final colors. A lighter underpainting produces more brilliancy in the final painting. Also, if I decide to glaze directly over my underpainting, only a lighter ground will let light bounce back through the glaze.
One of the reasons for doing a monochrome underpainting is that it helps to unify the finished painting. Because burnt sienna is a useful color that I use a lot in my work, I often leave bits of the underpainting uncovered, to show through in the finished work. These areas of color showing throughout the painting help give the impression that the whole work is existing in the same space, lit by the same light. If you were looking at a snow scene, for example, everything would have the same bluish cool cast. The objects on a sunlit window sill all are bathed in the same warm, yellow glow. If any of the objects from the snow scene were painted with a yellowish tinge, or if one of the things on the sill were painted with a cool, blue light, they would stand out and not be seen as belonging in the picture.
I don’t paint in many details in the underpainting. I would just end up painting over them in the final layers, and I would have wasted my time. I am careful, though, not to loose the drawing. To this end, I leave edges much sharper than they’ll ultimately be. The underpainting serves as a guide for the painting to show me the outlines of objects, their placement and their relative values. Subtleties, such as the reflections in the vase, the shadings of color in the box, or the variations of values in the cloth are dealt with in the later painting stage. There’s no need for subtlety yet!
I do have to paint some details in the basket, though. If I were to loose the drawing at this stage, all of my work in locating the strips of bamboo would be lost. As I was painting the basket, I found that some parts of my drawing weren’t quite right, so I made corrections as I painted. Every time I redraw or paint an area, I take it as an opportunity to re-see and correct. As I’ve mentioned before, not all of these details will make it into the final painting, but I’d rather have them there in case I need them!
An advantage of doing an underpainting is that it makes it so much less intimidating when you begin to paint in full color. It’s easier to judge the correct value to paint if the area is already close to the correct value, as opposed to the stark white of the canvas. Also, it’s so nice to have all of the problems of drawing already solved!
I’m careful to keep the paint layer very thin in the underpainting. The thinner it is, the quicker it dries, and the earlier I can begin painting over it! I’m also careful not to leave many brush strokes in the paint. Brushstrokes can’t be very well-considered at this point in the painting, so I wouldn’t necessarily want them to show through to my finished layers! Also, if I were to need to re-paint anything, or move an object’s position, I wouldn’t want the texture of brushstrokes to reveal the original location. I use a feather brush to smooth away visible strokes.
With the drawing conquered, and the values set, I can begin the final painting with a lot of the difficulties behind me. Now, in the next stage of painting, I’ll be free to observe the subtleties of color and light without having to worry about placement, perspective, and values.