Oil Painting Lesson 6: Underdrawing & Underpainting
Understanding the Underdrawing
Underdrawings can be incredibly useful, especially if you are embarking on a complicated still-life composition. There is no rule to say that you should always do an underdrawing first, but even the simplest outline on your canvas can really pay off.
I find that I can begin painting with much more confidence knowing that I have already figured out the most important elements of my subject. There is also much less chance of my painting going wrong from the start.
An underdrawing can be approached in a number of ways, using different materials, including charcoal, pencil, pastel, and diluted oil paint. Ultimately, it comes down to personal choice and whatever works best for you.
Each project in this series focuses on a single everyday object, which automatically makes the composition more straightforward. Even so, I always begin by looking at my subject through a viewfinder to check that I am happy with the composition.
Creating an Underdrawing Step by Step
Establish the Center and Main Outline
Start by measuring the vertical halfway point of the canvas. Using a sanguine pastel pencil or graphite pencil, make small marks at the top and bottom. These marks will help you position your subject—in this example, an apple—in the center.
Next, mark out the horizon line, slightly off center. On my 4-inch (10 cm) square canvas, this falls about 1½ inches (4 cm) up from the base.
You can now begin drawing the outline of your subject. Take your time to check the proportions and overall placement before moving on.
Mark the Highlights and Shadows
Next, draw the outline of the highlight and the cast shadow. Squinting at your subject can help simplify the details and make the main tonal areas easier to identify.
Mark out the core shadow and the area of reflected light as well. The core shadow is the darker area on the form, away from the direct light, while reflected light is light that bounces back onto the shadow side from nearby surfaces.
At this point, your underdrawing already contains plenty of useful information, and you could leave it here and begin painting. However, adding some shading can make it easier to understand the tonal structure before you start applying color.
Add Shading to Understand Tonal Values
You may wish to add shading to the key areas of your subject. This will help you work out the tonal values, from darkest to lightest, and will in turn act as a guide when mixing colors.
Keep the shading simple. The aim is to identify the main light and dark areas, not to finish the painting before you have even started.
Understanding Underpainting
As with underdrawings, it is not compulsory to begin every painting with an underpainting. However, an underpainting can be an extremely useful way to establish the all-important values of your subject before adding color.
It allows you to control the tonal balance of your work from the very beginning. Instead of trying to solve drawing, values, and color all at once, you can first concentrate on the relationship between the lightest and darkest areas.
An underpainting is often made with faster-drying, earthy colors, such as Raw Umber. One of the best-known approaches is the simple grisaille, in which a single color is used to create a range of tonal values.
In a diluted grisaille, the paint is thinned to produce lighter-looking passages, while stronger, less diluted paint creates darker areas. The final appearance also depends on the paint, the surface, and how much of the ground remains visible.
Alternatively, you can create a more opaque grisaille by mixing your chosen color with white paint rather than relying only on dilution. This approach can produce a wider range of opaque values, but it may take longer to dry.
Creating an Underpainting Step by Step
Block In the Darkest Values First
My personal preference is to paint the darkest values first. Start with Raw Umber that has been only slightly diluted, using it almost straight out of the tube.
With a filbert brush, block in the darkest areas of your subject, following the guides established in the underdrawing. These areas may include the core shadow, the darkest part of the cast shadow, and other deep tones.
Keep the initial marks simple and concentrate on placing the dark shapes accurately.
Work from Dark to Light
Dilute the paint further as you move from dark to lighter values. In this example, the reflected light on the underside of the apple is blocked in with a much more diluted mixture than the dark paint used in the first step.
Compare each area with the others rather than judging it in isolation. Ask yourself which parts are darkest, which are lighter, and where the transition between them occurs.
Remember that an underpainting is intended to be painted over once it has dried. It does not have to be perfectly neat. The important thing is to establish the main areas of light and dark.
Complete the Monochromatic Underpainting
Block in the rest of the apple, as well as the background and foreground. You will now have a monochromatic version of the apple painting and a much clearer understanding of its tonal structure.
In principle, you can establish the main values using just one color, such as Raw Umber. A small amount of white can also be used to extend the range of values when needed, as shown in this example.
Compare the darkest areas with the lightest ones and check that the apple remains convincing in terms of form and lighting. You can make adjustments before introducing the complexity of color.
How Long Should an Underpainting Dry?
A thin underpainting made with a fast-drying earth color such as Raw Umber may become touch-dry relatively quickly. However, drying time depends on the paint formulation, how much medium or solvent has been used, the thickness of the layer, and the conditions in your workspace.
Before painting over your underpainting, make sure it is sufficiently dry for the next layer and follow the paint manufacturer's guidance. Do not rely on a fixed 24-hour rule for every painting.
Final Tips for Better Underdrawings and Underpaintings
- Start with proportions. Check the placement and size of your subject before adding details.
- Identify the major tonal shapes. Mark the highlights, core shadows, cast shadows, and reflected light.
- Keep your first marks simple. An underdrawing is a guide, not a finished work.
- Think in values before color. A convincing range of lights and darks gives your painting a strong foundation.
- Use materials thoughtfully. Follow the safety instructions for paints, solvents, fixatives, and other studio products.
- Allow adequate drying time. Check that the underpainting is ready before applying the next layer.
An underdrawing and underpainting are not compulsory for every oil painting, but both techniques can make the process more manageable. By establishing the composition, identifying the main shadows and highlights, and organizing the tonal values in advance, you can begin adding color with greater confidence.
Practice these steps with a simple everyday object, such as an apple. As you become more comfortable with the process, you will learn when a detailed preparation is helpful and when a simple outline is enough.