Painting with oil paint works in layers. In your first layer, you add solvent so your paint dries quickly and you can prepare a tonal surface for future layers. This layer is called the wash. A wash is a transparent application of paint that has been diluted with solvent. Underpainting develops the composition, placement and relationships between values from the start. The first layer is the best way to build contrast and tonal value into your painting. Underpainting also helps to create harmony in your final painting.
There are many ways to paint in layers, however, it's common to start with a sketch and then use diluted natural tones of one color (monochromatic) to paint in the broad areas of tone. When the first layer has dried, color can be added and paler tones worked in. Once these layers are dry, final applications of transparent glazes are added.
In a complementary underpainting, you select the color on the opposite side of the color wheel as your dominant final color.
Colors that are complementary to the dominant color of our painting subject will make the dominant color seem less overwhelming and easier to vary.
This layer will create backlighting shadows that will tone the entire painting and provide contrast.
For example, you would start a painting of blue water by a ground tone of orange.
In a monochromatic or tonal underpainting, you select a natural color like burnt sienna or ochre and map out the value structure of the painting.
This method is useful for creating light and dark structures that look more realistic and help to develop precision with light and shadow. It is also useful as it allows you to concentrate on form and tone first, rather than color.
When attempting an underpainting, one of the best ways to start is by thinning your paint with solvent so you can remove areas easily and the layer dries faster.
Glazing involves painting a thin layer of transparent or semi-transparent paint onto dry layers. In doing this, each subsequent layer changes the appearance of the color below giving the painting depth. This technique can achieve finely detailed results.
To thin the oil paint, you’ll need to use an alkyde medium like walnut oil or liquin. Alternatively, you can use linseed oil. This will add glossiness to your pigment.
Pick a reference photo of your choice and create an underpainting for it.
You can choose to make it complementary or monochromatic.