The underpainting is part of the indirect painting technique process, a complex, systematic approach to painting with oil medium that is created in layers; as its name suggests, the underpainting is the first layer of paint; it is generally viewed as a tonal layer of the final painting; in the Flemish schools, the underpainting would traditionally be a gray-toned version of the finished image created over an initial outline drawing; traditionally, underpaintings were created using warm earth tones, neutral grays or warm brown, such as the use of raw umber, often mixed with black.
The Purpose: of the underpainting is multifold, to allow the artist to focus exclusively on the tonal aspects of the painting, to create a first layer of paint to better serve the top layers of colour that follow, to fix the composition, to give volume and substance to the forms, and to create the distribution of darks and lights.
‘Dead Colouring’: the underpainting can also be called dead colouring phase, since it doesn’t use colours.
Layering Process: colours were then applied only when the underpainting was accurately dried.
Unique Advantages: underpaintings allows the artist to create specific optical effects that cannot be created otherwise; direct painting methods, cannot achieve the same brilliancy or luminancy.
Originally used by the Flemish and early Netherlandish masters, when painting began to be conceived as a multilayered object, where volume was developed in a monochromatic study during the underpainting, and then color layers were subsequently added; it is generally accepted that once the underpainting was complete, they used dozens of layers of glazes of colors, to achieve their rich vibrancy and brilliancy.
In the unfinished painting, Santa Barbara by Jan van Eyck, the underpainting is left half way through completion; in this case, an underdrawing defining contours is covered with a thin layer of paint, the imprimatura, establishing a middle tone value of color throughout. Andrea del Sarto’s Portrait of a Woman in Yellow, reveals a sketchy brown underpainting on the right side of the portrait. Leonardo da Vinci’s unfinished Adoration of the Magi, the initial drawing (the Virgin) and various parts and stages of the underpainting can be seen, revealing Da Vinci’s painting process, which in general, was always very accurate and used the underpainting very rigorously. Vermeer’s works were created with a rather sketchy underpainting, usually created with brown and black.
It is believed that both Rembrandt and Rubens used underpaintings prolifically, and that they had a number of paintings only at the underpainting stage, waiting for clients to want to buy them in order to devote the time to finish them.