Wiktionary
n. (context arts English) An initial layer of paint, often monochromatic, applied to a ground as a base for subsequent layers.
Wikipedia
In art, an underpainting is an initial layer of paint applied to a ground, which serves as a base for subsequent layers of paint. Underpaintings are often monochromatic and help to define color values for later painting. There are several different types of underpainting, such as veneda, verdaccio, morellone and grisaille.
Underpainting gets its name because it is painting that is intended to be painted over (see overpainting) in a system of working in layers. There is a popular misconception that underpainting should be monochromatic, perhaps in gray-scales. A multi-color underpainting was thought to be more useful by artists such as Giotto (whose technique is described in detail by Cennino Cennini), as well as by Jan van Eyck and Rogier van der Weyden (whose technique has been studied with modern scientific analysis). This technique was pioneered by Titian in the High Renaissance. The colors of the underpainting can be optically mingled with the subsequent overpainting, without the danger of the colors physically blending and becoming muddy. If underpainting is done properly, it facilitates overpainting. If it seems that if one has to fight to obscure the underpainting, it is a sign that it was not done properly.
Usage examples of "underpainting".
Using reddish outlines, he lays in washes of ochre, highlighted with white when the underpainting is dry.
Virgin, where she looked now, the highlights were not opaque colors on the surface, but from the light underpainting tinted with ultramarine.
On that Tuesday, on the grey-white underpainting, I lightly drew in pencil the head of a still-young woman, with a face already strongly defined by character, a face of good bone structure, of intelligence, of purpose.
Clear, unmuddied gray, unsullied by underpainting, by impure pigments.
Yet he must paint with the perfection of a finished piece which would normally have had time to dry after the underpainting was complete.
He regarded the portrait of Renayo, still in half-tones, deadcolor and underpainting visible.
Then, into the interstices and the dark corners of the painting, the shading and the shadows, he traced the chain of signs that linked illness and poison and death, insinuating them into the underpainting so no outward face would ever show of this spell.
It should have been an awkward composition, and indeed one section of the painting remained unfinished, white ground unsullied by sketch or underpainting or the glazes and frotties of a finished portrait.
Tuesday, on the grey-white underpainting, I lightly drew in pencil the head of a still-young woman, with a face already strongly defined by character, a face of good bone structure, of intelligence, of purpose.
Clear, unmuddied gray, unsullied by underpainting, by impure pigments.
He regarded the portrait of Renayo, still in half-tones, deadcolor and underpainting visible.
It should have been an awkward composition, and indeed one section of the painting remained unfinished, white ground unsullied by sketch or underpainting or the glazes and frotties of a finished portrait.