8
Well aware of the optical properties of both light and color, the artist worked
on a highly reflective, white ground layer. The underpainting could be a
complete gray-toned version of the finished image, painted in a manner such
as that described in the preceding basic technique. It could also be constructed
through a more sophisticated technique, as seen in the unfinished panel of
Santa Barbara by Jan van Eyck. An underdrawing, which establishes contours
and darks on the white ground layer, is covered with an imprimatura, a thin,
transparent layer of paint that allows the drawing to show through the ground
while also establishing a middle tone throughout the painting. Highlights
could then be added in white paint where appropriate, thus, with less work,
completing the values and creating a finished monochromatic underpainting.Regardless of the approach taken toward the underpainting, its creation was
essential to the technique itself. Color applied as thin transparent glazes al
lowed the fully developed underpainting to define the fo rms while the color
itself remained clean, pure, and unadulterated. Highlighted areas could be
achieved with the thinnest possible application of local color, as the white of
the underpainting had merely to be tinted appropriately. Dark tones, however,
posed some problems with the clear transparent pigments: many layers were
required to cover the underdrawing and establish the proper local color.By fo cusing on these highlights and shadows, visual identification of the tech
nique is quite simple. Highlighted areas are very thin and fine. Color applied
in thin glazes tends to be clear, luminous, and devoid of brush marks. Shadows
and dark colors, however, appear as thickly built-up surfaces, creating ridges
clearly visible in raking light where they come into contact with the delicate
light areas (Plate 2a, b).Highlighting with impasto white. Allowing a freer painting style and fa cilitating
larger fo rmats, this more flexible technique is typical of the Baroque masters.
Any support suffices; the underdrawing is optional. The artist tones the surface
with a middle or darker value, then creates the image with an underpainting
of washes that may be controlled or completely free and spontaneous. The
areas of the painting to be highlighted are now created with a heavy impasto
white paint.This simple procedure accomplishes the same optical effects as the complete
monochromatic underpainting of the previous transparent oil technique, yet
it allows the image to evolve as it is constructed. The continued separation
of value from color still allows fo r beautiful luminous color. Because the image
originates in the loose, dark washes, contours need not be highly defined and
extreme chiaroscuro is possible. The resulting work is often quite dramatic in
nature.This technique provides very specific optical markers. The darks are thin and
transparent, often revealing the preliminary wash or imprimatura. The high
lights that define the volume appear thick and visibly raised from the painted
surface (Plate 3a, b).Direct suiface blending. In the controlled technique of surface blending, indi
vidual colors and values are mixed and applied to appropriate locations of
the surface to indicate highlight and shadow. Each new application of color
is carefully blended into the surrounding paint, resulting in a smooth, con
tinuous flow. The underdrawing and underpainting serve only as a guide fo r
the surface painting; they do not actively affect the surface itself.All traces of brushwork can be blended out if desired; consequently, the tech
nique lends itself well to smooth, detailed, controlled styles such as fo und in
the work of the Neoclassicists.Visual markers fo r the technique include a smooth, continuous surface with
gradual, imperceptible shifts from highlight to shadow. Direct blending of the
pigments creates an opaque quality in contrast to the luminous character of
colors in the multilayered approaches (Plate 4a, b).Historical Painting Techniques, Materials, and Studio Practice