The Oil Painter's Bible - chapter 6
glazes, which are then worked into, while wet, with opaque pigments. The paint is worked together wet
into wet until the desired effect is achieved, or until the paint becomes slightly tacky, at which time it is
allowed to dry thoroughly. This process may be repeated as many times as necessary.
At some point, someone, perhaps Titian, discovered that a light, opaque tone, rendered
semitransparent by the addition of a bit more oil and/or simply by scrubbing it on thinly with a stiff brush,
applied over a darker area produced an effect that could be put to good use. This is what we now call a
scumble. It was found that a scumble over a flesh tone would produce the same effect as powder on a
woman's face; that is, it made its texture appear softer. This is a useful device when painting women and
young people of both sexes. It is also useful for indicating atmospheric density over distance, or
atmospheric perspective. See Chapter Five, Principles of Visual Reality. Both glazing and scumbling
create optical illusions. As such they effectively expand the capabilities of the limited palette of the early
painters in oil. It was imperative that they get the most out of the materials they had.
Glazing is the application of a darker transparent paint over a lighter area. The optical illusion created
by the light rays’ having passed through a transparent darker layer, bouncing off the lighter surface
underneath, then traveling back through the transparent layer to the viewer’s eyes, is unique to glazing,
and cannot be obtained in any other manner. A warm glow is created, and the color thus produced appears
warmer and more saturated (higher in chroma) than the same pigment applied more thickly and opaquely.
The effect, in the darker passages, is that of a shadow seen up close, with no atmosphere between the
viewer’s eyes and itself. The rich, golden glow in Rembrandt's dark browns is produced in this way.
Rembrandt was influenced by Titian, and is reported to have at one time owned at least one of his
paintings. Glazed darks appear darker than opaque darks, because the light rays are allowed to penetrate
more deeply into the paint layer, and are thus subjected to a great deal of filtration before reflecting back
out to the viewer’s eyes. This effectively expands the value range possible with paints, which are
handicapped on the light end of the spectrum by the fact that white paint is not as light as light in Nature.
The Old Masters compensated by carrying their darks as far as they could, to create as wide a range of
values as possible. This can only be accommodated through the use of transparent paints on the dark
extreme. Furthermore, as light contains color, the artist must make the highlights darker than white in
order to include color in them. This further limits the value range, and makes necessary the darkening of
all tones by a corresponding amount in order to maintain the proper contrast and relationships between
each category of light or shadow. Transparent darks allow the expansion of the dark end of the range.
Scumbling is the opposite of glazing. A scumble uses a lighter opaque paint, spread thinly enough so
as to become translucent, over a darker passage. The optical effect thus produced is bluer than the paint
applied, as the underlying layer is not completely obscured, and exerts its influence on the overall
sensation, as has been previously described. It is very effective in softening surface textures, as soft cloth,
such as velvet or cotton, or youthful complexions, the surface of a peach, etc., and, as mentioned, for
indicating atmospheric haze over distant land planes and in the sky near the horizon. Overcast skies may
be scumbled all over, as in Bouguereau’s “The Broken Pitcher.”
There are still more advanced and sophisticated developments of the Venetian Technique. The
"semiglaze", which can be either transparent or semiopaque, or anywhere in between, is a very thin
application of color to an area of the same value as the paint being applied. Its purpose is to modify the
color of a given area after that area is dry, as in the addition of a tiny bit of vermilion to a cheek or nose,
and/or to allow subsequent wet into wet painting over an area in which the paint has dried. It tends to
soften unintended too-harsh transitions of tone from the previous sitting, if used properly, and thereby
adds a higher degree of refinement to the image. It is applied thinly, by scrubbing it on with a stiff brush,
after the addition of a small amount of oil or a painting medium to lubricate the dry surface of the area to
be repainted. Titian is reported to have sometimes applied glazes and semiglazes with his fingers, or
perhaps he was wiping the excess away after having put too much on with a brush. Stippling with a flat
tipped brush is a good technique for applying glazes, scumbles, and semiglazes, though other means work
very well in skilled hands. As a further development of the Venetian Technique, the underpainting, or
certain parts of it, may be executed in opaque color, rather than totally in neutral greys. One popular
variation was Venetian Red and Flake White. The underpainting palette should be limited to lean paints
(paints with low oil absorption) which are opaque and/or very high in tinting strength. High tinting
strength fat paints (paints with high oil absorption) may be used if mixed in very small quantities with
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