The Painter in oil

The scumble may be used with the richer and darker colors, too, to modify towards
richness the tone of parts of the picture, or to darken the value. Most often, however, its
value lies in its use to bring harsher and sharper parts together, and to give a hazy effect
when it is needed.
Scumbling will not have a good effect when it is not intended to varnish the picture
afterwards; for the oil in the paint is absorbed immediately, and the rubbing of color
gives a dead look to the canvas which is very unpleasant, and decidedly the reverse of
artistic.
Glazing. - A very valuable process, the reverse of scumbling, is glazing. It has always
been in use since the invention of the oil medium. All the Italian painters used it; it is an
essential part of their system of coloring. The rich, deep color of Titan, the warm flesh of
Raphael, and jewel-like quality of the early German painters are impossible without
some form of glaze. The Germans perhaps made glazes with white of egg before oil was
used as a vehicle. But the glaze is the only way to get the fullest effect of the quality
characteristics of the transparent paints.
A glaze is a thin wash of transparent color flowed over an under-painting to modify its
tone or to add to its effect. It is not always transparent color, but usually it is. Sometimes
opaque or semi-opaque color may be used, and it is a glaze by virtue of the fact that it is
thinned with a vehicle either oil or varnish, and flowed on. A scumble is rubbed on, and
is never pure transparent color.
Advantages of Glazing. - The advantages are the gain in harmony, in force, in
brilliancy; you may correct a color when it is wrong, or perfect it when it is not possible
to get the force or richness required without it. These are qualities which have made use
by all schools more or less.
Disadvantages. - There are, however, quite as evident and marked disadvantages.
The free use of oil as a thinning vehicle, although it makes possible a greater degree of
richness of color, is very likely to turn the picture brown in time. Oil will always
eventually have a browning effect on all paints, even when mixed with them as little as is
absolutely necessary. If you make a tinted varnish of oil (which is practically what a glaze
is), you add so much, to the surely darkening action of the oil on the picture.
If, again, you depend upon a glaze for the richness of color for your picture, and you
use a color which is not permanent, you glaze fades, and your color is not there. A glaze
is particularly liable to be injured by the cleaner if it ever gets into his hands. He works
down to fresh color, and what with the browning of the glaze and the fact that the
cleaner is more anxious that the picture should be cleaned than that its colors should be
fine, he will, in nine cases out of ten, clean off the glaze which may be the final and most
expensive color the painter has put on it.
Glazing is little used nowadays, compared with what it once was. But there are times
when you cannot get what you want in any other way, and when you are sure that the
glazing is the only thing which will give you your result, the only law for the painter
comes in, — get your result.
Precautions. - If you do glaze, however, there is a right and a wrong way. You should
not use a glaze as a last resort. It is better to calculate on it beforehand; for you always
glaze with a darker tint upon a lighter one, so that if you have not allowed for this, you
will get your picture too low in tone before you know it.