Although BLACK and WHITE pigments have nothing to do with color, they both, particularly white, play an important role in painting. The mixing tests we have illustrated show that all pigments mix with white in their own way. It lightens them but dulls them at the same time. This is an effect contrary to a glaze, in which the white of the underpainting lightens the color without altering its character.
White is quantitatively the dominant pigment in all painting, unless the work is done primarily in transparent color, or glazes. Only watercolor and fresco use hardly any white. Watercolor in particular loses all character if much white is used.
The natural white pigments are chalk, gypsum, heavy spar (sulphate of baryta), and clay (white bole). They can be used only as a priming or as a filling material for "cutting" other colors, not for painting proper. They go gray with all oil, resin, and wax binders, and keep their lightness only in glue. For house paint and pastel chalks the color pigments can be "cut" with natural white pigments in large quantities without reducing the depth of color of the "cut" substances-but only if glue is used exclusively as the binder or fixative. This is why some house paints are recommended for use only with glue; a limitation which does not exist for pure, uncut colors.
The most usual white pigments for pictures are white lead and zinc white, although they may soon be replaced entirely by titanium white.
WHITE LEAD (basic lead carbonate), generally called Cremnitz white in its finest varieties, has strong covering power and is thus the main constituent of all opaque whites. It has a warm tone, hardens quickly in oil, and would be the only white used in painting, except that it tends to blacken in combination with many sulphur colors (cadmium pigments, for example). For these pigments the wholly neutral ZINC WHITE is the only possible choice. It has weak covering power, little coloring strength, is cold in tone, and delays drying.
To counter the properties of both whites there are ready-prepared mixtures of the two, but as with all mixtures it is not advisable to buy them, as mistakes can be made in their use. If they are needed they must be mixed by the artist himself.
TITANIUM WHITE (titanium dioxide) occurs naturally, but for the quantities required is generally made artificially. It has a very strong covering power, is neutral in tone and as unaffected by
light as the two other pigments. Little is known as yet about how it behaves in pictures, but there seems no reason to fear that its excellent qualities will have to be paid for in the course of time. It may well make lead and zinc white superfluous.
BLACK is totally unnecessary in the painter's palette. The two most important black pigments, ivory black and lamp black, mix disagreeably with colored pigments. If they are used solid they make "holes" in the picture, and as tinting they have a deadening and muddy effect; used as a glaze, they produce an equally dead, gray effect. Much more subtle grays are obtained from mixtures of complementary colors, and the colored darks that the layman will always see as black.
Gray does not exist light; moreover, one of them, VERDIGRIS, has the fatal characteristic of dissolving in the acid of linseed oil and "bleeding." The old masters laid verdigris as an unmixed glaze in egg white between isolating layers of varnish in order to be able to use the lovely green tone which became obsolete only with the discovery of viridian. Used as described, the organic substance (copper acetate) is also unaffected by light.
The famous, infamous EMERALD, or Schweinfurt, green was as necessary an evil as verdigris as long as there was no nonpoisonous, stable, strong green pigment. Emerald green (copper arsenate)
is one of the few really dangerous poisons used as a pigment, and still used today as an insecticide. It can be deadly to men as well, whereas most of the poisonous qualities of pigments are rather the exaggerations of romantic horror, being dangerous only to small children who are at the stage of consuming everything they see.
ASPHALTUM, or bitumen, on the contrary, has fallen out of fashion. It is a
natural organic substance and was used in the last century mainly for underpainting, as its gray-brown tone ideally suited the taste of the period as an underlay for glowing glazes. In the course of time, however, it was found that this underpainting either began to "bleed" or the thick layers of paint above it literally peeled off as they lost all hold on the underpainting. Some of the "black Madonnas" that from Czenstochau, for instance - turned black not from heavenly intervention but because the asphaltum underpainting was striking out.
SEPIA is extracted from the ink bag of certain species of Mediterranean cuttle fish. It was favored as a substratum color and as ink in the Romantic period and gave an antiquated coloration to pictures. It soon turns gray, however.
The well-known VANDYE or CASSEL BROWN has a good brown tone but was never necessary, as umber was known earlier. It is simply brown coal, a mixture of organic substances, and thus sensitive to light. It is still much used, out of ignorance.
In the color assortments of many stores you still find a great number of names which, in the great majority of cases, disguise only half-usable pigments or mixtures.
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