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Lessons in Color Theory

Lesson #9

Characteristics of Manufactured Colors

Up to this point, I've discussed the history, the theories, terminology, and meaning of colors. I've shown their vital role in perspective; described the many optical illusions caused by colors or color combinations, and how those optical illusions might help artists to avoid visual mistakes, or to achieve interesting results. I've explained the difference between color theories established by physicist and the practical use of colors by artists. Now I am going into the factual features of the colors: the paints with which artists work. I am going to describe the materials and media, and explain the purpose, the use, the physical properties, potentialities, and limitations of each.

A Brief Survey of Painting Media

Prehistoric man noticed that the color of the earth was varied, and, after a rainfall, that wet earth could be smeared or spread on the rocks to imitate the color of real things.

Later on, he found that fat dripping from roasted meat made the earth easier to use as paint , and that such paint would become permanent. As he began to employ colors on utensils and perhaps on some clothing, too, besides painting on the wall of his cave, he found other sources of paint in fruits and vegetables.


At first, man applied all colors with water only. He discovered, no doubt by accident, that eggs - especially eggwhites - became hard, almost unremovable, and that powdered colors mixed with eggs could thus be turned into permanent paints. Eggs could also be used upon already painted surfaces as a protective varnish.

Colors mixed with eggs are called tempera, but similar mixtures may be obtained by combining colors with various gums or glues, such as rabbit skin glue or fish glue. Some primitive tribes are still using pigments - colored substances - mixed only with water; but most ancient people realized that pigments must have a binder, a substance which makes them adhere to the surface on which they are used.


Beeswax, as both a binder and a protective varnish, was also discovered at an early date, probably soon after man found honey to his taste. Man must have noticed how easy it is to melt wax, how quickly it cools and dries, and how well it protects whatever it happens to cover. Pigments (powered colors) mixed with wax are called encaustics, and have been used in many parts of the ancient world.

There's much overlapping in the development of paints. Wax may have been employed as a protective coat over tempera, before being used as a binder for pigments. Discoveries seem to have been made almost simultaneously in various sections of the world; or skills and knowledge were carried by adventurous persons from one place to another.


Enamel, a vitreous (glasslike) compound, probably discovered at the same time as glass, was employed by the ancient Assyrians, mostly on bricks decorating the fronts of temples and palaces. Egyptians used it on pottery. Enamel later became a highly-treasured permanent decoration on metallic objects, in China as well as in France.

At one time, enamel was used almost exclusively on jewelry and objects of art. Now, enamels are utilized on articles and materials exposed to the weather.


Fresco painting - really a kind of watercolor applied to wet plaster - was evolved directly from tempera, when workers tried to make the white plaster walls look less harsh by applying a coat of watercolor. They realized that water paint is solidified by the drying lime, and becomes waterproof. Fresco was employed by so many ancient peoples that it isn't possible to tell who used it first or where.

Oil Paints

Although oil painting, as we understand the term, was introduced in the fifteenth century by the famous Flemish masters, Hubert and Jan Van Eyck, it also goes back many hundreds of years.

Some Egyptian mummy cases appear to have been varnished with an oil, rather than with egg varnish. The earliest mention of the use of fast-drying vegetable oils in paintings is in a book by Aetius, a medical writer, from the early part of the sixth century of the Christian era. He recommends nut oil for protecting gilt surfaces and encaustics. We have much evidence, from the eighteenth century to about 1100, of the use of such drying oils in painting and in varnishing. The binders in our oil colors are linseed and poppyseed oils.


Watercolor, as I mentioned before, was known since the most ancient times. Artists illuminating papyrus scrolls in Egypt, silk and ricepaper scrolls in the Orient, manuscripts in the Dark and Middle Ages, all worked with a water medium, usually of an opaque kind.

Present-day aquarelle, often called transparent watercolor, did not evolve from these forms of painting, though. Aquarelle is the direct descendant of the pen-and-ink-wash drawings made by artists of the Renaissance and Baroque. An English artist, Paul Sandby (1725 - 1797), is called the "Father of English Watercolor." He must actually be considered the father of all Western watercolor. In modern watercolor, gum arabic ( a water soluble glue) is the binder, mixed with very finely powered pigment.

An important principle of transparent watercolor is never to work with white paint, which destroys the transparency, the charm of the medium.


Gouache (pronounced gwash) is an opaque watercolor. The pigments usually contain some honey, besides gum arabic; the paint is applied without much water, and you have to mix a color with white if you want to make it lighter. White is used in gouache as in oils. Miniaturists often work with gouache.


Pastel is erroneously believed to be the invention of the German landscape painter, Johann Alexander Thiele (1685 - 1752), but we're sure that at least Guido Reni, the noted Italian master - who died more than forty years before Thiele was born - had already worked in pastel. This medium is pure powered pigment, compressed into small, cylindrical sticks. Recently, semi-hard pastels have been introduced. These contain a small amount of wax. The medium didn't become popular until 1775, when pastels by the Swiss artist, Jean Etienne Liotard, were shown at the Royal Academy in London.


Casein is an ingredient of curdled milk, used by cabinetmakers as a waterproof glue for at least eight hundred years before it occurred to someone to employ it in paint. First, in the 1930's, it was marketed as a white housepaint, and it had a nauseating odor. Later, the odor was eliminated and casein was produced in tubes, exactly like oil colors. It dries rapidly and is quite waterproof.

Casein can be used as a watercolor but, unlike watercolor, one stroke covers another because the color is relatively opaque. Changes and corrections are easy, not as in transparent aquarelle. Today, tempera, gouache, and casein are almost identical. Some artists add eggwhite or the whole egg to casein to make it harder.


A relatively new medium is polymer, the general name for all kinds of plastic colors, which are marketed under various trade names. Prepared from mostly diverse combinations of acrylic and vinyl, these colors are applied with water, but dry almost instantly and dry waterproof. They can be handled like watercolors or oils, in any technique, thick or thin, opaque or transparent. They can be varnished with plastic varnishes, a feature which makes polymer paintings or objects painted in polymer literally scuffproof.

Polymer is employed in commercial fields as well as in the fine arts. It works on any surface, except an oily one. Some plastic colors are produced with an oil soluble base; these have to be thinned and applied with oil or turpentine. The only advantage of oil based polymer over regular oils is that the polymer dries faster.

Pigments We Use

Pigments are the coloring matter we need for paints. They must be substances which can be powderized so that they can be mixed with a liquefied binder. There are four sources of pigments: natural, artificial, organic, and inorganic. It's probably simpler, though, to list them as earth colors, mineral (or metallic) colors, organic colors, and chemical colors.

Earth Colors

Earth colors are not really made of earth. The name was applied to them when earth was believed to be one of the four elements constituting the world, the other three being air, water, and fire. Needless to say, this belief was completely wrong.

Earth colors are prepared from various iron ores, but we call them earth colors, because they are found practically anywhere, in inexhaustible quantities, and they are obtained on the very surface of the earth. They range from yellow through diverse shades of buff, brown, and green, to red and violet. The colors may be used as they are, but many of them (like raw sienna and raw umber) can also be burnt, a procedure which gives us such hues as burnt sienna and burnt umber. None of these colors are very brilliant. For example, Indian Yellow (an earth color) can never be as vivid as a cadmium yellow. Earth colors are lowest in price, in all brands, as they are permanent. Most of them are absolutely necessary for every fine arts painter.

Mineral Colors

Mineral colors are obtained from metallic elements. White is made from lead, zinc, and titanium. A beautiful blue, and an equally lovely violet, are made from cobalt. Cadmium gives us the most valuable pigments of yellow, orange, and red. Chromium oxide provides us with a brilliant green.

Most colors made from these metallic elements are permanent. Since they have to be mined and carefully processed, they are costlier than earth colors, but are a must for fine artists who cannot afford to work with colors which turn dark or change completely.

Lead chromates, however, from which the so-called chrome colors are prepared, are not permanent. Chrome yellow and chrome orange look like cadmium colors of the same names, but darken very quickly. Don't use them in fine arts.

Organic Colors

Organic colors are made from animal or vegetable matter. Many of these were used in past ages. Red, especially, was prepared from animals. Even today, carmines - a kind of red employed in watercolor - come from animal matter. A vegetable substance, madder, is also used in aquarelle. None of these is truly reliable, and manufacturers are trying top replace them with metallic or chemical pigments.

Chemical Colors

Chemical pigments are born in laboratories. For a hundred years or so, chemical pigments were unreliable. They looked fine when applied, but faded or changed rapidly, often ruining the whole work. Furthermore, one chemical would react to another one, and destroy the effect planned by the artist. Before World War I, certain colors bore warning labels: Do not mix with such-and-such colors!

Today, the major manufacturers of artist's colors, and even of household paints, have chemists to check all qualities of their products. As a result, chemically created pigments are often more uniform in color and quality than natural ones. Mars colors are a notable case. All Mars colors - yellow, red, violet, black - are fully reliable. Reliability, however, doesn't necessarily imply brilliance. If you want truly bright colors in reds and yellows, spend a few extra cents, and buy cadmium colors.

Manufacturers indicate the permanency of each color on the label or in their catalog lists. In a good brand, the lack of ABSOLUTE permanency means only that a certain color is bound to weaken a little if you expose it to the sun for a long period. In normal circumstances, even these colors are quite satisfactory. After all, paintings are normally intended to be displayed in the home, not outdoors.

In our age, all fine art colors marked permanent are absolutely intermixable. They may be mixed with any color without fear of some adverse chemical reaction. Furthermore, each brand may be safely mixed with any other brand, whether the colors are manufactured in the United States or Europe. There is only one exception: polymer (plastic) colors do not always mix with other brands. Some do, some don't. You might inquire when you buy them. Or you can test them. If they are prepared from similar ingredients, they'll mix easily with the brush. If their ingredients are not harmonious, you'll find that the paint doesn't mix smoothly; it crawls or curdles a little as you try to brush it.

Inherent Properties: Opacity, Transparency

Regardless of the medium - oil, watercolor, casein, polymer, tempera, gouache, pastel - the main property of each pigment is its opacity or transparency. Certain colors are listed as semi-opaque by some manufacturers; others call the same colors semi-transparent. In all likelihood, the two terms refer to exactly the same property. It's of great practical significance to the artist to know which color is opaque, which is transparent, which is halfway between the two. Otherwise, he'll waste time and material on the impossible, such as trying to cover black with alizarin crimson, or blue with zinc white. Both alizarin crimson and zinc white are very transparent, without sufficient covering power.

Although every medium requires a different technique of application, basic properties remain identical and have to be remembered. Casein dries fast and fairly waterproof; thus, it's possible to go over one color with an entirely different one as soon as the first layer is dry. Watercolor is called transparent as a medium, because we apply it in washes one on top of the other; but that doesn't mean that each color is transparent. Not at all. The same colors are transparent, opaque, or semi-opaque in every medium. Moreover, every color, in each medium, can be transparentized by adding vehicles: water to water-based paints; linseed oil, turpentine, copal glazing medium, or other liquid, to oils. There are transparentizers, such as gel, now available in each medium.

Nonetheless, the inherent opacity or transparency of a color plays an important role in painting. First of all, a basically transparent color may be employed as a glaze (a transparent layer, like colored glass) without any effect. Secondly, it's important to know its opacity or transparency because you cannot make a transparent color opaque, no matter what you do, without changing it. The moment you mix it with an opaque color, it becomes a different hue. It's necessary, therefore, to plan your work according to the opaque and transparent qualities of your colors. Don't think that this will handicap you, that it will destroy your spontaneity. What does destroy an artist's spontaneity, and even general inspiration, is to find some technical hurdle he's unable to surmount, because he doesn't understand it.

Polymer dries and becomes waterproof in a minute or so. This means that you can go over black with blue, or over blue with yellow, without stirring up the first layer, and messing up the second layer. But you still cannot paint alizarin crimson over black or blue and expect it to look like alizarin crimson. You can, however, paint white over black or blue, let it dry a couple of minutes, then paint alizarin crimson over the white as if it were the original clean support.

In transparent watercolor, artists work with thin, literally transparent, washes. Nevertheless, you can quite easily paint cadmium red, orange, or yellow spots over other watercolors by using very little water and more paint than usual, because cadmium colors are sufficiently opaque. An experienced aquarellist saves himself a great deal of trouble by planning his work according to such possibilities.

In all painting media, the use of transparent color as glazes adds depth to your work. The beauty of paintings by old masters is due to a very large extent to the fact that those artists executed an underpainting first, often in tempera, then glazed it in oils. Many artists now do a casein underpainting, and glaze it in oils or in polymer.

The degree of opacity also has a bearing on the mixing of colors. Certain opaque hues are amazingly powerful. For example, you would need an incredible heap of white to make cadmium yellow noticeably lighter. On the other hand, the slightest touch of white is enough to turn alizarin crimson into a pale pink, in any medium. (Provided, of course, that you have a strong white, such as titanium or flake, not the very weak, transparent zinc white.)

Some manufacturers indicate the opacity, transparency, or semi-opacity of each color on the label in oil paints. Others offer folders and catalogs, in which such properties are marked for watercolors as well as oils. As I've stated before, the same colors are opaque, the same colors are transparent, in each medium. You'll learn from experience, without looking at labels or catalogs. Observe what you're doing, look at the results. This is the best advice I, or anyone else, can offer you.

Check back soon as we press on to a richer understanding of color.