Every pigment has an individual level of opacity, ranging from opaque to transparent.  These natural characteristics contribute to the behaviour of the pigment, for when ground into different vehicles, pigments give off different light energy, depending upon their natural opacity.  Equally important in controlling this energy, are the quality of the brushstrokes and the particular medium's degree of gloss.  For example, the shinier the surface, the darker the color appears.  Medium and texture, in other words alter a color's light effect.

The best way for the beginning painter to test how medium and texture change the value of a pigment is to conduct the following experiment.  Take a masonite panel about 20 by 24 inches; prime it carefully (at least three smooth coats, followed by sanding) with either the traditional gesso formula or acrylic gesso.  Employing only one color manufactured by one company, design a composition of flat shapes.  Apply a different oil medium to each shape, choosing from the various recipes given in the section "Media".  Make sure you use linseed oil, stand oil, sun-thickened linseed, and resins--dammar, Elvacite, and wax.  Also, vary the textures within each medium by working with different kinds of brushstrokes; vary, too, the density of the application and the degree of smoothness.  A painting knife can be used in one or two sections.

The exercise reveals that just by changing the medium and surface texture you can transform one color into many.  The broad variety of hues thus created should make it clear that any general color theory, or any of the numerous "rules" that painters encounter, must take into account the surface quality and the medium.  These conditions provide a frame of reference that is essential if the artist is to turn theory into practice.

The Interaction of Color: Josef Albers

Nothing could better illuminate the exciting wealth of possibilities in color dynamics than the work of Josef Albers.  "A knowing colorist," he wrote, "can make equal colors look different and different colors alike."  The colorist "not only recognizes that color is deceiving us all the time, but uses color as an acting agent, changing its identity in many ways."  Albers called these phenomena the "interaction of color" and even published a comprehensive study of the same name."

In his famous series of paintings, Homage to the Square, Albers went beyond our simple experiment with media and textures, demonstrating that color is affected by other colors and, consequently, by aspects of placement, size, and the character of boundaries.  Whether the boundaries are firm or loose, for instance, changes the appearance of a color.  Locating a color above, below, to the left, or to the right of another also will transform it.   Adjacent colors interact in definite ways: a stronger color pushes the neighboring color toward its opposite, or complementary, hue; a light color makes a neighboring color look darker, and the reverse.  If one color area is larger than an adjacent one, it will influence the neighboring color in the same way as does pronunciation of shape.

For Albers, these ideas constituted not simply a theory, but a working thesis that he practiced from day to day in his long painting career.  Albers' paintings reveal far more than mere information about color relationships.  Indeed, critics have compared them to icons in their light-giving quality.  Unlike paintings where light is created by the contrast between light and dark, Albers' color is the real "light source".  Many critics considered Albers to be a geometric painter, but his interest in geometry always took second place to his fascination with color interaction.  Geometric subdivisions in the Homage to the Square series remain constant, yet color seems to alter the size and relative distance of the squares.  When viewed in sequence, the identical squares appear either to shrink or to expand and, on occasion, even to blend with the adjacent squares.  In short, color is that "acting agent" which forces shapes as well as other colors to lose their identity.
 

The painter can learn much from a step-by-step explanation of Albers' experiments with various supports, grounds, and colors.  While it is not necessary to emulate his procedure, the account discloses how deeply concerned artist labored to capture the most subtle and fugitive properties of color.  To achieve this goal, Albers did not start with preconceived ideas.  Instead, he utilized his painting experience to develop a working theory.

Albers came to prefer masonite--untempered, 1/8 inch thick-over canvas because masonite had "wall character".  Canvas, on the other hand, had little resistance, and canvas stretchers, being available only in full-inch dimensions, limited proportion.  In addition, he chose the rough, mechanically textured side of the masonite.  When combined with transparent oil color scraped on with a painting knife, the surface became highly sensuous, although Albers claimed that this tactility was only a by-product, and not a conscious effort on his part.

The desire to render colors as brilliant as possible led Albers to experiment constantly with grounds.  A semiabsorbent white casein ground initially attracted him, since it kept the pigment, rather than the oil, on top of the surface.  But this ground dulled the deep earth colors so much that Albers had to apply varnish in order to judge color relationships.  He also found it impossible to repair simple scratches--to match the tone created by the gradual sinking in of the colors.  Albers then tried alkyd (resin) enamel, a nonabsorbent ground.  (This was a type used for housepainting, not the new Winsor & Newton product.)  Alkyd enamel presented opposing problems: it was so resistant that it greatly prolonged drying time; and colors that took a lot of oil in grinding, such as ivory black, produced a very slick surface.  Albers countered the excess oil by adding to the black pure calcium carbonate (whiting), which does not affect color.  He even dried out the oiliest of colors on a blotter before use.  Ultimately, Albers settled on acrylic emulsion gesso (Liquitex), which he felt to be the ground that yielded color with full brilliance.  A pure white ground, first of all, displayed every color to its greatest intensity.  Secondly, as the oil film became thinner with aging, it reflected the white undercoat, thereby adding to the luminosity.

Albers avoided mixing colors whenever possible, believing that the process reduced color or light intensity, and often both.  Only in mixing blues and pinks did he add white to his colors.  To give himself a real choice of color, Albers had to acquire a large collection of tube paints.  Since similarly named colors differ from manufacturer to manufacturer, he was able to collect, for example, up to six different shades of cadmium yellow medium.  With this rich and subtle range of color at hand, Albers proceeded to apply the paint in one primary coat with a palette knife.  Needless to say he rejected all painting media, for he observed that additional oil modified the color value--something you have already seen in the experiment described at the beginning.  Albers allowed the texture of the masonite to show through only when transparent or semitransparent pigments made such an effect unavoidable.  For this reason he asserted that tactility was only an incidental product of his art.

When his paintings were thoroughly dry, Albers varnished them with a polyvinyl acetate spray similar to Magna varnish or one made up of Elvacite thinned with xylene.  The final varnish, he felt, was a necessary protection for an oil film.

Albers also pondered the relationship between color and the external source of light, a problem that every painter faces.  He began with the old rule that landscape paintings begun outdoors should be finished indoors, because it is there that they will be shown.  While not in any way binding for the individual painter, the precept does acknowledge the difference between outdoor light and indoor light, and its consequent influence on color.  Indoor light changes a great deal throughout the day.  Generally warmer than outdoor light, indoor light becomes relatively cooler toward the evening, since outdoor light turns warmer late in the day.  Albers noted that as a result of these shifts the reds in a painting dominate during the daytime, while in twilight the blues become more active.  Still more modifications occur later in the evening with artificial light.  Today, the artist must remember that far more people now view paintings in artificial light than in natural illumination, particularly because an increasingly large number of galleries and museums prefer cold and warm artificial light to constantly changing natural light.

In the end, Albers decided that his goals were best accomplished under artificial light.  He chose a fluorescent source for its combination of warm and cool, just as in good galleries.  Occasionally, he did switch to the warm incandescent light when he wanted to compare warm colors.  Albers thus saw no reason to depend upon daylight, which continually changes in both its light and its color intensities.  "The very famous north light for ateliers," he concluded, "though it provides reflected light and protection from direct sunlight, seems not only superfluous, but unnatural and more artificial than all truly artificial light."

For the sake of consistency and expedience, Albers taught his course, "Interaction of Color," without using paint.   Instead, the students arranged silk screened sheets of colored paper, known as Color-Aid and sold in sets at art supply stores, in a variety of compositions.  These exercises in cut paper, born of Albers' vision as a painter, were exciting to observe.  Making hard edges seem to melt, cool tones advance and warm ones recede (contrary to what was previously taught), turning opaque into transparent-all these optical effects and more created a stimulating visual tonic.  Students with previous painting experience, as well as those taking painting courses simultaneously with the color course, thus could apply the results of the exercises to their own work.

Some of the students who had to translate such conceptual information into painting at a later date initially found it very difficult.  Gone were the premixed, flat, and even tones of the silk screened Color-Aid sheets; instead, they confronted colors with strange new names and, worst of all, pigments that varied in opacity.  Even these problems could not diminish the value of the course.  Students emerged with a profound understanding of the remarkable dynamics of color.

Color as Light:  Gauguin and Van Gogh

The somewhat didactic nature of Albers' Interaction of Color makes it a fundamental study for beginning painters.  Albers himself acquired his passionate interest in color from earlier artists.  As a student, he was exposed to the color theories of the late 19th-century Munich School, where the painters began with a Venetian red ground and, following Rembrandt, made all the shadows warm and the lights cool.

This interaction of complementary color values characterizes the work of other artists who influenced Albers and who continue to influence painters of widely divergent aesthetic postures.  Among the most important are Gauguin and Van Gogh.  Gauguin produced his original and, at times, exotic orchestrations in the service of an aesthetic that released color from its descriptive function.  By applying color in broad, flat areas, he rejected its traditionally crucial role in the articulation of plastic forms.  Gauguin's individual approach to color led him, rather unjustly, to criticize Van Gogh for being a one-note colorist who created only a single color sensation--the vibration of complementary colors.  In truth, Van Gogh's color extended beyond the complementaries to the use of subtle, close-keyed harmonies.

Whatever the differences between them, both Van Gogh and Gauguin treated color in a manner entirely new in Western art.  They revealed for the first time that light could be produced by color areas rather than by the mere contrast of light and dark.  The pink sand in Gauguin's Riders on the Beach illuminates the shallow picture space, all the while that it emits a light that advances towards the viewer.  Color-created light also radiates from Van Gogh's Portrait of a Peasant, where the yellow hat, no less than the bright blue background, gives off energetic vibrations.  (This is just the kind of complementary combination that Gauguin found too obvious.)  Van Gogh also designed dissonant color relationships, as in View at Arles with Blooming Trees.  The tree, a clashing note of cobalt violet, startles the large color field of heavy green.  This painting underscores a concept shared by Van Gogh and Gauguin: that light can be produced by a flat zone of color, and that this color becomes the light source.

Matisse

For Henri Matisse, one of the great colorists of the 20th century, color again served as the primary source of light.  In his 1911 work, The Red Studio, although objects and line do establish a light-dark contrast against the ground, the Venetian red surface that covers the picture plane actually creates most of the light.

Matisse employed other color ideas in his long career, each of which has a foundation in pictures painted between 1899 and 1911, his early period.

In L'Algerienne of 1909 Matisse packed opposing aggressive colors and patterns together to bring about a series of explosions.  These opposing energies cooperate in a dangerously balanced unity, for Matisse believed that colors should evolve into a "living harmony of tones"--a concordance in which, like a musical composition, "both harmonies and dissonances of color are agreeable."  Nine years before L'Algerienne, Matisse struggled with complementary color accents placed on top of heavily painted slabs filled with broken color, rather than continuous or modulated hues.  By means of this system, Matisse used the color logic of Gauguin and Van Gogh, as well as Cezanne, to build his own color vocabulary.  Early in his professional career, Matisse had explored Seurat's pointillist technique.  He broke up the surface into dots and spots of color that interact to create a third, optical color.  But in Buffet and Table, Matisse did not imitate Seurat's touch.  Rather, he painted in a broader, looser way, with longer and more irregular patches.

Optical Mixture: Seurat

Seurat himself is often misunderstood by young painters, because his dot technique is too easy to classify, and the catchwords Pointillism or Divisionism replace careful looking.  In fact, as Matisse well understood, Seurat treated colors as optical mixtures--an additive principle whereby, in visual terms, one color blends with a second to produce a third.  The process is easily illustrated by Gravelines.  Here, when viewed at a distance, the blue and red dashes form a third color, violet.  This small painting also invites close inspection for the magnificent handling of paint.  Note how the red and blue strokes are being melted by the large white ones that receive them in a wet-on-wet technique.

Seurat used the principle that color 1 plus color 2 equals a new color (3) only when this demanded it.  He began with small, directly brushed sketches from nature that served as studies for his large, ambitious paintings.  In these one-session studies Seurat did not always incorporate the optical mixture formula, since his main goal was to gather visual information for the final work.  Even so, Seurat could become committed to making a complete statement.  In Lisiere de Bois au Printemps, he dragged, scraped, and pressed into the surface a warm-cool color relationship without the dot technique, but with great textural variety and a combination of relatively dry and wet paint.  Clearly, the demands of the particular motif engendered Seurat's textural and color choices, in this case, warm against cool, yellow against blue--but with great modulation.  In the bottom blue area, greens and blues intermingle, while in the single vertical tree on the right, the blue moves toward violet.  The white-blue sky also has touches of cobalt violet.

So successful was Seurat's reconciliation of method and pictorial invention that we are not necessarily aware of the famous pointillist technique.  In Une Baignade, Asnieres, one of his finest compositions, the blinding magic light of this silent monumental painting dominates the viewer's response.  Once you see this light from a distance, you must examine the image up close--only to discover that the pointillist optical mixture principle is used gently and sparingly, woven into the forms' all over surface.  Of course, the effect can be isolated here and there, but it is neither the artist's overriding concern nor the hidden subject of the painting.  As in surface handling,  Seurat's color vocabulary is dictated by the picture's thematic needs, not by a preconceived technique.

Optical Mixture: Rubens

The Old Masters employed different kinds of optical mixtures.  Rubens, for example, relied on a visual blend of superimposed colors, rather than adjacent ones.  As part of his characteristic painting style, he applied flesh tones over a thinly painted neutral gray ground.  These layers of pink, ochre, and white--all components of his rose like flesh tints--force the gray underneath to produce a third tone, an optical blue-violet iridescence, as if the veins were showing through the pink flesh.  Unfortunately, the effect is difficult to reproduce, since translucent oil films do not photograph well.  You can test the method by placing some strokes of pink pastel on gray paper.

The Limited Palette

Experimenting with a limited palette is another way of learning how to attain a variation that fools the view into believing that many colors are present.  Whistler was a master at painting within a narrow color range.  Indeed, he could make a grayish-green painting appear color saturated by applying layers of variant tones to different parts of the painting.  Likewise, Guardi's Laguna Grigia, has its vast space created with little more than one modulated color representing water and sky.

Value and Color

A painter cannot make a distinction between the light effect of a color and the color itself.  To put it another way: value and color are one.  Corot had two methods of applying paint, each with a different color-light effect.  In the first manner, usually reserved for small landscapes and works from models, he used a direct paint approach.  As in The Roman Campagna, with the Claudian Aqueduct, he toned down any color without ever letting it appear muddy.  When working with this process, Corot had the remarkable ability to apply, seemingly in one coat, the exact tone in the color-value scale to each of the forms depicted.  Even Corot's darkest darks, his murkiest tones, have a definite warm or cool character, so that the deepest shadows, toned-down ochres, and raw siennas still give off light.  This is the test that determines whether a tone is "alive," for if you cannot tell whether it is warm or cool, it is not giving off light and is, therefore, a dead area.

In Corot's second method the manner of creating the light and applying the pigment is hard to discern.  The whole surface of Le Port de La Rochelle emanates in opalescent golden glow, as if separate, thin films of paint interpenetrate.  Corot seemed able to paint two layers at the same time.  One coat addresses itself to the manipulation of the exact light value of each section, keeping it in perfect balance with all the values on the surface.  The second coat addresses itself to the total glow of the surface.  This interpenetration of effects parallels the imagery where sky and water reflect each other.

Light and Space

Color in the art of painting includes not only light coming from color (Van Gogh), color vibrations producing light (Seurat), and other phenomena, but it may also include light in space-- that is, pigments creating light inside the picture plane.  In The Stone Bridge Rembrandt manipulates the pigment so as to contrast tonal values, transforming pigment into light.  This light, deep inside the painting's space, seems to be more than the product of pigment on canvas.  Rather, it has an inner glow, as if it were artificially illuminated.

Turner also engineered the effect of internal illumination in Rockets and Blue Lights.  At the same time, he entraps us by constantly spinning the large end of a funnel-like arc of light-energy out of the space.  Our physical reaction is either to feel pulled into the space or to want to pull back and away.  In Sun Setting Over a Lake, Turner created another, related kind of sensation, one that inspired the Impressionists--atmospheric pigmentation.  Using layers of thick and thin paint films, Turner released a colored, weighted mist into the air.  Miraculously, he projected this atmosphere into a controlled space, but one in which circles of light, moving gently in slow motion, tend to pull us into his invention, his concoction of light and air.

Paint and the Canvas

Atmospheric effects can be produced even with thin washes of paint.  Rothko used Magna colors diluted with turpentine.  Thinning his paint almost to a stain, he left just enough opacity to cover the simple shapes with a consistent color, a frontal film that radiates like an atmospheric glow.  These thin coats of paint create a silent aura of light, an expanding atmosphere.  The paint's texture cannot be seen; all we see is the weave of the canvas.  In other words, the paint and the canvas are one.

Glazed Light

Glazed light is yet another color effect.  The light created by Grunewald's brilliant, deep-glazed surface is too dense to conform to the traditional definition of a glaze--a thin film of transparent paint placed over an opaque, lighter color.  Grunewald's enamel-like surfaces emanate a dense color-light unlike any other.  This light is so fiery, so deep, that it seems to penetrate the support.  In the detail the blinding light engulfing the Christ figure melts his face and transforms it into pure light.  Seen at a distance, the glow spreads out to cover the whole surface.  Although this painting was finished some 500 years ago, the feeling of color-light is so fresh that one feels as if the painter has just recently applied the last brushstroke.

Light from Dry Pigment

Light also can be created by the special brilliance of dry pigment or its compressed equivalent, pastel.  The wetness of oil, darkens blues and blue-greens and tones down the intensity of high-keyed colors.  Similarly, water base media tend to flatten all the tones slightly.  After accepting the fact that pastel gives us the full brilliance of pigment in its dry state, the real question is what do you do with it?  Redon found an answer.  He used unconventional harmonies and dissonances with surprising resonance--blues that exist in no other media, and pink, violet, green, and golden accents that, by employing the medium in an innovative way, open up a whole new color world.