Watercolors are pigments ground with gum arabic and gall and thinned with water in use. Sable and squirrel (“camel”) hair brushes are used on white or tinted paper and card.

Three hundred years before the late 18th-century English watercolorists, German artist Albrecht Dürer anticipated their technique of transparent color washes in a remarkable series of plant studies and panoramic landscapes. Until the emergence of the English school, however, watercolor became a medium merely for color tinting outlined drawings or, combined with opaque body color to produce effects similar to gouache or tempera, was used in preparatory studies for oil paintings.

The chief exponents of the English method were Thomas Girtin, John Sell Cotman, John Robert Cozens, Richard Parkes Bonington, David Cox, and Constable. Turner, however, true to his unorthodox approaches, added white to his watercolor and used rags, sponges, and knives to obtain unique effects of light and texture. Victorian watercolorists, such as Birket Foster, used a laborious method of color washing a monochrome underpainting, similar in principle to the tempera-oil technique. Following the direct, vigorous watercolors of the French Impressionists and Post-Impressionists, however, the medium was established in Europe and America as an expressive picture medium in its own right. Notable 20th-century watercolorists were Wassily Kandinsky, Paul Klee, Raoul Dufy, and Georges Rouault; the American artists Winslow Homer, Thomas Eakins, Maurice Prendergast, Charles Burchfield, John Marin, Lyonel Feininger, Rhoda Holmes Nicholls, and Jim Dine; the English painters John and Paul Nash; and the Swedish artist Hilma af Klint.

In the “pure” watercolor technique, often referred to as the English method, no white or other opaque pigment is applied, color intensity and tonal depth being built up by successive, transparent washes on damp paper. Patches of white paper are left unpainted to represent white objects and to create effects of reflected light. These flecks of bare paper produce the sparkle characteristic of pure watercolor. Tonal gradations and soft, atmospheric qualities are rendered by staining the paper when it is very wet with varying proportions of pigment. Sharp accents, lines, and coarse textures are introduced when the paper has dried. The paper should be of the type sold as “handmade from rags”; this is generally thick and grained. Cockling is avoided when the surface dries out if the dampened paper has been first stretched across a special frame or held in position during painting by an edging of tape.

Ink

Ink is the traditional painting medium of China and Japan, where it has been used with long-haired brushes of wolf, goat, or badger on silk or absorbent paper. Asian black ink is a gum-bound carbon stick that is ground on rough stone and mixed with varying amounts of water to create a wide range of modulated tones or applied almost dry, with lightly brushed strokes, to produce coarser textures. The calligraphic brush technique is expressive of Zen Buddhist and Confucian philosophies, brush-stroke formulas for the spiritual interpretation of nature in painting dictating the use of the lifted brush tip for the “bone,” or “lean,” structure of things and the spreading belly of the hairs for their “flesh,” or “fat,” volumes. The East Asian artist poises the brush vertically above the paper and controls its rhythmic movements from the shoulder. Distant forms represented in landscapes painted on silk were sometimes brushed on from the reverse side.

In the Western world, ink has been used rather more for preparatory studies and topographical and literary illustrations than as a medium for easel paintings. Western artists have generally combined ink washes with contours and textures in quill or steel pen. Among the finest of these are by Rembrandt, Nicolas Poussin, Francisco Goya, Samuel Palmer, Constable, and Édouard Manet. Claude Lorrain, Turner, Daumier, Braque, Picasso, Reginald Marsh, Henri Michaux, John Piper, Margaret Neilson Armstrong, and Qin Feng are some of those who have exploited its unique qualities. Contemporary artists also use markers as well as ballpoint and felt pens.

Gouache

Gouache is opaque watercolor, known also as poster paint and designer’s color. It is thinned with water for applying, with sable- and hog-hair brushes, to white or tinted paper and card and, occasionally, to silk. Honey, starch, or acrylic is sometimes added to slacken its quick-drying property. Liquid glue is preferred as a thinner by painters wishing to retain the tonality of colors (which otherwise dry slightly lighter in key) and to prevent thick paint from flaking. Gouache paints have the advantages that they dry out almost immediately to a matte finish and, if required, without visible brush marks. These qualities, with the capacities to be washed thinly or applied in thick impasto and a wide color range that now includes fluorescent and metallic pigments, make the medium particularly suited to preparatory studies for oil and acrylic paintings. It is the medium that produces the suede finish and crisp lines characteristic of many Indian and Islamic miniatures, and it has been used in Western screen and fan decoration and by artists such as Rouault, Klee, Jean Dubuffet, Morris Graves, Jacob Lawrence, Laylah Ali, and Amy Sherald.

Encaustic

Encaustic painting (from the Greek: “burnt in”) was the ancient method, recorded by Pliny, of fixing pigments with heated wax. It was probably first practiced in Egypt about 3000 bce and is thought to have reached its peak in Classical Greece, although no examples from that period survive. Pigments, mixed with melted beeswax, were brushed onto stone or plaster, smoothed with a metal spatula, and then blended and driven into the wall with a heated iron. The surface was later polished with a cloth. Leonardo and others attempted unsuccessfully to revive the technique. North American Indians used an encaustic method whereby pigments mixed with hot animal fat were pressed into a design engraved on smoothed buffalo hide.

A simplified encaustic technique uses a spatula to apply wax mixed with solvent and pigment to wood or canvas, producing a ridged, impasto surface. This is an ancient and most durable medium. Coptic mummy portraits from the 1st and 2nd centuries ce retain the softly blended, translucent coloring typical of waxwork effigies. In the 19th century Vincent van Gogh also used this method to give body to his oil pigment; the Neo-Impressionist artist Louis Hayet applied encaustic to paper, and it was used by American painter Jasper Johns for his iconic paintings of maps, targets, and flags. Colored wax crayons have also been used by modern painters such as Picasso, Klee, Arshile Gorky, and Hockney.

Casein

Casein, or “cheese painting,” is a medium in which pigments are tempered with the gluey curd of cheese or milk precipitate. For handling, an emulsion of casein and lime is thinned with water. The active element of casein contains nitrogen, which forms a soluble caseate of calcium in the presence of lime. It is applied in thin washes to rigid surfaces, such as cardboard, wood, and plastered walls.

Casein colors dry quickly, although lighter in tone than when first applied. Since they have more body than egg-tempera paints, they can be applied with bristle brushes to create impasto textures not unlike those of oils. Casein paints were used in ancient Rome. They are now available ready-made in tubes and have been used by such modern artists as Robert Motherwell and Claes Oldenburg.

Casein is also an ingredient of some charcoal and pastel fixatives and was a traditional primer for walls and panels.