Whether a painting reached completion by careful stages or was executed directly by a hit-or-miss alla prima method (in which pigments are laid on in a single application) was once largely determined by the ideals and established techniques of its cultural tradition. For example, the medieval European illuminator’s painstaking procedure, by which a complex linear pattern was gradually enriched with gold leaf and precious pigments, was contemporary with the Song Chinese Chan (Zen) practice of immediate, calligraphic brush painting, following a contemplative period of spiritual self-preparation. More recently, the artist has decided the technique and working method best suited to his aims and temperament. In France in the 1880s, for instance, Seurat might be working in his studio on drawings, tone studies, and colour schemes in preparation for a large composition at the same time that, outdoors, Monet was endeavouring to capture the effects of afternoon light and atmosphere, while Cézanne analyzed the structure of the mountain Sainte-Victoire with deliberated brush strokes, laid as irrevocably as mosaic tesserae (small pieces, such as marble or tile).
Mont Sainte-Victoire, Seen from the Bibemus Quarry, oil on canvas by Paul Cézanne, 1897; in the Baltimore Museum of Art, Baltimore, Maryland, U.S.Erich Lessing/Art Resource, New York
The kind of relationship established between artist and patron, the site and subject matter of a painting commission, and the physical properties of the medium employed may also dictate working procedure. Peter Paul Rubens, for example, followed the businesslike 17th-century custom of submitting a small oil sketch, or modella, for his client’s approval before carrying out a large-scale commission. Siting problems peculiar to mural painting, such as spectator eye level and the scale, style, and function of a building interior, had first to be solved in preparatory drawings and sometimes with the use of wax figurines or scale models of the interior. Scale working drawings are essential to the speed and precision of execution demanded by quick-drying mediums, such as buon’ fresco (see below) on wet plaster and acrylic resin on canvas. The drawings traditionally are covered with a network of squares, or “squared-up,” for enlarging on the surface of the support. Some modern painters prefer to outline the enlargement of a sketch projected directly onto the support by epidiascope (a projector for images of both opaque and transparent objects).
In Renaissance painters’ workshops, pupil assistants not only ground and mixed the pigments and prepared the supports and painting surfaces but often laid in the outlines and broad masses of the painting from the master’s design and studies.
The inherent properties of its medium or the atmospheric conditions of its site may themselves preserve a painting. The wax solvent binder of encaustic paintings (see below) both retains the intensity and tonality of the original colours and protects the surface from damp. And, while prehistoric rock paintings and buon’ frescoes are preserved by natural chemical action, the tempera pigments thought to be bound only with water on many ancient Egyptian murals are protected by the dry atmosphere and unvarying temperature of the tombs. It has, however, been customary to varnish oil paintings, both to protect the surface against damage by dirt and handling and to restore the tonality lost when some darker pigments dry out into a higher key. Unfortunately, varnish tends to darken and yellow with time into the sometimes disastrously imitated “Old Masters’ mellow patina.” Once cherished, this amber-gravy film is now generally removed to reveal the colours in their original intensity. Glass began to replace varnish toward the end of the 19th century, when painters wished to retain the fresh, luminous finish of pigments applied directly to a pure white ground. The air-conditioning and temperature-control systems of modern museums make both varnishing and glazing unnecessary, except for older and more fragile exhibits.
The frames surrounding early altarpieces, icons, and cassone panels (painted panels on the chest used for a bride’s household linen) were often structural parts of the support. With the introduction of portable easel pictures, heavy frames not only provided some protection against theft and damage but were considered an aesthetic enhancement to a painting, and frame making became a specialized craft. Gilded gesso moldings (consisting of plaster of paris and sizing that forms the surface for low relief) in extravagant swags of fruit and flowers certainly seem almost an extension of the restless, exuberant design of a Baroque or Rococo painting. A substantial frame also provided a proscenium (in a theatre, the area between the orchestra and the curtain) in which the picture was isolated from its immediate surroundings, thus adding to the window view illusion intended by the artist. Deep, ornate frames are unsuitable for many modern paintings, where the artist’s intention is for his forms to appear to advance toward the spectator rather than be viewed by him as if through a wall aperture. In contemporary Minimal paintings, no effects of spatial illusionism are intended; and, in order to emphasize the physical shape of the support itself and to stress its flatness, these abstract, geometrical designs are displayed without frames or are merely edged with thin protective strips of wood or metal.
Renaissance cassone, painted and gilded wood, Florence, 15th century; in the Victoria and Albert Museum, London. Courtesy of the Victoria and Albert Museum, London; photograph, John Webb
Mediums
By technical definition, mediums are the liquids added to paints to bind them and make them workable. They are discussed here, however, in the wider meaning of all the various paints, tools, supports, surfaces, and techniques employed by painters. The basis of all paints is variously coloured pigment, ground to a fine powder. The different expressive capacities and characteristic final surface texture of each medium are determined by the vehicle with which it is bound and thinned, the nature and surface preparation of the support, and the tools and technique with which it is handled.
Pigments are derived from various natural and artificial sources. The oldest and most permanent pigments are the blacks, prepared from bone and charcoal, and the clay earths, such as raw umber and raw sienna, which can be changed by heating into darker, warmer browns. In early periods of painting, readily available pigments were few. Certain intense hues were obtainable only from the rarer minerals, such as cinnabar (orange-red vermilion), lapis lazuli (violet-blue ultramarine), and malachite (green). These were expensive and therefore reserved for focal accents and important symbolic features in the design. The opening of trade routes and the manufacture of synthetic substitutes gradually extended the range of colours available to painters.
Tempera
A tempera medium is dry pigment tempered with an emulsion and thinned with water. The ancient medium was in constant use in most world cultures, until in Europe it was gradually superseded by oil paints during the Renaissance. Tempera was the mural medium in the ancient dynasties of Egypt, Babylonia, Mycenean Greece, and China and was used to decorate the early Christian catacombs. It was employed on a variety of supports, from the stone stelae (or commemorative pillars), mummy cases, and papyrus rolls of ancient Egypt to the wood panels of Byzantine icons and altarpieces and the vellum leaves of medieval illuminated manuscripts.
Painting from the tomb of Nebamun at ThebesBanquet scene with musicians, tempera painting on gesso from the tomb of Nebamun at Thebes, 18th dynasty (c. 1400 bc); in the British Museum, London.Courtesy of the trustees of the British Museum