fresco [Ital.,=fresh], in its pure form the art of painting upon damp, fresh, lime plaster. In Renaissance Italy it was called buon fresco to distinguish it from fresco secco, which was executed upon dry plaster with pigments having a glue or casein base. In true fresco the binder is provided by the lime of the plaster; in drying this forms a calcium carbonate that incorporates the pure pigments, mixed only with water, with the material of the wall. During the Renaissance it was customary to prepare a cartoon of the same dimensions as the contemplated fresco. To transfer the design to the wall, pounce, or dust, was applied through perforations in the cartoon to the wet coat of plaster (intonaco). The plaster was made of fine sand, lime, and marble dust that was applied in small sections daily. A large fresco therefore consists of many small sections, each painted in a day. The sections were planned in such a way as to make the joinings inconspicuous. As not all colors are lime-proof, fresco does not permit as large a palette or as delicate a manipulation of transitional tones as the oil medium. However, its clear, luminous color, fine surface, and permanence make it ideal for bold, monumental murals. The Minoans decorated the palace at Knossos and the Romans painted the villas at Pompeii in this fashion. The technique has not altered substantially since the 15th cent., when it was brought to perfection by the great masters of the Italian Renaissance. Only dry climates are hospitable to the medium, so fresco was used rarely in N Europe. The art of fresco painting declined until the 20th cent., when it was revived in Mexico by Diego Rivera and José Clemente Orozco.

Method of wall painting in which water-based pigments are applied to wet, freshly laid lime plaster. The dry-powder colours, when mixed with water, penetrate the surface and become a permanent part of the wall. This technique is also known as buon fresco, or “true fresco,” to distinguish it from fresco secco, or “dry fresco” (painting on dry plaster). Early Minoan, Greek, and Roman wall paintings were frescoes. The Italian Renaissance was the greatest period of fresco painting, as seen in the works of Cimabue, Giotto, Masaccio, Fra Angelico, Correggio, and others. Michelangelo's frescoes in the Sistine Chapel and Raphael's in the Vatican are the most famous of all. By the 18th century, fresco had been largely replaced by oil painting. In the early 20th century it was revived by Diego Rivera and others, often as a medium for political art. Fresco painting is also found in China and India.

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