Fresco

Fresco — from the Italian fresco, meaning fresh — is the technique of painting with water-based pigments applied directly onto freshly laid, still-wet lime plaster. As the plaster dries, a chemical process (carbonation) bonds the pigment permanently into the surface, making the finished work extremely durable. The technique was the dominant medium for large-scale wall and ceiling decoration in Italy from antiquity through the Renaissance, and produced the greatest monumental painting cycles of the period: Giotto's Arena Chapel (c. 1305), Masaccio's Brancacci Chapel (c. 1424–1428), and above all Michelangelo's Sistine Chapel ceiling (1508–1512) and Raphael's Stanze (1508–1520).

True fresco (buon fresco) is distinguished from fresco secco (dry fresco), in which pigments are applied to dry plaster using a binding agent. Fresco secco is less durable — the pigment is not chemically bonded to the surface — and was generally used only for finishing details or corrections. Leonardo's Last Supper was painted in a hybrid technique that is not true fresco; its rapid deterioration, beginning within decades of its completion, is the consequence of this technical choice.

Fresco painting requires the painter to work in sections (giornate — "day's work"), each section corresponding to the area of fresh plaster that can be painted in a single session before it dries. The painter prepares a full-scale cartoon of the composition and transfers it to the plaster section by pouncing (dusting charcoal through perforated lines) or incising. The plaster is then laid, and the painting must be completed before the plaster sets — typically within six to eight hours.

The technique imposes extraordinary discipline on the painter. There can be no overpainting, no correction of errors in the finished work; every passage must be planned in advance and executed with precision and speed. The palette is limited to pigments that are chemically stable in an alkaline environment; many of the more brilliant colours available to oil painters are unusable in fresco. Within these constraints, the great fresco painters — Giotto, Masaccio, Michelangelo, Raphael — achieved an extraordinary range of pictorial effects.

Fresco painting was practised in ancient Rome and the medieval period, but was elevated to its highest form in the Italian Renaissance, beginning with Giotto's Arena Chapel in Padua (completed c. 1305). Masaccio refined the technique in the Brancacci Chapel (c. 1424–1428), introducing perspective and sculptural volume into fresco for the first time. Piero della Francesca demonstrated its capacity for geometric precision in his Legend of the True Cross cycle in Arezzo (c. 1452–1466). Michelangelo and Raphael, working simultaneously in the Vatican between 1508 and 1520, brought the tradition to its culmination.

Fresco's dominance in Italian painting continued through the Baroque — Pietro da Cortona's ceiling in the Palazzo Barberini (1633–1639) and Tiepolo's eighteenth-century illusionistic ceilings represent its culmination — but declined sharply with the rise of oil on canvas as the preferred large-scale medium. In the twentieth century, the Mexican muralists Diego Rivera, José Clemente Orozco, and David Alfaro Siqueiros revived fresco as a medium of public art, consciously invoking the Italian Renaissance tradition.