Tempera

Tempera — specifically egg tempera — is a painting medium in which dry pigments are suspended in egg yolk, creating a fast-drying paint that is applied in thin, transparent or semi-transparent layers. It was the dominant painting medium of Italian painting from the thirteenth through the fifteenth centuries, and produced the characteristic luminous, jewel-like surfaces of the Early Renaissance panel paintings of Fra Angelico, Masaccio, Piero della Francesca, and early Leonardo and Botticelli. It was gradually displaced by oil paint in the course of the fifteenth and sixteenth centuries, as the slower-drying, more blendable oil medium became available and its advantages became apparent.

Tempera's quick-drying quality — a passage of tempera is typically dry in minutes — means that it cannot be blended on the surface in the way oil paint can. Instead, tempera painters build up form and colour through a distinctive technique of fine parallel hatching, applying layer after layer of thin strokes to build up tone and colour gradually. This technique gives tempera painting its characteristic appearance: a surface of fine, almost invisible strokes whose cumulative effect is a warm, slightly grainy luminosity.

Egg tempera is prepared by mixing dry pigment with egg yolk (the yolk separated from the white) and a small amount of water or distilled vinegar to aid flow and prevent fermentation. The mixture must be prepared fresh for each session, as it deteriorates rapidly. It is applied to a prepared ground — typically gesso, a mixture of chalk or plaster and glue applied to a wooden panel in multiple layers and sanded smooth.

The painter builds up form and colour through hatching — fine parallel strokes of transparent or semi-transparent paint, applied in multiple layers, each one dry before the next is applied. Highlights are achieved by leaving the lighter ground visible or by applying thin semi-opaque passages of lighter paint; shadows are built up through successive layers of darker hatching.

Egg tempera was the dominant painting medium of the medieval Italian tradition, and was standardised and refined in the early Renaissance workshops of Florence. The technical procedures for preparing and applying tempera are described in detail by Cennino Cennini in his handbook Il libro dell'arte (c. 1400), which provides a comprehensive account of Early Renaissance workshop practice.

The medium's decline began with the introduction of oil painting from the North in the 1470s. Botticelli worked primarily in tempera throughout his career; Leonardo used both tempera and oil in his early works, transitioning definitively to oil by the 1490s. By the sixteenth century, tempera had been largely displaced as a medium for panel painting, surviving mainly in the preparation of grounds and in the painting of decorative objects.

Tempera survived as a medium for decorative and devotional painting through the sixteenth century, then largely disappeared from European practice until its revival by the Pre-Raphaelites and the Arts and Crafts movement in the nineteenth century. In the twentieth century, the American painter Andrew Wyeth made tempera his primary medium and produced in it some of the most celebrated realist paintings of the century. The medium remains in active use today among classical painters working in the Renaissance tradition.