tempera

tempera.
A term originally applied to any paint in which the pigment is dissolved in water and mixed (tempered) with an organic gum or glue, but now generally confined to the most common form of the medium—egg tempera. Egg has probably been used in paint since antiquity and it remains the principal medium for icons produced in the service of the Greek and Russian Orthodox churches. However, tempera is mainly associated with European art from the beginning of the 13th century until the end of the 15th century; it was the standard technique for panel painting in this period, until it began to be overtaken by oil. A detailed description of the technique as practised by Italian painters of the time is given in Cennino Cennini's treatise, written c.1400. According to Cennini (and later Vasari), only the yolk of the egg was used, but scientific examination of pictures suggests that the white by itself or both yolk and white together may occasionally have been used. The yellowness of the egg had little effect on the colours, though Cennini says that town hens produce the palest and best yolks, and adds that darker yolks will do for the flesh colour of ‘old people, or such, who are darker in colouring’. Pale yolks are still preferred today.

Painting with tempera is a demanding craft. Unlike in oil painting, each colour or tone required has to be pre-mixed, for they cannot be blended on the picture surface. The variety and subtlety obtained by skilful painters depended on a slow building-up process, in which each stage—ground, underpainting, and various layers of semi-transparent paint—would have a calculated effect upon the next. Tempera has more luminosity and depth than fresco, but its range of colour and tone is limited and it cannot achieve the close imitation of natural effects attainable in oil painting. In the late 15th and early 16th centuries it was very common for pictures to be painted in a mixture of the two techniques, with tempera typically providing a quick-drying underpaint to which oil glazes were applied. Subsequently tempera was virtually forgotten for centuries, until there was a revival of interest in the 19th century, stimulated by the rediscovery and publication of Cennini's treatise. Restorers, forgers, and also a few artists began to experiment with the technique, and certain 20th-century artists have favoured it, notably the Americans Cadmus, Tooker, and Wyeth.