Egg tempera predates oil painting and was used by the Ancient Egyptians and Greeks and perfected by icon painters during the Byzantine period; it flourished again in the hands of the early Renaissance artists and was superseded by the invention of oil paint in the 1500s.
Egg tempera consists of raw pigment, egg yolk and water. Pigments are ground with water to form a paste and then mixed (or tempered) with the yolk of an egg. Egg tempera paintings comprise of many thin and often transparent layers of colour. The medium is applied using brush strokes in a cross-hatching technique onto a wooden panel which has been coated with several layers of gesso (rabbit skin, glue and whiting), and then sanded to a smooth finish. Dozens of layers of interacting colour are necessary to build up an image and result in a rich, reflective and luminous surface.