Tempera

Tempera (also known as egg tempera, poster color or poster paint) is a type of artist's paint and associated art techniques that were known from the classical world, where it appears to have taken over from encaustic and was the main medium used for panel painting and illuminated manuscript in the Byzantine world and the Middle Ages in Europe, until it was replaced by oil painting in Europe. It has remained the required medium for Orthodox icons. It is paint made by binding pigment in an egg medium. However, the term tempera in modern times is also used by some manufacturers to refer to ordinary poster paint, which is a form of gouache that has nothing to do with real egg tempera. One might observe simply by washing breakfast dishes that egg yolk dries quickly and adheres firmly. Tempera was traditionally created by hand-grinding dry powdered pigment into egg yolk (which was the primary binding agent or medium), sometimes along with other materials such as honey, water, milk (in the... full article at wikipedia