Eitempera is an emulsion of egg as emulsifier, oil and water as painting agent for the colour pigments. Minor additives, such as beeswax, may vary the properties of the emulsion.
Due to its low oil content, it is far less yellowing than oil paint, and also more resistant to atmospheric and mechanical influences. After drying, egg tempera is no longer soluble in water and is hardly prone to cracking.
The colours remain constantly airy and light. They do not require any varnish or other coatings and therefore do not suffer from their negative influences.
How do I mix egg tempera paint myself?
The tempera colour that was generally preferred in ancient times until the 16th century was rediscovered by Böcklin and other painters of the 19th century.
Theodor Gerkens
Definition egg tempera/Egg tempera painting