Tempura, also know as tempera refer to a number of things. First of all it was a word for liquid binder or vehicle for mixing powdered colour pigment.
Subsequently, it became synonymous for paint with binder/vehicle being egg yolk and water. As a natural progression to this, the word was associated with the technique of creating art with tempura. Egg tempura originated in medieval Europe and principally used for painting on wood and later easel painting on canvas until the development of oil painting.
Tempura painting requires a certain flair to master, and is still practiced by artists as well as art restores today. The point of the brush is used to hatching or laying tempura on in pre-mixed grades to create gradients because tempura colours do not blend.
Tempura lends itself to a very linearly planned method of developing art. The paint dries extremely quickly, and the soft glowing colour of tempura is not easily copied by any other medium. The protein content of the binder hardens up and makes the layers of paint water resistant and incredibly hard-wearing without the need for varnishing. It goes some way to explain why Centuries later, tempura art still has a lustre and quality that we admire. As the pigment itself was made of things such as ground crystal and gem stones (e.g. Lapis lazuli), the colours stay vivid. The colours are then rather being compromised with a film of dirt and grease than actual fading due to exposure of light.
Tempura has arguably been used by the ancient civilisations of Egypt, Greece and the Roman empire.
But tempura, as the reliable technique we know it today, was only really perfected fully in the Byzantine era. In the 14th and 15th Century Italy, it became the preferred artist medium for early Renaissance painters Duccio, Cimabue, Giotto and Lorenzetti brothers. Subsequently Fra Angelico and Botticelli mastered tempura painting.