1. What is it?
Tempera is a type of painting medium that consist of a colored pigment mixed in with a binder, usually an emulsion of water and egg yolk. This type of painting medium is very fast to dry and is very long-lasting. Tempera painting simply refers to paintings done using this sort of medium. The artist will first grind the pigment into a powdered form and will then place a small amount of this on to a palette. Next the artist will add a few drops of distilled water to the pigment. Then the egg yolk binder is added in small amounts until the solution is as transparent as the artist wants it to be. The amount of binder that's required depends on the pigment being used. While painting, the consistency of the paint needs to be preserved and this can be done simply by adding more water to the paint.
2. When was it used?
Tempera paintings appear to have originated in classical times. There are references to this sort of painting through Latin, Greek and ancient Egyptian literature. Numerous important works of art were said to have been made using this medium, so it appears that was quite popular with artists of the time. Some examples of tempera painting from antiquity do survive, such as the 'Severan Tondo,' which is a portrait of Septimus Severus, the Roman emperor. After the collapse of the Roman Empire, tempera gradually overtook encaustic as the main painting medium. Encaustic painting is the technique of adding heated beeswax to colored pigments. Tempera painting became wildly popular through Europe and Asia and was favored by many top artists. However, with the advent of oil painting in the 16th century, tempera painting gradually became less popular, although it is still favored by some and enjoys revisions from time to time.
3. What are some of its properties?
One of the main properties of tempera paint is that it's not a flexible painting medium. What this means is that it needs to be applied to solid surfaces; wood panels were commonly used, for example. If it is applied to a softer surface, such as a canvas, it will end up cracking. This paint medium dries very quickly and the colors stay the same over time. Tempera paint can not be applied in really thick layers, so it can not produce the same richness of color that oil paints can. Artists have to work with tempera paint quite quickly as once it's been prepared, it can not be stored and has to be used up.