Answer:
Tempera paint is made by mixing egg yolk with water.
It was widely used throughout history because it was cheap.
Step-by-step explanation:
Because the production of Tempera Paint was very cheap, it was widely used throughout history. It is also fairly easy to obtain: it is created by the mixture of water and egg yolk, along with the pigment. Nowadays, other materials such as glue can be used for the production.