Casein Paint is a water-base paint made using Casein as the base.  Casein is a white colored protein that is colorless and odorless. Casein is precipitated from milk using rennin. It is the earliest known medium. In Asia, there are cave paintings done using the medium.  Ancient artists of the eastern Roman Empire have used this in  Byzantine art. This paint is fast drying and water soluble. It can be used on surfaces such as board, paper, and wall. However, it cannot be used to paint on canvas. Casein paint can be varnished to get a shinier look. Now casein paint is available in tubes.