Encaustic Medium is the encaustic paint without pigment. It is used to extend the colours in order to create transparencies. It is important when extending the colours to use the encaustic medium rather than plain beeswax. There are two reasons for this:

1) It maintains the hardness of the film.

2) Encaustic made only with beeswax will develop a bloom in cold temperature that can only be removed by reheating the paint. The damar helps to prevent this blooming.