Paint created by mixing dry pigments with molten wax, usually beeswax. Sometimes small amounts of natural resins, such as dammar or Venice turpentine, are added for hardness. Oils, such as linseed oil, are added for increased workability. Encaustic paint was used as early as the 4th and 5th centuries BCE in Greece. The paint was applied warm with a spatula or brush. It hardened quickly and fused to the surface.

Source: AAT

http://vocab.getty.edu/page/aat/300183750