encaustic, painting medium in which the binder for the pigment is wax or wax and resin. Examples of encaustic tomb portraits from Roman Egypt bear witness to the durability of the medium, which is thought to have been widely used in ancient times. Pliny describes the process in which hot liquid colors were applied to the wall by means of heated irons. The technique was briefly revived in the 19th cent. and is now used by a number of contemporary artists.