Encaustic painting was practiced by Greek artists as far back as the 5th century B.C. Most of our knowledge of this early use comes from the Roman historian Pliny the Elder whose Natural History, written in the 1st century A.D., was a monumental encyclopedia of art and science. According to Pliny, encaustic had a variety of applications: for the painting of portraits and scenes of mythology on panels, for the coloring of marble and terra cotta, and for work on ivory (probably the tinting of incised lines).
The Fayum portraits are the best known of all encaustic work. These funeral portraits were painted in the 1st and 2nd centuries A.D. by Greek painters in Egypt. Encaustic enjoyed a revival beginning in the 18th and 19th centuries when the buried cities of Pompeii and Herculaneum were uncovered. Modern encaustic painting was made possible by the invention of portable electric heating implements and the availability of commercial encaustic paint, and was popularized by it usage among many prominent artists.
For more information, download The History of Encaustic.