Encaustic painting, also called "hot wax painting", involves using heated beeswax to which colored pigments are added. The liquid/paste is then applied to a surface - usually prepared wood, though also canvas and other materials. Metal tools are used to shape the paint before it cools; also special brushes. The most renowned use of this medium is in the Fayum mummy portraits from Eygpt around A.D. 100-300. See http://www.encaustic.com/ for more details on the subject.