Encaustic is an ancient technique of painting with pigments mixed in wax. The technique dates to at least the second century BC in Egypt, but was also used in Rome, Greece, and other countries in the area. The word encaustic comes from the Greek word encaustikos, meaning "to burn in." This etymology can be used to distinguish encaustic painting from other uses of wax to create art. Encaustic refers specifically to the process of painting with wax in which the layers are fused together with heat, or burned in. This does not include other techniques such as drawing with crayon or using wax based painting mediums. Notable 20th Century artists who have used encaustic techniques include: Diego Rivera, Karl Zerbe, David Aronson, and Jasper Johns.