The technique of encaustic dates back to ancient Greece. It is a mixture of beeswax and damar gum to which are added the pigments. Encaustic is considered the most permanent among the painting techniques because of the propensity of wax to remain impervious to moisture (and the mold it causes) and to reject dust.
Besides having a wide range of effects from opacity to transparency, it allows the use of strong impastos therefore accentuating the materiality and makes the viewer want to touch the painting.