What was encaustic

"The best wax is that known as Punic wax, the next best being that of a remarkably yellow colour, with the smell of honey. This last comes from Pontus, and, to my surprise, it is in no way affected by the poisonous honey which it has contained. The next in quality is the Cretan wax, which contains the largest proportion of propolis, a substance of which we have previously made mention when treating of bees. Next to these varieties comes the Corsican wax, which, being the produce of the box-tree, is generally thought to be possessed of certain medicinal properties". Pliny, H.N. 21, 49.