What was encaustic
"The true composition of the so-called Punic wax and the interpretation of Pliny´s first-century recipe have been the subject of heated discussion until the present century". Kurt Wehlte. The materials and techniques of painting. 1982, 410.
"In Berger's recipe to reproduce Punic wax, white wax is used, so the treatment with sea water and sun exposure seems superfluous. 100 grams of white wax are boiled with 10 grams of potassium carbonate, until wax is dissolved. [...] According to Laurie, Berger was wrong, and the conditions under which he prepared the original product did not make the wax is saponified, but simply to whiten it and refine it. If this is true, Punic wax would have been simply refined white beeswax; most researchers agree share this opinion". Ralph Mayer. Materiales y técnicas del arte. 1985, 366.
The actual composition of Punic wax has given scholars much cause for debate. [...] It is unclear from these references [Pliny´s recipe] wether Punic wax was merely a form of purified beeswax or whether the addition of potassium carbonate actually caused it to become saponified. Danielle Rice. Encaustic painting. The dictionary of art, 1996, 197.