What was encaustic

"A certain youth was selling a little [encaustic] painting of Eros [Erota kérinón]". Anacreon, Odes 14.

"Soon, painting [keré], like her, you’ll talk to me". Anacreon, Odes 18.

"Even as paintings [cerae], that the artist’s thumb will bring alive, take on form, following the fire and the hand, such was the picture of the goddess as she transformed her son". Statius, Achilleid 1, 332-334. (1st century AD).