Typically, priming will be done with Encaustic Medium on an absorbent ground.
 
But.
 
Encaustic Gesso provides an alternative for wax priming and prepares almost any surface for the encaustic painting process.
 
It is ideal for integrating other mediums such as watercolor, graphite, charcoal, pastel and collages with encaustic painting. Just place the art work on the primed surface and cover with encaustic paint.
 
How to make your own Encaustic Gesso
Mix 5 parts of Acrylic Paint (wall paint works well) with 3 parts of the Encaustic Gesso Mix and stir until dissolved.