You have three problems here. The first is that the encaustic has been applied to an acrylic gesso, which is not absorbent enough for encaustic to bond to. Second, is the stretched canvas. Stretched canvas is flexible and expands and contracts with changes in temperature and humidity far more than wax. This difference in movement exacerbates wax’s inability to adhere to acrylic. Third, if the melted crayon is something like Crayola, the wax is paraffin wax, which has very low adhesive properties compared to beeswax. So, while you can warm the painting (I suggest from the back of the canvas so that the bottom of the wax where it bonds to the canvas is melted first), the problems with the paraffin and the acrylic gesso remain. You can solve the problem of the flexible canvas by adhering it to a rigid surface. If the wax hasn’t seeped through, any archival glue like PVA or acrylic gel medium will do. Richard Frumess, R&F Handmade Paints
Could you perhaps share more information about the canvas (cotton? linen?), sizing (if present), ground (what type of gesso), and specific brand of crayon (if known)?
