Im experimenting with thin layers of plaster mixed with pva and water on a large canvas to get a slight relief.Im painitngn it onn then scultig it into a thick paint like texture, to mimmic thick layers of paint, but allows for more texturing. Do you think when it dries I can just paint acrylic over the top of it , or will it need priming ?? Just hoping that if sold it doesnt start to crumble off with the central heating in places!!!!