I love using all kinds of watersoluble mediums on the surface of an encaustic painting. Keep in mind, using such mediums on an encaustic painting are "delicate" and need to be handled gently when you heat/fuse these layers in. I often use such mediums as either the final top layer, or lightly fuse in and apply encaustic medium or paints carefully over the top, again being careful to fuse each layer in.