What is an isolation coat and why is it necessary?
Before applying the varnishes to an acrylic painting, GOLDEN recommends to apply an "isolation coat" over the entire painting for a variety of reasons. The isolation coat separates the painting from the varnish by sealing off any absorbent areas and adding a protective acrylic layer preventing color from lifting if the varnish ever needs to be removed. Even if you think you'll NEVER want to remove the varnish, the isolation coat allows for a more even varnish application, and in cases of varying absorbency, can prevent satin and matte Varnishes from "frosting". Frosting occurs when a varnish with matting solids absorbs into the substrate, like gessoed canvas. These solids cannot be absorbed and sit on the surface, now stripped of their varnish resins. Once the film dries, they return to their natural dry state, an opaque white. The isolation coat prevents the varnish from being absorbed, and the result is an even matte finish.