Screen Goo Premier Primer is a non-toxic, 100% acrylic, water-based coating. It is suited for priming all porous surfaces such as drywall, plywood, plaster and masonry. Its principal advantage over conventional primers is its 100% acrylic base. The vast majority of water-based primers include a class of budget medium/extender called PVA which is substituted for a pure acrylic base for cost reasons. PVAs, however, are very susceptible to yellowing when exposed to UV light and will eventually discolour and compromise the performance of Screen Goo.