Jo Sonja's All Purpose Sealer is a surface 'primer' and will seal a wide variety of items in preparation for painting. Pre-priming with All Purpose Sealer or Gesso will ensure good paint adhesion and will prevent moisture loss into absorbent surfaces. Use All Purpose Sealer rather than Gesso on items which require sealing without 'tooth' or opaque colour. Great for sealing surfaces such as wood, MDF (Fibreboard), cardboard, paper, canvas, metal, unglazed bisque and terracotta. All Purpose Sealer is a primer, not a finishing varnish. If used as a varnish it may become tacky in warm weather and cause surfaces to stick together. It is also not as durable as Jo Sonja's Polyurethane Varnish and is not recommended for this purpose.