Clear Stain and Tannin Blocking Sealer. Penetrates & Seals Wood Grain Fibers creating a waterproof barrier. Can be used on bare wood as well as under paints and top coats. All the benefits of Shellac but it's "knot". This is an easy to use water based formula that can be brushed or sprayed and will not yellow or amber over time. Use 2 or more coats.