Old Masters Penetrating Sealer. A clear, penetrating oil formulated with natural tung oil to protect and seal a variety of surfaces including wood, masonry and concrete. This product seals surfaces to resist weather, mold and mildew. Suitable for both interior and exterior applications, this product can be used as a seal coat under clear finishes or paint. Produces a moisture seal that reduces concrete dusting, staining and efflorescence of masonry and brick surfaces. Also hardens masonry and natural rock surfaces and reduces frost damage.