Waterlox ORIGINAL Tung oil finishes and URETHANE finishes can be used over top dried and cured Epoxy as long as it is lightly sanded first. The Epoxy should be lightly sanded with 220-grit sandpaper to “break the surface gloss”. There should not be adhesion issues with the epoxy; however, the film will build faster over top of it since it won’t really be soaking in like the rest of the bare wood. Eventually the film will even-out with more coats and more film build. The only fail-safe way to ensure that there won’t be an adhesion issue is to conduct a cross-hatch test.
A cross-hatch test is an industry test for adhesion. Waterlox ORIGINAL Tung oil sealers are penetrating oil sealers and are therefore best used on bare wood (does not refer to stain coat(s) if used). Sometimes, sanding the surface is not an option for a project. To test the adhesion properties of a combination of finishes, test on an inconspicuous area first.
Directions to test for adhesion: Scuff sand a small inconspicuous area with 320 grit sandpaper. If you will not be sanding the surface to bare wood in the actual project, clean the area with TSP (trisodium phosphate) and water and complete a clear water rinse. Apply 1 coat of the intended Waterlox Sealer or Finish. Allow the finish to cure for 4 days. Scratch a “tic-tac-toe” board into the cured finish by cutting through the film and into the wood. Place a piece of Scotch® tape over the cross-hatch and press it down firmly with your finger(s). Pull one end of the tape off with a steady motion. If there is any film on the tape, other than the pattern of cuts you made into the substrate, this finish combination will not have adequate adhesion.
If the test fails, the system is incompatible.
