Waterlox
Original Tung oil finishes can be used overtop of 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 finishes are penetrating oil finishes 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 Waterlox Original Sealer/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.