Can I apply epoxy over tung oil, linseed oil, or a hardwax oil finish?

Not directly. Epoxy does not stick to oil-based finishes. Tung oil, linseed oil, hardwax oils, Thompson's Water Seal, oil-based stains, wax, and mineral oil all leave a residue that repels the epoxy, and oil-based products take a long time to fully dry. The epoxy will either bead up on the surface or stick at first and peel off months later.

You have two options.

Seal the finish in: apply at least 3 coats of oil-based polyurethane over every inch of the surface, let it dry 24 hours, then apply UltraClear Bar & Table Top Epoxy as normal, seal coat first, then flood coat. If the epoxy pools up or pushes away anywhere, that spot did not get enough poly. Once cured, the epoxy seals the poly in, which makes the surface food safe.

Strip it: take the finish completely off, back to raw wood. Sanding alone may not be enough; old oil can still cause adhesion problems unless it is fully stripped. For wax, that means multiple applications of a strong degreaser followed by thorough sanding. On raw wood the epoxy goes on directly, no poly needed.

If you haven't finished the wood yet, skip the oil or wax; the epoxy itself makes the grain pop. For color, use a water-based or alcohol-based stain, let it dry at least 24 hours, then apply the epoxy.

Bar & Table Top Epoxy Instructions: https://cdn.shopify.com/s/files/1/0320/7168/0140/files/Epoxy-Instructions.pdf?v=1616443869 Tutorial Videos: https://www.bestbartopepoxy.com/tutorial-videos/