You can apply TotalBoat epoxies over shellac that has fully cured and is unwaxed. Before you apply the epoxy, make sure the shellac surface is clean, then scuff very lightly with 320-grit sandpaper or a Scotch-Brite pad, taking care not to remove the finish. We recommend testing this in a small inconspicuous area first to ensure you get the desired finish before doing it on your final project.