What is the surface preparation to apply a varnish or urethane coating to an epoxy surface?

Generally, all varnishes and urethane materials will have the same surface preparation before being applied to an epoxy surface.

1. The epoxy material must be fully cured for at least 5-7 days, under normal curing conditions.
2. Wash the surface of the epoxy with a mild soap and warm water. This is very important to remove any possible amine blush from the surface prior to sanding. It may not be apparent if there is any amine blush, and it may also occur from epoxy products that are considered non-blushing.
3. Dry the surface completely.
4. Sand the surface with an appropriate sandpaper grit — usually 220- to 400-grit sandpaper will give these coatings a good surface to achieve a strong mechanical bond.
5. Remove all sanding residue.
6. Wipe the surface with an appropriate, approved solvent wipe that is safe to use before the varnish.
7. Allow any surface preparation solvents to fully evaporate before applying.
8. Apply the varnish or urethane coating, as specified.