Is it OK to use a water-based polyurethane such as Minwax Polycrylic over an interior door surface that had previously been finished with oil-based? Minwax says it’s OK, but the lady at the home improvement store said no. Could you please break the tie?
In most cases, it is OK to use a water-based polyurethane over an oil-based finish in good condition. You should remove grease, dirt and wax by scrubbing the surface with a wood prep/cleaner/de-glosser, or mineral spirits and synthetic steel wool. Then “roughen” the surface finish lightly with medium or fine-grit sandpaper in the direction of the grain. You want to remove the gloss from the finish. Remove all the dust with a vacuum or tack rag.
Apply the new water-based finish per label directions. The application is typically done with a lint-free cloth and several coats are recommended. The advantage of the water-based finish is ease of use, quick drying, no odor, and easy cleanup.
One word of caution – read the label carefully and follow the specific instructions. Some of these water-based finishes are not for use over lacquer or shellac. Spray lacquer is commonly used on new furniture and in new construction. A great finish to try is ZAR brand ULTRA Max – a waterborne oil modified polyurethane.