When amateur painters try to paint over a surfaces treated with a polyurethane finish, flaking often occurs. Polyurethane is a waterproof sealant that protects surfaces from moisture. Unfortunately, its waterproof characteristics also leave polyurethane ill-suited for paint. In addition, because polyurethane finishes are oil-based, they will reject water-based latex finishes. Combat this by treating the polyurethane with a special oil primer, specifically formulated to work with latex topcoats.
- Skill level:
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Things you need
- Water-based soap
- Oil-based primer
- 2- to 4-inch natural-bristled paintbrush
- White spirit
- Latex paint
- 2- to 4-inch polyester paintbrush
Wash the polyurethane finish with water-based soap, using a sponge. Rinse the finish with wet rags. Allow 24 hours of dry time.
Sand the polyurethane finish until it appears dull.
Coat the polyurethane finish with the oil-based primer that is compatible with water-based topcoats, using a two-to-four inch natural-bristled brush. Wait two hours for the oil primer to dry.
Clean the brush with white spirit. Don't use tap water, as this will destroy the brush.
Coat the primed polyurethane finish with latex paint, using a two-to-four inch polyester brush. Wait two hours for the finish coat to dry.
Use water to clean the brush. Don't use white spirit, as this will destroy the brush.
Tips and warnings
- Kilz makes an oil primer that is compatible with latex paint.
- Most oil-based primers will reject latex paint. Study the labelling to make sure that the primer you select will work with latex topcoats.
- Do not paint over an unprimed polyurethane finish, or peeling will result.
- Do not prime an unsanded polyurethane finish, or flaking will result.