Medium-density fiberboard, or MDF, is commonly used for interior doors. MDF is a low-cost material with outstanding durability, great for regularly used door surfaces. Unfortunately, MDF itself is a rather ugly material. A raw MDF door accepts basic primer and paint, but many MDF doors are coated with thin, glossy veneers to improve the door's look. Plastic and vinyl finishes are tough to paint without the right type of primer. When you paint over an MDF door, you need to make sure the surface is prepped and primed for best results.
Sand raw MDF doors or wood-veneer MDF doors with 150-grit sandpaper. If your MDF door is coated with a vinyl or plastic veneer, don't sand the door.
Wash the door with a trisodium phosphate cleanser, or TSP, and a rag. TSP cuts through dirt and fingerprint oils commonly found on door surfaces. The cleanser will also wash away leftover sandpaper dust.
Lay a plastic tarp on your workspace, and place two sawhorses over the tarp.
Remove the door from its hinges and take off the doorknob with a screwdriver.
Place the door on the sawhorses.
Prime raw MDF or wood-veneer MDF doors with general purpose primer. Prime plastic or vinyl-coated MDF doors with bonding primer. For either type of primer, use a medium-nap roller for quick primer coverage. Wait for the primer to dry.
Paint the MDF door using high-gloss latex paint and a foam roller. Glossy finishes are preferred on most doors, because they are easier to keep clean. Wait for the paint to dry.
Flip the door over and repeat Steps 6 and 7 to paint the back side of the door.
Reattach the MDF door hinges and knob with a screwdriver.