Whether you want to paint an old wood door or you want to add paint to a new, unfinished door, proper prep work is important. Wood surfaces need special attention prior to applying paint. If you don't sand the surface or apply the right primer, you could end up with poor paint adhesion or unwanted stains from the wood's natural oils. Preparing wood doors for painting takes several hours, but this early labour will prevent time-wasting complications down the road.
Unscrew the door from its hinges and place it on a plastic sheet or canvas dust sheet. The door will be much easier to prepare if it is on a flat surface. You'll need to work on one side of the door at a time, but overall this method will lead to fewer primer drip marks and better results.
Remove knobs or handles from the door. Many doorknobs are removed using a simple screwdriver.
Wash the door with a trisodium phosphate (TSP) cleanser. On a used wood door, the TSP cleanser removes fingerprint oils. On new doors, this cleanser gets rid of any natural oils from the raw wooden surface. Flip the door over to wash both sides of the door.
Sand both sides of the door with 220-grit sandpaper.
Wipe away any sandpaper dust with a damp cloth.
Apply stain-blocking primer to one side of your wood door. Brush the primer on using a regular paintbrush, starting with any raised or receded details on the door. Once you've painted any ornamental details, start priming at the door's edges and work inward.
Flip the door over after the first side has fully dried. Coat the other side of the door with stain-blocking primer, beginning with intricate details, then moving to the edges and, finally, the centre of the door. Once this layer of primer dries, the wood door is ready for painting. Do not reattach the door's hinges, as painting a loose door is easier than painting a door attached to its frame.