How To Get A Door Ready For Painting
Regardless of the material a door is made from, it's important to make the proper preparations prior to painting so that the job will go smoothly. If you don't make these preparations, your paint might not fully cover the door's surface. Or it might not even adequately stick to the door, resulting in wasted money and time. By taking the time to make sure the job is done right (meaning sanding, applying primer, and masking hardware) chances are better that you'll achieve a professional looking finish that will last for years to come.
Cleaning the Door
A complete cleaning (regardless of the age of the door) will help to get it ready for priming and then painting. It will remove coatings or oils that might be on the surface along with grime, pollen, pollution, or dirt. A regular household cleaner will normally work just fine. You may need a degreaser for any grimy buildup that might have accumulated (especially on doorknobs).
Masking protects areas not being painted, such as glass panes, lock assemblies, kick plates, and handles. If you aren't taking the door off its hinges to be painted, but instead plan to paint the door in place, you should also mask the floor and hinges. Masking or painter's tape can be used to cover smaller areas like hardware. For your floor, use either a painter's drop cloth, a tarp, or newspaper.
Sanding Doors and Filling
Even in cases in which a door is not wood, carefully sanding the door can help both the primer and the paint you've selected adhere better. Either a sanding block or sandpaper (fine-grit) will work for most doors. Always use a cloth to wipe a door off after sanding to remove dust. If the door is wood and a bit older, you may see some chips or holes. You can repair this by applying wood putty and then sanding these areas down to make them flush with your door's surface. Remember that doors made before 1979 may be hazardous, since paints made prior to this date sometimes contained lead. If this is the case, you should get help from a professional when removing paint.
Some wood and metal doors now being manufactured are pre-primed, so it's not actually necessary that you add an additional primer coat. For other doors, you will have to apply a primer. Primer can help to provide a much better grip for paint. Make sure to use a plastic or metal primer for plastic or metal doors. However, an exterior or interior latex primer is a better choice for wood doors.