How to Caulk and Mask before You Paint
After you have cleaned and repaired your interior surfaces, you have to caulk and mask before you start applying paint. Caulk covers a multitude of sins and prevents many problems from occurring. Masking protects the surfaces you don't want to paint.
Cracks show up better after priming, and caulk adheres better to primed wood, so complete any priming before you caulk. For a neat job, caulk all joints. Caulk all the joints between trim and wall surfaces to prevent penetration of moisture vapor into walls.
Cut the tips of two tubes of caulk. Cut a very small opening in one tube and use it for narrow cracks at nearly all joints between the woodwork and walls or between different trim members, such as window stops and frame joints. Cut the tip of the second tube with a larger opening for caulking wider cracks.
Apply caulk by squeezing the trigger as you either push or pull the tip along the joint. Use as little caulk as needed to fill the crack, or the excess will spread out onto the surface and be visible. Use a wet fingertip to fill very small holes and smooth the caulk. Allow adequate curing time (read the label instructions) before you paint.
Take a little time to mask areas that you don't want to paint with the following supplies:
Painter's tape: This tape, available in various degrees of tackiness and width, is designed for masking. It seals well but comes off much easier than regular masking tape does. Read the label to choose the correct type for your situation.
Pretaped masking paper or plastic: The self-stick edges adhere to surfaces, such as the tops of window and door trim, for a straight painting edge. The paper or plastic, which ranges in width from a couple of inches to many feet, drapes the surface. The seal isn't as reliable as that of painter's tape.
Don't use regular masking tape. It has too much adhesive, making it harder to remove; plus, paint bleeds under regular masking tape more easily, creating a rougher edge.
After you apply painter's tape or other masking systems, keep these tips in mind:
Press the edge with a putty knife, a block of wood, or another hard material to seal it. Doing so prevents paint from bleeding under the tape.
Remove the tape as soon as the paint has dried to the touch. Generally, you should wait three to four hours but not more than 24 hours. It's especially important not to leave the tape on for longer than 24 hours if the sun might bake the tape on or if the tape might get wet.
When you remove the tape, slowly peel it back at an angle away from the painted surface to avoid peeling off the freshly applied paint.
When you plan to paint walls and ceilings, consider masking the following areas:
The tops of base moldings
The tops of windows and door casings
The tops of chair rail moldings
The tops of baseboard heating trim
Heating or air conditioning grilles that you can't remove
The base of wall- or ceiling-mounted light fixtures