Summer is a great time for a home improvement painting project. This is a project that even novices can take on, and painting a room is one of the quickest ways to get a lot of bang for your buck.
Proper preparation is the key to a successful paint job. Contrary to popular belief, primers are not cure-alls. If the existing surface is in poor condition (peeling, chalking, cracking, and so forth) you have some work to do prior to priming.
CAREFUL SURFACE PREPARATION
Remove all loose plaster, wood, or peeling paint with a scraper or putty knife. (Be certain it’s not lead-based paint. If it is, call the Childhood Lead Prevention Program at 415-252-3956.) Patch the area and any other surface cracks with spackle, paintable caulk, or a wood-patching product (depending on the type of surface). Let the filler dry thoroughly, sand, and feather sand to hide the edges of the patch. Remember: Surface irregularities will be more pronounced after painting; especially if you are using a semigloss or high-gloss paint.
The surface you plan to paint needs to be both clean and dull. If you’re not sure it’s free of dirt, stains, soap, and grease, wash it with TSP (trisodium phosphate): Mix with water as directed and wipe the area with a sponge from the bottom up; then wipe off with a clean cloth, turning the cloth frequently. TSP cleans and deglosses the surface in just one step. Use a sponge that is solvent-resistant.
Walls or ceilings with mildew need special preparation. Painting directly over mildew just encourages it to grow. Mildew might be indistinguishable from dirt, so first swab a small area with bleach and wait — dirt will be unaffected but mildew will disappear. If some of the discoloration disappears and some stays, you’ve got mildew and dirt — treat it as follows, and then clean with TSP.
To kill the mildew, saturate the surface with a solution of one part bleach to three parts water. (Wear safety glasses and gloves, and never use bleach with ammonia or any detergent containing ammonia — the resulting fumes are poisonous.) Paint within a day or two, and add mildewcide to the paint. Increase ventilation in the room; this will diminish the chances the mildew will reappear.
If the surface is glossy but definitely clean, you have two options:
One: Apply a water-based primer sealer directly to the glossy surface. Use one with a stain killer, too, if possible.
Two: Rough up the surface with a poll-sander, vacuum up the sanding dust or wipe it up with a tack cloth, and then apply a high-quality primer.
WHAT MAKES A PRIMER DIFFERENT?
One of the most often overlooked jobs in painting is priming the surface. Priming is not simply applying any type of paint prior to the final coat of paint; using the correct primer for the job will result in a more uniform topcoat and help adhesion. Primers are quite different than regular finish coat paint: They are specially formulated for sealing surfaces and increasing adhesion, and they are manufactured to have a high percentage of resins or binders to seal a surface properly.
WHAT DOES A PRIMER DO?
Primer is specially formulated to do two things. Primer provides a level, smooth surface for the finish coat of paint to bond to. Paint contains a high percentage of pigment to cover better, but may not contain enough binder to adhere effectively to a porous, uneven surface. A good primer contains a high percentage of binders (has a higher binder-to-pigment ratio than paint), so primer ensures the top coat of paint will adhere to or “bite into” the surface beneath it. Also, primer seals the surface so the finish coat of paint has a uniform appearance. This is especially important if the topcoat is going to be a satin, semigloss, or gloss paint.
WHEN DO YOU NEED A PRIMER?
High-quality paint can be used to seal a surface, but it generally takes two or more coats. A high-quality primer can do the job in one coat. So save yourself some time and money and use the correct primer from the start.
New, unpainted surfaces like bare metal, wood, plaster, and sheetrock should always be primed before they are painted. Primer should also be applied anytime the existing paint surface is of low quality. Primer seals porous paints, such as low-grade “contractor” paints. Low-quality paints can actually be more porous than a bare surface. If you don’t seal down low-grade paint, the new coat of paint might not adhere well to the old paint, resulting in peeling paint at a later date — or you may experience “flashing,” a series of high and low spots that look like blotches on the paint film.
You’ll be glad that you took these extra steps to prepare your room for painting.