Lightening up the wall color is a good way to bring a sense of space, and, of course, more light into a room, but if the paint doesn't hide the color properly, streaking and bleed-through can negate the benefits of the color change. The keys to good coverage are that quality materials and best painting practices that you should use for all your projects.
Clean and Scuff the Walls
Any dust or grease you leave on the walls prevents paint adhesion, and you may not notice voids and streaking until after the paint dries. To prevent this, wash the walls with a soap-and-water solution. If you're painting over gloss or semigloss paint -- especially in the kitchen -- mix a cup of trisodium phosphate with a gallon of warm water for a cleaning solution. This strong detergent, which requires the use of rubber gloves, etches while it cleans grease and grime. Let the walls dry; then scuff gloss or semigloss paint with 120-grit sandpaper to give the surface "tooth" and ensure proper paint adhesion.
Undercoat With High-Solids Primer
If you're repainting walls with a matching color, you can sometimes skip the primer or use a product that combines primer and topcoat in one application. But this is a self-defeating strategy when you're painting a light color over a dark one. Primer isn't the same as paint; a quality primer is formulated with extra pigments and binders to prevent color bleed-through. Don't use conventional drywall primer for this; instead, choose an interior stain-blocking primer intended for use on walls. It will be a little more expensive, but if you tint it toward the color of the topcoat, you may be able to save by avoiding extra coats of wall color.
Use Quality Paint and Apply It Correctly
The paint you use matters -- premium-grade products contain higher concentrations of pigments and solids for better hiding.
- Check the coverage on the can and buy enough for at least two coats -- that way, you won't run out to get a new batch that may not be a perfect match.
- Mix the paint at the paint store; then mix it again before you use it as insurance against minor color variations during application.
- Use the paint full strength from the can; thinning it only undermines the coverage. This applies even when spraying unless you encounter clogging, spitting or other problems.
- Apply latex paint with a nylon roller or synthetic bristle brush. When rolling, use a 3/8-inch nap cover for best leveling and hiding.
- Go for uniformity of coverage rather than laying paint on thick in the hopes of finishing the job with a single coat. Two light coats are better than a single heavy one.
You probably won't need more than two coats, but to be sure, let the second coat dry; then examine the walls from several angles using a work light. If you can see dark spots, touch them up with a roller; if you notice many spots, you may need a third coat.