Do you have a stained dresser that you want to paint with white furniture paint to blend with your updated bedroom design? Maybe you want to spruce up the stained wood paneling in your living room with a coat of flat wall paint. Either way, it won't take any extra effort to paint over stain than it would to paint over unfinished wood. In fact, it will probably take less effort if you know the tricks of the trade.
You have to sand unfinished wood but usually not stained wood. You may have to degloss it with a chemical deglosser, but that's easier than sanding. You do have to apply a primer over stained wood to prevent the stain from bleeding through, but you have to prime unfinished wood too, so this isn't an extra step.
Sand or Degloss Before You Paint Over Stain
Most stains fill the wood grain to a small but significant degree, and that's good news when you're painting because it probably means you need less paint. Stains leave the surface slightly furry, though, so you need to cut down the grain by scuffing with 150-grit or finer paper. Always scuff with the grain because cross-grain scratches are visible even under paint. If the stain is under a coat of lacquer or polyurethane, it's even more important to scuff because the glossy surface may prevent the paint from adhering.
As a time-saving alternative to sanding a poly or lacquer coating, wipe down the finish with a chemical deglosser. Be sure to wear gloves and a respirator when applying the deglosser because deglossers are highly volatile and hard on the skin. If you're interested in painting cabinets without sanding, this is the way to do it.
Use a Primer for Stained Wood
It's important to apply a primer to bare wood before you paint to ensure even coverage, and it's even more important to prime over stained wood. Besides improving paint adhesion, the primer locks in the stain and prevents it from bleeding through. Bleed-through is a common problem with stained wood, and it results in patchy areas of discoloration.
You can generally use any water-based, high-solids, stain-blocking primer for interior woodwork, but if you continue to have a bleed-through or you're working outside, you should use a shellac-based primer. It's smelly and requires paint thinner, which is even more odorous, but it's the gold standard when it comes to blocking bleed-through. It's the best primer for stained wood.
Apply a single coat of primer, and if you're using a brush, always stroke with the grain of the wood. Remember that brush strokes will be visible under the paint.
Make Repairs and Scuff After You Prime
Whenever you paint over old woodwork, you'll have holes and cracks to fill and chipped edges to repair. The best time to make these repairs is after the primer has dried. Not only does primer improve paint adhesion, but it does the same for filling materials such as plastic wood and spackling compound.
Primer also improves caulk adhesion, so if you're painting over previously stained baseboards or interior trim, do any necessary recaulking after the primer has dried. When the caulk dries, it's a good idea to prime it, but if you're in a hurry, you can just go ahead and paint it.
The final thing you should do when you paint over stain is to scuff the primer. Use 150- or 220-grit sandpaper and apply light pressure. The idea is to flatten brush-stroke lines without actually wearing through the primer. Wipe off sanding dust when you're done, and you're ready to paint.