To work efficiently, first set up a work area. If you don’t have a garage or other place to paint, or if you have a built-in bookcase, clear away nearby clutter and spread a dropcloth to protect your flooring. Use a stepladder if you can’t easily reach the top. And set up a staging area for the paint and tools. (Consolidating the mess on a big piece of cardboard minimizes dribbles across the dropcloth.)
Remove any hardware, such as shelf supports and door hinges, and label the parts.
Then prepare the surfaces for paint. If you’re starting with a new bookcase that’s never been painted or varnished, you probably just need to vacuum or dust thoroughly. A previously finished bookcase might also just need that. But if it has grimy fingerprints, oily deposits or mysterious gunk, then you need to wash the finish. Moisten a cloth in warm water mixed with a little bit of hand dishwashing soap. (For especially oily deposits, use a TSP-type cleaner or a degreaser, such as Simple Green’s all-purpose cleaner.) When no more grime comes off, go over the surface again with a clean cloth moistened with plain water.
A word of caution: If the bookcase is made of particleboard, a category that includes medium-density fiberboard (MDF), be careful to wring out the cleaning and rinsing cloths thoroughly, and immediately dry the surface with another cloth. You need to clean the finish but keep the particleboard dry. Particleboard swells if it gets wet, and the distortion doesn’t revert when it dries out.
Once surface is dry, inspect the finish. If paint or varnish is cracked or flaking off in numerous areas, you might need to remove it, probably with a chemical stripper, which greatly increases the amount of work and mess. But if just a patch or two is loose, scrape off the chips, then lightly sand to round over the sharp edges where the paint came off. Go over the whole surface with 120- or 180-grit sandpaper until it’s evenly dull. The idea is to scuff it up, so paint sticks better, not to remove the old finish. (If your bookcase is from before 1978, first test for lead, and skip sanding if lead is found.)
Then, in many cases, you’ll prime. You definitely need a primer for a new bookcase that’s never been painted or varnished. Water-based primer works well on natural wood, but use a solvent-based primer for particleboard, because a water-based primer can cause the fibers to swell. Also prime if you are switching from a clear finish to paint, switching from oil-based paint to water-based paint, or making a dramatic color change. A primer might not be necessary if you are sticking with the same type of paint or are making only a slight color change. If in doubt, prime. Use a primer labeled as suitable for slick surfaces if you are going over a finish such as polyurethane or lacquer.
Wait the recommended time, then lightly sand again, this time with a finer grit, maybe 220. The idea here is to knock off any bits of paint that stick out. Wipe off the sanding debris. Then apply the topcoat paint. Wait the suggested time, then apply a second coat.
For both primer and topcoats, the process is similar. Paint from the innermost areas to the outermost, so you don’t have to reach over wet paint to get to the next section. By using both a small roller of about one inch in diameter and a 1½-inch angled brush, you can achieve a surface that’s nearly as flat and blemish-free as if you sprayed the paint.
Open the can and thoroughly stir the contents. Pour some of the paint into a tray sized for this type of roller. Use the brush to paint inside corners and edges, and use the roller to spread paint over the flat areas. You can leave the rolled areas as-is (paints generally flatten as they dry), or you can immediately brush over the area with the nearly dry brush to level the paint. But places where you go over partially dried paint will show, as will places where you overlap dry paint with wet paint, so work in manageable areas, ideally in sections that span the whole length of the board. Once you go over an area one time to smooth out the paint, move on to the next section. Resist the temptation to go back to touch up bare spots; leave those for the second coat.
It’s not necessary to wash tools between coats, provided you apply the additional layers in the next day or two. Wrap the brush and roller in plastic to keep the paint from drying out. Covering the opened paint can with a plastic bag while you are painting also helps keep the paint at the right consistency.
Water-based paint dries to the touch fairly quickly, but it continues to cure over the next 30 days or so. During that time, two newly painted surfaces that touch will probably bond, causing the paint on one surface to peel off when the two are pulled apart, something the paint industry calls “blocking.” So feel free to reinstall your hardware soon after the paint is dry, but wait as long as you can to close any doors, or they will probably stick.
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