Techniques for Sanding Before Painting
Sanding isn't difficult, but it's a labor-intensive, dusty job and one you can't avoid if you want your painting efforts to produce the best results. Various sanding machines are available to speed up the job, but the only one you're likely to need is an orbital, or pad, sander. Models with rectangular, square, round and triangular pads are pretty much equivalent unless you have to sand a lot of corners and crevices. In that case, a triangular pad works best. Stick with more expensive, higher-quality sandpaper. It lasts longer and sands more efficiently than lower-quality paper.
Trim and Interior Woodwork
Smooth new, unfinished trim with a sanding sponge. It molds to the surface you're sanding, thus avoiding wear on ridges and raised features. Sand with the grain, and don't overdo it. A single pass with a 120-grit sponge will remove splinters and get the wood ready for primer.
Prepare old trim with peeling paint for a fresh coat by sanding with a pad sander and 100-grit sandpaper. The sander will remove loose paint faster than you can do it with a scraper, and it will flatten edges around areas where paint has fallen away. Follow up by sanding by hand with a 120-grit sanding sponge.
Hand-sand unfinished interior woodwork with 120-grit sandpaper. Tear a sheet of paper into thirds, then fold one piece into thirds and use it to sand along the grain of the wood. Follow up by sanding with 150-grit paper in the same way prior to priming and painting.
Smooth unfinished furniture by hand-sanding with 120-grit sandpaper. Use the edge of a folded sheet to knock down the grain in turnings and carvings. Follow up with 150-grit paper.
Fit a pad sander with 100-grit paper to sand a piece of furniture that has been stripped. Sand all the flat areas, and work the edges of the paper into turnings and carvings. A sander with a triangular pad works best for this job. Erase scratch marks by hand-sanding with 120-grit sandpaper, then finish up with 150-grit paper.
Etch each coat of paint before you recoat it by hand-sanding it with 220-grit sandpaper after it dries. It isn't necessary to follow the wood grain, because you're only sanding the finish -- not the wood.
Prepare freshly mudded walls for paint by sanding them with 120-grit sandpaper. The best tool for sanding walls is a pole sander.
Tear a sheet of sandpaper in half, attach one half to the pad on the end of a pole sander and sand the wall lightly to smooth the joint compound. Move the paper along the seams whenever possible to avoid exposing the drywall tape.
Sand an entire wall or ceiling painted with gloss paint before painting over it. Use the pole sander and 120-grit sandpaper to do this. The sandpaper will etch the paint so that the new paint will adhere better.
If you live in a house built before 1978, some of your walls and woodwork may have a layer of lead-based paint. If you suspect this, don't sand them yourself because lead is toxic. Call a professional painter for help.
Wear a dust mask while sanding to protect yourself from dust inhalation. You may also need goggles when sanding newly mudded walls.
Things You Will Need
- 120-grit sanding sponge
- Pad sander
- Sandpaper, various grades
- Pole sander
Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.
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- Stockbyte/Stockbyte/Getty Images