Keys to Successful Hand-Sanding
We're all for power-sanding, but once the heavy work is done, corded tools can't compete with a little elbow grease. That's because power sanders leave small but detectable scratch patterns that can telegraph through your finish.
In contrast, a final hand-sanding (even when using the same grit as the power sander) produces a finer, grain-aligned scratch pattern that disappears under the first coat of stain, oil, or film-forming finish. Plus, hand-sanding offers more flexibility and control you won't find from the corded competition. For smoothing curves, corners, and other small or delicate under-sanded spots, it's hard to beat a custom-made sanding block.
In this article, we'll tell you everything you need to create an economical hand-sanding starter kit. This selection of abrasives, blocks, and other materials—and the proper technique—helps you tackle most raw wood, mid-finish, and final polishing chores. You'll also learn how to make simple specialty blocks to smooth over complex profiles and custom curves.
Selecting sandpaper: Stock up to sand less
Good news! Your first goal is to sand as little as possible. Usually, this means stopping at 180 grit before applying a film-forming finish, such as lacquer or poly, and at 220 grit before oil. (Some woodworkers prefer working up to 320 grit. Test a sample piece of wood to see and feel if the extra sanding is worth it.) Getting a super-smooth finish also means lightly sanding each coat with 320- or 400-grit paper and then polishing the final coat.
If you're using a random-orbit sander, you don't need to buy a lot of extra sandpaper. For sanding raw wood, buy a few rolls of aluminum-oxide sandpaper (120, 150, and 220 grit) to complement your existing collection of sanding discs. Trash that box of partially used sandpaper scraps. You may think you're saving money, but overused scraps cut more slowly, and can leave an uneven scratch pattern or burnish the surface. In either case, you wind up with an uneven looking finish. With the rolls, you tear off only as much as you need and toss it when you're done. (For larger surfaces, buy a hand-sanding pad, equipped with hook-and-loop discs from your random-orbit sander.)
Because power sanders cut through a finish in no time flat, it's best to sand finishes by hand. And here, you have two choices: dry- or wet-sanding. Dry-sanding offers more control than wet-, plus it's easier to see what you're doing. However, the finish can clog the paper, especially if the finish isn't fully cured. To prevent this, use a zinc-stearated abrasive. The stearate coating resists clogs by lubricating the paper, but the soaplike residue that remains after sanding may cause bonding problems with some water-based finishes. To be safe, dry-sand those finishes with silicon-carbide paper, or switch to wet-sanding.
In wet-sanding, use a liquid, such as mineral oil, mineral spirits, or soapy water, to provide lubrication and float off debris that otherwise would clog the sandpaper. For this, you want silicon- carbide wet/dry sandpaper that can stand up to wet work. The disadvantage of wet-sanding, besides the mess, is that the liquid creates the illusion of a thicker finish. To avoid accidentally cutting through your finish, periodically wipe off the residue to check your progress.
Finally, invest in a few nonwoven synthetic pads for final polishing. The ultrafine (gray) pads contain just enough abrasive to remove minor imperfections without cutting through the finish. Use the nonabrasive (white) pads with a little wax; then buff with a rag to work up a showroom glow.
Save big by making your own sanding block set
Good backup is as important as the right sandpaper. By keeping the sandpaper in constant, even contact with the wood, a sanding block helps you finish faster and prevents unintentionally dishing or rounding-over your work. Luckily, you don't need to spend big bucks for good backup. Before you buy anything, search your shop for scraps, such as ceiling tile, sheet foam, and cork, that might provide firm support with just enough flex to prevent premature paper wear-out.
Leave those chunks of hardwood in the scrap bin. Because they don't allow the paper to flex, hardwood blocks tend to wear out paper in record time and leave wood looking more scratched than smooth. But by gluing sandpaper to hardwood strips, you can make wooden files that excel at shaping corners and smoothing tight spots.
Or, wrap a scrap of mating joint stock with self-adhesive paper that perfectly matches the profile. For wet-sanding, choose blocks that don't warp, swell, or disintegrate when wet, such as sponges, rubber erasers, or even old mouse pads.
Size matters, too. In this case, smaller is better. You shouldn't need to resort to a big hand-sanding block, especially if you've already used a power sander. Smaller blocks—no bigger than a quarter sheet of standard paper—offer more control and a better feel for what you're sanding. Make the blocks about an inch narrower than your sandpaper so you can wrap and comfortably grip the paper along the sides.
When it's time to sand complex profiles, small sanding blocks really shine. In most cases, it's faster and easier to smooth a tricky curve in parts, simply by using a few smaller blocks, as shown at top, than it is to make a custom-shaped block. For broad curves, try using rigid foam insulation. Shape the foam to fit the curve, and then attach sandpaper.