Rubbing the finish
The smooth, clear look that you see on expensive furniture and high-end musical instruments, such as pianos and guitars, is achieved by rubbing out the finish. Rubbing the finish removes dust nibs, brush marks and other imperfections, levels the surface, and gives an even sheen. The only way you can get a super high gloss look is by rubbing the finish. Essentially, rubbing is sanding the finish with successively finer grits of sandpaper, along with a lubricant.
There are two basic steps in rubbing. The first step involves sanding the surface flat. The second step involves rubbing the finish to the level of gloss (or sheen) that you want. After you have rubbed out a few surfaces you can begin to adjust the basic rubbing schedule presented here.
Finishes to Rub
The best finishes to rub are the evaporative finishes, shellac and lacquer. Multiple coats fuse together into one layer, and they cure brittle and hard. The reactive finishes (varnish and polyurethane) and coalescing finishes (water based) are more difficult to rub out. The layers of these finishes do not fuse together – each layer sits on top of the previous layer, so if you rub through one layer into another layer you’ll leave a visible mark. Although these finishes are time consuming to sand, they cure tough and, unlike brittle finishes, don’t scratch easily.
Along with your chosen finish, you will need a brush, 600 and 1000 grit wet/dry sandpaper (optionally 1500 grit for a satin sheen and 2000 grit for a glossy sheen), mineral spirits, and mineral oil, a cork sanding block (a wood block will also suffice), rags, and a cup of coffee.
Applying the Finish
Finish sand your project to 220 grit. For open pored woods like oak, mahagony and walnut, you may want to apply a pore filler. If colour is called for, apply a stain. Optionally, finish off with a coat of shellac, then lightly sand. (Note, don’t apply shellac under lacquer, and be sure that you use de-waxed shellac under polyurethane).
If you are aiming for a glossy sheen, then use a gloss finish. Lay on at least six coats, lightly sanding between each coat. Be sure to wipe up the dust from each sanding. Allow each coat to dry for a full day before applying a subsequent coat. After you’ve applied all the coats, you’ll want to let the finish cure for about a month before rubbing it out. Minimally, let it cure for a week. I’ve had excellent results using shellac flakes, Defts’ ‘Gloss Clear Wood Finish’ brushing lacquer, and good results with Minwax’s ‘Fast Drying Polyurethane’.
Laying down sufficient coats of your finish is important, as you run a risk of rubbing through the finish as you move to the next step.
Rubbing the Finish
You need a lubricant to use with the wet/dry sandpaper. A mixture of 2 parts mineral spirits to 1 part mineral oil will cut quickly, but not too aggressively. You can also use water with a couple of drops of soap added, though this cuts very fast, so proceed with caution.
Wet your surface, and begin sanding with 600 grit wet/dry sandpaper. On flat surfaces use a cork or wood block. Your aim is to produce an evenly dull sheen without any shiny spots. Check your sandpaper frequently – as soon as it becomes clogged (‘corned’ with tiny balls of finish) clean the paper, or use a fresh piece. Every so often clean off the surface and have a look at your progress. Be careful of rubbing too much along the edges, or you will cut through the finish. If your finish has a lot of brush marks, bubbles, and/or dust nibs you can try using 400 grit paper before the 600 grit. Just go a bit slower and check your work often. Once you’ve removed all the shiny spots, clean off the surface. Now repeat the rubbing process with 1000 grit wet/dry paper and lubricant or 0000 steel wool until you produce an even shine. You can continue rubbing with finer grit paper until you’ve reached the level of sheen you desire. Once you get to the higher grits you can optionally use an Abralon sanding pad, which are available up to 4000 grit. Use the Abralon pads by hand or with your random orbital sander.
You can achieve even more sheen by using a rubbing compound, such as the Menzerna compounds. These compounds are applied by hand, with a soft cloth or buffer, after you have levelled the finish with sandpaper. Whether I use a rubbing compound or not, I always end off by applying a coat of wax.
Your first rubbing session may not give you stellar results. Don’t get discouraged, like much in life, practice and patience make all the difference.