Fill, Level, and Buff for the Win!

The Lowdown: With all film building finishes (polyurethane, tabletop varnish, shellac, and lacquer), there’s just a few critical elements missing from achieving a flawless, glass-like surface. The first is the pores of the wood. Some woods have small enough pores that it doesn’t matter (maple, cherry, beech, boxwood, holly, and poplar), which are sometimes referred to as close-grained woods. But many other woods have larger pores that the finish will sink into, creating unevenness in the finish film, and ruining the smooth-as-glass effect. These open-pored or open-grained woods include a bunch of common favorites, as well as many exotics, such as: oak, walnut, mahogany, ash, sapele, purpleheart, zebrawood, bubinga, teak, cocobolo, and so forth.

The foundation to every mirror-like gloss finish is an underlying smooth wood surface. It is absolutely critical with open-grained woods that the pores be filled in order to obtain a smooth wood surface before any finish is even applied to the wood. For natural colored woods (in varying shades of brown), an oil-based pore filler can be used. (I greatly prefer oil-based fillers over water-based products because they have less of a tendency to shrink back into the pores over time, material won’t come out of the pores during sanding, and they generally fill the pores in a single application.) These fillers can also be stained to roughly match the color of the wood being filled. With multi-colored woods (such as zebrawood) or colorful woods (like padauk), a transparent grain filler should be used. I prefer spreading a thin layer of thick CA glue over the wood surface with an old credit card or playing card (using a fan for ventilation), spraying accelerator, and then sanding the surface flat with 200 – 300 grit sandpaper.

Besides the pores, the second obstacle standing in the way of achieving a glassy wood surface is minor imperfections. No matter how perfectly a finish is brushed, sprayed, or wiped on, there will always be imperfections in the final topcoat. These make a bigger difference than you may realize. Dust, drips, unevenness, brush hair, lint, haze, and a host of other imperfections mar the work of even the most assiduous of laborers. The finish will need to be leveled with fine-grit sandpaper, and then buffed up to the desired sheen. Leveling should be done carefully with 200 – 600 grit sandpaper. Because of the risk of sanding through to raw wood, most finishers that intend to level a finish will intentionally build up a thicker film to have a greater margin of error. For spray lacquer, the norm seems to be about 10 coats—brushed finishes should generally require slightly less than that.

Once the finish has been adequately leveled (the wood surface should be uniformly dull—any glossy/low spots remaining indicate incomplete leveling), you can be assured that every possible imperfection and irregularity has been removed from the finish film. The finish is flat and flawless—with no luster whatsoever. All that’s left is to restore the gloss using very fine sandpaper and buffing compounds. After using normal sandpaper up to about 800 grit, I’ve found that 1000 grit Abralon discs are absolutely fantastic at preparing the finish for the buffing wheel. After the Abralon, I use a cotton buffing wheel with some Menzerna buffing compound applied to the wheels to bring the finish up to a candy-like shine.