How to Properly Finish a Woodworking PieceBy David Marks
When I need a more durable finish for a woodworking piece, I'll usually apply lacquer or polyurethane. Both of these finishes are far more moisture- and mar-resistant than an oil finish.
Most lacquers are formulated for spraying, which means that they dry fast. Polyurethanes are oil based and tend to dry slowly so that when brushed onto a surface they have time to level out. Either product ends up being a coating that sits on top of the wood, as opposed to a hand-rubbed oil finish that gets buffed into the wood.
There are, of course, advantages and disadvantages to both. The hand-rubbed oil finishes don't have the same problems the surface coatings have--especially having particles of dust and hairs getting stuck in them before they dry--but they both lack the durability and water resistance that lacquers and polyurethanes have.
Polyurethanes can be brushed on or sprayed. If brushing, you usually end up with brush-stroke marks in the surface that dried before they could level, and if spraying, you will most likely have some dust that gets onto the surface. The same thing applies to spraying lacquer with regard to the dust, but you can probably add other challenges to the list because of its fast-drying nature.
Are you, for example, familiar with the term "orange peel?" This refers to the texture of an orange with its bumpy surface and sometimes occurs when either the temperature or the various solvent speeds (dry times) forces the lacquer to set up on the surface before it has had time enough to flow out and seek water level. There are a number of remedies for this, such as adding a retarder solvent to slow the dry time of the lacquer and wetting down the floor of your spray booth with water to keep the dust out of the air.
But inevitably the best way to achieve a great finish is to "finish the finish," otherwise known as rubbing out the finish.
Tabletops and other horizontal surfaces are the most demanding because they are subject to the harshest scrutiny. I usually begin by wet-sanding the surface. The purpose of this is to flatten the finish. I'll use 600-grit wet/dry sandpaper wrapped around a rubber block. You can purchase these rubber blocks for wet sanding from a store that sells supplies for auto-body work. A little water will help lubricate the surface and speed up the sanding.
Keep in mind that if the surface looks pretty good it may only need rubbing with fine steel wool or Scotch bright pads. These abrasives will smooth the surface and cut the sheen from a gloss down to a satin, but they ride over the hills and valleys. In other words they won't flatten or level any high spots such as dust bumps, orange peel, runs, sags, overspray etc.
After wet-sanding at 600, work your way up through the various grits. You can purchase sandpaper that goes up to 2,000 grit. At this point, you can switch to pumice and rottenstone, automotive compounds or a product like Micromesh. All of these are abrasives that will polish the surface to finer and finer grit stages until the finish looks like glass. You can purchase an electric buffer with lamb's wool pads to speed up the process, but it will leave a circular pattern. I like to do my final rubbing by hand, keeping my pattern in long straight parallel lines. This way any scratch pattern is minimized.
(Master craftsman David J. Marks hosts Wood Works on the DIY Network. For more information, visit www.djmarks.com.)
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