SECRETS OF PAINT AND STAIN CHEMISTRY

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If you are refinishing a just lye-stripped antique pine dry sink or finishing a rock maple bunk bed frame for the grandchildren, the first step is preparing a well-sanded wood surface. Clean it free of all dust with a tack cloth, and degrease with the solvent appropriate for your varnish: alcohol for shellac, fine mineral spirits for varnishes.

Then, stain the wood to match the sides of the antique if you are just refinishing the worn top. You can mix stain with varnish or apply the stain as it comes. Thin according to container directions and try on scrap wood first.

Apply pigmented stains quickly, keeping a wet edge, and wipe off immediately. On end-grain—which will suck up stain and become much darker than long-grain surfaces—thin the stain to quarter strength and apply judiciously till ends match top. Keep the wiping cloth and a container of solvent handy to correct mistakes before they soak in for good.

The best way to get that glass finish is to apply several coats of thinned varnish with a spray gun and one of the new low-pressure/high-volume sprayers. They go for $700 new, but can be rented.

Unlike conventional hi-pressure compressors, they deliver 90-plus percent varnish, so you don't get the blow-back and waste of a regular spray unit that atomizes finish in a large volume of air. You can't fill the truck tires with it, but the investment is a good one for any woodcrafter. Practice on scrap wood before tackling the project.

You can brush on a glass finish if you do it right. Get the finest hogbristle brushes you can find. Test them by applying two coats of practice varnish, cleaning and drying brushes between, to catch any loose hairs so you don't have to pick them out and ruin a coat of varnish. Thin the varnish as much as you can stand, and brush it on in quick strokes, with the grain, going over the surface as few times as possible. Always keep a "wet edge." Let each coat dry for 24 hours unless container directions say otherwise. Buff with 220-grit sandpaper after the first coat (it will soak in the most) and 320-grit after the following coats. Clean with solvent and apply another coat and another, sanding in between. Let dry in a dust free environment. Buff out the final surface with 0000 superfine steel wool and a good hard wax.

Plan on brushing on three coats of oil-base varnish for a matte finish, six for satin, 10 and up for gloss.

Wipe-on Finish

More time-consuming but more foolproof than using a brush is to buy a wiping-type oil or oil/varnish mix. These go by diferent names and may contain cheap linseed oil. Learn linseed's sour smell and avoid it, preference to a truly fine oil—it will smell nutty and sweet. Pick a good-smelling oil or oil/varnish of a known brand such as Minwax Antique Oil, Behr Tung Oil, or Watco or Deft Danish Oil.

"Pure" tung and walnut oils (seldom really pure) will make a good finish after the fifth coat. However, if you can identify ingredients, you'll get better results with a partly cooked tungoil/phenolic-resin/ solvent mix such as WaterLox Transparent or Marine Sealer.

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