DIY Network

Choosing a Finish Woodworking expert Bruce Johnson covers the keys to choosing a wood finish. From "Ask DIY" episode ADI-101

Q: I bought a table at a yard sale and it needs to be refinished, but I don't know where to start. Any help? (Answer below)

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	Every wood needs a finish, and this mahogany thrives on oil-based polyurethane.
	Figure A

A: (Bruce Johnson, Woodworking Expert) Deciding on the best finish for each woodworking project can be confusing. But there is one basic rule, which is "All woods must have a finish." Wood needs a finish for two reasons:

1. A finish protects the wood from sunlight, moisture, scratches and anything else it might come in contact with.

2. A finish enhances the wood -- it simply looks better when it has a finish.

At the other end of the spectrum are the cheap, throwaway foam brushes. Avoid these like the plague. They're full of air, and air creates bubbles in your finish. What I find works just fine is a medium-priced brush -- something you'd spend $4 to $6 on (figure A, middle brush). And clean it up after the finish goes on, because this brush is good for more than one use.

Working smarter: A few bristles probably will work their way loose on the midprice brush, so make it a point to run your fingers through the brush and pluck off the loose bristles before you use it for the finish.

Now, for choosing a finish. On a mahogany end-table top, you would need a good protective finish. That's because you'd expect the table to get a lot of use and for people to set glasses on its top. I would recommend a fast-drying polyurethane. This is an oil-based finish, and you'll need to stir it thoroughly and then apply it with a brush. Only dip about a half-inch of the bristles into the polyurethane, and then start working them into the wood. Strive for a thin coat, one that won't leave you with a lot of runs and drips.

Tip: To avoid brushstrokes, after you've applied a coat of polyurethane, go back over it with one long brushstroke, holding the brush at a 45-degree angle and pulling it in just one direction. When you get to the end of the board, turn the brush over and come back for the next pass. Then allow the oil-based finish six to eight hours to dry.

Figure B

If you consider a different type of project, such as a table with a green stain on the sides, you should consider a different type of finish (figure B). The oil-based polyurethane would change the color a bit. Instead, use a water-based finish -- one example is Minwax Polycrylic -- that looks like skim milk when it's in the can. Use a synthetic-bristle brush to apply it. If you used a natural-bristle brush, the water in the finish would cause the bristles to swell out of shape and you could never use it again.

Dip about a half-inch of the bristles in the water-based polyurethane, and work it into the wood. It's particularly important to finish off with one-way long brushstrokes on a vertical surface, where the force of gravity tends to cause drips and runs. The water-based product needs to dry for only two to four hours.

Nobody's perfect: Keep in mind that oil-based polyurethane will alter the color of a finish, adding a yellow tinge. This is fine with brown woods, but not right for color stains or some lighter woods.

If you're not a big fan of brushes, you do have another option: tung oil, which you apply with a rag. Tung oil is a very thin form of an oil-based varnish, and like oil-based polyurethane it can leave a yellowish tinge. It gives a hand-rubbed, antique look. Use it for fine woods and furniture that isn't in high-traffic areas, because it doesn't offer as much protection as the polyurethane.

To apply, pour some tung oil on a rag, and work the finish into the wood in a circular motion. Finish by wiping it with the grain of the wood.

More questions for Bruce:

Q: Every time I use a rag during a staining or finishing project I end up leaving lots of lint behind. What's the trick to avoid this?

A: What you need to do is buy a higher quality of rag, or launder it first. Or switch to heavy-duty, lint-free paper towels.

Q How much sanding should I do between coats of finish?

A: Lightly sand each coat of finish with No. 220 sandpaper. You'll barely see the difference, but it will remove the dust that's fallen down in there. Then take a sticky tack rag and wipe off the dust.

Q : I bought an armoire that is painted black and I want to make it look distressed and old. Can you tell me how to do that?

A: With medium-grit sandpaper, sand off some of the stain or the paint on the edge. That will imitate the wear on a piece that's antique. But choose the places you sand carefully, because you wouldn't want to sand somewhere that wouldn't ordinarily receive wear, such as the side of an end table.