Finish Your Finish

Jim Heavey Headshot
by Jim Heavey

I’ve always believed that if a project’s finish doesn’t pass the “touch test”—when running your hands over the project, you feel a flawless, satin-smooth surface—that finish diminishes the impact of quality design or construction. So here are a few simple tricks that will make your finish a point of pride.

Focus on surface preparation

Nothing beats good preparation when it comes to attaining a great finish. First, sand all surfaces on your project, with the exception of end grain, to the same grit level. Sand the end grain to twice the grit level of the project to provide a more even appearance when stained or finished.

All sanding dust should be removed with a vacuum and a blast of compressed air. I use tack rags to remove fine dust immediately prior to applying a finish, wiping gently to avoid contaminating the surface with the sticky residue on the rag. 

Apply a finish when the time is right

Stains must dry completely prior to topcoat application. The drying and curing times found on the instruction labels typically assume a 70-degree temperature and 50 to 70 percent humidity. Very cool or humid conditions greatly prolong those times.

Don’t attempt any finish application the same day you’re working in the shop. Fine airborne dust from sawing or sanding causes those dreaded dust nibs in your finish, below.

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Nibs can ruin a good finish. They can embed in the finish while brushing, or airborne particles can settle on the wet surface prior to drying.

To help prevent “floaters” from settling on your fresh finish, shield the piece while it dries, below.  

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Shelter your workpiece. Polyurethane finishes dry slowly, so their surfaces are more likely to collect dust. Protect those surfaces by suspending poster board slightly above the workpiece, or covering the project with a box with holes in the sides.

When possible, apply finish on horizontal surfaces. Gravity helps the finish self-level, creating a flatter, smoother surface. This may involve rotating the project for each side, but the results are well worth it. Remember, self-leveling on a vertical surface is called a drip.

If you’re brushing on a finish, always start with a clean brush. Brushes stored uncovered in a dusty shop transfer accumulated dust to a project’s surface. Store brushes in their original packaging, or wrap them in newspaper.

In general, three coats of finish on any project is sufficient. The first coat is pulled into the pores and acts as a seal. The second and third coats add protection and sheen. 

Overcoming finish flaws

Now, let’s deal with the inevitable finish imperfections and make that good finish a great one. Fix major flaws in a coat by sanding the surface flat using 320-grit sandpaper and applying one last coat of a thinned finish. Thinner finish flows out easier and dries quicker, thereby reducing the chance of bubbles, below.

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Smooth out brush marks to hasten leveling by tipping off the finish prior to drying. Hold the nearly dry brush at about a 45° angle and lightly drag it in the direction of the grain.

Solvent-based finishes, such as polyurethane and varnish, can be thinned from 25 percent to as much as 50 percent using mineral spirits. Waterborne finishes can be diluted only about 10 percent with water. Instead of brushing or wiping a diluted finish, you can spray on a thin coat, below.

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Spray the final coat. Aerosol cans do not leave brush marks and result in very smooth surfaces. Spray evenly, holding the can approximately 12" from the surface.

Penetrating finishes, such as Danish oil, absorb into the wood surface instead of building up, like polyurethane. Once cured, smooth the surfaces by applying paste wax with 0000 steel wool [Opening photo]. Working in the direction of the grain, that fine steel wool (equivalent to 600–800 grit sandpaper) removes any surface imperfections and provides the grip for the wax. Buffing the wax finishes the job. 

In a perfect world, every woodworker would have a finishing guru available at a moment’s notice. With practice and patience you won’t need one. Now, go ahead and touch it! 

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