Wipe-on finishes

To create a surface free of runs, sags, and brush marks, consider wipe-on finishes. Once you get comfortable with them, you may never clean a brush again. Here's what you need to know.

When you shop for these finishes, you'll find only a few labeled as "wipe-on." Examples include Minwax Wipe On Poly and Wipe-On Arm-R-Seal from General Finishes. But other products apply the same way, though you'd never know it without closely examining the label.

Many of these others bear names that imply they are oils, such as Watco Danish Oil Finish, Minwax Antique Oil, and Deft Deftoil. None of these finishes, however, is 100% pure oil.

No matter how they're named, you'll find by reading the label that all of these products wipe on, and all do contain either tung or linseed oil. They combine oil with other ingredients to create either an "oil/varnish blend" or a "wiping varnish." Read "Wipe out confusion," (sidebar at end of article) to learn how they're blended.

Before you use a wipe-on finish, you need to determine whether the product is an oil/varnish blend or a wiping varnish. A simple test, below, will tell you.

If you're shopping for a finish, check the label. It won't likely say what type it is, but clues exist. Oil/varnish blends are labeled "finish" most of the time. Also, the "Danish" oils are all oil/varnish blends.

The words "wipe-on" or "varnish" often identify a wiping varnish, as does the presence of mineral spirits as an ingredient or as the recommended solvent.

Most woodworkers strive to maintain wood's natural texture. Oil/varnish blends do this especially well because their oils penetrate the wood fibers. In fact, blends look and feel almost like a pure-oil finish.

A wiping varnish builds to a thicker, glossier film. This will mask the wood's natural texture if you build up enough coats (more than about six), but also gives the wood a greater amount of protection against damage and moisture.

Note: Beware of pure-oil products, such as raw tung oil or raw linseed oil. They give wood a natural feel, but never dry, and can remain tacky for weeks and even months. Pure tung oil may turn white if you apply too many coats. Boiled linseed oil contains metallic driers, but doesn't build well with successive applications.

Many times, of course, you'll want to accentuate wood's natural color. Wipe-on finishes impart a warm amber tone that brings vibrancy to the grain, as seen in the photos top and below. The wood's color does change slightly, but in a familiar, inviting way.

To add color to the wood, use an oil/varnish blend premixed with pigments, such as Watco Danish Oil, as shown, below. Or, make a custom color by adding an oil-base stain to an untinted finish.

Applying wipe-on finishes is easy. For either type, start by saturating the bare wood using a rag or, on large su faces, a foam brush. Let the finish stand, and check after a few minutes for areas that have dried. Recoat where needed to dampen the entire surface.

With an oil/varnish blend, wipe off any excess finish after about 15 minutes. Check in a couple of hours and wipe off any finish that bleeds out of the pores. Let the finish dry for 12 to 24 hours.

Recoat an oil/varnish blend only after the first coat dries thoroughly, and stop adding coats when another application no longer improves the sheen (the shininess of the surface). Usually two or three coats will do.

If you're using a wiping varnish, start by saturating the surface, as previously discussed. Spread any excess finish evenly, and then let it dry (usually 6 to 10 hours) rather than wiping it off. Lightly roughen the finish using 220 grit sandpaper, 0000 steel wool, or a fine synthetic steel wool pad. Then add two to three more coats (sanding between coats), stopping when you achieve the sheen you desire.

End grain requires special attention when using wipe-on finishes. Because the pores are open, end grain can soak up more finish, causing it to take on a darker color than edge and face grain. Prevent this by sanding end grain to a finer grit than you use on the other surfaces, as shown, below.

A wipe-on finish isn't ideal for every situation. Oil/varnish blends look great, but offer little protection against scratches, dents, and moisture. Wiping varnishes combat damage better, but build up in very thin coats. That means they require many applications to create a surface that will stand up to wear and tear.

For tabletops, dining chairs, floors, or other heavily used surfaces, opt for a brushed- or sprayed-on varnish, such as polyurethane. You'll get a thick, durable film in just two or three coats.

With so many wipe-on finishes to choose from, you'll probably find one you like right off the shelf. But you can easily make your own. To make an oil/varnish blend, mix equal parts of oil-base varnish, tung or boiled linseed oil, and mineral spirits, as shown, below. You can alter the mixture to suit your need. More oil increases penetration and color, and slows drying. Additional mineral spirits speeds drying and decreases the thickness of the film. Increase the quantity of varnish to create a thicker film.

Making a wiping varnish is even simpler. Just mix conventional varnish with an equal amount of mineral spirits.

* Raw linseed oil: One of the oldest wood finishes around, raw linseed oil offers little protection because it remains soft after curing, which takes several days. Adding metallic driers creates "boiled" linseed oil, which cures in about a day, but imparts no more protection.

* Raw tung oil: This finish offers a natural look, some water resistance, and darkens the wood less severely than linseed oil. Tung oil cures in a couple of days but remains soft. Tung oil remains a woodworkers' favorite, but performs best when used as an ingredient in varnish (see the note, below), or when blended with varnish.

* Oil/varnish blends: This is a mixture of conventional varnish and pure oil. The oil reduces the glossiness of the sheen, and makes the finish easier to apply than varnish, thanks to the slower drying time of the oil.

* Wiping varnish: This type is simply conventional varnish thinned with mineral spirits for easy application. Note: Varnish and wiping varnish contain oil, but only as an ingredient. Varnish combines oil (tung, linseed, or safflower) with natural or synthetic resins, such as polyurethane. Heating the mixture causes the oil and resin to combine chemically, creating a new substance: varnish.

Note: Varnish and wiping varnish contain oil, but only as an ingredient. Varnish combines oil (tung, linseed, or safflower) with natural or synthetic resins, such as polyurethane. Heating the mixture causes the oil and resin to combine chemically, creating a new substance: varnish.