Home and Garden | Choosing and Applying Varnish - Wall Covering

Varnish, which imparts a clear, transparent coating when applied, is a popular choice for producing a durable, hard finished surface. Available in varying degrees of sheen from flat to very high gloss, varnishes may be water-based or oil-based. Generally, from two to four coats, applied in thin layers, are required to maximize the protective value of the varnish and enhance the beauty of the surface. Polyurethane varnish produces a more long-lasting surface than other types do.

Varnish is best applied in a warm, not-too-humid room, with ambient temperature between 70 to 75 degrees Fahrenheit. To protect against dust and debris settling into the finish as it is applied or before it dries, the room in which you work should be as free of dust as possible. If feasible, to keep dust down, wet mop the floor in the work area. Alternately, you may want to lay down brown craft paper to cover the floor.

To reduce the possibility of runs, sags, or drips on the working surface, try to position the work horizontally. This may require partial disassembly, such as removing doors and drawers so they can lay flat. Lighting is also important. Place the piece you're finishing between you and the light source so you can see the light reflecting across the surface to check how the finish is going on.

When mixing varnish in preparation for application, stir it rather than shake it; shaking can produce bubbles that will remain in the finish. Use a good-quality china bristle brush; the finer the bristles, the less you'll have to contend with brush marks. Make sure the brush is clean and free of loose bristles.

The basic steps for applying varnish are below; refer to them as a guide while also following the instructions that accompany the product. Use the appropriate solvent—mineral spirits for oil-based varnish, water for water-based varnish. Make sure that the surface to be varnished is clean, dry, free of any finishes or wax, and ready to accept a final finish. Work in a well-ventilated area. If using oil-based (volatile) varnish, be especially careful to work away from open flames and other forms of heat, and do not smoke while working. While applying the varnish, wear neoprene gloves to protect your hands. Wear a NIOSH-approved respirator or dust mask, as necessary.

INSTRUCTIONS

1) Prepare the varnish To prevent any contamination, do not work directly from the can. Pour a modest amount of varnish (more than enough for a first coat) into a clean can or pail from which you will work. The first coat may require that the varnish be thinned before it's applied. Follow the manufacturer's instructions for thinning it.

2) Prepare the brush
Soak the brush in the correct solvent and remove the excess before dipping it in the varnish. Soaking helps condition the bristles to accept the varnish and makes cleanup easier. When you load the brush with the finish, dip the bristles about one-half to one-third into the finish, and then flex the brush on the inside of the can to work the varnish into the brush. Don't drag the brush across the rim—this can produce bubbles. Use a 2- to 3-inch tapered or wedge-shaped brush for large flat areas and a smaller brush for details.

Fig. 1

3) Apply the first coat of varnish
Initially, apply the first coat of varnish by brushing diagonally across the grain in short strokes to help spread the finish (Fig. 1). Then, brushing with the grain, hold the brush almost perpendicular and drag it lightly across the surface in the direction of the grain. Work over one area at a time until the entire surface is done.

To remove dust particles, hair, or lint from a freshly varnished surface that has not begun to dry, use a pointed artist's brush that has been made tacky with varnish. Lightly touch the particle with the brush's tip to remove it. Properly dispose of any varnish remaining in the working can

4) Tip off the finish Before the varnish begins to dry, unload the brush of varnish, and tip off the finish by again holding the brush at a right angle to the surface. Lightly drag the tip all the way across the surface in the direction of the grain. Begin your strokes in the air before lowering the brush onto the surface, and lift the brush off the surface immediately when reaching the other edge.

5) Sand the first coat
Allow the first coat to dry for the amount of time specified by the varnish manufacturer. (Sanding varnish before it's dried sufficiently can damage the finish coat and may require refinishing.) Scuff-sand the finish with 280-grit silicone carbide paper to remove any roughness or dust and to provide intercoat adhesion.