Finishing a wood floor is the most rewarding step. Finishes are applied to wood for two principal reasons. First, a finish should protect the wood from damage such as stains, moisture and mechanical wear. Second, a properly applied clear finish will accentuate woods' natural beauty and color. Penetrating seals (sealers) and surface finishes are the two principal types of protective coatings used on wood floors. Either will give satisfactory performance if applied correctly.
These are probably the most common finish on residential floors. Sealers are usually thinned varnishes which, when applied to wood, penetrate into the wood pores on the surface. The result is usually a low gloss or satin finish that wears only as the wood wears. The eventual effects of traffic are far less apparent than with other finishes that only coat the surface. Scratching and chipping of this finish is not a serious problem. One coat of a penetrating sealer can give satisfactory performance, but two coats are generally better.
There are two basic types of sealers. Normal (slow drying) sealers can be used successfully by most anyone. Fast drying sealers are more difficult to use since it is easy to form lap marks or a splotchy appearance. Therefore, they are usually applied only by experienced professionals.
Surface Finishes are relatively easy to apply will give satisfactory service and include polyurethane, varnish, shellac, lacquer, and some others. The polyurethane is the most popular surface finish today because of their high resistance to moisture, mechanical wear, stains and spills. They are available with a high gloss or matte finish. Polyurethanes are either oil modified or moisture-cured. The oil modified types are the easiest to apply.
Varnishes can also give satisfactory performance. However, varnishes do have a greater tendency to scratch, and worn spots are difficult to patch without showing lines between the old and new finish. Varnishes specifically designated for floors tend to be more durable. A glossy or matte finish is available. Varnishes may be based on phenolic, alkyd, epoxy, or polyurethane resins.
Shellac and lacquer are sometimes used as floor finishes. These finishes will dry rapidly, and more than one coat can often be applied in the same day. However, shellac and lacquer are not as resistant to moisture, spills and mechanical wear as are the penetrating sealers, polyurethane and varnish. Surface finishes will usually give a longer life than penetrating sealers without any attention other than regular sweeping or dry mopping. However, when surface finishes must be renewed, it is usually necessary to refinish the entire room.
In most cases, it is preferable to maintain the natural color of hardwood floors by using a clear finish. However, if a color different than the natural wood color is desired or if the natural wood color is too variable, a stain may be used. Stains do not penetrate wood deeply, and they may fade with continued exposure to bright light. Open grained woods such as oak, ash, pecan and walnut will take stain easily while the close grained woods such as maple, and to a lesser extent, birch and beech, will take stain much more slowly. Soft-woods do not stain well since the less dense spring wood easily stains dark whereas the dense late wood will hardly stain at all. Be certain to use "non-grain-raising'" stains. Take the same care in cleaning and preparing a surface to be stained as would be done in finishing it.
Oil-based pigmented wiping stains are probably the most common. The pigments are in suspension so the material must be stirred regularly during use to maintain a uniform color. The pigment collects in the open pores of the wood and thus accentuates the grain pattern and alters the wood color. Pigmented stains are usually applied by brushing. After the stain has penetrated the surface and the desired effect is achieved, all excess is wiped off with clean rags. Colored or pigmented penetrating sealers are also available.
In this case, the pigment is mixed with the sealer, and both are applied at the same time. Pigmented penetrating sealers will not obscure the natural wood grain or shorten the life of the floor. Varnish stains are similar to penetrating sealers since the coloring pigment is formulated with the varnish. Therefore, the wood is colored at the same time it is finished. Since the coloring pigment remains in the varnish as it cures on the surface, much of the natural wood grain and color is obscured.
Dust and dirt are an important factor in causing a rough surface. When applying the first coat of finish, be certain that the wood is perfectly clean and free of dust, dirt and other foreign materials. Dust and dirt must also be removed from cracks or other floor irregularities. The walls, windows and doors should also be cleaned to keep dust motes from dropping into wet finishing materials to mar their appearance. A painter's tack rag or turpentine-dampened rag will help pick up much of this dirt. A careful cleaning is also necessary before a second or third coat of finish is applied.
Most finishes will not stick to wax, oil and other materials which may contaminate the surface. Be certain that the finish is applied only to bare, clean wood.
The temperature of the floor, room and finishing solution should be about 70 degrees F or somewhat warmer to assure that the finish flows on evenly and cures properly.
Most finishes cure faster in dry weather. Therefore low humidity conditions are also ideal.
A rough finish can also result if dust or small piece of dried finish are transferred from an old applicator or from a partially used can of finish. For each job, it is probably best to start with a new applicator and supply of finish.
Provide adequate ventilation to carry off any fumes. Application of finishing materials should begin promptly after sanding so that there will be no time for changing moisture conditions to raise the wood grain.
Penetrating sealers are best mopped on using a clean string mop or long-handled applicator with a lamb's wool pad. Apply generous amounts of the sealer, making sure that final stroking is in the direction of the wood grain if possible. Any excess sealer which remains on the wood surface should be wiped up with a clean cloth or squeegee. A wide brush can also be used for application.
After the first coat has dried it should be buffed with No. 2 steel wool. Buffing can be done by hand or with an electric polisher equipped with a steel wool pad. A second coat of penetrating seal will result in longer service life, but is not always necessary, particularly on close grained woods. Penetrating sealers can usually be refinished in heavy traffic areas without showing patch marks.
This may be applied using a brush or lamb's wool applicator. Because polyurethane are a surface finish, care should be taken to work along the grain. Polyurethane should be flowed on in a continuous manner so that the leading edge does not have time to dry out. After the first coat is thoroughly dry, buff it with steel wool, dust well, and then apply the final coat.
They are usually applied with a brush and flowed on evenly and smoothly. The first coat can be thinned lightly so that it will penetrate into the wood like a sealer. After the first coat has dried, smooth it with fine sandpaper, dust well and then apply the top coat full strength.
For the final touch of beauty and to protect the finish, apply one or more coats of good wax recommended for use on floors. Use either a liquid buffing wax/cleaner or paste wax. Use only brands that are designated for hardwood floors and if a liquid, be sure it has a solvent base, not a water base.
Apply the wax after the finish coat is thoroughly dry and polish it with a machine buffer. The wax will give a lustrous sheen to the floor and form a protective film that prevents dirt from penetrating the finish. Some manufacturers of urethane finishes do not recommend waxing, especially for commercial jobs, because wax may make the floor slippery.
Wood floors finished with penetrating seals are not too difficult to repair should they show early signs of wear in the traffic channels or become stained or water damaged in localized areas. Floors finished with polyurethane or varnish can also be repaired, but lap marks or a splotchy appearance is more difficult to avoid. Floors finished with lacquer or shellac are nearly impossible to repair successfully.
Finishes are best renewed when they begin to show signs of wear in traffic channels but before the bare wood is exposed. In this case, the floor must be cleaned of all dirt and debris, and all floor wax must be removed as it may interfere with the drying and adhesion of any new finish. Most of the wax can be stripped with rags kept moistened with mineral spirits or other paint thinners. The rest of the wax should be washed off with soap and warm water, doing the work as rapidly as possible so that the water will have little time to contact the wood. After the surface has thoroughly dried, a new finish may be applied.
If a penetrating seal is being restored, apply it to the worn areas as already described. Be careful to wipe up any excess, particularly in those areas where the old finish is still in good repair. If a surface finish such as polyurethane or varnish is being used, it may be a good idea to apply one coat of finish to the worn areas first. End all brush strokes at joints between boards. After the first coat is thoroughly dry, apply a second coat over the entire floor.
If only a small stained or water damaged area is being repaired, try to remove the discoloration first. Use steel wool or a fine grade of sandpaper to smooth out the affected area and an inch or two of the surrounding floor. Remove all dust. Then brush on one or more thin coats of finish, feathering it in to the old finish to prevent lap marks. All plenty of time for drying between coats. Wax the repaired area if appropriate.
Wood floor finishing isn't too complicated of a task. The most difficult part is deciding which is right for you!
This article has been contributed in part by Michigan State University Extension