Finishing and Maintaining Wood Floors
Part 4 –Selecting a Finish

Introduction

Finishing a wood floor is perhaps one of the most critical but rewarding steps of installing a new wood floor.  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 the natural beauty and color of the wood.  Penetrating seals (sealers) and surface finishes are the two main types of protective coatings used on wood floors.  Either will give good performance if applied correctly.

Penetrating Seals

Penetrating seals are probably the most common finish on residential floors.  Sealers are usually thinned varnishes which when applied to wood, will penetrate into the wood pores on the surface.  The result is usually a low glass 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 on a splotchy appearance.  Therefore, they are usually applied only by experienced professionals.

Surface Finishes

Surface finishes which are relatively easy to apply and will give satisfactory service include polyurethanes, varnish, shellac lacquer, and others.  The polyurethanes are some of the most popular surface finishes because of their high resistance to moisture, mechanical wear, and stains and spills.  Polyurethanes are blends of synthetic resins, plasticizers, and other film-forming agents.  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, they 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, polyurethanes, and sealers.

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 or house.

Staining

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 preferable.

Stains do not deeply penetrate wood, and they may fade with continued exposure to UV 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 more slowly.  Softwoods do not stain well since the dense latewood will hardly stain at all.  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 my favorite and probably the most common.  The pigments are in suspension so the stain 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 desire 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.