Hardwood floors are sought after and admired for their beauty, treasured for their history, and enjoyed for their practicality. If you’re home is on the market, your hardwood floors may attract more buyers and possibly even add to your home’s value, according to the National Wood Flooring Association.
But, you have to keep your floors finished and sealed in order to keep them looking nice. With the proper finish, a hardwood floor will keep the color and sheen you love throughout the years. Sure, an appealing stain dresses up the wood, but it’s the finish that protects it and keeps it worth looking at. Whether you are refinishing a floor or adding new wood flooring, a quality finish job will repel stains and moisture, block dirt, and lessen if not eliminate daily wear and tear.
Modern technology has delivered an array of finish choices, each with different qualities, advantages and disadvantages. Professionals generally divide all finishes into two broad categories: Penetrating sealers and surface sealers.
Types of Hardwood Floor Finishes
As the term implies, a surface sealer coats the top of your hardwood floor, creating a plastic-like barrier between the wood and the environment. The way it works is simple – a mixture of resin and solvent, a surface sealer begins to dry when applied to the flooring. What’s left, after the solvent evaporates in the process, is the resin, which hardens to form the coating. Thus, when you touch a surface-sealed hardwood floor, you’re actually touching the surface sealer, not the wood. Of course, eventually the finish wears away, so occasionally it must be reapplied. Performed properly, a surface-sealed hardwood floor remains water resistant and durable with a minimum of maintenance or cleaning.
- Shellac: One of the oldest finishes available, in spite of its recent decline in popularity, shellac remains a particular favorite of some woodworkers. It’s easy to understand why. Shellac not only provides a pleasing gloss to the floor, it’s versatile and natural.
Shellac is made from the droppings of the Lac bug, which feeds on trees in Thailand and India. Lac bugs then secrete the resin, called lac, in cocoon tunnels, in which it lays thousands of eggs. Workers scrape these encrusted branches and dry the lac into chips. When mixed with denatured alcohol, shellac is formed. Thus, shellac is a “green,” sustainable product as well.
Shellac comes in several formulas. It can be tinted with custom color or used in its natural state, which is slightly orange. A bleached formula is clear, and another formula removes the naturally occurring wax content to allow shellac to be used in combination with other products.
One of the cheapest finish products, shellac dries quickly, doesn’t re-wet stain, doesn’t require sanding between coats and doesn’t yellow like oil-based varnish or polyurethanes. The fast drying time does demand confident application, however. Additionally, shellac isn’t as hard as other surface sealers and is vulnerable to ammonia, alcohol and water spotting. Take care to avoid cleaning products that contain these ingredients.
- Varnish: If the hardwood floor was installed or last finished before the 1960s, chances are good the finish applied was either shellac or varnish. The first varnishes were vegetable oil-based, but today’s varnish uses synthetic resins (vinyl-alkyds) instead.
Tougher to wear or penetrate than shellac, varnish is unfortunately still not as durable as polyurethanes. In fact, even though it’s fairly inexpensive, it’s rarely used on hardwood floors today, largely replaced by urethane-based finishes. Those who choose varnish typically appreciate the fact that varnish can be tinted a variety of colors. Varnish can also be thinned slightly with an oil to make application easier. Thinning with oil is a double-edged sword, however – it also makes the finish softer.
Varnish is considered fairly high in volatile organic compounds (VOCs) due to the solvent content. Thus, varnish isn’t the environmentally friendly choice. Another disadvantage with varnish is the difficulty in application. Similar to shellac, it takes something of a talent to apply..Unlike shellac, it dries slower, making dust and other contaminants a complication. Also, a varnish finish requires wet sanding between layers.
Don’t let products labeled varnish confuse you. There are products called wiping varnishes and others called oil-varnish blends. Wiping varnish is thinned with paint thinner. This makes it somewhat easier to apply and allows some of the varnish to sink into the wood like a penetrating finish, while creating a buildup like a surface finish. An oil-varnish blend, in contrast, mixes varnish with tung or linseed oil. The result is a penetrating surface that acts – and is applied – like an oil, with no buildup on the floor surface. See more information on this product below, under penetrating sealers.
- Lacquer: Not to be confused with shellac, lacquer is a fast-drying wood finish typically applied with a sprayer. It dries extremely fast, making dust and contaminants less of a problem, although slower-drying brushing lacquers are also available.
In general, you will rarely see a lacquer finish on modern hardwood floors. Not because of the finish quality, which is glossy and fairly hard, but because the fumes are hazardous to your health and the dust is combustible. In addition, lacquer is high in VOCs. The exception is some water-based lacquers currently on the market, which are more environmentally friendly, but at a higher cost.
- Polyurethanes: For the highest gloss possible in a hard, durable finish, use a polyurethane product – also called urethane. This, along with the variety of urethane types, can become somewhat confusing, so it’s important to pay attention to labels when purchasing any poly-urethane finish product to ensure you know what you are getting.
Of all the surface finishes used for hardwood floors, urethane formulas are the most common today. Oil-modified urethane is particularly popular as it is fairly inexpensive and easy to apply, although it dries fairly slowly. Because it is solvent based, it will of course contain VOCs as well. It also has a tendency to turn an amber color with age, especially when exposed to bright sunlight.
A water-based urethane formula dries quicker than oil-based and is non-yellowing, but isn’t nearly as hard as other urethanes, so it may not be suitable for floors with high traffic or small children and pets. Non-yellowing and low in odor, a water-based formula is also thinner than an oil-based finish, so it takes an additional coat or two to cover the hardwood floor well. It’s also the most expensive of the urethane finish products. Since any water-based finish is more environmentally friendly, it remains a popular hardwood finish choice.
A third urethane finish formula is the moisture-cure urethane. Available in either satin or gloss, in a non-yellowing formula or the regular amber-tinted finish typical of most penetrating sealers, moisture-cure is usually a little more expensive than other sealers such as shellac or varnish. The term moisture-cure refers to the fact that the humidity in the air helps this formula dry faster.
The last type of urethane finish, acid-cured, is called a Swedish finish due to its country of origin. Also known as a conversion varnish, a Swedish finish is a clear formula that won’t turn yellow and dries extremely quickly. It’s also flammable, like all urethanes except for the water-based finish. High in fumes and extremely difficult to apply, it’s generally best applied by a professional, making it even more expensive than other urethanes.
- Wax: It’s been around forever, and it’s likely not going anywhere soon. A wax finish soaks into the pores of the wood and hardens, like a penetrating finish, but leaves a layer on top like a surface finish. Often used in combination with a stain (and working with most stains easily) the result is a hardwood floor of the color you desire with a low-luster, slightly amber-tinted finish.
Most waxes are applied as a paste and buffed to cure and shine. Low in odor and fairly durable, wax is vulnerable to water and some solvents along with environmental damage such as scrapes and scratches. Since it’s fairly inexpensive, it’s the easiest to reapply as needed – if you overlook the elbow grease that goes into applying it.
Unlike surface finishes, a penetrating sealant soaks into the wood and fills the pores to protect it. A favored method of treating wood in the past (along with wax, varnish and shellac), it has largely fallen out of favor with the advent of the wide variety of polyurethane finishes. One reason is likely that penetrating finishes don’t produce the gloss of surface finishes. Another reason could be that the wood isn’t coated as much, so the surface itself experiences more wear and tear. Also, many homeowners aren’t as familiar with it as other finishes. Most of all, a floor treated with a penetrating sealer must be oiled consistently or coated with wax. Like so many finishes, you can’t simply add a layer of a different product when it’s time to refinish a floor – you must sand down the wood to remove wax, penetrating sealers and surface sealers to remove every trace of the finish before applying a new product. Penetrating sealers are favored for showing the wood to its best advantage.
- Tung Oil: Probably the most popular penetrating sealer used on hardwood floors, tung oil comes from tung tree nuts. Used for centuries by the Chinese, tung oil is easy to apply, has an amber hue, and doesn’t darken the wood as much as linseed oil.
Tung oil does have drawbacks. It dries slowly and requires several coats – with sanding in between – to achieve a durable surface. It also tends to turn a whitish color if any layer is applied too thickly. However, as a natural product, it’s sustainable and environmentally friendly. In fact, it’s even food safe – just in case you ever decide to eat off your floors.
- Linseed Oil: Together with tung oil, linseed is known not only as a finish and sealer but also a “drying oil.” This is because, unlike solvent oils in surface sealers, the oil in tung or linseed absorbs air and hardens as it cures, unlike surface sealers that cure when the oils evaporate.
Made from seeds taken from the flax plant, linseed is another natural product and also low in VOCs like tung oil. Sometimes, either linseed or tung oil is boiled or mixed with solvents to speed the drying time.
There are, however, slight differences in these two oils. For one, linseed oil isn’t quite as water resistant as tung oil. In addition, linseed is slightly darker, so it will affect the hardwood floorboards differently.
Applied similarly, linseed and tung oils are not difficult to use as long as you can wait for the floor to dry afterward. Touch ups, to cover scratches, also work better than with most other finish products.
- Danish Oil: As if it wasn’t confusing enough to keep urethane finishes straight, Danish oil is neither Danish nor a “true” oil – it’s a mixture of tung oil with varnish. And although varnish is classified as surface sealer, Danish oil penetrates instead. The result, however, is slightly different than either product would suggest. More durable than oil, more environmentally friendly than varnish and offering a satin sheen, Danish oil dries fairly quickly and is considered food safe as well. It also requires fewer coats than drying oils, but the same reapplication and touch ups in between are required as needed.