Wood Floor Finishes

Initial Considerations

There are many ways to finish wood floors. Before deciding to install such a large and permanent component of your space, we highly recommend answering the following questions in order to clarify which finishes would be best for your space and needs.

1.Where is the wood floor being installed?

  • Is it in a high traffic area?
  • Is it in a home, a public commercial space, or maybe a private office?

2. What is your lifestyle?

  • Are there children or pets present?
  • Are the occupants diligent with maintenance?

3. Do you consider the environment when making purchasing decisions?

  • Is indoor air quality a concern?
  • Are environmental impacts a factor when making purchasing decisions?

4. What is the look you would like to achieve?

  • Do you want a shiny finish?
  • Would you like to achieve a natural look?
Finished versus Unfinished Wood Floors

Depending on the answers to the above questions, the next decision to be made is whether to install finished or unfinished wood floors. Both options have their own set of costs and benefits. Unfinished floors will be finished on-site and after installation. Finished floors are prefinished in a factory and is often referred to as prefinished.

Installing unfinished wood floors allows for a greater variety of benefits over prefinished floors when it comes to the design aspect of the space.

  • The finish can be more unique to the interior space.
  • Finishing on-site allows for a better uniformity that cannot always be achieved with prefinished planks.
  • The installers can add custom touches—such as borders, and inlays.
  • Laying unfinished floors helps to highlight and maintain the wood’s natural characteristics.
  • Being able to color match other wood accents that already exist in the space.

Some of the drawbacks include:

  • A longer installation time.
  • Health risks due to dust, fumes, and initial off-gassing of Volatile Organic Compounds (VOCs) while the finish cures.

Installing prefinished wood floors allows for a faster and cleaner process.

  • Factory finished flooring mitigates initial off-gassing of VOCs and enables a cleaner indoor air quality after installation.
  • Prefinished floors can be walked upon immediately after installation.
  • Factories apply stronger commercial finishes with special finishing equipment.

Some of the drawbacks include:

  • Unavoidable non-uniformity after the planks have been laid.
  • Due to the strength of commercially applied finishes, if the floor needs to be refinished in the future, sanding will need to go further into the wood to remove all the finish.
  • If a piece of the floor is damaged, either the whole floor needs to be refinished or that piece must be replaced.

Types of Finishes

There are two main types of finishes: surface sealer and penetrating sealer. Both have pros and cons. All options should be considered in order to make the best decision for each specific project.

Surface sealers cover the surface of the wood. When the solvent evaporates, the resin hardens, and remains firmly bonded to the surface of the wood. They are easy to apply and come in a wide selection of products. Surface sealers include polyurethane, urethane, lacquer, epoxy, varnish, wax, and shellac. The most widely used and most durable of these is polyurethane. Some finishes are slow drying, while others are fast drying. Professionals use special tools to apply fast drying finishes to ensure evenness. If a dent or scratch occurs, the damage will leave a white mark. This visual imperfection will require that the whole floor to be refinished, which causes a lot of health concerns from the dust and emissions off-gassing after the finish is applied to cure.

Penetrating sealers soak into the wood to become part of its cellular structure. Penetrating finishes accentuate the natural elements of the wood. Penetrating sealers include natural oils and penetrating resins. These finishes do not offer protection against moisture. Since penetrating oils do not form a synthetic protective layer on the surface of the wood, if a dent or scratch occurs, it can easily be fixed by rubbing the surface with a steel wool, and applying more oil. However, there is a lot more care that goes into maintaining a beautifully oiled wood floor. Every six months, these wood floors will require touch ups with the penetrating sealer. The entire wood floor will need to be re-oiled every few years.

Surface Sealer

Acrylic – Acrylic is a plastic resin which does not contain solvent fumes. Similar to polyurethane, but a slightly different chemical make-up.

Conversion varnish (Swedish Finish) – An acid-curing urethane and alcohol-based sealer. Contains two parts: a resin and a catalyst. Amino resin and alkyd. Emits formaldehyde as it cures. Strong odor and has a very high VOC content. Combustible.

Epoxy – A two-component finish. Remains liquid even after the solvent evaporates but quickly begins to cure. Made of polymers. Caution must be taken with epoxies and oil-based formulas that contain dryers.

Lacquer– Synthetic coating made by dissolving nitrocellulose, or other cellulose derivatives, with plasticizers in a mixture such as amyl acetate. Solvent based. Highly flammable usually containing butyl acetate and xylene ortoluene. Should be avoided and not recommended by manufacturers. Thinner used in this is explosive.

Moisture-cure polyurethane – Solvent-based, has a strong odor, and a very high VOC content. Dependent on relative humidity, better left to professionals. Flammable.

Oil-based Polyurethane – Combustible. Strong odor lasts for a few days.

Paste Wax – Wax can be applied on top of stains, shellac, varnish, polyurethane, enamel, or lacquer. Will protect the wood floor from minor scuffs and stains but not from heavy wear or moisture. Wax is vulnerable to stains. Has a mild odor, and low VOC content.

Polyurethane (aluminum oxide) – a Plastic resin in liquid form; a petrochemical resin that contains isocyanates, which is a known respiratory toxin. Uncured polyurethane can cause breathing problems such as asthma. People near uncured polyurethane floors can also experience eye and throat irritation, headaches, nausea, vomiting, coughing and shortness of breath. Children and people with respiratory diseases are especially sensitive to the toxic chemicals in polyurethane.  Over time, the polyurethane’s toxicity will diminish. Main ingredients include: acids derived from vegetable oil, nitrogen-based chemical amalgams (keeps finish from chipping), isocyanates (makes finish hardier) and mineral spirits (constitutes the base that supports the other components). Aluminum oxide particles added to the polyurethane finish increases the abrasion resistance of the top layer of the wood floor.

Shellac – Derived from lac, a substance secreted by insects found mostly in India. Shellac is made by dissolving the lac gum in denatured alcohol. Alcohol soluble. Fast drying. Natural shellac contains wax. Dewaxed shellac is more popular. The thinner used in this is explosive. Shellac is not resistant to moisture, heat, alcohol, scratches, and chips.

UV Lacquer– Quick-drying, solvent-based varnishes. This finish is cured with ultraviolet lights instead of using heat.

UV-Polyurethane – Floors are finished at the factory and the polyurethane finish is cured with ultraviolet lights instead of using heat. Avoid oil-based formulas with dryers.

Varnish (spar varnish) – Usually alkyd-modified polyurethane and are available in solvent-borne and waterborne formulations. Can also be based on epoxy, or phenolic. Used to be made from vegetable oils and was the most commonly used finish before urethanes were introduced.

Water-based Polyurethane – Water-borne with a blend of synthetic resins, plasticizers and other film forming ingredients that produces a durable surface that is moisture-resistant. Has a mild odor and a very low VOC content. More prone to wear and tear than oil-based finishes, and dries rapidly. Requires more coats. Avoid using on top of an oil-based stain. Non-flammable.

Penetrating Sealer

Linseed Oil – Made from flax which makes linseed oil a natural product. Does not protect against water or moisture. Boiled linseed oil has drying metallic chemicals. May later bleed out. Doesn’t fully harden.

Natural Oils – Can contain Isoaliphate, which is known to be a harmless solvent to man. Isoaliphates are made from petroleum but are highly purified so it has a low odor.

Smoked – Occurs through oxidation. Oxidation formulas speed up the aging process of wood’s natural colors. Applied to woods with tannins like oak. Penetration occurs a few millimeters’ depth into the wood, therefore if the wood is scratched, the smoked color stays the same.

Stain – Solid particles of pigment in a solvent, used to darken wood. Penetration depends on the species of the wood.

Tung Oil – Made from the nut of the tung tree. Has a wet-look when cured. Hardens with exposure to oxygen. Can completely harden. Often diluted with hydrocarbon thinner. Tung oil is resistant to water, and is often mixed with mineral spirits.

UV Oil – Made of 100% solids and contains no solvents. Thin coat finish. Specifically formulated to dry under ultraviolet lights in a factory.

Hardwax Oil –Allows the oil to penetrate the wood, while the wax stays on the surface to protect the wood. Must be reapplied twice a year. Not recommended for high foot traffic areas, as it dulls the finish quicker. Hardwax oil is not water resistant or stain resistant.

Wood Treatments

Bleached – This method uses oxalic acid mixed in water to lighten the color of wood. Also known as, grey-washing, to achieve a sun bleached look. However, this treatment weakens wood fibers which makes it more vulnerable to wear from foot traffic.

Charred / Carbonized – Originates from Japan in the 1700’s, known as ‘Shou Sugi Ban’. This treatment involves burning the wood until it produces the amount of desired char. Carbon on the outside releases moisture inside the board. It creates a chemical compound change by turning the exterior into a pure carbon. This treatment makes the wood resistant to decay. Good for high traffic areas due to its high durability properties.

Fumed / Smoked – The wood is placed into a chamber that has a small amount of ammonia in its atmosphere. Oxidation ages the wood creating rich, dark brown colors. Applied to woods with tannins like oak. Penetration occurs a few millimeters’ depth into the wood, therefore if the wood is scratched, the smoked color stays the same.

Lye-stained – Lye is a chemical that which reacts with the tannin inside of oak wood, and certain wood species such as beech, birch, maple and other light hardwoods, as well as, softwoods. Lye-stain creates effects such as: bleaching, driftwood look, antique look, and such.

Painted – Certain paints can be applied to wood floors to achieve any color in the rainbow, which would not be possible otherwise. Patterns and straight lines painted can create endless design options.

Pickled – This method works best with woods that are high in tannin content. The process involves using a basic household vinegar and steel wool to create gray and black shades. The iron acetate reacts with the natural tannins in the wood.

Polished – Polishing wood floors is part of a regular maintenance or cleaning regiment in properly caring for wood floors. Since water and moisture damages wood floors, it is not recommended to clean wood floors using a conventional wet mop system. Rather, it is recommended that all debris be swept or vacuumed up, then using a reputable polishing system, recommended by the wood floor manufacturer, to clean grime off of the wood surface and rubbed till a nice shine is produced. Repeated as recommended for properly maintaining and prolonging the life of your wood floors.

Sandblasted – Sandblasting is used to shape, remove debris or surface finishes, and smooth wood surfaces through blasting solid particles across that surface at high speeds. The effect is that of an evenly textured surface.

Sanded – This method involves sand being projected at the wood at high pressures. The soft portion of the wood is removed and leaves a textured, brushed-like surface.

Thermo / Heated – Wood is placed under high heat conditions in anoxic heat chambers which reach temperatures of 450°F. This heat changes the composition of the wood making it more dimensionally stable, protect it against rot, and gives the wood a rich brown color. In high heat, the polysaccharides in the wood decompose, the residual humidity and water eliminates the conditions for the creation of fungus and microorganisms. Moisture related warping is reduced, as is cracking and checking of the wood surface. This is a chemical free wood treatment.

White-washed – Covering the wood floor with a white paste and wiping away excess, while allowing the white paste to fill in the grooves and natural pores in the wood.

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