The Finish I Dreaded
An introduction to sealers and finishes for wood floors
There is a lack of clear and complete information about floor finishing products. Most articles don’t differentiate sealers from finishes or provide a clear overview of available options. If you don’t understand the options and differences you may make a choice that you later regret.
When browsing photos of interiors, a beautiful hardwood floor will often catch one's attention. People invariably point to a photo and say "I want a floor that looks like that!" However, I've come to realize that merely showing and telling contractors what we want doesn't always work. Contractors may not care, they may not make the effort or they may only be familiar with certain products. It’s been my experience that old school contractors will steer you towards traditional finishes like shellac and oils, while newer contractors lean toward newer products like Bona.
I must have told my contractor multiple times that I didn’t want a yellow-looking finish on my oak floor, only to end up with exactly that. Not only did my contractor leave a yellow finish, but they also used at least three different kinds of sealers, and some areas were left without any sealer or finish.
The yellow finish was the result of an oil-based urethane, which will usually change in color over time. Obviously, I wasn't happy with the yellow floor, but there's much more to finishes than just the color. The type of sealer and finish determines the durability, maintenance protocol, and the amount of effort required for upkeep and refinishing. It's also essential to consider whether a sealer contains toxic materials that may leach into the air, impacting air quality, and health. But first, here’s a basic overview.
Why do you need to seal and finish a wood floor?
Sealing means to apply a coating to the wood to create a protective barrier which prevents dirt and liquids from penetrating the floor and making it easier to clean and maintain. It also helps enhance the wood's natural beauty and prolong its lifespan. A sealer is usually applied to a floor after it has been sanded and buffed. Both hardwood and engineered wood flooring need to be sealed.
Wood is a porous material, and if left unsealed, it can be susceptible to damage from dirt, liquids, and stains. When dirt and liquids come into contact with an unsealed wood floor, they can penetrate the surface, making it appear dirty. Additionally, spills and stains can be absorbed by the wood; leading to discoloration and potential damage.
Unfinished hardwood will always need to be sealed and finished. Pre-finished wood flooring comes with sealers and finishes applied during manufacturing and it is ready for installation. However, it's essential to follow the manufacturer's guidelines for maintenance to ensure that the finish remains effective over time.
Sealers vs. finishes
Frequently, the term sealer and finish are used interchangeably when they are the distinct products that each have a purpose. Adding to the confusion is the ambiguity surrounding whether a product functions as a sealer, a finish, or both. I also couldn’t find a clear overview of the various types of sealers and finishes available which made it challenging to understand the differences, proper usage, and application of these products.
A sealer acts like oil on your skin, entering the wood pores and blocking them to prevent moisture, dust, and dirt from infiltrating the floor. This protection helps prevent issues like warping, splitting, and cracking when exposed to moisture or water.
A finish or top coat is comparable to sunscreen. It forms an invisible protective layer over the wood surface, acting as a shield against potential damage or stains caused by various substances. The finish adds an extra layer of protection on top of the sealer.
Why you need to seal before applying a finish
A sealer not only protects your floor but also evens out the surface of the wood, increases the durability of the floor and finish, enhances or preserves any color, and reduces the chance of a negative reaction between the wood and the finish. All floors, with the exception of solid vinyl, need a sealer.
Creating an even surface:
Wood, especially in its raw state, can have natural imperfections, such as grain variations, knots, or pores. These irregularities can lead to an uneven finish if the finish is directly applied without a sealer. The sealer levels out the irregularities and creates a smooth surface, which helps the finish be absorbed more evenly for a consistent appearance without patches or streaks.
Providing a good base coat:
When you apply a finish to unsealed wood, it will soak into the wood. This can lead to damage to your hardwood floors and increase the amount of finish you need to complete the job (a waste of money). By sealing the wood first, you create a base for the finish to sit upon. The sealer acts as a barrier between the wood and the finish to protect the wood from damage and increase the life of the finish.
Enhancing color and grain:
Sealers can bring out the natural beauty of the wood by enhancing its color and grain pattern. They also help in preserving the wood's original appearance over time, adding richness and depth to the overall finish.
Preventing tannin migration:
Tannins and extractives are naturally occurring substances found in various types of wood, especially oily and resinous woods. Wood sealers minimize the migration of tannins and other extractives from the wood into the finish, preventing issues such as uneven discoloration, blotching, and staining that can occur over time. Extractives can also interfere with the adhesion of the finish resulting in a finish that can peel off over time.
Reducing reactivity:
If the wood is not sealed properly, the chemicals present in the finish can interact with the wood, leading to potential damage. Unsealed wood may absorb the finish unevenly, causing an inconsistent appearance and potential issues over time. The sealer acts as a protective barrier between the wood and the finish, preventing such adverse reactions.
Types of sealers
Sealers can be classified by application (surface or penetrating) or their material composition (urethane, oils, etc.). Polyurethane sealers come as water-based or solvent-based (often referred to as oil-based but the solvents are usually chemicals). In general, water-based products tend to be environmentally friendly and release fewer chemicals into the air. There are also sealers in the form of oils like tung oil, uv oil, etc., and then there are non-oils like shellac and lacquer.
Depending on the type of product, the finish will provide varying levels of performance, maintenance, and durability. These characteristics can also change when products are mixed with additives. For example, tung oil is often mixed with a solvent to make it durable and easier to apply but this can affect the toxicity.
Depending on the type of finish, you may need one product that both seals and finishes or several different products. Polyurethane finishes like Bona are typically two products (a sealer and a finish). On the other hand, penetrating oils may only require the oil itself, applied in multiple coats, to seal and finish the floor.
Surface sealers vs. penetrating sealers
Surface sealers and penetrating sealers are two types of sealers used to protect and enhance different types of surfaces. The main difference between them lies in their application and the way they interact with the surface.
Surface Sealers
Surface sealers, also known as film-forming sealers, create a protective layer on the surface of the wood. They form a visible film that sits on top of the wood, providing a barrier against dirt, moisture, UV rays, and other environmental factors.
Examples: polyurethanes, varnish, lacquer, shellac, UV-cured oil, and moisture-cure urethane. Polyurethane finish (e.g. Bona Traffic) can be bought separately. Shellac, lacquer and varnish do not need a finish but can take certain kinds of finishes.
Benefits:
Excellent protection against moisture and spills.
Provides a durable and hard finish that can withstand wear and abrasion.
Often enhances the wood's appearance, giving it a glossy or satin sheen.
Disadvantages:
Can be prone to peeling or flaking if not applied correctly or if the wood expands and contracts.
The film can trap moisture, potentially leading to wood rot if water gets underneath the sealer.
May require sanding and refinishing when damaged or worn.
Oil-based products can yellow.
Penetrating Sealers
Penetrating sealers, as the name suggests, penetrate into the wood's pores and fibers. They do not leave a visible film on the surface like surface sealers but rather enhance the wood's natural characteristics while providing protection from within.
Examples: Tung, linseed, danish oil, and hard wax oils. You can apply coats so you do not need a separate finish but you can choose to use one that is compatible. (There will be a follow-up post in the future with more detail on different sealers and finishes)
Benefits:
Allow the wood to breathe and retain its natural look and feel.
Provide protection from within, making them suitable for outdoor applications.
Easy to apply and maintain, often requiring reapplication over time.
Disadvantages:
Offer less surface protection compared to surface sealers, especially against spills and stains.
Require more frequent reapplication to maintain effectiveness.
Some penetrating sealers may darken the wood's appearance, which may or may not be desired.
Other Products
You might also hear about other products like wax, aluminum oxide, and acid-cured finish, which are all finishing products applied on top of a sealer.
Wax: Wax is a traditional finishing product that provides a protective layer and adds a soft, natural sheen to the wood. It can be applied over a sealer to enhance the wood's appearance and offer additional protection.
Aluminum Oxide: Aluminum oxide is a type of finish commonly used on prefinished hardwood flooring. It is a highly durable and scratch-resistant coating that is applied over a sealer.
UV-cured hardwax finish
UV-cured hardwax oil is similar to hardwax oil in that it uses a plant-based liquid oil but then each board is passed under a specialized ultra violet light which instantly cures the oil finish. This is only available as an option with pre-finished flooring.
Acid-Cured Finish: Acid-cured finish, also known as a conversion varnish, is a high-performance finish that provides excellent durability and chemical resistance. It is typically applied over a sealer.
What you’ll need to consider when choosing a sealer and finishes
When choosing a sealer and finishes for a particular project, there are several factors to consider to ensure you get the desired results. Here are some key considerations:
Durability (abrasion/scratch resistance): Consider the level of wear and tear the surface will endure.
Color and sheen level: Different sealers and finishes offer varying levels of gloss or sheen, and some may enhance the color or appearance of the material.
Potential color changes over time: Some sealers and finishes may alter the color or appearance of the substrate over time.
VOCs/green options: Consider eco-friendly, low-VOC, or water-based options if you are concerned about environmental impact and indoor air quality. Volatile Organic Compounds (VOCs) are chemicals that can be emitted as gases from certain sealers and finishes, contributing to air pollution and potential health concerns
Maintenance: Different sealers and finishes require varying levels of maintenance. Some may need periodic reapplication, while others are more long-lasting.
Dry/cure time: Take into account the time it takes for the sealer and finish to dry and cure fully. Longer drying times may impact project timelines.
Effort to remove: If the sealer and finish need to be removed or replaced in the future, consider the effort and processes required for removal. Some finishes may be more challenging to strip and may require specialized tools or chemicals.
Application method: Consider whether you are comfortable with the application process of the chosen sealer and finish. Some may require professional application, while others are more DIY-friendly.
A note on stains and stain sealers
Stain is a colored liquid that is applied to wood surfaces to add color while allowing the natural grain of the wood to show through. Unlike paint, which forms a film on the surface, stain penetrates the wood fibers to achieve its coloring effect. Stains and sealers are separate products, though some products may combine both stain and sealer. When using two products, the stain is applied to add color, and then a separate sealer or finish is typically used to protect the stained wood and enhance its durability.
It's important to follow the manufacturer's instructions and consider compatibility between the stain, sealer, and finish. Additionally, proper surface preparation and application techniques are crucial for achieving the desired results and ensuring the longevity of the finish.
Ultimately, one must consider not only the aesthetics but also the demands of daily life. The finishing choice should strike a balance between beauty and functionality, resulting in a floor that withstands use over time.
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(Paid post) When I see posts like ‘The top natural oils for floors’, I am skeptical that most people would know why they should use oil vs. another finishing product. People also don’t know that most lacquers on the market are actually made out of plastics. Here’s a clear overview of most of the sealers and finishes available today.
Queen’s Repository
What are tannins?
Tannins are organic compounds found in various plants, including trees, fruits, and vegetables. They are commonly found in bark, leaves, wood, and fruit skins. They act as natural deterrents to prevent animals from consuming plant tissues, as tannins can be bitter and astringent.
In the context of wood, tannins are present in the tree's cells and can migrate to the wood's surface when it's exposed to moisture or other factors. When using wood for various purposes, the presence of tannins can have implications for the finishing process. If not properly sealed, tannins can migrate into finish coats and cause discoloration or adhesion issues.
This was really in-depth and informative RenoQueen!
What I find really interesting is just how much you have learnt about each step of the renovation process by going through it.
I have always found that one of the reasons there are so many mishaps in the construction industry is that each trade knows a whole lot (hopefully) about their specific trade - doing the floors or ceilings etc etc - but most do not have enough overall understanding of how the whole construction has to come together (nor do they care most of the time).
And so, I feel like just the fact that you have gone through the process from start to finish (or at least ‘to flooring’) actually makes you more informed about the overall process than the average Tradie.
And to prove my point (and possibly embarrass myself), I do not know anything about flooring, the closest I’ve come to the flooring is when I worked on skirting.
I also find - as you pointed out - there is often a discordance between what the manufacturers instructions are and what the Tradie does, which also causes issues.
Anyway, great piece, thanks for the shoutout/welcome at the start, and just to clear something up - I’m not actually working in the construction industry anymore, I left after 12 years because I just couldn’t take it anymore.
Thanks RenoQueen.