Although finish isn't something that you might think about when installing hardwood flooring, it can have a major impact on aesthetics and even durability. Two common finishes for hardwood floors are aluminum oxide and polyurethane.
Aluminum oxide is an additive to water-based urethane finishes, while polyurethane is a traditionally oil-based finish that doesn't contain aluminum oxide. The application of either product has definite benefits, with some disadvantages. In some instances, the softer polyurethane is more appropriate than the glassy, hard surface offered by aluminum oxide urethane.
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What is the Difference Between Urethane and Polyurethane?
Urethane and polyurethane are sometimes confused with each other because both products contain urethane. The differences are in the formulations between the two. When additives such as aluminum oxide are added to urethane, it becomes a high-performance urethane, with different characteristics than polyurethane, or basic urethane.
Aluminum Oxide Basics
Aluminum oxide is a naturally occurring element, typically found in a crystal form, that is commonly used as an abrasive for sandpaper. When ground into a white powder, it's used as a filler ingredient for paints, plastics, sunscreen, and cosmetics. When used as a fortifier for urethane, it imparts hardness and abrasion-resistant qualities lacking in polyurethane.
Polyurethane has additives that resemble the elasticity and physical properties of rubber or plastic. Polyurethane provides greater flexibility but less wear-resistance than aluminum oxide urethane. Polyurethane is available in two basic types, water-based and oil-based. For the sake of comparison, old-school, oil-based polyurethane is typically compared to water-based aluminum oxide urethane, because oil-based polyurethane performs better than water-based polyurethane.
Aluminum Oxide and Polyurethane Differences
Aside from the chemical differences between aluminum oxide and polyurethane, there are obvious differences in performance that have a direct effect on your floor.
- Dries clear
- Glassy shine
- Scratches can be difficult to fix
- Extremely durable
- Used in many commercial settings
- Typically applied in a factory
- Has an amber tint
- Shiny, but less sheen than aluminum oxide
- Easy to buff scratches
- Comfortable on your feet
- Easy to refinish
- Simple for a DIYer to apply
Polyurethane ages to a warm, amber tint, bringing out the natural beauty and grain of a particular wood species. Aluminum oxide urethane dries clear, with minimal changes in color, enhancing grain patterns to a lesser extent. If you prize the old school appearance of golden hues and grain patterns, polyurethane is a better choice.
Glassy or Dull
Aluminum oxide urethane dries to a glassy shine. Polyurethane, even though shiny, dries with less sheen.
Polyurethane scratches can often be buffed out and are not highly visible. The scratches in aluminum oxide show up with a whitish powdery look, and are more difficult to repair due to the hardness of the material.
Polyurethane finishes are softer than aluminum oxide urethane, and feel better on bare feet and paws, which makes them more appropriate for children and pets.
Re-coating and Refurbishing
Polyurethane finishes are easier to redo than aluminum oxide urethane, which typically requires a complete stripping before the addition of new coats. Polyurethane finishes in relatively good condition often can be screened (roughened with abrasives) and recoated.
Because aluminum oxide urethane is more durable than polyurethane, it's used more often commercially than polyurethane.
The majority of prefinished, engineered wood has an aluminum oxide finish, with high-end grades almost always finished with aluminum oxide urethane. Polyurethane on engineered wood is not as common.
Ease of Application
Polyurethane is easy to apply and is the standard choice for site-finishing hardwood flooring, whether it's newly installed or part of a refinishing project. It's even suitable for DIYers to work with. Aluminum oxide finishes are typically applied in a factory, where they undergo a UV curing process.
Which Floor Finish Should I Choose?
If you're buying new solid or engineered hardwood flooring and you want it to be prefinished, chances are it will have an aluminum oxide finish. If you are having traditional solid hardwood flooring installed and finished on-site, polyurethane is what most installers will use, but there are other specialty finishes available.