A Guide to Using Polyurethane Finish On Wood
Discover how polyurethane coatings can add longevity and enhance the look of wooden furniture and floors
Polyurethane is a protective coating that forms a solid layer of plastic when applied on a wooden surface. This finish primarily comprises resins that makes it much stronger than standard varnishes or lacquers; it is highly flexible so it works well even on curved surfaces. Polyurethane coatings give wood excellent resistance to abrasion,scratches, rough use and spills; additionally, it is highly resistant to boiling water and harsh chemicals like alkalis or acids. So, if you are looking for a hard-wearing clear finish for wood, here is all you need to know about polyurethane coatings.
Areas of application
- Polyurethane coatings are recommended for wooden furniture that is subjected to rough use, such as wooden doors, windows and countertops.
- These coatings work very well for wooden furniture in the coastal areas because polyurethane is resistant to moisture and provides good chemical resistance against salt-laden air.
- Another application of polyurethane is in places where it provides the highest degree of protection to high-traffic floors that are subjected to wear and tear. How? The top coat stays for a longer period of time.
Types of finishes
Polyurethane gives a very high-end premium look to wooden surfaces, as in this image. It is available in numerous finishes like high-gloss, semi-gloss and satin. The level of gloss does not affect the durability of the polyurethane coating but each additional coat makes the finish smoother.
Note: One drawback of polyurethane is that since it is a thick plastic coating, it is susceptible to cracking and once damaged, it cannot be repaired.
Application technique
These are the steps to the application of polyurethane on wood:
Polyurethane gives a very high-end premium look to wooden surfaces, as in this image. It is available in numerous finishes like high-gloss, semi-gloss and satin. The level of gloss does not affect the durability of the polyurethane coating but each additional coat makes the finish smoother.
Note: One drawback of polyurethane is that since it is a thick plastic coating, it is susceptible to cracking and once damaged, it cannot be repaired.
Application technique
These are the steps to the application of polyurethane on wood:
- Sand the wooden surface till smooth; fill uneven surfaces with a sealer. The working environment and surroundings should be clean and dust-free to prevent any dust from sticking on the surface while it is wet.
- It is essential to keep the area well ventilated and switch on the exhaust fans so that any strong and toxic fumes emitted by the polyurethane are instantly replaced with fresh air. Use a respirator while working to avoid inhalation of toxic gases. As a precaution, keep children and older people away from the site.
- Open the polyurethane container and stir it slowly. Do not churn the contents of the container, as it can cause air bubbles to form, which might show after you paint it on the wooden surface. It is important that you read the manufacturer’s instructions; you might have to thin the polyurethane with mineral spirit before application.
- Now apply the first coat of polyurethane on the wooden surface with a spray, brush or a roller. When applying on vertical surfaces the coating may drip (in that case you must sand it immediately when dry). Allow the polyurethane coating to dry properly.
- Re-sand the coating before applying the next coat of polyurethane.
- Repeat the process till you achieve the desired level of protection. Indoor furniture will require a minimum of two coats of polyurethane while wooden floors shall require three coats for optimum protection.
- The drying time between each coat is usually two hours. It is advisable to wait at least 24 hours after application of the final coat before using the wooden floors or furniture, because the polyurethane coating might still be sticky.
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Polyurethane can be classified as water-based and solvent-based coatings.