How to Apply Polyurethane Without Bubbles

Stephen Hochstrasser

Stephen started his own hardwood flooring company 35 years ago. He is a perfectionist at his craft and exceptionally passionate about his industry, guaranteeing you’ll love your floors while achieving the highest return on every flooring investment.

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Nothing takes your wood floors to the next level quite like beautiful wood flooring finishes. However, be warned, applying polyurethane takes a lot of skill and patience. And if you mess things up, you could end up with unsightly bubbles in your polyurethane. Tiny bubbles in polyurethane not only look bad, but they can also weaken the finish and make it more susceptible to scratches and other damage. So, here is how to apply polyurethane without bubbles.

At G3 Flooring, we are professional wood contractors located in Colorado Springs. We do everything from new wood floor installation to wood floor repair and much more. Our team of wood flooring experts has countless years of experience in the industry. Beautiful wood flooring is our passion. Ready to learn more about how to apply polyurethane without bubbles? Let’s get started.

a picture of refinished hardwood floors

What Causes Bubbles in Polyurethane?

Before discussing how to apply polyurethane without bubbles, it’s important to understand what causes them. Most of the time, bubbles in polyurethane are caused by improper application or shaking of the can.

For example, before you stick your brush into the can of polyurethane, make sure you soak it with mineral spirits or water (more on that later). Also, never shake your can of polyurethane. Shaking the can will create bubbles that will end up in your finish. Instead, stir it slowly and gently.

Keep these things in mind as you read through the process of how to apply polyurethane without bubbles step-by-step.

Step-by-Step Guide: How to Apply Polyurethane Without Bubbles

Now that you know what causes bubbles in polyurethane, let’s move on to the process of how to apply polyurethane without bubbles.

1. Remove All Dust

When you’re ready to apply polyurethane to your wood floors, the first thing you need to do is make sure the surface is completely clean and free of any dust or dirt.

The best way to do this is to use a vacuum with a soft bristle attachment to remove any loose particles. Then, go over the surface with a damp cloth to pick up any remaining dust. This ensures you start with a clean slate and gives you the best chance for a smooth, bubble-free finish.

2. Sand the Surface

Once the surface is clean, it’s time to sand it down. This will help create a smooth surface for the polyurethane to adhere to. Start with a rough grit sandpaper and work your way up to a finer grit. Remember to sand with the grain of the wood, not against it. You are looking for your wood to be smooth and splinter-free.

3. Wipe Down After Sanding

After you’re done sanding, use a cloth to wipe away any remaining dust on the surface. Remember that you want your floors to be free of any dust or debris before putting down a layer of polyurethane. This step is essential before you start applying your wood finish.

4. Mix Your Polyurethane

When you’re ready to apply the polyurethane, mix it well before starting. This will help ensure that you get an even coat. However, you don’t want to shake the can, as this can create bubbles in the polyurethane. Use a stir stick instead.

a picture of someone applying polyurethane to wood floors with a paint brush

5. Apply Your First Coat

Once your polyurethane is mixed, it’s time to start applying it to the surface. Use a paint brush or roller to evenly spread the polyurethane over the floor. If you are using an oil-based finish, it is recommended to first soak your brush in mineral spirits before applying. For water-based finishes, use water.

Also, make sure you’re working in small sections so that the polyurethane doesn’t have a chance to dry before you’re done applying it. Be sure to apply a thin layer of polyurethane, too. You don’t want to glob it on, as this can also cause bubbles.

When you apply your polyurethane, work with the grain of the wood. Be careful not to apply too much pressure to the brush. You don’t want to splash your brush or wipe off excess on the container of your polyurethane either, as that can cause bubbles as well.

6. Sand Before The Next Coat

Once you’ve applied the first coat of polyurethane, let it dry before sanding. The drying process requires lots of patience. Your polyurethane can take up to 24 hours to dry, and you want to err on the side of caution.

This will help ensure that the polyurethane is completely dry and won’t be disturbed when you sand. Use fine-grit sandpaper to lightly sand the surface. Then, use a cloth to wipe away any dust that’s been created. Remember to sand after each coat of polyurethane to ensure a smooth, even finish!

7. Apply Your Next Coat of Polyurethane

After you’ve sanded, you’re ready to apply the next coat of polyurethane. Follow the same steps as before, being sure to mix (not shake) your polyurethane well and apply it in thin, even coats. Remember to let each coat of polyurethane dry thoroughly before sanding and applying the next one.

8. Repeat This Process

Repeat steps six through eight until you’ve reached the desired number of coats. You’ll want to apply at least three coats of polyurethane for a durable, long-lasting finish. However, you may need to apply more or less depending on your specific project.

Now that you know how to apply polyurethane without bubbles, you’re ready to get started on your own project! Just remember to take your time and be patient. Applying polyurethane is a process, but the end result is always worth it.

a picture of someone using a paint brush to apply polyurethane

How to Apply Water-Based Polyurethane Without Bubbles

If you are using water-based polyurethane, the process for applying it without bubbles is slightly different. It is recommended to use a high-quality synthetic brush instead of a natural one. You should also soak your brush with water to avoid your polyurethane from running or puddling. Doing so causes the bristles of your brush to stick together and removes any trapped air that can cause bubbles.

How to Roll Polyurethane Without Bubbles

If you would rather use a roller to apply your polyurethane, that’s totally fine! Just remember you want to use a high-quality one. For example, lambswool is great for an oil-based polyurethane whereas microfiber is better suited for a water-based one.

How to Get Rid of Bubbles in Polyurethane

What happens if your final coat of polyurethane dries and you notice bubbles? Don’t panic!

The first thing you’ll want to do is lightly sand the surface with a fine-grit sandpaper. This will help to remove any imperfections and allow the new coat of polyurethane to go on smoothly. However, this method may not work for larger bubbles.

If you have larger bubbles that just won’t pop with light sanding, you’ll have to sand down all the polyurethane. This can be a time-consuming process, but it’s the only way to get rid of all the bubbles. Once you’ve sanded down the surface, you’ll start from scratch and apply new coats of polyurethane.

Get Professional Wood Refinishing With G3 Flooring

With these tips in mind, you’re ready to apply polyurethane like a pro! Just remember to take your time, work in thin coats, and sand between each coat until your last one. Also, don’t forget to soak your brush and never shake the can! With a little patience, you’ll be left with a smooth, bubble-free finish that will last for years to come.

At G3 Flooring, we are here to help you with all of your polyurethane questions! As a wood flooring contractor located in Colorado Springs, we provide top-quality installation, maintenance, and refinishing services. Have questions about your hardwood floors? Contact us today for an estimate!

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