How to Clean a Polyurethane Brush Effortlessly

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I know the feeling: you’ve just finished painting your wall or sprucing up that old furniture piece, and it feels great! But then, there’s that messy brush covered in polyurethane. Don’t worry, I’ve learned from some of the best woodworkers and painters out there. 

Let me show you a simple way to clean that brush. Just have your materials handy, and let’s get it cleaned up!

What Types of Brush Can You Use to Apply Polyurethane?

You can use two different brushes to apply polyurethane as a table top finish or a sealer on various wooden products. 

For oil-based polyurethane formulas, you need to use a brush made with natural bristles. These are better suited for soaking in and spreading the oil. However, they can be costly. 

paint brushes on a table

When it comes to water-based polyurethane, synthetic bristles are the best choice. They do not enthrall as much moisture as natural bristles, making them ideal for this type of application. They are also cheaper and can render a more even coat.

If you don’t have any, you can easily purchase one at the nearest local hardware store near you!

Steps on How to Clean Water-Based Polyurethane from a Brush

Cleaning water-based polyurethane paint from a brush can be simple as the following:

Tools and Materials You'll Need

Step #1: Pour Three Cups With Water

Get three cups, which are large enough to submerge your brush in. Then, clean polyurethane brush up to its ferrule, the metal part that’s binding all the bristles.

three white cups

Step #2: Put the Brush in the First Cup

Dip the brush into the cup and move it back and forth to ensure water penetrates between the bristles and the ferrule. Repeat this process three more times and observe if the water changes color.

Step #3: Put the Brush in the Next Cup

After one cup of water changes into a dirty color, proceed to the next cup. Repeat this entire process until the water in the cup becomes a tad clearer.

Step #4: Clean the Brush With Soap

Next, head over to the nearest sink and clean the brush with clean, running water. It is better to rub it with a soap dish and scrub with your hands. Many pro painters advised to wash it about two to three times until you achieve squeaky clean bristles. 

cleaning brush with soap and water

Step #5: Hang the Brush and Leave to Dry

Once you’re done thoroughly cleaning, you can either hang it on the sink or somewhere dry. Once the brush is fully dry, you can reuse it the following day. 

Steps on How to Clean Oil-Based Polyurethane from a Brush

Compared to synthetic brushes, these brushes are more prone to dirt. But, cleaning oil-based polyurethane brushes can be as simple as the following:

Tools and Materials You'll Need

Step #1: Fill Three or Four Cups with Mineral Spirits

In three or four cups, pour mineral spirits (paint thinner or turpentine). When the cups are ready, soak the brush up to its ferrule.

pouring mineral spirit into a jar

Step #2: Put the Brush in the First Cup

Immerse it in the first cup with mineral spirits. Make sure to hold the brush down so that all of its bristles are fully soaked. Next, stir it inside the cup to get the mineral spirit in between the bristles.

Step #3: Proceed With the Next Cup

After the first cup, pour the mineral spirits into the next cup. Keep going until the water color no longer changes. 

soaking the brush in mineral spirit

Step #4: Scrub it in Running Water

Bring the brush into the sink and rinse it with clean, running water. Also, rub it with dish soap to ensure it’s rid of chemicals. Continue doing this until you get a clear lather. 

Step #5: Scrub with a Nylon Brush

Once again, put the brush in the sink and rub it with soap. Using a nylon brush, gently rub it in  to clean the bristles. Repeat the process until you get an oil-free, squeaky clean polyurethane brush.  

Step #6: Leave the Brush to Dry

Then, allow for it to dry in the sink or someplace dry. After a day, the brush will be completely dry.

person drying a brush

Why You Need to Clean Polyurethane Brushes

Handy and Convenient

Having your brush ready can help you avoid buying one every time. You can always reuse it. 

Ensures the Quality of Your Project

It’s essential to clean a brush with polyurethane to prevent exposure to a dried polyurethane coating. Without proper cleaning, the brush won’t be as even as before, affecting the quality of your project. 

Extends the Life of the Brush

Based on my experience, good-quality brushes can be used for 10 years before it starts to wear out. 

paint brush and a plastic cup

Synthetic and natural brushes can last long as good as a new brush if you thoroughly clean them after each use.

Professional Use

When people know you as a skilled do-it-yourselfer, they expect you to have various tools handy. Having a good quality brush is essential to ensure that you achieve the quality of work  as a professional. 

For Your Health and Safety

While it’s common knowledge that polyurethane can contain toxic chemicals, it’s also important to remember that extended exposure can cause health problems. To minimize exposure, keep all of your chemicals in their original containers. 

Can You Use The Same Polyurethane Brush For Water-Based and Oil-Based Use?

Utilizing the same brush for oil-based and water-based polyurethane applications is okay but not recommended. 

paint brush

The results will not be the same because oil-based poly applications will require the use of natural bristles. And for water-based poly applications, use a synthetic brush. 

In addition, different cleaning agents are recommended for the two types of polyurethane; paint thinner for oil-based and dish soap for water-based.

However, if you don’t have these types of brushes, you can still use one brush for both poly coats. Just make sure you clean it thoroughly after use. 

Check this out: Best Brushes for Polyurethane Application 

How and Where to Store the Brushes

Depending on the core of your project, you may need to take breaks for a few hours. 

blue paint brushes

You know, instead of just setting the brush on a newspaper or cloth, it’s best to leave about a third of the bristles dipped in the paint when taking a break. This way, the paint doesn’t dry out on the brush.

Where to Store When Taking a Long Break

After you have finished your project, it’s time to remove polyurethane from the brush and store it. These steps will help keep them in their best condition until they need to be used again.  

FAQ

How do you clean a polyurethane brush without paint thinner?

To clean polyurethane brushes without paint thinner after the polyurethane application on paint, you can use warm soapy water if it’s water-based. 

In removing oil-based polyurethane brush, you’ll need to dip it in turpentine or mineral spirit if you don’t have a paint thinner.  

What you should do with a brush between polyurethane coats?

After each coat of paint, wash the polyurethane brush using a mild cleaning agent. Then, rinse the paintbrush with clean water and remove polyurethane residue. Finally, leave the paintbrush flat on a hard surface to dry. 

Can you use acetone to clean a polyurethane brush?

You can use acetone to clean polyurethane brush. Acetone can be a natural paint thinner that can be used to clean water-based polyurethane brushes and remove oil-based polyurethane from synthetic bristles. 

Conclusion

Learning how to clean a polyurethane brush really saves money and keeps things safe. A clean brush not only lasts longer but also ensures your projects turn out great. Trust me, whether you’re using water-based or oil-based polyurethane, a clean brush makes all the difference.

robert headshot

Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

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