How to Clean Polyurethane Brush – 6 Easy Ways

How do I clean a polyurethane brush after use? If you consider the amount of money that goes into buying a poly brush, you’ll learn how to remove polyurethane from a dried brush.

Here’s what I know from looking into it:

How to Clean Polyurethane Brush?

Start by washing water-based urethane brushes with soapy water and oil-based urethane brushes with mineral oil. Then scrub the polyurethane brush repeatedly with a nylon brush and clean water. Finally, let the brush dry and hang it for storage.

But that’s just a quick glimpse. In this article, you’ll learn the six easy methods to clean polyurethane from a paintbrush:

• Using soap
• Using mineral spirits
• Using paint thinner
• Using acetone
• Using denatured alcohol
• Using gasoline

In addition, we’ll also go into how you can get rid of Minwax polyurethane from a brush. Plus, it includes how you maintain your paintbrush after use.

Why need to clean the polyurethane stain off the brush?

Cleaning polyurethane stain off your paintbrush is essential for the following reasons:

• Prolong the life of the brush while saving yourself a lot of money. 
• Protects you and your health from the toxicity of VOCs contained in the poly.
• You’ll be showing professionalism. 
• You can reuse the brush as many times as possible.
• Maintaining the quality of your work.   

What to clean the polyurethane brush with?

Here are materials and solvents that you can use to remove stains from your poly brush. Each of these methods will work perfectly, depending on the type of polyurethane varnish you used the brush to apply. 

• Clean water
• Cup
• Soap
• Mineral spirits
• Paint thinner
• Acetone
• Denatured alcohol
• Gasoline

Six easy ways to clean Polyurethane brush

1. Using soap

• Step 1: Fill three large cups to the brim with water: Make sure the water is sufficient to submerge the entire frame of the brush. 
• Step 2: Submerge the brush in the water: Put the brush in the first cup and turn it back and forth. This will ensure water soaks up the entire varnish. 
• Step 3: Remove the brush and insert it in the second cup: repeat step 1. Depending on the number of bristles on the brush, the water should be a bit clear. 
• Step 4: Submerge in the third cup: repeat steps 2 and 3 until the water is very clear.
• Step 5: Hand-scrub and rinse the brush: take the brush to the sink and rinse it with soap as you scrub with your hand.  
• Step 6: Wash the brush severally 
• Step 7: Allow the brush to dry: Hang the brush to dry for about 24 hours, and it’s ready for reuse.

2. Using mineral spirits

Mineral spirit is one of the recommended solutions you can use to remove polyurethane from the brush. It is a safe home remedy and won’t cause any toxicity. It is excellent to rid oil-based polyurethane from a brush. Dip the brush in a mineral spirit, and the entire finish will remove.

Mineral spirit is ideal for oil-based polyurethane. Here’s the step-by-step guide to cleaning poly brush:

• Step 1: Pour mineral spirit into three or four cups. 
• Step 2: Hold the cup down until the solvent covers the entire frame of the brush
• Step 3: Stir the brush around the cup. Alternatively, you can bend the cup back and forth. Make sure the mineral spirit gets in-between the brush bristles. 
• Step 4: Repeat steps 2 and 3. But, allow the color of the mineral spirit to change –from white to dark brown – before moving to the next cup.
• Step 5: Scrub and rinse the brush under running water. Make sure you use soaps.
• Step 6: Thoroughly run your fingers in-between the brush bristles.

Turpentine and mineral spirits are two of the most common solvents to clean a polyurethane brush. Whereas these solvents are considered harsh and toxic, there are other safer means of getting things done. Alternatively, you can choose a mixture of mineral oil and liquid detergent. You’ll get the same result and effect.

3. Using paint thinner

• Step 1: Get three to four cups and fill each with water. Mix the water in one of the cups with three to five drops of dish soap or vinegar and stir vigorously. You can also use liquid hand soap or hydrogen peroxide.
• Step 2: Insert the brush into the soapy water and bend back and forth to ensure every part of it gets into the water. Let the brush stay for 10 minutes if you’re using vinegar. 
• Step 3: The water in the first cup will have turned dark brown. Remove the brush and put it inside the bowl of clean water for about 15 minutes. 
• Step 4: Once the glue is dried on the bristles, place the poly brush in paint thinner for about 15 minutes. The thinner will chop off the glue off the bristles.
• Step 5: Dry the brush by hanging or laying it on paper or a dry towel.

Because paint thinner is a toxic substance for cleaning your polyurethane brush, you’ve got to opt for a safe, non-toxic, and fast way. One of the safest ways is to use mineral oil or baby oil. You can also combine liquid detergent plus baby oil to clean synthetic and bristle poly brushes.  

4. Using acetone

Although using acetone to clean a poly brush is not recommended, some crafters go for it. Typically, acetone is too strong and harsh and can be unsafe on your brush. Here are the steps to clean your poly brush with acetone.

• Step 1: Get a bowl and fill it with some acetone solution 
• Step 2: Dip the poly brush into the acetone-filled bowl. Make sure the entire body of the brush is submerged
• Step 3: Allow it to stay in acetone solution for about 15 minutes. Acetone will weaken the glue in-between the brush
• Step 4: Remove the brush and put in soapy water (use hand bar soap)
• Step 5: Rub the bristles in the soapy water  
• Step 6: Rinse the brush in clean water

5. Using denatured

• Step 1: Get 3-4 bowls and fill them with denatured alcohol
• Step 2: Wrap the brush in the denatured alcohol
• Step 3: Shake it well so that the alcohol can get into the bristles of the brush
• Step 4: Remove the brush and put it inside the second bowl
• Step 5: Repeat steps 1 and 2 but rinses it well
• Step 6: Hang the brush to dry out.

Note: poly dissolves very quickly in alcohol

Gasoline is not recommended

Never consider gasoline when you need to remove polyurethane finish from your paintbrush. Apart from being highly inflammable, gasoline comes with a lot of toxicity. This makes it quite unsafe and dangerous to use to remove polyurethane from your bush.  

How to get dried polyurethane off the brush?

After cleaning your poly brush, you should get it dry. The tools you’ll need to dry your brush are paper towels. 

Here are the steps:

1. Saturate a small section of the paper towel with mineral spirit. Alternatively, you can choose either lacquer thinner or paint thinner if that’s on hand. 
2. Follow the steps to remove the polyurethane finish from the brush bristles.
3. Rinse the clean brush with hot water.
4. Use a paper towel to pat the brush bristles.
5. Wrap in a plastic material or aluminum foil if it’s synthetic. For a natural brush, wrapping in an old newspaper will be all you need

How to clean polyurethane off foam brush?

To remove poly from a foam brush, you’ll need the same process for cleaning water-based poly from the brush.

Tools needed:  

• Dish soap
• 2 or 3 cups
• Running water

Steps include:

1. Fill your cups with clean your 
2. Dip the brush into the water-filled cup, starting with the first to the third cup.
3. Apply dish soap to rinse the brush foam under running water
4. Scrub with your hand and stroke your finger in-between the foams to ensure the brush is clear from the foam
5. Wring the foam to take off all water and soap from inside
6. Hang to dry 
7. Store the brush  

How to clean an oil-based polyurethane brush?

Tools needed:

• Nylon scrub brush
• Running water
• Cup (3-4)
• Dish soap
• Follow the instruction on the paint bottle (mineral spirits, paint thinner, or turpentine)
• A pair of protective gloves

We’ll use the mineral spirits as the cleaner. You can replace it with either turpentine or paint thinner. 

Step-by-step:

1. Pour the mineral spirit into about 3-4 separate cups. 
2. Dip the brush into the solution. 
3. Stir the brush gently inside the cup to make the spirit get in between the bristles
4. Take the brush off and move to the next cup. Repeat the same process in all three cups. 
5. Take the brush under running water and start to wash and rinse it thoroughly. Apply some household dish soap to the water and stroke your finger in-between the bristles
6. Using a nylon brush, scrub the bristles.
7. Dry the brush  

How to clean water-based polyurethane brush?

Tools and supplies needed:

• Dish soap
• 2 or 3 cups
• Running water
• A pair of gloves

Steps to clean water-based polyurethane brush:

1. Get three to four cups and fill them with water
2. Insert the brush into the water-filled cups, taking it from one cup to another. This will make the water in-between the bristles and clean them.
3. Apply dish soap to wash the brush under running water
4. Scrub with your hands and rinse the brush. Make sure the brush becomes clean and free from stains before you stop 
5. Hang the brush to dry 

Maintenance of the polyurethane brush after use

Once you’re done with painting your project, do the following to maintain your poly brush after use:

• Clean the brush immediately: You shouldn’t allow your brush to dry out and get stuck with paint on it. If you’re going on a break to rest or eat, there are things you can do to prevent your brush from hardening or drying out. If you’re going on an extended break, wrap the brush in aluminum foil.
• Remove all stains: Remove every stain on the bristles of the brush. Follow the steps for removing water-based and oil-based poly stains.
• Hang to dry: Wring the brush thoroughly. Hang it to dry out.
• Wrap it: Please don’t leave the coated brush unwrapped on a rag or a newspaper; it will dry out.
• Dry Storing: Storing your brush is another thing to consider.

FAQs about how to clean Polyurethane brush

What is the best way to clean a polyurethane brush?

If you’re cleaning a water-based poly brush, use water and soap. This method works pretty well. Another way is to soak the brush inside a jar of water, but it’s not recommended. Cleaning an oil-based poly brush will require the use of mineral spirit. It would help if you allowed the brush to dry before storing it.   

Will denatured alcohol clean the polyurethane brush?

Yes, denatured alcohol can effectively clean polyurethane brushes. However, this solution is suitable for removing shellac, lacquer, or latex finishes. Although using denatured alcohol may take some time, it is less toxic and will work better than paint strippers.

How to clean Minwax polyurethane off brush?

Being an oil-based finish, Minwax polyurethane can only be removed from your brush using mineral spirit, paint thinner, or turpentine. Submerge the brush bristles inside the solution and remove and put them into another can of mineral spirit. Scrub and rinse the brush under running water before hanging to dry.  

Final Words

Reusing painting tools isn’t wrong, and the brush is one of the tools you can use repeatedly. From this article, I hope we’ve been able to exhaustively answer all the questions concerning how to get poly off the brush.

To remove oil-based poly from a paintbrush, you’ll need some chemical solution, using either white spirit or paint thinner. Whereas cleaning water-based poly from a brush requires thorough flushing with water and drying. There are methods available for both types of poly.

Learning to clean polyurethane brushes will extend their life and will save you a lot of money. On top of that, it protects your health and your professional image.

It’s essential that you follow all the steps and not assume anything before equipping yourself with proper knowledge. Ensure that you exhaust all the primary ways before you opt for the alternative methods of cleaning poly from the bush.