As a professional painter, it becomes very crucial to clean brushes after applying the paint. Cleaning brushes not only saves your money that is going to be wasted in purchasing new brushes but also keeps backup brushes in the store.

In this article, we will describe various methods to clean Polyurethane brushes for both wet brushes and dried brushes.

But before diving into the depths first let us know a little about Polyurethane.

What Is Polyurethane?

Polyurethane or also called “PU” is often a transparent liquid coating that is applied on painted surfaces to make them shine and last longer. Polyurethane can also be colored by adding pigments to it but generally when we say Polyurethane that means transparent coating.

The main usage of this substance is to provide a strong transparent layer on wooden substances. It not only protects the wooden surfaces but also retains the natural look of wood. PU is extremely strong in nature, strong enough to prevent the development of cracks on wooden surfaces.

The cleaning process is one characteristic that makes polyurethane challenging to work with. The most difficult task is to clean PU from brushes. The PU is transparent in nature and it becomes very difficult to know whether the brush has been cleaned properly or not.

When working with polyurethane, keep in mind that it has a thick viscosity and is difficult to work with. As a result, polyurethane is more demanding than standard paint.

Different Types of Polyuthereane 

Like most paints, Polyuthreane paint is of generally two types.

1. Water-Based Polyurethane

clean polyurethane paint

Water-based polyurethane paint is the newer version of paint as compared to oil-based PU. Water-based PU paint has a stronger surface and is stronger than oils based PU paints. It gives a more transparent look and the coating of this paint is thinner than oil-based PU.

Water-based PU paint is slightly more expensive than Oild-based PU due to its advantages like rapid drying time, more transparency, and harder surface.

2. Oil-Based Polyurethane

clean polyurethane brush

This is the older and more widely used type of PU paint. Some people still believe that oil-based PU is better than water-based PU but it is actually not.

However, the thickness of one coat of oil-based polyurethane is more than that water-based polyurethane paint but it isn’t as hard as water-based polyurethane paint. The oil-based PU paint has a strong odor that is harmful when the paint is drying.

One more disadvantage of oil-based PU paint is that it does not retain the original color of wooden surfaces and makes them slightly darker in shade. With time, the color of this coat keeps on going darker.

Various Methods To Clean Polyurethane Brush Bristles

Different type of polyurethane paint needs to be cleaned in different ways, below we are describing various method to clean polyurethane brushes

Method 1: Cleaning Water-Based Polyurethane

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First, identify the type of PU you have been applying. The easiest way to know is to look at the container of paint. Be informed that water-based paints are also called latex paint and the container may have written latex-based paint over it.

If you are still unaware of the type of paint just pour some drops of denatured alcohol on a piece of cotton and rub it over the dried surface of PU. If the paint gets a lit bit washed off it means its a water-based paint and not oiled based.

You will need the following things to clean water-based PU paint

  • Water
  • A container
  • Pair of gloves


  1. Start by adding water to your container so that you may clean your brush. 
  1. After that, thoroughly rinse your brush in the container with gloves on to remove any leftover water-based polyurethane. 
  1. Use clean water each time you go through the first step, and repeat it about four times. Ideally, you will be able to tell when to stop when your water is still pure and unclouded.
  1. Go to your sink area and flush it thoroughly with clean running water to ensure all of the water-based polyurethane has been eliminated. 
  1. Any leftover poly residues will be removed from your brush during this subsequent process. 
  1. To prevent paint from splattering everywhere, use caution while using the sink. Overall, make sure always to use gloves and squeeze as much water out of your brush as possible.
  1. Let your polyurethane brush soak in water occasionally. 
  1. To completely remove the water-based polyurethane from the brush hairs, you can leave it soaking for a while. However, it’d be best if you didn’t soak for an excessively long period because prolonged contact with moisture can bend the bristles.

Method 2: Cleaning Oil-Based Polyurethane

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Cleaning oil-based polyurethane paint is not as easy as water-based paint but is still doable. Follow the same method to identify the type of paint as described above. Oil-based polyurethane paint can also be identified by the strong odor that it has.

Things you will need to clean oil-based polyurethane from the brush:

  • Paint thinner/white spirit
  • Acetone
  • Water
  • Dish soap
  • Mask
  • Gloves
  • Container


  1. Oil-based polyurethane can’t be cleaned with water alone. For freshly applied polyurethane, the first step is to soak your brush in paint thinner for a few hours. You can only get rid of polyurethane from brush hairs with paint thinner because it is an oil solvent. 
  2. After giving your brush a thorough bath, run your fingers through its hairs to make sure all the oil-based polyurethane is still in the thinner.
  3. After adequate washing and massaging in the thinner, apply some acetone on the brush to remove the thinner. 
  4. Then, follow up the acetone wash with a final wash using water and dish soap. Again, water and soap are used to get rid of the acetone. 
  5. This last step might feel like too much, but it is necessary for more extended service, even with good-quality brushes.
  6. Soap will assist in the last washing stage in softening the bristles to preserve their flexibility for future use. 
  7. Wash the polyurethane brush hairs with water to get rid of the soap traces.

To completely remove polyurethane from a brush, you should perform the water wash in a sink. You should keep your windows open and put on gloves and a dust mask while working on this project.

How To Clean Polyurethane Brush If It Is Dried?

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Painting is a tedious and exhausting task, sometimes you are so tired that you may leave your brushes unwashed. When you leave your brushes unwashed they get hard and it becomes very difficult to remove the paint afterward. The methods described above won’t work in this case.

But hopefully, we also have a solution for this situation which we have described below.

What You Need

Although it may seem complicated, this method needs a few common ingredients. The majority of what we’ll list is probably already in stock or accessible at your neighborhood hardware store. This is the list:

  • Mineral spirits.
  • Paper towels
  • Brush comb
  • Plastic bag
  • Two glass or plastic containers

Some people may prefer using common cleaning materials, such as fabric softeners, for the softening process to remove dried paint. However, this technique might not work with polyurethane and oil paint. Some people may also decide to utilize solvents like paint thinner or lacquer thinner in place of mineral spirits but it is not advisable at all as these alternatives can damage the brush


  1. The first step is softening the hardened polyurethane by applying mineral spirits on the brush with the help of the paper towel
  1. After removing the excessive polyurethane in the first step now it is time to dip the brush into mineral spirits for at least 8 hours. Make sure to rinse only the hairs of the brush and not the metal capping above as the spirit can damage the metal.
  1. make sure to stir the brush every 1-2 hours to allow the mineral spirit to pass through every hair of the brush.
  1. take the brush out of spirit and check if it has softened a little bit or not. Dispose of the use of spirit minerals carefully.
  1. Clean this process a couple of times until the paint has left off the brush completely
  1. Once you have confirmed that your brush is clean and that the bristles have softened, rinse it in hot water. Due to the dangers of mineral spirits and polyurethane, perform the hot water soaking in a separate container. You can use dish soap to get rid of any leftover solvent after a sufficient soak. 
  1. You will use a brush comb at this stage to comb through the brush hairs and remove any extra paint and polyurethane.
  1. Finally, dry your brush with paper towels to complete your cleaning. To avoid tugging the bristle too hard, gently pat the bristles of your brush dry. You can use a plastic bag or wrap to shield the bristles once your brush has dried. For example, you can wrap your brush in an old newspaper if it has natural bristles.

How To Clean a Brush Using a Brush Comb?

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Consider purchasing a paint comb to make cleaning your brushes less complicated. 

This double-headed wire brush has stainless steel needles on one side and brass bristles on the other. It expedites the process of cleansing the brush’s bristles of paint or varnish. For instance, brush combs are available online.

The comb is designed to be softly placed into the bristles of the brush and continuously stroked downward to help remove any paint or varnish residue from the brush.

After using a clean rag to dry the brush, you can turn it upside down in an open jar, so the bristles are facing up. The bristles will dry first in this manner, preventing the growth of mold and mildew.

This will ensure that your brushes may be used repeatedly for many years by cleaning the brush not only on the outside but also on the interior bristles more wholly and quickly than if you were to rinse it.

Where To Store Your Brush

After cleaning it well, you can store your brush in a cool, dry location. You can keep moisture out while maintaining airflow by creating such circumstances.

So long as your brush is stored on cardboard, you can count on it to maintain a flawless coat over time.

Tips To Guide You Through The Brush Cleaning Process

1. Distinguishing The Type Of Brush

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The biggest difference here is between natural and synthetic brushes. Both synthetic and natural hair bristles can be cleaned using the methods that are mentioned.

Additionally, genuine hair bristles are softer than synthetic ones. In contrast to a quality brush with synthetic bristles, which can be bent without risk of harm, strong scrubbing does not suit natural bristles.

2. Caution Working With Solvents

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Solvents used to remove oil-based paints can be dangerous if not handled appropriately. 

In addition, you should be aware that paint thinner and mineral spirits are manufactured using harsh chemicals similar to those used to create polyurethane paint and other oil-based paints as you learn how to clean polyurethane brush bristles.

In order to ensure proper ventilation, we advise wiping polyurethane brushes or dried paint in such places. 

Additionally, when using solvents to clean brushes, you should wear protective clothing to prevent contacting your skin, eyes, or mouth with the chemicals. 

You may experience health issues if inhaled, consumed, or absorbed via the skin, necessitating medical intervention. 

Gloves, goggles, ventilated masks, and dust masks are a few examples of safety equipment to use.

Taking this precaution a step further, any oil paints or solvents used to clean polyurethane, such as mineral spirits or paint thinner, shouldn’t be flushed down the toilet.

Instead, gather spent solvents in a separate container and dispose of them safely in a hazardous recycling facility.

Frequently Asked Questions

Be careful to soak the brushes in water until the polyurethane melts, then lather them with soap. Continue doing this until the stains are gone.

Absolutely Yes!

It is not only safe but also encouraged.

You can reuse your polyurethane brush indefinitely if you clean it carefully after each usage. This will not only save you money, but it will also benefit the environment by eliminating waste.

Polyurethane brushes are far more expensive than regular brushes. Therefore you should make the most of them.

Mineral spirits work well for cleaning polyurethane brushes. Some craftspeople prefer mineral spirits over paint thinners. 

The procedure is the same if mineral spirits are your preference. First, you immerse your paintbrush in mineral spirits until the bristles are pliable enough to separate from one another. 

Then, after rinsing the brushes, you brush them against your gloves while submerged in water until you can no longer detect any polyurethane residue. After completing this, you can dry your brushes with a microfiber cloth. 

Use a gentle cleaner to wash the polyurethane brush between coats of paint. After that, rinse the paintbrush with fresh water to get rid of any remaining polyurethane. Lastly, let the dry paintbrush flat on a solid surface.

Polyurethane brushes can be cleaned using acetone. Cleaning water-based polyurethane brushes and removing oil-based polyurethane from synthetic bristles can be accomplished using the natural paint thinner acetone.


Cleaning polyurethane brushes may be a hectic exercise when compared to other types of paint. Especially in the case of clear PU polish, it is hard to distinguish between a clean and dirty brush. You may leave the brush thinking that it is cleaned properly but later you will find the same brush in a hardened position.

Each time when you apply polyurethane paint make sure to follow the proper cleaning procedure as described above.

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