How to Clean Polyurethane Brush? (6 Steps)

It’s always advised to clean paintbrushes after painting to keep the paintbrush in good condition. So how do you clean polyurethane brushes? Here is the answer to that.

To clean a polyurethane brush, you need to first squeeze as much polyurethane as you can off the brush. Then you need to soak the polyurethane brush in a bucket of solvent or paint thinner for 10 minutes.

You may need to dilute the concentration of the paint thinner depending on the potency of the liquid. After 10 minutes, take the brush out and wipe it with a clean rag.

Stuck polyurethane residue can be removed using a soft toothbrush. When the brush is clean, rinse it in clean warm water and store it properly.

Why Do You Need To Clean Polyurethane Brush?

You need to clean polyurethane paintbrushes to keep the paintbrush in good condition. After painting polyurethane with a paintbrush, polyurethane residue is bound to be glued to the paintbrush.

If you don’t clean the brush, the polyurethane residue will dry and harden on the paintbrush. The solidification process of the polyurethane on the paintbrush can cause the bristles on the brush to dry out.

Here are a few other reasons to clean polyurethane brush after painting:

1. To Prevent Color Mixing On Your Next Painting Task.

If you don’t clean a paintbrush after using it to apply tinted polyurethane, you risk the polyurethane color dissolving and affecting the color of your next paint job if you use the same brush.

The color of the tinted polyurethane can easily come off and mix with the color of your next paint while mixing or during paint application. This can make your results ugly and have uneven color.

2. To Save Polyurethane

Sometimes, the paintbrush takes more polyurethane than is needed from the paint can. After painting, you might still have leftover polyurethane on the paintbrush that you can squeeze back into the can while cleaning the brush. This helps to prevent polyurethane wastage.

3. For Easy Paint Application Next Time

Cleaning polyurethane brush after applying the paint makes your next painting task easier. With the paintbrush clean, you can easily apply paint with it next time.

Cleaning also saves the time you would have spent cleaning the paintbrush during your next task.

So what can you use to clean polyurethane brushes? Let’s find out.

What Can You Use To Clean Polyurethane Brushes?

What Can You Use To Clean Polyurethane Brushes

You can use several solvents and paint thinners to clean a polyurethane brush. However, the cleaning agent you should use will depend on the type of polyurethane that you used.

For water-based polyurethane, you should use water to clean the polyurethane brush. For oil-based polyurethane, you should use mineral spirits to remove the oil-based polyurethane.

Let’s check out some common solvents and see if you can clean a polyurethane paintbrush with them.

Mineral Spirits

You can use mineral spirit to clean a polyurethane brush. But, the solvent is more ideal for cleaning oil-based polyurethane than water-based polyurethane brushes. This is because mineral spirit can dissolve oil-based polyurethane.

To clean oil-based polyurethane, you’ll need a solvent strong enough to dissolve the oils and chemicals in the polyurethane. Mineral spirit is strong enough.

This doesn’t mean that mineral spirits can’t clean water-based polyurethane brushes. But, the solvent will be too strong for cleaning water-based polyurethane. It’s like using a bomb to kill an ant.

Tip: You shouldn’t soak paintbrushes in mineral spirits for too long as this can weaken the brush.

Water

You can use water to clean a polyurethane brush but water is more ideal for cleaning water-based polyurethane brushes. This is because water-based polyurethane contains water and as such, the paint can be easily dissolved and removed in water.

Since water can’t dissolve oil-based polyurethane, it means that water can’t clean an oil-based polyurethane brush.

However, after removing oil-based polyurethane from a paintbrush with a solvent, you should rinse the brush in water. This is to remove leftover solvent from the paintbrush as this can corrode the delicate parts of the brush.

Acetone

You can use acetone to clean a polyurethane brush. Acetone is a naturally occurring paint thinner that is effective for cleaning both water-based and oil-based polyurethane from paintbrushes.

However, you should only use acetone to clean or wipe polyurethane brushes. Never soak a paintbrush in acetone because acetone can soften the plastic parts of the paintbrush. If left in the acetone for too long, the paintbrush will dissolve and lose shape. So only wipe paintbrushes with acetone.

Alcohol

Alcohol is an effective paint-removing compound that can be used to clean a polyurethane brush. Alcohol can be used for removing water-based and oil-based polyurethane from paintbrushes.

You can even soak paintbrushes or swirl them around in a bucket of alcohol to dissolve the polyurethane residue since alcohol doesn’t corrode or damage the plastic.

Paint Thinner

Paint thinners can be used to clean polyurethane paintbrushes but do not soak your paintbrush in the paint thinner for too long.

At most, you should expose the polyurethane paintbrush to paint thinner for 30 seconds. Longer than that and the brush could be affected.

This is because paint thinners are produced from one of or a combination of several chemicals including acetone, xylene, mineral spirits, and turpentine.

All these substances are chemically strong and can cause corrosion or melting if left too long on a polyurethane brush.

You should know that paintbrushes should always be rinsed in clean water after using paint thinner to clean the brush.

You can also clean polyurethane brush with:

  • Turpentine (for oil-based polyurethane)
  • Denatured Alcohol (for water-based polyurethane)
  • Warm Soapy Water (for water-based polyurethane)
  • Lacquer Thinner (for oil-based polyurethane. Don’t soak the brush in lacquer thinner)
  • White Spirits (For water-based polyurethane).

Now that you know what to clean a polyurethane brush with, how should you clean the paintbrush? Let’s find out.

How To Clean Polyurethane From A Brush (Made Easy)?

Cleaning polyurethane from a paintbrush is an easy task. You’ll need the following tools and supplies:

  • An empty bucket
  • Water
  • Paint thinner
  • A pair of gloves
  • Dish soap
  • A soft toothbrush

Here is a quick rundown of how to clean a polyurethane brush:

  1. Squeeze excess polyurethane from the paintbrush into the paint container
  2. Fill a bucket halfway with paint thinner
  3. Soak and swirl the brush in the bucket
  4. Remove stuck paint with a soft toothbrush
  5. Rinse the brush in clean water
  6. Leave the brush to dry

Now, let’s get to work

1. Squeeze The Excess Polyurethane

Squeeze The Excess Polyurethane

The first step is to squeeze out the excess polyurethane on the brush. To do this, you’ll need to first put on a pair of gloves. Then manually squeeze the polyurethane out. You can squeeze the excess polyurethane back into the polyurethane container.

Be careful while doing this because if you squeeze too hard, you can ruin the shape of the paintbrush. This will make it difficult to apply paint with the brush.

2. Fill A Bucket Halfway With Paint Thinner

Fill A Bucket Halfway With Paint Thinner

For water-based polyurethane, the paint thinner to use is water. For oil-based polyurethane, you can use mineral spirits. You need to pour enough paint thinner into the bucket to remove the polyurethane from the paintbrush.

Seeing as it can be expensive to purchase enough mineral spirits to fill a bucket halfway, you can dilute the mineral spirits with water. This way, you won’t need that many mineral spirits to fill the bucket.

If you want to mix mineral spirits with water, ensure the mineral spirit concentration is more than the water. If not, the mineral spirits will be heavily diluted and won’t get rid of the oil-based polyurethane.

3. Soak and Swirl The Brush In The Bucket

Soak and Swirl The Brush In The Bucket

Soak the polyurethane brush in the bucket for about 10 minutes. After, swirl the brush inside the paint thinner to shake off loose polyurethane.

4. Remove Stuck Paint With a Soft Toothbrush

Remove Stuck Paint With a Soft Toothbrush

After 10 minutes of soaking the brush in the paint thinner, take it out and inspect the brush. Chances are you’ll notice stuck polyurethane residue between the bristles of the brush.

The polyurethane should be removed using a soft toothbrush. Just glide the toothbrush through the polyurethane brush to remove stuck poly.

If you notice tough or stubborn polyurethane residue, add some dish soap to water and use the soapy water to remove the polyurethane residue for water-based polyurethane.

For oil-based polyurethane, add a few drops of mineral spirit directly to the polyurethane residue and stoke it out with a toothbrush.

5. Rinse The Brush In Clean Water

Rinse The Brush In Clean Water

This is to remove leftover polyurethane from the brush. Rinsing also helps to remove leftover paint thinner. This step is very important especially after removing oil-based polyurethane with a strong paint thinner.

This is because the paint thinner that can remove oil-based polyurethane is strong enough to damage the brush if left on it for too long.

But rinsing after removing the polyurethane helps to get rid of leftover paint thinner that can damage the brush.

6. Leave The Brush To Dry

Leave The Brush To Dry

Let the brush dry. Then inspect it before storing it properly.

Should You Clean Polyurethane Brush Between Coats?

You don’t have to clean your polyurethane brush between coats. You can simply seal the paintbrush in a plastic bag and place the bag in the fridge for the next few hours or till you are ready to re-coat.

Also, the polyurethane brush should be moist while sealing it. This means that the polyurethane brush should have some polyurethane on it before being sealed off in the plastic bag. This will keep the paintbrush fresh and ready for paint application even after hours of waiting for the existing polyurethane coat to dry.

However, you may clean the polyurethane brush between coats if you suspect there will be a lot of hours before the polyurethane is re-coated. For instance, if you are to wait 48 hours before a re-coat of polyurethane, you can clean the paintbrush between coats.

I’m sure you already know that polyurethane takes a while to dry between coats. On average, you have to wait at least 2 hours before a re-coat of polyurethane. Oil-based polyurethane can take up to 12 hours before being ready for a re-coat. This is enough time for the polyurethane residue on the paintbrush to dry and solidify.

However, you don’t have to clean the brush every time you wait between coats. You can simply seal the brush in a plastic bag and place it in the fridge to keep the paintbrush fresh and ready for re-coat. This will also save you valuable time during your painting task.

Related Read: Can You Thin Polyurethane Paint?

Final Words

Overall, cleaning your polyurethane brush after painting with it helps to keep the brush in good condition.

But you don’t have to clean the brush between coats. Just seal it in a plastic bag and refrigerate it for a few hours. This will keep the brush fresh and ready to use.

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