With the significant amount of money you have invested in polyurethane and paint tools, you may wonder if you can repurpose some equipment.
The good news is – everything from polyurethane to rags, sandpaper, mineral spirits, and cotton tack cloths can only be used once, but that’s not the case with a paintbrush.
This means if you want, you can use a polyurethane brush more than once!
As long as the bristles of your used brush are in good condition, feel free to keep using them for either water-based or oil-based applications.
But as with anything, there are some pros and cons to reusing a polyurethane brush.
The main con is that because you have already used the brush, there is a higher chance that bristles will fall out during your next project.
Another con is that if you do not properly clean the brush after each use, the old polyurethane will mix with the new, which can impact the look and quality of your project.
The key to success here is cleaning the polyurethane brush right and storing it properly.
So, in this guide, I will discuss polyurethane brushes and then show you how you can clean water-based and oil-based polyurethane brushes, along with some tips and ideas for storing them right.
These tips will hopefully help you extend the life of your polyurethane brushes so you can get the most bang for your buck!
Brushes for Polyurethane Application
If you haven’t started yet and are planning to get started, it helps to know what kind of brush you should actually use to apply polyurethane in the first place.
For oil-based poly
A natural bristle brush that is made of animal hair is the best choice for applying oil-based polyurethane.
They will not only absorb the polyurethane better but are also very good at spreading the finishes on the surfaces much better than any other brushes.
The only downside of natural bristle brushes for poly finishes is that they are slightly more expensive.
For water-based poly
For water-based polyurethane finishes, synthetic nylon bristles are a good choice since they do not pick up a lot of moisture from water-based poly.
They are also cheaper and are more versatile so you can use them for other purposes such as painting too.
A word of caution here
Please, in any case, do not use foam brushes or anything like a sponge for polyurethane application, as it will make a real mess.
Also, if you decide to use the same brush to apply both water-based polyurethane over oil-based, you can do that, but the results you will get will not be as good.
While natural bristles are better for oil-based products, synthetic nylon is much more functional for water-based polyurethane.
If you don’t have a choice in the matter, though, you can always recycle the same brush as long as you gave it a thorough cleaning after your most recent project.
Now that you know about what type of brushes are best to use for poly application on wood surfaces let’s come to washing the brushes.
Steps for Cleaning Oil-Based Polyurethane Brush
Oil-based polyurethane is often applied with brushes that have a high level of dirt. But that doesn’t mean you can’t clean or reuse them.
Cleaning the polyurethane brush with mineral spirits may take only a few minutes if you clean it when it is still moist.
When the polyurethane is dried on the bristles, you will need a bit more elbow grease, and there’s no guarantee you will be able to clean them 100%.
Things you will require:
- 3-4 cups
- Dish soap
- Running water
- Nylon scrub brush
- Pair of latex gloves
- Mineral spirits or paint thinner
Here is how you can clean an oil-based polyurethane brush:
Step 1- Pour Mineral Spirits and Dip the Brush
First, add enough mineral spirits into three or four cups. If you don’t have mineral spirits, you can use paint thinner or even turpentine.
Pour enough quantity into each cup so that you can easily submerge the dirty brush up until the ferrule.
Start by submerging the poly brush into the first cup to get all the bristles covered with solvent.
Stir the brush in the cup from side to side, bending over from one side to the other so that the mineral spirit can flow between the bristles.
Step 2- Dip the Brush into Other Cups
Move on to other cups when the mineral spirits darken to brown. Be patient and repeat the brush dipping process with all three cups.
Continue until the color does not alter when the brush is swished in the cleaning solution.
You may need to go through this process four or five times before it’s ready for the next phase, so if necessary, add more mineral spirit cups.
Step 3- Wash and Scrub the Brush under Running Water
Even if the mineral spirits manage to take all the polyurethane off of the brush, you will still need to give it a thorough wash.
First, wet the brush bristles under running water. Apply some dish soap and scrub the bristles gently with your fingers.
Be sure to run your fingers in between the bristles, then press the bristles against your palm to clean them as best you can.
Bear in mind that the first time you try to lather your brush with dish soap, it probably won’t work too well.
This is because there are still traces of mineral spirits in the brush, and you need to get rid of them all.
So, keep rinsing and repeating until you finally see a clear, generous lather from the brush with just the right amount of soap.
Step 4- Scrub Lightly with a Nylon Brush
Next, place the partially cleaned poly brush at the bottom of your sink, rinse it with water to clean off any soap residue, and then use a nylon brush to scrub it gently.
The nylon brush will help clean between the bristles more effectively than your hand and fingers can with less pressure.
This is especially useful if the brush is heavily coated with oil-based polyurethane.
If you find that the bristles are still filthy after repeating this process once or twice, simply repeat the procedure until the brush is completely oil-free.
Step 5- Drying the Brushes Naturally
After all the cleaning, it’s time to dry the brushes. You can either let them air dry on their own or use a hair dryer set on low heat.
Don’t try to speed up the drying process by using a higher heat setting, as this can damage the bristles.
It’s best to let them dry overnight by hanging them in your workshop so that they are completely ready for their next use.
Steps for Cleaning Water-Based Polyurethane Brushes
Synthetic brushes are considerably easier to clean when you have used water-based polyurethane.
The process is pretty much the same as for oil-based polyurethane, only that you will use water instead of mineral spirits.
Things you will need:
- 3-4 cups
- Dish soap
- Running water
- Nylon scrub brush
- Pair of latex gloves
- Fresh, clean water
Here’s how you should clean water-based polyurethane off the brush…
Step 1- Pour Water and Dip the Brush
Start by pouring some water into three to four cups.
Dip the brush in the first cup filled with water, making sure that all bristles are fully submerged.
Let the brush sit in the water for a few minutes.
Step 2- Move to Other Cups and Repeat
After a few minutes have passed, you will see the water dirty and changing its color, take the brush out of the first cup of water and dip it into the second cup.
Let it sit for a few minutes before moving to the third cup.
You can repeat the process until the water in all three cups is dirty.
Step 3- Time to Scrub with Dish Soap
After you have moved the brush through all three cups of water, it is time to start scrubbing the brush with a nylon scrub brush and some dish soap.
Wet the nylon scrub brush in water and add a few drops of dish soap.
Start scrubbing the brush until all polyurethane is gone and only bristles are left.
Step 4- Rinse the Brush Under Running Water
Once you have scrubbed the brush clean, it is time to rinse it with water.
Turn on the faucet and hold the brush under running water.
Let all the soap suds rinse off the brush.
If necessary, you can repeat Step 3 to get your brush squeaky clean.
Step 5- Let the Brush Dry
After you have rinsed the brush, shake off any excess water and let the brush dry.
You can lay the brush on a towel or speed up the drying process by hanging it outside in the shade.
Do not expose the brush to direct sunlight or heat, as this can damage the nylon bristles of your synthetic brush.
And that’s it! Your brush is now clean and ready to reuse.
Storing Polyurethane Brushes After Cleaning – for Reuse
If you decide you keep your cleaned-up polyurethane brush for future projects, make sure that you store it properly.
The best way to store a brush is by hanging it upside down by the bristles.
You can use a hanger or simply nail a small piece of wood to the wall in your workshop and hang the brush on that.
Just make sure that the bristles are not touching anything, as this can damage them.
Another way to store a brush is by wrapping it in a clean cloth and then placing it in an airtight container – use an old coffee can or mason jar for this.
Again ensure that the bristles are not touching the sides or the bottom of the container, as this will tend to damage them.
If you want, you can also keep the cleaned and dried brushes in cupboard packages.
Do not store them with other things like paint cans or other tools, as this can damage the bristles if they get rubbed.
Why Cleaning a Polyurethane Brush is Important – What if You Do Not Clean Them?
Just in case you decide not to clean your polyurethane brushes after use, or maybe you forgot to get them cleaned after the usage, the dried polyurethane will eventually become hard and crusty, making the brush unusable.
Once the polyurethane has dried and hardened on the brush, it will be very difficult to remove it.
Timely cleaning of your poly brushes is therefore crucial if you plan to reuse them for future projects.
Besides that, there are a few other benefits of cleaning polyurethane brushes regularly; they are as follows:
It’s good for your health
Did you know that polyurethane contains VOCs? Well, now you do, and long-term exposure to VOCs can be poisonous.
So it’s important to take the necessary precautions in order to avoid any risks. These include keeping your tools clean and making sure all chemicals are covered when not in use.
Shows your professionalism and preparedness
As the go-to person for all things DIY, it’s expected that you always have the tools necessary for the job – even if that job is as small as loaning out a brush.
Never underestimate the importance of first impressions; rather than having to say – give me a second for clean up – keep your work area presentable at all times.
Helps in maintaining the work quality and being professional
Not regularly washing your brush will result in the bristles hardening and calcifying from the polyurethane.
This then makes it more difficult to clean without potentially damaging the bristles, which leads to an uneven application that requires more work for a smooth finish.
You might be thinking that because it’s water-based and thin, there won’t be any long-term effects or need to wash the brush–you would be wrong.
Even if you use clean water, not washing the brush will still lead to negative consequences for future projects.
Cleaning keeps the bristles in good condition and keeps the brush handy all the time
If you plan to make a career out of woodworking, or even if you’re not, you should pay attention to being prepared at all times.
Some jobs might give advanced notice while others might surprise you, so it’s always best to be ready just in case.
For example, having your brush ready can prevent any last-minute surprises or trying to clean a hardened brush from your last job.
The Bottom Line
Cleaning a polyurethane brush is definitely not a pleasant task, but with the right tools and techniques, it can be easily done.
Plus, the benefits of doing so – like extending the life of your brush and preventing any health risks – definitely outweigh the negatives.
So, what are you waiting for? Get cleaning done and prepare your poly brushes for your next use!
Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for more than a decade to serve the customers in areas such as Charleston, Mount Pleasant, Beaufort, Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques that are being implemented in his profession. You may read more about him here or get in touch with him here.
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