With the significant amount of money, you have invested in polyurethane and application tools, you may wonder if you can repurpose some of them.
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.
If needed, you can use your polyurethane brush more than once. But as with anything, there are some pros and cons to reusing them and you will need to know the proper steps for doing that.
In this guide, I will discuss all the details of polyurethane brushes along with some tips and ideas for reusing them in the right way. These will hopefully help you extend the life of your poly 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.
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 poly better but are also very good at spreading the finish on the surface 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 polyurethane finishes, Wooster angle paintbrushes with synthetic nylon bristles are a good choice since they do not pick up a lot of moisture from water-based poly and can be used in hard-to-reach areas as well.
They are also cheaper and are more versatile so you can use them for other purposes such as painting or staining other surfaces in your home when required.
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, the results you 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.
Can You Reuse Polyurethane Brushes?
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. The key to success is cleaning and storing them right for every use.
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. Also, if you have already used the brush and haven’t cleaned/stored it correctly, there is a higher chance that the bristles will fall out during the next project because of the hard and crusty dried polyurethane.
Once the polyurethane has dried and hardened on the brush, it will be very difficult to remove it, eventually making the brush unusable.
Steps for Cleaning Oil-Based Polyurethane Brush
Cleaning and reusing the brush with oil-based polyurethane is usually made feasible when you use mineral spirits.
But remember, 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%. However, it takes only a few minutes if you clean the brush when it’s still moist.
Things you will require for the brush clean-up:
- 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 (paint thinner or even turpentine) into three to four cups placed on the floor. 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 the brush to other cups when the mineral spirits in the first cup 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
When the mineral spirits manage to take all the polyurethane off the brush, you will need to give the bristles a thorough wash under running water.
Apply some dish soap and scrub the bristles gently with your fingers. 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 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 – 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 it sit there for a few minutes.
Step 2- Move to Other Cups and Repeat
After a few minutes have passed, you will see the water getting dirty and changing its color, take the brush out of the first cup and dip it into the second cup.
Let it sit for a few minutes before moving to the third cup. Repeat the process until the water in all three-four cups is dirty.
Step 3- Time to Scrub with Dish Soap
After you have moved the brush through all the cups, scrub it with a nylon scrub brush and some dish soap.
Keep on scrubbing the brush until all polyurethane is gone away and only clean bristles are left behind.
Step 4- Rinse the Brush Under Running Water
To rinse your brush turn on the faucet and hold the brush under running water. Let all the soap suds rinse off the brush. If necessary, 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 by laying it on a towel. Or you can 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.
Storing Polyurethane Brushes After Cleaning – for Reuse
The best way to store your cleaned brush (for future use) is by hanging it upside down by the bristles. Use a hanger or simply nail a small piece of wood to the wall in your workshop and hang the brush on that. Make sure that the bristles are not touching anything, as this can damage them.
Another way to store a paintbrush 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.
The Bottom Line
Picking the right polyurethane brush and cleaning it is definitely not an easy task, but the benefits of doing so definitely outweigh any negatives if there are any.
Particularly if you are a pro woodworker or a painter, 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.
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 over a decade serving customers in areas such as Charleston, Mount Pleasant, Beaufort, and Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques implemented in his profession. You may read more about him here or get in touch with him here.