In this part, Flowyline shares the best way to apply polyurethane that woodworkers are using to get glass-smooth polyurethane finishes every single time. Our guide works for oil-based or water-based, tabletops, or even hardwood floors.
You'll learn:
- Which brush to use (and why most people pick the wrong one)
- The "thin coat" rule that prevents 90% of polyurethane problems
- Exactly how long to wait between coats (it's not what the can says)
- The sanding technique that creates that professional, smooth-as-glass finish
- 5 Common mistakes that ruin your work (and how to avoid them)
Ready to finally get the best way to apply polyurethane to wood. Let's get started!
Understanding 2 Types of Polyurethane: Oil-Based vs Water-Based
Let's discuss the two main types of polyurethane and when each one makes sense first. The table below is just for an overview. Thus, you can scroll down for detailed information on the best way to apply polyurethane to wood.
| Feature | Oil-Based | Water-Based |
| Dry time between coats | 12 to 24 hours | 2 to 4 hours |
| Durability | Excellent | Very good |
| Color change | Amber tone | Clear |
| Odor | Strong | Mild |
| Cleanup | Mineral spirits | Soap and water |
| Best for | Dark woods, tables, and floors | Light woods, painted pieces |
1. Oil Based Polyurethane
Oil-based polyurethane is the old-school option for finishing wood. It's thicker than water-based, has that unmistakable strong smell, and gives your wood a warm amber glow. You can see this tint more on lighter woods like maple or white oak.
- Gives wood a warm, amber tone (especially noticeable on lighter woods like maple)
- Takes longer to dry between coats (typically 24 hours)
- The most durable finish you can get
- Needs paint thinner for cleanup
- Clean your brushes with mineral spirits or paint thinner
- Fumes are pretty strong, so crack open some windows
Best for: Dark woods, kitchen tables, desktops, wood floors, high-traffic furniture
Before and after applying oil vs water-based polyurethane on wood
Photo: YouTube | NewmanSpecialsWoodwork
2. Water-Based Polyurethane (Polycrylic)
Conversely, water-based polyurethane is the faster, cleaner option. Unlike oil-based poly, it dries completely clear and won't change your wood's natural color.
That's why so many woodworkers reach for it when they're working with lighter woods.
- Stays clear, barely any yellowing happens over time
- Dries much faster in just 2 to 4 hours (you can do multiple coats in one day)
- Easy cleanup with just soap and water
- A bit trickier to apply smoothly
- A bit less durable than oil-based (but still pretty tough)
- Doesn't soak into the wood as deeply
Best for: Light-colored woods (maple, birch, pine) when you want to keep them looking natural, painted furniture, projects where you want fast completion, and indoor use if you worry about strong fumes.
Shopping List You'll Need to Apply Polyurethane on Wood
From our perspective, oil-based and water-based polyurethane really need different brushes. After this shopping list, Flowyline will also have a talk about the importance of brush quality in the next section.
| Supply Item | Oil-Based Polyurethane | Water-Based Polyurethane |
| Brush Type | Natural bristle brush (quality matters) | Synthetic bristle or nylon brush |
| Alternative Applicator | Clean, lint-free cloth (for wiping) | Foam brush |
| Cleaning/Thinning Agent | Mineral spirits or paint thinner | Distilled water (if on well water) |
| Mixing Container | Airtight lid required | Standard container |
| Sandpaper Grit | 220 grit | 220 — 320 grit |
| Between-Coat Smoothing | Brown paper bag | Brown paper bag |
| Safety Gear | Respirator or mask, rubber gloves | Rubber gloves |
| Prep Tool | Tack cloth | Tack cloth |
Why is Brush Quality Important for Applying Polyurethane?
A decent finishing brush will run you anywhere from $40 to $60. Sounds like a lot, but it's absolutely worth it. What we mean is a quality brush holds more finish, spreads it evenly, and won't leave random bristles stuck in your work.
1. Foam Brushes ($1 — 2, or $3 — 5 for Better Ones)
Most people will tell you to avoid foam brushes for polyurethane, and they're mostly right — especially when it comes to the really basic ones. The budget foam brushes create air bubbles if you press too hard, spread unevenly, and barely hold any finish.
That said, if you're set on using foam, at least grab a higher-quality one in the $3 — 5 range instead of the dollar store version.
Some people actually have good luck with decent foam brushes on small projects or when they're using water-based polyurethane specifically.
A foam brush is the best way to apply polyurethane water based
Photo: YouTube | SterlingsWoodcrafts
2. Chip Brushes ($2 — 3)
Chip brushes are stiff, thin, and just don't hold enough finish to work smoothly. At the end, your wood surface deals with drips, runs, and puddles all over your project. Besides, the problem is that these brushes do shed the first few times, which is quite annoying.
We do agree that they're fine for spreading glue or other rough work, but when it comes to applying polyurethane? Pass them on. Unless you don't care how the final result turns out, chip brushes will just frustrate you.
Chip brushes shed the first few times
Photo: Youtube | The Honest Carpenter
3. Medium-Range Brushes ($18 — 25)
Noticeably, these brushes are thicker than chip brushes, with softer bristles that hold more polyurethane and spread it evenly without pooling or running. And yes, you might lose a bristle or two in your finish here and there, but it's not a big deal.
The difference is obvious when you pick one up. The bristle bundle has real thickness to it, and they feel way softer than those basic brushes. It's one of those things where you can just tell you're holding something of better quality.
4. Professional Finishing Brushes ($40 — 60)
A professional brush, like one made with ox hair, feels almost like the fur on a nice coat. It's incredibly soft and thick, way more substantial than those medium-range brushes. And more than that:
- They hold a lot of finish without any dripping
- The polyurethane comes off slowly and spreads perfectly even
- Don't leave brush marks behind
- Won't shed bristles into your work
- They last for years if you clean them right
- The finish looks smooth and professional every time
Natural vs Synthetic Brush: Which One is Best for Polyurethane?
The general rule for the best way to apply polyurethane to wood:
Oil-based polyurethane = Natural fiber brush (ox hair, China bristle, hog hair)
Water-based polyurethane = Synthetic brush (nylon, polyester)
What does all of this mean?
- Natural bristles soak up water like a sponge. So, when you try using them with water-based products, they get limp and completely useless. They fan out, lose their shape, and basically make it impossible to apply anything smoothly.
- Another reason you don't want to use natural bristles with water-based polyurethane is that the water causes natural bristles to swell, which causes large brush marks.
- Synthetic bristles have the opposite problem with oil-based finishes. They just don't hold the material as well, and you'll end up with more visible brush marks in your work. Therefore, a synthetic bristle is the best way to apply water based polyurethane.
Natural brushes are the best way to apply oil based polyurethane, and synthetic bristles for water-based
Photo: Redtree and The Honest Carpenter
| Feature | Natural Fiber Brush | Synthetic Brush |
| Material | Ox hair, China bristle, hog hair | Nylon, polyester |
| Use with | Oil-based polyurethane, oil-based stains, and shellac | Water-based polyurethane, water-based finishes, and latex paint |
| Texture | Soft, feels like fur | Firm but flexible |
| Water reaction | Absorbs water, becomes limp and useless | Maintains shape in water |
| Durability | Very durable with proper care | Water-resistant, very durable, and easier to clean |
| Price range | $18 — 60+ depending on quality | $15 — 50+ depending on quality |
| Cleaning | Mineral spirits, paint thinner, or turpentine | Water and soap |
| Best for beginners | Yes, if using oil-based products | Yes, if using water-based products |
| Professional choice | Ox hair brushes ($40 — 60) for oil-based | High-quality nylon ($30 — 50) for water-based |
Our recommendation for most DIYers:
- Except if you're perfect at your brushing technique, just skip the foam brushes and chip brushes for polyurethane work.
- If you're doing the occasional project, a medium-range brush is probably your best choice.
- For high-end furniture or planning to do a lot of finishing work, you'd better buy a professional brush. I know it's quite expensive, but you buy it once and use it for years.
Best Way to Apply Polyurethane: 6 Easy Steps for Flawless Finishes
Alright, let's get into how to actually apply oil based and water based polyurethane. This technique works whether you're finishing a table, a cabinet, or any wood project.
If you can work somewhere between 65 and 75°F, that's ideal, but not critical. And, please make sure the wood is dry, and the workspace isn't too dusty before you begin with step 1.
Step 1: Prepare Your Wood Surface with 220 Grit
You can't slap polyurethane on poorly prepped wood and expect it to look good. It doesn't work that way. This is the right way that we're using:
- Sand your wood with 220 grit and don't go any finer than that.
- Once you're done sanding, grab your vacuum and get all the dust off.
- Then, we follow up with a tack cloth to catch anything the vacuum missed.
- Run your hand over the wood surface to check if it feels smooth with no rough patches.
- Slope the wood for finishing, which makes it easy for you to see imperfections after sanding.
After sanding, we slope the wood to see the imperfections clearly
Photo: Youtube | ENCurtis
Note: If you stained the wood first, you should wait at least 24 — 48 hours to dry entirely before applying polyurethane.
Step 2: Mix and Thin Your Polyurethane
In fact, polyurethane straight out of the can is way too thick. It's almost like syrup, which makes it really hard to spread smoothly. So, it's best to follow our process below:
- Don't shake the can. Simply stir it slowly and gently with a stir stick instead.
- For a fantastic result, you should thin the polyurethane down as it allows the finish to run smoother and penetrate into the wood better.
- Mix 3 parts polyurethane with 1 part thinner (25% dilution). You should also check manufacturer recommendations, as some formulas are designed not to be thinned.
- Do this mixing in a separate container with an airtight lid.
- If you're using oil-based, grab some mineral spirits or paint thinner.
- For water-based polyurethane, regular water works fine, though if you're on well water, distilled is better.
We're building up protection with several thin coats, not trying to get it all done in one thick layer.
There's an old saying that really nails it: "Lay it down thin, lay it down thin." Thin coats dry better, look better, and give you stronger protection than thick polyurethane coats ever could.
Step 3: Prep your Brush the Right Way
We soak the bristles in the appropriate solvent for a few minutes.
- If you're using natural bristles, that means mineral spirits.
- For synthetic bristles, just use water.
That way, it softens up the bristles so they spread the finish more smoothly. Once they've soaked, dab off the excess on a paper towel. You don't need to get it bone dry.
Actually, leaving a little bit of solvent in the brush is the best way to apply polyurethane.
Step 3 of the best way to apply oil based polyurethane with natural bristles
Photo: Popular Woodworking
Step 4: Apply the First Polyurethane Coat
Alright, here's how to apply polyurethane to get that smooth, professional finish you're after:
Loading your brush:
- Dip your brush about 1/4 to 1/3 of the way into the polyurethane.
- Lift it out and let the excess drip back into the container for 1 to 2 seconds. Don't wipe it on the edge of the can because it will create bubbles.
- If it's dripping too much, gently dab it on a paper towel instead.
The best way to apply polyurethane with the first coat:
- Start somewhere in the middle of your surface, NOT at an edge.
- Lay the brush down flat against the wood and pull it across in ONE smooth motion, following the grain.
- Use long strokes and don't press down. We just let the weight of the brush do all the work.
- Overlap each stroke by about half an inch as you go. Work at a steady pace, but don't rush yourself.
How to apply polyurethane step by step
Photo: Popular Woodworking
Pro tips: Once you've pulled the brush across an area, leave it alone. It's not recommended to go back over it, or you will create drag marks and mess up the finish.
In case you're doing something like a tabletop, work in sections. Finish one board or area at a time, and keep a wet edge going so you don't end up with lap marks where the sections meet.
Step 5: The "Tipping Off" Technique (also Called Feathering)
Now, you've covered the whole surface, there's one more thing pros do:
- Grab your brush and wipe off most of the excess polyurethane on a paper towel so it's pretty dry.
- Then, starting at one end, lightly drag it across the entire surface with barely any pressure.
This is what we called "feathering", and it evens out any spots where the polyurethane pooled up or went on too thick. With this, you're going to have a nice, uniform coat across the whole piece.
Step 6: Handling Edges
In terms of edges and detailed areas, we'll have a slightly different approach.
- Use the same basic technique, just with a lighter touch.
- A drier brush works better on edges since it won't drip as much.
- If you're dealing with spindles, curved surfaces, or anything with a lot of detail, you should switch to wiping it on instead.
- Just thin the poly down even more and apply it with a cloth.
Step 7: Don't Worry about Bubbles
You might see some tiny bubbles in your finish, especially the first few times you do this. That's totally fine, you can leave them alone. Those small bubbles will pop on their own as everything dries.
Secondly, if you're seeing lots of big bubbles, something's off. You're probably shaking the can instead of stirring it, putting the finish on too thick, using a foam brush when you should be using bristles, or brushing back and forth too hard.
Thirdly, no matter how careful you are, you'll get dust, hair, bristles, or even the occasional bug landing in your wet finish. When you spot something, use the edge of your brush to lift it off right away. If the poly's already starting to set up, you've missed your window.
After we get it out, brush lightly over that spot from end to end to smooth out any marks left behind.
How Many Coats of Polyurethane Do You Need?
It really depends on what kind of wear and tear your piece is going to get.
Here's a general guide:
- At minimum, do 3 thin coats on anything
- For furniture that gets regular use (like bookshelves, dressers, bed frames): 3 to 4 thin coats
- For surfaces that see a lot of action (kitchen tables, desks, countertops): 4 to 6 thin coats
- Floors: 4 to 6 thin coats
You might wonder, "Why don't we save time by applying 2 thick coats instead of 3 or 4 thin ones?" Honestly, it doesn't work. Those 2 thick coats can take forever to dry and may never fully cure. Worse, they're more likely to sag, run, or puddle.
Should read: Best Polyurethane for Kitchen Table: 6 Tested & Ranked Options
How Long Between Coats of Polyurethane?
In reality, timing matters a lot when it comes to the best way to apply polyurethane.
Put on the next coat too soon, and you'll end up with a gummy mess. This is probably the most common question people ask, so let us break it down for you:
1. Oil-Based Polyurethane Drying Times
- Touch dry: 12+ hours
- Minimum wait between coats: 12 — 24 hours
- If it's humid, cold, or temperatures below 65°F: Wait 48+ hours
- Dry time for light use: 7 — 10 days
- Completely cured: 30 days
How long to wait between coats of polyurethane
Photo: General Finish | Text: Flowyline
This General Finishes oil-based polyurethane needs a full day between coats. We know it feels dry after 8 hours, but it's not ready yet. The solvents are still working their way out, and the finish hasn't fully hardened underneath.
Fast Drying formula of MinWax for faster waiting time between coats
Photo: MinWax | Text: Flowyline
Alternatively, with the Fast Drying formula of MinWax, you can recoat in just 3 to 4 hours. However, fast-drying poly is less forgiving than the regular polyurethane.
With traditional oil-based poly, you can take your time, go back over areas, fix little mistakes, and generally work at a relaxed pace. The slow drying gives the finish time to flow out and self-level, hiding minor brush marks.
2. Water-Based Polyurethane Drying Times
- Touch dry: 30+ minutes
- Time between coats: 2+ hours in ideal conditions
- You can apply multiple coats in a single day
- Dry time for light use: 7 — 10 days
- Full cure: 21 days
General Finishes, water-based polyurethane
Photo: General Finish | Text: Flowyline
In this example of General Finishes, water-based dries way faster, which is kind of a double-edged sword. On one hand, you can wrap up a whole project in 1 or 2 days instead of waiting around for a week.
On the other hand, you've got less time to catch and fix mistakes before they start getting tacky.
*All products were purchased at retail price with no manufacturer sponsorship. Always check the manufacturer's instructions.
Read more at: Best Polyurethane for Table Top: 6 Top-Rated Oil & Water-Based Finishes
Sanding Between Coats of Polyurethane: Is It a MUST?
Yes, sanding between coats really is essential if you want a perfect, smooth, and professional finish. Sanding does three things for you:
- First, it removes those dust nibs and any other imperfections from the coat you just put down.
- Second, it creates a slightly rough texture that gives the next coat something to grip onto.
- And third, sanding knocks down any high spots or drips, so everything ends up more uniform.
1. How to Sand Between Polyurethane Coats
Wait until the poly is completely dry, based on those drying times we mentioned earlier. Then use really light pressure and let the sandpaper do the work. Sand with the grain, not against it.
It's advised to stick with 220 to 320 grit sandpaper. That's fine to very fine. For most jobs, 220 grit works great. If you want an ultra-smooth finish between your final coats, go with 320. Only do the high grits to finish.
Sanding between coats of polyurethane
Photo: Freepik
2. What Happens If You Don't Sand Between Coats of Polyurethane?
People ask us this all the time: "What if I just don't sand between coats?"
If you skip it, those dust nibs stay trapped in your finish. The surface feels bumpy and rough. Each new coat you add just makes it worse. Your final result ends up looking and feeling pretty amateur.
Plus, the coats might not stick to each other as well, which can lead to peeling or chipping down the road.
3. Don't Sand the Final Coat with Regular Sandpaper
That means if you use regular sandpaper on the final coat, you'll change the sheen from satin to dull and cloudy. It can even create this milky white look that ruins everything you just worked on.
If your final coat has a couple of tiny dust nibs, you can very gently use that brown paper bag trick to knock them down.
4. The Brown Paper Bag Method for Final Coat
As mentioned earlier, the brown paper bag is specifically for the FINAL coat only, not between coats. A paper bag is rough enough to knock off dust nibs but gentle enough that it won't mess up stained wood or pull up any color.
We crumple up the bag and then flatten it back out. Put it on a wooden block so you get even pressure, then rub it over the dried poly. It takes care of imperfections without being harsh.
Top 5 Mistakes to Avoid When Applying Polyurethane
There are 5 five not-so-good things that stand in opposition to the best way to apply polyurethane. Let's see what they are so we can stay away from them as soon as possible:
- Shaking the can: This is the biggest mistake that prevents you from practicing the best way to apply polyurethane. When you shake the can, you create thousands of tiny bubbles that end up trapped in your finish. All you need to do is simply stir it slowly and gently instead.
- Applying thick coats: Thick coats might look good at first, but they cause nothing but headaches. They take forever to dry, stay soft way too long, and develop all kinds of flaws. Keep your coats thin every time.
- Not thinning the polyurethane: Poly straight out of the can is just too thick to work with properly. Thin it down to 3 parts poly and 1 part solvent. You'll get way better results for that first coat. Don't forget to check manufacturer recommendations, as some formulas are designed not to be thinned.
- Going back over wet areas: Once you've brushed through a section, leave it alone. If you go back over it while it's starting to dry, you'll create drag marks and more bubbles. Resist the urge.
- Not waiting long enough between coats: Rush this, and you'll own a gummy, tacky mess that might never fully cure. Stick to those drying times, no matter how impatient you get.
FAQs
1. Is It Better to Apply Polyurethane with a Brush or Rag?
Both have their advantages:
- A rag works best for contoured surfaces or when you want a really smooth, thin finish using wipe-on poly.
- A brush (either natural or foam) is better for flat surfaces or when you need to build up thicker coats. Brushes give you more control and let you apply more material, but you need to be careful to avoid runs and drips.
2. Can I Apply Polyurethane With a Roller?
Yes, you can definitely use a roller for polyurethane. It works really well on large, flat surfaces like tabletops or floors. A foam or lambswool roller gives you a faster, smoother finish without those brush marks.
However, with edges and detailed areas, you should use a brush.
3. What is the Best Way to Apply Polyurethane?
The best way to apply polyurethane depends on what wood project working on and which type of poly you're using.
- For oil-based poly, use a high-quality natural bristle brush.
- For water-based, we recommend synthetic bristles.
- If you've thinned your poly down for wiping, a foam applicator or even a clean rag works great.
- When you're dealing with large, flat surfaces, foam rollers (oil-based only) or an HVLP sprayer can give you a smooth, bubble-free finish much faster.
- The best way to apply polyurethane on floors is to use a microfiber roller/lambswool.
4. How Do You Get a Smooth Finish with Polyurethane?
Here is an overview of how to get a smooth finish with Polyurethane:
- Step 1: Prepare the wood surface properly with sandpaper and vacuum all dust after that
- Step 2: Apply thin polyurethane coats, not thick ones
- Step 3: Sand lightly between coats with 220-320 grit sandpaper
- Step 4: Use proper brushing technique for oil-based or water-based polyurethane
- Step 5: Control dust and temperature
Best Way to Apply Polyurethane: Final Thoughts
Well, you now have everything you need to apply polyurethane like a pro:
- The right tools: Natural bristle brush for oil-based polyurethane, synthetic for water-based
- The correct technique: Thin coats, proper brushing, tipping off
- The right timing: 24 hours for oil-based, 2 to 4 hours for water-based
- The right process: Sand between coats, control your environment, be patient
Yeah, it takes time. And yeah, it requires patience. But when you run your hand across that final coat and feel nothing but smooth, glass-like perfection, when your friends ask if you had it professionally done, you'll know it was worth it.
Your next project deserves a finish this good. Now you know how to make it happen.
Also, we post new blogs every week at Flowyline covering everything from finishing techniques to DIY furniture projects.
And, if you need metal table legs for your next project, or just have questions about the best way to apply polyurethane, reach out anytime. Thank you for reading!