Spray polyurethane with a paint sprayer rather than applying with a paintbrush for a quick, easy, professional looking finish on DIY furniture projects.
Why spray polyurethane? Because poly is a tricky finish to apply with a paintbrush, but spraying polyurethane with a paint sprayer is quick, easy and gives DIY furniture a factory looking finish.
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What is Polyurethane Used For?
Before we go any further, we should answer the question what is polyurethane used for? Polyurethane provides a clear, durable layer of protection for DIY furniture. It can also be used for floors, doors, woodwork around windows and doors, and cabinets.
Related: Polycrylic vs Polyurethane (Are They The Same?)
I’ve never been a fan of polyurethane. If you have been following for a bit you may have read 3 Reasons Why I Don’t Use Polyurethane. In that article, I warned of the pitfalls of applying poly with a brush. I felt polyurethane was a finicky finish, that the application was difficult and that it didn’t give me the look I wanted for my DIY furniture projects.
Instead of polyurethane I used a DIY finish made with equal parts of gloss spar varnish, boiled linseed oil and paint thinner. It’s easy to make and an easy to apply finish that gives furniture a “hand rubbed” look. I’ve used this finish on many of my furniture projects like the bar cart, vintage industrial shadowbox, chalkboard shelf, electric fireplace mantel, wine cabinet and even my craft beer growler carrier.
Related: Bob’s Miracle DIY Finish for Wood
Pitfalls of Applying Polyurethane with a Brush
In the 3 reasons I don’t use polyurethane article I wrote poly was way too fussy for me. And it can be. All you have to do is read the instructions on the back of the container and you’ll see what I mean. First, polyurethane must be applied in a dust-free environment. For most DIYers that rules out applying poly in our workshops or applying poly outdoors.
Continue reading the instructions and you’ll see air bubbles are also an issue with polyurethane. Don’t shake the can or wipe your brush on the rim of the can because you’ll introduce bubbles into the poly and those bubbles will be transferred to the surface of your furniture project. The bubbles will dry in your finish and leave the surface bumpy. The only way to remove the bubbles is to sand them out.
Application is Difficult
Applying polyurethane with a brush is difficult. When brushing poly you must do so with long, even strokes. You must also keep a wet edge. If you touch an area with your brush where the poly is dry or drying, you’ll pull the finish which could leave bumps when it finally dries. These bumps will need to be sanded to make the finish smooth.
Related: Best Way to Clean Paint Brushes
Doesn’t Give the Look I Want
Poly provides a clear, durable finish, but when applied with a brush it can sometimes look like plastic. Polyurethane does not soak into the wood. If you look closely, you can see it just sits on top of the surface.
Is there a Better Way to Apply Poly?
Can you use a roller to apply polyurethane? You could. Can you use a rag to apply polyurethane? Yes, you can apply a wipe-on poly with a rag. Can you use a foam brush to apply polyurethane? Again, you could but I’ve discovered the BEST way to apply polyurethane!
My Polyurethane Change of Heart
Earlier this year I was getting ready to paint the outdoor coffee table and estimated it was going to take me SEVEN HOURS to paint the pieces with a brush! That’s when I decided to buy a HomeRight Super Finish Max paint sprayer. Thanks to the sprayer I was able to spray a coat of primer and spray two coats of paint in only a few hours. WHAT A TIME-SAVER!
Related: 9 Paint Sprayer Mistakes You Don’t Want to Make
Since buying a paint sprayer I’ve been sprayin’ like crazy! I started with the outdoor coffee table. Then I sprayed the cedar clapboard siding of my house, updated the look of my air conditioner dresser with a coat of paint, and freshened up a pair of Adirondack chairs. I’ve also primed and painted a new project I’m working on.
While reading the HomeRight Super Finish Max paint sprayer instructions I noticed it could be used to spray polyurethane. Really? I never thought of spraying poly. Could this be the way to solve the poly pitfalls I mentioned earlier? I had to test it out and my DIY wine bar was going to be the test project.
The results are in and I’m totally convinced… I’m NEVER applying poly with a brush EVER again! The finish on the wall-mounted wine bar is amazing. The poly was quick to apply and the piece looks like it came from a factory. If you can spray paint, you can totally spray polyurethane.
Before we turn on our paint sprayer or pick up any tool for that matter we need to think about safety. Read, follow, and understand the safety instructions for your tools. If you don’t understand, contact the manufacturer or ask a pro.
Just like we use protection when we’re cutting wood for our DIY furniture projects, we must protect our eyes and lungs when using a paint sprayer.
How to Choose Polyurethane
Oil-based products are combustible. They are mixed (or thinned) and are cleaned up with paint thinner.
Water-based products are mixed (or thinned) and are cleaned up with water. Both products provide a clear, durable finish but in my opinion oil-based poly has an advantage over water-based poly.
Oil-based polyurethane gives DIY furniture an additional depth of color that you just don’t get with water-based poly. If you used an oil-based stain on your project I would use an oil-based poly. If you used a water-based stain on your project I would use a water-based poly.
❕ IMPORTANT: HomeRight says “For use with only water-based or mineral spirit-type materials with a minimum flash point of 100ºF (38ºC) — Do not spray or clean with liquids having a flash point of less than 100ºF 38ºC). Flash point is the temperature at which a fluid can produce enough vapor to ignite. Always check the information on your material label/can before spraying.
I asked my friend Makayla at HomeRight what products meet those requirements, and she said: “A few brands of polyurethane that are good go-to’s are Minwax, General Finishes, and Varathane.”
Here are few options you can buy online and have sent to your home.
Steps to Spray Polyurethane
- Prep your project
- Setup a dust-free environment
- Setup the sprayer
- Thin or mix the polyurethane
- Spray the polyurethane
- Sand between coats
- Apply 2-3 coats (repeat steps 4-6)
Step 1. Prep Your Project
A quality finish begins by properly prepping the surface of your furniture project. All of the stain and polyurethane in the world won’t cover the mistakes of a poorly prepped project. Start by sanding all of the surfaces perfectly smooth. Check out the how to sand your project for flawless finish tutorial for easy tips and helpful tricks for properly prepping your project.
Fill any Holes or Cracks
Then fill any holes or cracks with wood filler. I prefer to make my own two ingredient DIY wood filler so I know it will compliment my furniture project.
Related: How to Make a DIY Wood Filler
After my project has been sanded, holes/cracks filled with a DIY wood filler and a coat of black tea has been applied I’ll then apply a quality wood stain. I LOVE Rust-Oleum Ultimate Wood Stains. Rust-Oleum stains dry quickly and produce a deep, rich color.
Related: How to Stain Wood with Coffee
💡 TIP: The instructions for the Rust-Oleum stain says you can apply a top coat after one hour, but I always wait 24 hours before applying my top coat.
Step 2. Setup a Dust-Free Environment
Polyurethane is like a dust magnet while it’s drying. And any of those specks of dust that fall into the poly while it was drying will need to be sanded out otherwise your finish won’t be smooth. Recently I discovered a great way to set up a dust-free environment. It’s the HomeRight spray shelter. I received this spray shelter in exchange for my honest review. All thoughts and opinions my own.
The spray shelter protects surrounding objects from overspray and prevents dust and debris from landing on your furniture project while it’s drying. The spray shelter is also great for painting furniture projects. You can read more about the spray shelter in my 9 Paint Sprayer Mistakes You Don’t Want to Make tutorial.
Step 3. Setup the Sprayer
Select the Correct Tip
The HomeRight Super Finish Max paint sprayer includes three spray tips.
The blue tip sprays stain and polyurethane in a 1″-6″ spray pattern which is great for furniture projects. This is the one we want to use. The tip is easy to install with the included wrench.
There are two other tips included with the sprayer, green and red. The green tip sprays latex paint, chalk paint and milk paint in a 1″-6″ spray pattern which is also great for furniture projects.
The red tip sprays primer and latex paint in a 10″-12″ spray pattern which is great for walls, ceilings, decks, and fences.
Adjust the Volume Control Knob
Spraying the “right” amount of poly is critical. Spraying too much poly will produce runs or drips. The instructions for my HomeRight Super Finish Max sprayer recommends overlapping each stroke or pass by a third.
We want just enough poly to flow through the sprayer to coat the piece AND be able to overlap each stroke or pass by a third without spraying too much which would produce runs.
Luckily for us, that is easy to adjust with the HomeRight Super Finish Max. The volume control knob controls the amount of product allowed to flow through the sprayer.
Rotate the volume control knob towards the “+” to allow more product to flow and rotate towards the “-” to reduce the amount of product flowing through the sprayer.
The instructions for my HomeRight Super Finish Max sprayer recommends turning the volume control knob all the way to the “+” and then adjust to the best amount of product for your project. But when spraying polyurethane I would recommend you start with the volume control knob turned all the way to the “-” and then adjust from there.
Remember, we want just enough poly so that we can spray without producing runs or drips. It’s easier to spray more poly if you spray too little because there isn’t much you can do if you sprayed too much other than wait for it to dry and then sand out the drips.
I like to test the amount of product being sprayed on a drop cloth or a cardboard box and then adjust the dial until I’m satisfied with the amount being sprayed.
Step 4. Mix or Thin the Poly
Polyurethane has a nasty little habit. It doesn’t like to stick to itself, so not only is it necessary to sand between coats, but you also have to start with a base coat. Just like you would prime bare wood if you were going to paint, we need to prime the piece with a base coat so we can apply additional coats of poly.
What do you use to thin polyurethane?
Oil-based poly is mixed with paint thinner and water-based poly is mixed with water.
To make the base coat mix two (2) parts of polyurethane with one (1) part of paint thinner.
For additional coats I first add polyurethane to the sprayer container.
Then, based on the amount of poly I added to the sprayer container I thin it 5% using my mixing cheat sheet. You can get your own paint mixing cheat sheet here.
💡 TIP: Remember to test and adjust the volume control knob before spraying your project. See Step 3 for details.
Step 5. Spray Polyurethane
There are a few important things you’ll want to remember when spraying. First, switch the trigger on as you approach the piece, follow through with a long, continuous movement and switch the trigger off when the sprayer is beyond the piece.
Following through with a long, continuous movement is really important. If you start and stop while spraying the piece you’ll end up with more poly in some areas and less in others. As I mentioned earlier, you’ll want to overlap each stroke or pass by one third.
Second, keep your wrist stiff and keep the sprayer 10″ to 12″ away from the surface you’re spraying.
If you bend your wrist as you approach the piece and as you move away from the piece you’ll create an arc. This means the beginning and end of your stroke will be farther away from the piece than in the middle. And that means less poly will be applied at the beginning and end of your stroke and more will be applied in the middle We want a consistent amount of poly applied to the surface, so be sure to keep your wrist stiff.
My HomeRight Super Finish Max sprayer has three spray patterns which can handle just about any surface where you’ll need to spray polyurethane. Below are just a few ideas how you can use the spray patterns.
The horizontal spray pattern is the spray pattern I use the most. It’s perfect for spraying surfaces like table tops and the front and sides of dressers, etc.
The vertical spray pattern is perfect for spraying vertical surfaces like table legs.
The horizontal/vertical spray pattern, or cone shape as I like to call it, can be used for horizontal and vertical surfaces. It’s great for spraying inside corners and edges of table tops.
Step 6. Sand Between Coats
Remember earlier how I said poly doesn’t like to stick to itself? It doesn’t, so we need a way to make additional coats stick to the previous coat. The way we do that is lightly sanding between coats. The sandpaper creates fine scratches. Those fine scratches create a place for the next coat of poly to “bite” in to.
I use 220 grit sandpaper to lightly sand the poly. Remember, the keyword is lightly. We’re not trying to shape the wood like when were prepping it, we’re just trying to scuff the poly. If you sand too aggressively you could sand right through the poly and even sand off the stain
Once the piece is sanded I remove the majority of the poly dust with a Shop-Vac.
This next step is a little controversial. I use a tack cloth to remove any remaining poly dust. Why is it controversial? Tack cloths are soaked with beeswax or oil which makes them sticky. The stickiness of the tack cloth is what grabs onto and pickups the poly dust.
Related: What is a Tack Cloth? (+ What I Used Instead)
The problem is beeswax or oil can resist or prevent stains and poly from sticking to it. That means you could end up with areas of your project that look like a “fisheye”.
In all the years I’ve been using a tack cloth I’ve never had that problem, but it’s always possible that it could cause a problem. Here’s how I use a tack cloth. First, I cut off a small section and then pull it apart to form a loose ball. Then I gently dust the piece. I don’t rub the tack cloth on the piece I almost allow the tack cloth to hover over the piece.
💡 TIP: Do not sand the final coat of polyurethane. Only sand in between coats of polyurethane.
Step 7. Apply Additional Coats
When I would apply poly with a brush, I would apply a base coat and then two regular coats. When I spray polyurethane, I will spray a base coat and then spray two to three regular coats (repeat steps 4-6).
Remember earlier how I said when I applied poly with a brush that it didn’t give me the look I wanted for my furniture projects? I said to me it almost looks like plastic. But when I spray polyurethane I think it looks totally different. Less product is being applied with a sprayer than with brush, so the result is a finish that looks like less plastic and more like it came from furniture factory.
Spray polyurethane with a paint sprayer rather than with a brush. It’s so much easier to apply and gives DIY furniture professional look!
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