What Does Polyurethane Do? [2023 Updated]

What Does Polyurethane Do? In this post, you’ll learn all about polyurethane, and what exactly it does for your woodworking projects. Enjoy.

Updated 2023

What Does Polyurethane Do?

Polyurethane is a very common wood finish that’s used in a lot of different applications in for a lot of different projects. It’s a finish that many new woodworkers use, and many experienced woodworkers alike.

It’s one of those finishes that is not super difficult to apply, and it does a really good job of protecting a surface. This is a couple of the reasons why newer woodworkers tend to encounter this finish right away.

Another reason is that it’s a very common finish. This means you will likely find it in home improvement stores and even larger home stores that sell everything including groceries. So, you might as well learn what it does, and how it can be beneficial to you.

See Also: 10 Step Guide to Wood Finishing

What is Polyurethane Made From?

Polyurethane is made from a resin and a solvent. Basically what this means is there is a solid component in a liquid component that when mixed together create a syrupy liquid that you call polyurethane finish.

It’s because of the solvent that the solid resin turns into a liquid. Once you brush polyurethane onto a surface, the solvents evaporate away, leaving the solid portion behind. Since it was flat when it was applied, the solid portion becomes one flat sheet.

If you were to pour some polyurethane into a small paper cup, once all of the solvent evaporated it would take the shape of the bottom of the cup. It would still be solid, because all of the solvents used to keep it a liquid are now gone.

See Also: 23 Common Wood Finishing Mistakes for Beginners

How to Apply Polyurethane Finish

Polyurethane finish is actually pretty easy to apply. All you need to do is prepare your surface really well, and then follow the directions on the product that you buy. Some are brushed on, and some are sprayed.

When you apply polyurethane with a brush, it’s important that you work quickly, and you use overlapping strokes to ensure that you create one big wet layer. As this layer dries, it will level itself out and create a nice looking finish.

When spraying polyurethane, you want to do the same thing, and work in a way that creates a solid wet layer that can all dry as one. This way, you avoid lap marks and bare spots where you didn’t get enough finish during the application process.

See Also: Why You Need to Seal Wood After Staining

Caring for a Poly Finish

One of the really cool things about polyurethane is that it’s very resistant to abrasion as well as other chemicals and solvents. It’s actually so resistant that it’s even resistant to its own chemicals when you try to put poly layers over each other.

Though you can’t beat the daylights out of a project that you finish with polyurethane, you can handle it a little bit more than if you were to use an oil finish or another type of finish that doesn’t create a film on the surface.

This is also one of the clear distinctions about polyurethane versus other hand applied finishes. A poly is a film finish, which means it creates a new layer on the top of the wood rather than just sinking in like an oil would.

Since it creates a layer, it actually gives your project a lot more protection than other types of finishes that do not. This is great for items that are going to see a little bit more use and perhaps a pinch less care.

See Also: 18 Great Tips for Finishing Wood Furniture

Tips and Tricks for Using Polyurethane

Here are a few tips and tricks for using polyurethane that can help you get the most out of the experience right from the beginning.

• Just like any finish, you’re going to need to practice a little bit. Watch a few YouTube videos on applying polyurethane and you should be able to absorb all of the techniques that you are going to need to be successful.
• When you apply one layer of poly over another, make sure that you use steel wool or very fine sandpaper to lightly rough up the surface before applying the next layer. This will help the two layers stick together better.
• Don’t use bottom shelf polyurethane. Just like any finishing product, if you buy a crappy product, you’ll have a crappy finish. Either that or you’ll have an absolutely miserable time of applying it in order to get a kind of nice looking finish.
• Follow the directions on the can, and make sure that you give a little extra time over what’s recommended for the product to fully cure.

See Also: 2 Best Table Top Finishes You Can Buy

People Also Ask:

What are the benefits of polyurethane finish? The benefits of a polyurethane finish is that it will be a strong layer of protection for your project, it resists solvents well, and provides a lot more protection than other finishes. A good polyurethane finish can last a very long time because of it’s strength and ability to protect. 

Is polyurethane necessary after staining? No, polyurethane is not necessary after staining, but some kind of sealent or finish is helpful to ensure that the stain shows the correct color, and is sealed to the surface of your project so it does not wipe off onto people and other things.

Is polyurethane a sealer or a finish? Polyurethane can be used both as a sealer and a finish, because it has the ability to seal wood on the surface, and act as a finish too. It’s primarily a finish, but if you do a light layer, you can use it as a selaer as well.

What are the negatives of polyurethane? The negative that is most often associated with polyurethane is that the finish can look like a plastic coating. This can be avoided though if you don’t hose your project with finish, and keep the layer thin. It doesn’t need to look like your project is dipped in polyurethane to be an effective coating. You can also use a wipe on polyurethane to get a better looking and closer to the wood lookign finish. 

Your Action Assignment

Now that you know what polyurethane does, and you have a much better idea about using the product, it’s time to get out into your shop and take action. If you are looking for a fairly easy finish to work with, and a common finish to find, then polyurethane may be your answer.

The first thing that I recommend is buying a small can of poly and getting it out in your shop and trying it out. There’s no substitute for hands-on learning, and the product is not very expensive so it’s worth checking out.

After you’ve finished some scraps and have taken a look at the final results, you’ll know right away if you want to continue to use polyurethane in the future.

If you have any questions about this finishing product, please post a question and I’ll be happy to answer them. Happy building.

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