How To Fix Polyurethane Mistakes? (15 PROVEN Methods!) (2024)

Polyurethane is a popular wood finish available in oil-based and water-based options. They come in different varieties from satin to glossy. When applying polyurethane fish to your beautiful woodwork, we do follow different methods.

Whatever method you have followed, mistakes can happen during the application or even after the application is done. There were lots of mistakes I have done with the polyurethane finish.

I have found the solutions for all the mistakes that I have done when applying polyurethane finish. So, How to fix Polyurethane mistakes?

Here’s what I know from being a woodworker for several years:

Most of the polyurethane mistakes can fix by sanding, re-application of the polyurethane finish, by using quality, a new can of polyurethane finish, not subjecting polyurethane can to extreme weather, cleaning the surface well before applying polyurethane, and following proper guidelines when applying polyurethane coats.

But these aren’t the only solutions that can fix polyurethane mistakes. Here are some common polyurethane mistakes and issues.

1. Bubbles in polyurethane finish
2. Puddles in polyurethane finish
3. Uneven polyurethane finish
4. Separating issue
5. Discoloration of polyurethane
6. Surface roughness
7. Orange peel effect
8. Streaking
9. Alligatoring
10. Cratering
11. Cloudy polyurethane finish
12. Scratches in polyurethane finish
13. Blushing
14. Polyurethane runs
15. Trapping insects and dust in polyurethane finish

So, in this article, we’ll deep into every single mistake mentioned above and talk about how to fix polyurethane mistakes.

By the time you’re done reading this article, you’ll have no doubt about how to fix the polyurethane finish.

You’ll also have some cool techniques to use when applying polyurethane finish to your next woodwork without making any mistakes.

Just keep reading!

36″ x 12″ shelves for consoles. Cut, sanded, stained, and hit with a nice coat of polyurethane.
After these are up, I’ll have only two more 12 foot shelves to build.
The game room is coming together! #gameroomgoals #buildingagameroom pic.twitter.com/HZo6xGE8wM

— Muzz (@L1Games) July 25, 2021

1. Bubbles in Polyurethane Finish

Bubbles in polyurethane finish can occur due to various reasons. The most common reasons for bubbles in polyurethane finish are,

• Shaking the polyurethane can properly before use.

By shaking polyurethane can before applying, air can trap inside the polyurethane.

This trapped air can result in bubbles after applying the polyurethane layer, which is hard to avoid.

• Wipe brush with the side of polyurethane can

By wiping the brush along the side of the polyurethane can, air bubbles can trap inside the brush fibers.

Then these air bubbles mix with polyurethane when applying, they got hard can cause permanent bubbles in a polyurethane finish.

• Poor surface and brush preparation

Before applying polyurethane finish, you need to clean the wood surface and also prepare the brush by soaking the brush in the solvent.

Otherwise, air bubbles can trap between ferrule and bristle.

• Not using the correct brush type

By selecting the wrong brush type, won’t do the job smoothly and doesn’t go well with a polyurethane finish.

If the application surface is not compatible with the brush type, brushing will be difficult, and bubbles can easily occur.

Help! @MinwaxCANADA polyurethane for floors left tiny bubbles everywhere! we followed directions. how do we fix this? pic.twitter.com/7l1tWJdvyx

— Julie Mora (@AllJsAllTheTime) May 18, 2015

How to Fix Polyurethane Bubbles?

Here I have listed how you can fix polyurethane bubbles when and after applying polyurethane finish.

• Stir the can without shaking

You need to stir the polyurethane can before use without shaking rapidly. By stirring, not only you’ll get a uniform composition of polyurethane all over the can, but also no air bubbles will trap inside.

• Clean the surface

Cleaning the surface before applying a polyurethane finish is a must. So, I highly recommend sanding and wipe the surface using a cloth before the first polyurethane coat.

Before wiping the surface with a cloth, you need to dip it in mineral oil (if you’re using oil-based polyurethane) or alcohol (if you’re using water-based polyurethane).

By wiping the surface with a dipped cloth, air bubbles that are trapped inside the surface will remove and don’t occur polyurethane bubbles after the application is done.

• Apply thin coats

Never go for thick coats, because they not only have long drying times but also have enough rooms for air to trap inside while applying. So, always go for thin coats.

• Tap on bubbles before it dries

Once you apply the polyurethane finish, if you notice the bubbles are occurring, gently tap on bubbles using the top of your brush until they flattened up.

This only works before your finish are dried. After it dries, there is no use in tapping.

Getting hardwood floors to be perfect is a nightmare. Bubbles in polyurethane especially suck. #hardwood #flooring pic.twitter.com/PpPPnwIn6M

— James Schooling (@st1100pilot) September 29, 2016

• Sanding after it dries

If you notice bubbles in the polyurethane finish after it is completely dried, the only option you can go to do the sanding until bubbles go and reapply the polyurethane coat in a proper method to avoid bubbles.

2. Puddles in polyurethane finish

After the final finish was done, most of the people notice puddle marks in the polyurethane finish.

Like bubbles, puddles also can occur due o various reasons and mistakes. So, let’s talk about what are the reasons for puddles in polyurethane finish under how to fix polyurethane mistakes.

Causes for Puddles in Polyurethane Finish

• Apply another coat of polyurethane before the previous layer dries completely.

After applying the first coat of polyurethane you need to wait till it 100% dries before go for the next coat. Otherwise, puddle marks will occur once the finishing is done and cannot reverse easily.

• Application of thick layers

By applying thick layers of polyurethane, the puddles can easily occur, because you cannot apply a uniform layer throughout the surface. Some places will be thin and some are extra thick and cause getting puddles.

How to Fix Polyurethane Puddles?

• Wipe with rag-soaked mineral spirits

If you notice puddles in polyurethane finish, I highly recommend wiping your oil with a rag soaked with mineral spirit.

1. Wipe off water-based polyurethane with a damp rag before 5-10 minutes.
2. Wipe off flawed oil with mineral spirits before 20 minutes.

With water-based polyurethane, you need to be pretty quick.

• Sand and start over

If you couldn’t wipe the surface before it completely dry, sad to say, you need to do the sanding again completely and reapply the polyurethane coats.

But this time, make sure to go for thin layers and wait for days until each coat dries completely before going for the next coat.

3. Uneven Polyurethane Finish

Getting even a polyurethane finish is a crucial task. The causes of uneven polyurethane finish are because of,

• Insufficient mixing
• Contaminated polyurethane
• Improper sanding and cleaning the surface
• Uneven application of polyurethane finish

Warned customer that a light stain might have the floors uneven. Unfortunately for me the polyurethane I used was not up to my standards so I sanded the floor down again anyway on my dime and let her choose a darker color. Now the floor matches the cabinets. Slightly darker. pic.twitter.com/CKklZ4U5MN

— Killswitch (OLED Model) キルスイッチ (@IamKillswitch) September 5, 2019

How to Fix Uneven Polyurethane Finish?

The only option you can do for fixing uneven polyurethane finish is, sanding everything and starting over.

Here I have listed the steps you need to follow to get an even polyurethane finish.

1.Sanding

Sand the whole surface with a fine-grit sandpaper. Don’t sand too hard because it can damage the surface easily.

2. Cleaning

Wipe the surface using a clean cloth to remove dust and debris. Dirty surfaces make lots of trouble.

3. Application

Get a soft brush and apply polyurethane finish smoothly with uniform thickness all over the surface. Always go for thin coats. Wait till the first coat dries completely before going for the second coat.

Likewise, I recommend going at least 3 coats to get the finish that you wish. Scuff sand between each coat if necessary.

4. Separating Issue in Polyurethane Finish

If you notice the polyurethane coats that you apply separately over time, that can happen because of the following mistakes,

• Polyurethane finish is not mixed properly
• Polyurethane is contaminated
• Product is expired
• The surface wasn’t clean between each coating
• Wood is oily and doesn’t bond well with the finisher
• Due to the application of thick layers

How to Fix Separation of Polyurethane Finish?

The only option you can do for fixing separation issue polyurethane finish is, sanding everything and starting over with a fresh new polyurethane finish from another manufacturer.

Here I have listed the steps you need to follow,

1.Sanding

Sand the whole surface with a fine-grit sandpaper. Don’t sand too hard because it can damage the surface easily.

2. Cleaning

Wipe the surface using a clean cloth to remove dust and debris. Do the cleaning after applying each coat before going for the next coat.

But make sure to wait until it completely dries before wiping the surface.

3. Application

Get a soft brush and apply polyurethane finish smoothly with uniform thickness all over the surface. Always go for thin coats.

Wait till the first coat dries completely before going for the second coat. Likewise, I recommend going at least 3 coats to get the finish that you wish. Scuff sand between each coat if necessary.

By following the above 3 steps properly, you won’t get any separation issues after the application of the polyurethane finish.

5. Discoloration of Polyurethane

Yellowing polyurethane is a natural process rather than consider a mistake. Once you apply polyurethane finish over your hardwood, you’ll notice it turns yellow over time.

But with proper care, you can prevent yellowing.

The main causes of discoloration of polyurethane finish are,

1. UV rays from the sun
2. Using Oil-based polyurethane finish
3. Moisture
4. Minerals

The above factors cause the discoloration of polyurethane and there are several things you can do to fix this.

Painted the trim and banister the same bright white but I put polyurethane on the banister. It yellowed. pic.twitter.com/ZujueDxJi8

— Foul Mouf 🤐 (@falmouf) October 27, 2014

How to Fix Discoloration of Polyurethane?

You can prevent discoloration of polyurethane by sanding and reapplying polyurethane finish from time to time because this is hard to avoid. Proper shading is also good to go.

I highly recommend going with water-based polyurethane because it doesn’t discolor like oil-based polyurethane.

Also, don’t forget to go with thin coats with each layer.

6. Surface Roughness of Polyurethane Finish

The surface roughness can occur because of following reasons,

• Insufficient preparation

If the surface is not cleaned properly before applying polyurethane finish, the surface will be rough when it is dried due to dust and debris.

• Contaminated product

If the polyurethane product is low quality or used, there is a high chance of it getting mixed with some other chemicals which cause roughness afterward.

• Not sanded properly

If the polyurethane is water-based and you’ve not sanded properly with fine-grit sandpaper after each coat, the roughening of the surface can occur over time.

How to Fix Surface Roughness of Polyurethane Finish?

1. Abrade and screen the finish well to get the gloss shiny look back
2. Clean the surface properly with a cloth after each coat of polyurethane finish to avoid getting dust, moisture, and water between the coatings.
3. Sand with fine-grit paper without damaging the surface after each coating has dried completely.

If none of the above methods work for the roughening issue, the only option you can do is sanding the surface and reapply the polyurethane finish from the beginning.

You can learn to form your mistakes!

7. Orange Peel Effect

The orange peel effect of polyurethane finish can occur because of using a roller instead of using brush or spray.

If the roller is not napped well, after application of polyurethane finish, it tends to give orange peel color.

Also, due to very low-temperature levels, the orange peel effect can occur in a polyurethane finish.

How to Fix the Orange Peel Effect of Polyurethane Finish?

The only option you can do for fixing orange skin of polyurethane finish is, sanding everything and starting over with brush or spray.

I don’t recommend using a roller when applying a polyurethane finish, without enough experience.

Also, make sure to keep the temperature level average (not extreme) while applying polyurethane coats and when they’re drying.

Extreme weather conditions can change the chemical compositions of the finisher and ruin the furniture or woodwork.

8. Streaking Polyurethane Finish

Streaking means brush marks. Those streaking marks appear because polyurethane finish dries before marks are gone.

This causes rapid gloss levels all over the surface. You may notice some areas have high gloss while some are not.

This is a common mistake when using a water-based polyurethane finish. Streaking happens when,

• Excess free movement of the brush
• Not properly mixed the finisher
• Not having a wet edge
• No uniform spreading

I just finished putting on the second, and regardless of how it turns out, final coat of polyurethane on my desk. For some reason something I used on the desk is causing it to almost but not quite reject the polyurethane and it’s causing it to streak. I may have to sand.

— Indie Comics Showcase (@indie_comics) February 6, 2019

How to Fix Streaking of Polyurethane Finish?

Screen the surface and recoat with a new polyurethane layer. Sanding is required before applying each layer with fine-grit sandpaper (220 grit).

Also, if you’re good at finishing woods, put another coat of polyurethane where you can see low gloss levels and fill brush streaks carefully.

After that wait till it is completely dry and reapply the polyurethane coat after a little sanding.

9. Alligator Skin Polyurethane Finish

Yes, you read that correctly, if you do some mistakes your polyurethane finish will finally end up like an alligator skin with cracks and interconnected parts and ugly texture.

This is known as crazing.

Here’re the reasons that can cause alligator skin in polyurethane finish,

• High moisture content

If the moisture content in wood is too high when applying a coating, once the polyurethane coating dries, the water will trap inside and can cause the alligator skin texture.

• Alligator skin can occur under cold weather conditions
• If you’ve not removed the previously applied polyurethane coat layer completely, when you apply the new coat on top of that, the interconnected cracks can happen as crazing.
• If the coats are too thick
• If the product is expired or of low quality

Crazing caulk. Time to replace. #sealant #polyurethane pic.twitter.com/bUtFtFPM0M

— Tim Bennett (@Facade_Fixer) December 15, 2015

So, let’s discuss how we can stop polyurethane finish getting alligator skin.

How to Fix Alligator Skin Polyurethane Finish?

Screen the surface and recoat with a new polyurethane layer. Sanding is required before applying each layer with fine-grit sandpaper (220 grit).

10. Cratering Polyurethane Finish

Crates happen when the polyurethane finish or the surface gets contaminated by dust, chemicals, or other effects. Silicon which is included in sand and dust causes cratering of the polyurethane finish.

How to Fix Cratering of Polyurethane Finish?

To fix cratering of polyurethane finish you need to sand the surface lightly and wipe the surface with a clean cloth and re-apply a thin polyurethane coat.

Once it is completely dried, you won’t notice any craters on the surface.

11. Cloudy Polyurethane Finish

Cloudy polyurethane finish happens because of several reasons. Such as,

• Using an old polyurethane finisher
• Extreme weather conditions
• Humid conditions
• Not stirring before application

Note to self – throw out the questionable polyurethane. First pic was first coat of old cloudy poly. Second pic is coated with fresh can wipe on poly. #neverstoplearning pic.twitter.com/ohe878zyLw

— Tony Austin (@GoodDogWoodwork) February 10, 2019

How to Fix Cloudy of Polyurethane Finish?

You can easily get rid of cloudy polyurethane finish by following these steps with good focus.

1. Check whether your polyurethane finish coat is completely dried.
2. Remove flames or any other hating of cooling sources nearby
3. Get a clean cloth and add some mineral spirit to it and wipe the surface to remove any dust and debris.
4. Repeat the same wiping procedure until the blotching is gone and let the surface dry.
5. Sand the surface with fine-grit sandpaper (220 grit) until the cloudiness disappears and until the polyurethane finish is removed.
6. Clean the surface and re-apply 3 thin coats of polyurethane finish and let each coat dry completely before applying the next coat.

12. Scratches In Polyurethane Finish

Any wood surface that applied a polyurethane finish can form scratches over time because of wear and tear. With heavy usage scratches are possible to happen.

Scratches can happen even when we are applying polyurethane finish because of some mistakes like sanding too tough etc.

Finally done with this table! Bought it secondhand, husband replaced the legs (w/ locally sourced wood), and I restained and smoothed out any scratches. Used barn paint to paint the legs white. Spent a lot of time making sure the polyurethane top coat was super smooth pic.twitter.com/7uhFtkf4AL

— MINSOOKY 민숙이 (@Minsooky) September 21, 2020

How to Fix Scratches of Polyurethane Finish?

We can fix any scratches of polyurethane finish by sanding everything and starting over. Here I have listed the steps you need to follow to get an even polyurethane finish.

1. Identify the scratches

First, you need to examine whether the scratch is too deep or not. If it is too deep you need to do more sanding and more finishing is required.

2. Sanding

Sand the whole surface with a fine-grit sandpaper. Don’t sand too hard because it can damage the surface easily.

3. Cleaning

Wipe the surface using a clean cloth to remove clouds of dust and debris. Dirty surfaces make lots of trouble.

4. Application

Get a soft brush and apply polyurethane finish smoothly with uniform thickness all over the surface. Always go for thin coats.

Wait till the first coat dries completely before going for the second coat. Scuff sand between each coat if necessary.

@alliek0630 Sandpaper – to get out scratches – then finer & finer grades, then polyurethane with foam brush. pic.twitter.com/OJSnLL4Njc

— Cynical Mike (@CynicalMike) August 20, 2014

13. Blushing in Polyurethane Finish

There is a light milky color that can be seen in some polyurethane wood finishes and happen with lacquers as well. This happens moisture and water are trapped inside the finisher.

This happens because of not cleaning the surface and not sanding properly before the finisher is applied. The moisture trapped inside the wood tends to penetrate to the finishing layers/coats with the changes of humidity.

Blushing can mainly happen due to the following reasons,

1. Incompatible stain – Like applying water-based polyurethane over an oil-based stain
2. High humidity
3. Placing wet objects or water droplets in the same area for a long period of time

So, let’s discuss how can we fix blushing in a polyurethane finish.

How to Fix Blushes of Polyurethane Finish?

1. Gently wipe the area that is blushed with a damp cloth after dipping it in alcohol. You should do this gently without much force. Wet the blushed surface with alcohol and let it evaporates and completely dries the surface.
2. Secondly, you need to wipe the surface with the same cloth after dipping again with alcohol until the blushes went completely all over the surface.
3. Sand with 180 grit sandpaper to remove excess blushing. Do this smoothly until you notice the dull look of the wood
4. Finally, apply a thin coat of new polyurethane finish and let it completely dry. After that go for its second coat and finish the process.

14. Polyurethane Runs

Runs can happen when drying the polyurethane finish. This is known as one of the biggest problems in the woodworking world.

Runs are common for polyurethane finishes because of being slow drying.

Runs can be seen when drying both water-based and oil-based polyurethane finishes. Runs can occur due to applying thick layers of polyurethane or by spreading too much.

So, let’s talk about how we can fix polyurethane runs effectively.

How to Fix Polyurethane Runs?

1. Check the surface while brushing the surface through reflected light. While moving your head and wood, you’ll be able to notice if any runs there in a polyurethane finish.
2. If you identified runs, you can easily eliminate them using the brush by removing excess polyurethane finish or drag it to where less amount of finish is applied.
3. If you identified runs after the finish has dried, wait till they harden more and do light sanding until all the runs are gone. Once you feel ok, re-apply the additional coat of polyurethane for a better finish.

15. Trapping Insects and Dust in Polyurethane Finish

This is the biggest headache that I suffered when working with a finisher. There are times bugs are landed on the surface as soon as I do clean the whole surface and start to apply finisher.

So, I do clean the surface again.

Some people ignore bugs and apply polyurethane coats over them. But eventually, that small mistake will cost you more than you imagine. So, you need to pay extra attention to keep the surface clean without touching any dust, insects, and debris.

@venadavenu do you know if these are some kind of insect’s eggs?….wood has polyurethane coat, so I assume it can’t be fungi pic.twitter.com/CKen7EmqHX

— Manish Chandi (@manishchandi) November 29, 2020

How to Fix Polyurethane Finish After Trapped Insects, dust?

If the insect landed on the polyurethane finish while the surface is wet, you can remove it simply using a toothpick or needle. Normally wet finishes will eventually recover once the insect is removed.

But I suggest you apply a small amount of finisher to the area insect landed.

If an insect has landed on the surface while it is drying, I don’t recommend using a toothpick. You need to wait until the surface is completely dried.

Once it is dry, remove the insect and do light dry sanding with fine-grit paper (400 grit).

Never go for wet sanding because the finish can be mimicked by the lubricant, and you won’t notice the cutting.

After light dry sanding, re-apply a thin layer of polyurethane finish and let it dry completely.

Yay I’m done! Last coat of polyurethane is drying. Desk knobs tomorrow….
💪💪💪 pic.twitter.com/N5Oe35mr2i

— Vibeaholic (@ThaGurlNxtDoor) July 5, 2020

So, those are the 15 proven methods to fix polyurethane mistakes.

Let’s have a look at the summary with all the mistakes and the most possible solution for each of them.

Summary: How to Fix Polyurethane Mistakes?

If you’re willing o apply wood stain instead of polyurethane as a finisher, better to know what mistakes can happen during wood staining and how to fix those as well.

Did I cover all you wanted to know about: How to Fix Polyurethane Mistakes?

In this article, we took an in-depth look at the common polyurethane mistakes and how to fix them.

We examined all the methods and techniques you can use to avoid problems when working with a polyurethane finish.

As I have mentioned, most of the mistakes you can simply avoid by sanding with fine-grit sandpaper and reapply the polyurethane finish using proper guidelines, and giving enough time to dry completely.

Hope this article gave you a proper understanding of how to fix polyurethane mistakes from your next woodworking project without any issues.

So, let’s give it a try!