How to Fix Polyurethane Mistakes (Explained)

Polyurethane is one of the most common materials used in home furnishings and is most commonly seen in the form of flexible foam. Polyurethane gives the furniture a glossy finish.

If it’s not applied properly, you can get a rough, cracked finish. There may be bubbles that are hardened in the layer. Sometimes the layer gets separated from the wood.

But these problems can get solved. How do fix polyurethane mistakes?

To avoid cloudy polyurethane, you need to mix it properly. To get an even finish, pour the mix slowly and avoid water-based polyurethane. To avoid bubbles you need to stir the mix without shaking it. Thus you can fix the issues.

How to Fix Polyurethane Mistakes (9 Common Mistakes)

Polyurethane is a sensitive material. If you don’t handle it very cautiously, many problems will occur. These polyurethane mistakes make you wait for a very long time.

1. Badly Applied Polyurethane

To repair a faulty polyurethane job, sand down the previous polyurethane and apply the finish again. To prevent making the same mistakes again, clean the surface well.

Before reapplying polyurethane, use a high-quality brush, don’t shake the can. And reapply polyurethane when the temperature of the polyurethane is still warm. 

There are some brushes that you can use for applying polyurethane. Check out the recommendations for choosing the perfect brushes.

2. Reapply Polyurethane After It Has Dried

In most cases, the procedure for removing old polyurethane and reapplying the finish is the same. Here are the measures to take. You can also remove the polycyclic finish from the wood.

As we go through the numerous faults that can happen with a polyurethane finish, we’ll return back to these processes. Identify the specific issues you are looking for and then make adjustments to solve them.

Step 1: Sanding

Sand the surface with 200 to 350-grit sandpaper till the defect or fault is gone. 

Step 2: Vacuuming 

To eliminate all traces of dust and sandpaper grit, vacuum the area and clean it with a craftsman’s cotton cloth.

Step 3: Reapplying Polyurethane

When you use oil-based polyurethane, dilute the initial application with natural solvents in a 50% proportion.

You don’t need to shake, instead, gently stir. Allow drying after applying a little coat with the point of a paintbrush. 

It is not necessary to dilute water-based polyurethane. The first coat should be applied lightly with the point of the brush.

Step 4: Smoothing the Surface and Reapply

Sand the dried coat very gently. The goal is to scrape the surface rather than eliminate it. This scuffing serves as a keying surface for the subsequent coat. Step two should be repeated before applying a second layer of polyurethane. 

If you are using oil-based polyurethane, thin it to a 75%  proportion. Do not dilute when using a water-based product.

Step 5: Recoating

Keep recoating the surface until you get your preferred appearance. The top layer should not be sanded.

3. Cloudy Polyurethane

Sometimes your polyurethane finish can get cloudy. It decreases the beauty of the product.

Moisture is the primary cause of polyurethane cloudiness. It could be due to the humidity in the atmosphere, or anything liquid being spilled on the surface.

If you don’t apply the polyurethane at the right temperature, it will also cause cloudiness. The age of polyurethane can hardly cause the cloudiness of the surface.

If you don’t stir the polyurethane thoroughly, the aftereffect can cause cloudiness.

If polyurethane is placed over a stain or oily timber, the staining of wood oils may be inconsistent. This will generate a chemical flush.

If water spills on the surface of your product, then you get a cloudy spot. Removing the water and allowing the tabletop to dry can sometimes make the stain vanish within a day. 

Or else, you’ll have to remove and replace the polyurethane as described above besides only one exception.

If you feel the issue is due to a genetic discoloration or greasy wood, follow the steps mentioned above. After that, apply a polishing sealant. To avoid leakage, the sealant will cover the stain and the wood. 

Continue with the aforementioned directions from the third step once the paint has dried.

4. Uneven Polyurethane Mistake

You need to be very careful while applying polyurethane. Otherwise, you will get an uneven finish. Where you get the different thicknesses of the polyurethane layer on the surface.

The main reason for this problem is the technique or method you use in this process. You should avoid polyurethane which is based on water in this process. Because it gets dried very fast so you don’t get enough time to correct your mistakes.

Sometimes one part of polyurethane has dried. And you somewhat exceed that dry area before applying polyurethane to the next area. Then you get overlap. 

As a result, you have a double layer at that point and a single layer on the other places. This can become fairly obvious after several coatings.

Sand the area which is overlapped and make it to the same level of the surface.

Then get a thin layer of polyurethane on the whole surface. To level the unevenness while you sand, you can follow the preceding directions.

5. Removing Streaks from Surface

Streaking in polyurethane is the brush marks on the surface. The most common cause of polyurethane streaking is using a low-quality brush. The one with a rough bristle while applying and working too hard the polyurethane. 

For oil-based polyurethane, get a remarkably high paintbrush, and for water-based polyurethane, get a slightly elevated artificial brush.

To remove and reapply polyurethane, follow steps one through five of the aforementioned instructions. Apply the new coatings with the suitable fine bristles brush, only utilizing the first quarter of the brush. 

Apply neutral or slightly with the brush tilted in the path of motion. Then thin out oil-based polyurethane according to the manufacturer’s instructions. 

You may also want to know how to remove Danish oil from the wood.

Apply thin coatings of varnish to the surface, being careful not to go through it. After you’ve chosen your cover, settle the polyurethane and spread it to make a level surface. 

You’ll almost certainly get streaks if you go over that drying area again.

6. Cracked Polyurethane

According to some suggestions, denatured alcohol can help you to fix the crackings of polyurethane. But it may not work sometimes.

Polyurethane dries in 2 phases: the solvent evaporates first. Followed by the chemical change in which the resins harden when they interact with oxygen.

While a paint remover can smooth the resultant film, denatured alcohol appears to be ineffective. 

You need to clean the broken area with brillo pads bathed in natural solvents, then wipe it clean with pure mineral spirits and let it dry. 

There are some products that you can use as a paint remover. Check out the recommendations for choosing paint remover-

Then you have to allow the above-mentioned guidelines for peeling and having to apply polyurethane. When it gets dried, repolish it and clean the surface.

7. Peeling of Polyurethane

There are three main reasons for the peeling of polyurethane. The main reason is:

  • Applying polyurethane on a surface that is oily and dirty.
  • The surface is not smoothed before applying polyurethane.
  • Overcoating the surface and making it heavy.

As a solution, you can apply a paint stripper according to the directions written on the can. And sand the surface with 200 to 350-grit sandpaper a little before applying. Clean the surface with a natural spirit.

Then you can apply polyurethane in the normal process.

8. Bubbles in Polyurethane

While applying the polyurethane, you can get some bubbles in the finish. Try to avoid them in the first place. But if you get bubbles anyway, there is a solution for that as well.

To avoid bubbles in the finish you need to stir the mixture without shaking it. Then you need to pour the mixture slowly otherwise it can create an air gap. Which will turn into bubbles. And most importantly, apply it in a thin layer gently.

If the bubbles are created while you are still pouring, you can easily knock them with a pin. Additional heat also can remove the bubbles from the polyurethane finish. 

While heating you can face problems with the Radiant tube heater but you can solve them easily.

9. Orange Peel Effect in Polyurethane

The most typical reason for an orange-peel roughness in polyurethane is if it dries before it has flowed and flattened. 

When applying the finish in freezing temperatures and using a roller as an applicator, this result is common.

You’ll need to smooth the surface until it’s completely flat and free of the orange peel look. Follow the five steps outlined at the top of this page to apply polyurethane.

It would be ideal if you could apply the polyurethane when the weather is warm.  But in some regions of the world, this is simply not possible. 

If you’re having trouble with this, thin the polyurethane to make it less viscous. Use a 50/50 or 75/25 polyurethane/mineral spirits ratio. 

There are some products that you can use as mineral spirits. Check out The other recommendations for choosing the perfect mineral spirits-

If you’re completing a floor, try using a brush or a T-bar applicator. 

For oil-based polyurethane, you can use a roller with a fine nap, lambswool. Use microfiber for water-based polyurethane.

Tips for Applying Polyurethane

You can see that you can make many mistakes while applying polyurethane. The tips below will help you to avoid mistakes.

  1. With a stick, gently whisk the polyurethane. The can should not be shaken. Be delicate when pipetting from the tin.
  2. Use brushes that have fine bristles and use the correct brushes. Natural brushes for water-based polyurethane and artificial for oil-based polyurethane. 
  3. If you’re applying polyurethane with a roller, choose a short-napped cover made of lambswool for oil-based polyurethane and microfiber for water-based polyurethane.
  4. Don’t remove the excess polyurethane from the brush before applying and apply it naturally.
  5. Don’t overlap the same area and level the whole surface area.
  6. Clean the surface before applying polyurethane. Vacuum and wipe the whole area to get an even finish.
  7. Dilute the oil-based polyurethane and make it thin.
  8. Maintain the temperature while applying polyurethane. It helps to level the surface and removes the bubbles.

That’s all about polyurethane mistakes!


What is the best way to keep polyurethane from running?

The best way to keep polyurethane from running is to remove any extra finish from the surface and transfer it to another area.  Or, drag it across the rim of both bottles and cans. If there are any runs or sags as in finishing, you’ll need to sand or scrape their level.

How do identify a bad polyurethane?

Sometimes polyurethane can get bad. Using it will give an indecent finish. You can identify it easily. If it is foggy, you can tell it is bad. Again if it hardens a little you can declare it bad. You should throw the bad polyurethane in a proper way without hampering nature.

Can you stain over a polyurethane finish?

Yes, you can stain over a polyurethane finish. For this, you will need gel stains. You won’t need any sanding or stripping to stain with gel stain. Gel stain itself contains a little amount of polyurethane. Besides, you can use a coat of Minwax poly shade over your polyurethane. 


I hope now you know all about how to fix polyurethane mistakes. You can fix all the basic mistakes by yourself. Even then if you can’t fix it, you can take some expert help.

If you face any other problems, you can let us know or comment below. Wishing you the best of luck in fixing polyurethane mistakes. Happy reading!

Kevin Smith

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