What to Do When Polyurethane Won’t Dry

Image of polyurethane finished floor, know what to do What to Do When Polyurethane Won’t DryThough frustrating, it is not strange to see that your polyurethane finish does not dry several hours or days after application. There are several explanations for such a happening; however, at this point, I want to look at what to do when polyurethane won’t dry. 

If you have applied your polyurethane finish and is not drying, the best way to speed up the drying is by applying heat to the surface. The best source of heat is a heat lamp; alternatively, you can use a blow dryer.

Usually, the water-based polyurethane requires about 6 hours to dry to touch while its oil-based counterpart takes up to 24 hours to dry. If your finish takes way more hours than the ones I’ve stated here, you should start thinking of ways to speed up the drying process, especially if you applied them in standard weather conditions.

Why is The Polyurethane Not Drying?

There are several explanations of why your polyurethane finish might take longer than expected to dry or may fail to dry entirely. So what could be the causes?

  • Wood Contains Oil

One possible explanation of why your finish is taking “forever” to dry is because the wood could be having natural oil. It is also possible that you applied oil to your structure and did not allow it enough time to dry completely. In this case, it’s the first layer of polyurethane that might take longer than expected to dry; if it dries, then the second coat will have no problems drying under the expected duration.

The majority of exotic woods, except mahogany, have a natural resin whose major component is oil. Sometimes, when you touch these woods, you can feel their oiliness. The mineral-spirits solvent present in the polyurethane acts as a solvent to the resins; when you apply the polyurethane to the bare wood, the two will mix(the oily resin and the polyurethane), leading to the oily resin affecting the drying of the polyurethane formula.


The same thing happens when you apply polyurethane over linseed. You can avoid it by allowing the oil to dry totally before the application of polyurethane.

  • Application Condition

The prevailing atmospheric condition of your region also plays a role in the drying of your polyurethane formula. If you are working in a highly humid condition with low temperatures, your formula will likely take longer than expected to dry. So, you might want to wait a little longer before considering other options. If you are working on a short timeline, you can use heating methods to speed up drying. Also, ensure that you are working in a room with proper ventilation to avoid having your finish unusually long to dry.

How Long Should You Wait for Polyurethane to Dry?

Different polyurethane formulas come with varying times of drying. Even so, the standard drying time for a water-based polyurethane is 6 hours. An oil-based polyurethane, however, requires up to 24 hours to dry.

The two, however, have a similar curing time of 3o days. After applying your formula, allow it 6 or 24 hours to dry if it’s water-based or oil-based polyurethane, respectively.

How Long Do You Wait Between Coats of Polyurethane?

Woodworker using Rigid, the Best Cordless Random Orbital SanderYou need a lot of patience if working with polyurethane to achieve the best finish possible on your structure.

After applying the first coat, I recommend that you allow it between 24-48 hours, use a wood sander for sanding it lightly, and apply a thin layer of the second layer. You can add third or more coats; however, two coats usually get the job done. 

Do not sand the final coat of polyurethane. Allow it to dry and cure into a beautiful, hard, and protective finish.


If applying multiple coats of polyurethane to your structure, such as a wooden floor, ensure that the layers are thin. The thin layer application allows for faster drying and results in a beautiful finish with no bubbles.

What Happens if You Recoat Polyurethane Too Soon?

Recoating your polyurethane finish too soon does not have a horrible effect on the surface. However, it does not give you the best finish as you should have if you allow your layer to dry before adding the next coat.

If you recoat too soon, the bottom layer will shrink to form tiny ripples in the top layer. These ripples make the surface less smooth. If this does not worry you, you can go ahead and recoat your polyurethane finish too soon.

How To Apply Polyurethane To A Wooden Floor

Polyurethane can give your wooden floor that excellent beautiful touch mainly if applied using the right procedure. Below is a step by step guide to applying a polyurethane finish to a wooden floor for the best results.

  • Step One: Choose Your Finish

Image of a water based polyurethane for hardwood floor refinishingIf you are working on a short timeline and looking for a polyurethane formula that will dry faster, allowing you to finish your project in a day, then go for water-based polyurethane. You will notice that while in the can, the water-based polyurethane is milky. However, once applied, it will dry and cure to a clear finish. This formula also contains low smell and has a faster drying time compared to its oil-based counterpart.

If you are interested in durability and deeper color on your surface, you can choose oil based polyurethane. However, the shortcomings of this formula are that it takes a little longer to dry compared to the water-based ones. Additionally, the oil-based polyurethane starts to yellow over time. On the plus side, you can apply a few coats of this formula to get the job.

Another choice of polyurethane formula to use on your floor could be the matte or glossy polyurethane finish. It does happen that you are not sure of the right one to pick and how the finish might appear on your surface; in such a case, you can try all the options on a small piece of wood and absorb the appearance settle for one that pleases you the most.


  • Keep in mind that glossier surfaces show fingerprints and other marks more than matte finishes
  • Ensure that you are working in a room with proper ventilation because most polyurethane formulas (oil-based) contain volatile organic compounds. These fumes can be dangerous to your health when inhaled.

Step Two: Preparation of Your Surface (Floor)

One key component of preparation is sanding the surface unless it is a brand new wooden floor. So, sanding must be in three steps using different textures of sandpaper. Start the process with 36-grit sandpaper, then 60-grit, and finalize the process using 100-grit sandpaper. Ensure that you sand the edges as well as the corners of your floor. You can attach the sandpapers to a belt sander considering the immense size of your project.

Image of a shop vac for dust collectionAfter sanding your surface, use a shop vac for dust collection or any available vacuum cleaner to clean the surface to ensure that it is free of any dust particles that might compromise the subsequent processes.

Once you have removed all the dust particles from sanding using a vacuum cleaner, go a step further to ensure that you will apply your formula to a clean surface by wiping down the surface using mineral spirits. The mineral spirit helps with the removal of all remaining debris and tiny dust particles. You can apply the mineral spirits with the help of a clean cloth moving across the floor’s entire surface. Allow your surface enough time to dry.

One last thing that you must do before you start applying your polyurethane formula is protecting your baseboards. Masking tape does excellent in this role. Sometimes you get so “excited” about the application so that you end up brushing polyurethane over your baseboards. So, masking them helps a great deal against such an accidental occurrence.

  • Step Three: The Application of First Coat of Polyurethane

Here’s what you need to do to ensure a successful application of the formula to your wooden floor:

Pour your poly formula into a paint tray but before that, ensure that you stir it thoroughly. Use a paint stirrer for the stirring process; this helps your polyurethane to mix correctly. Additionally, it helps eliminate the possibility of the formation of bubbles on your floor. Avoid by all means shaking the can containing the poly formula. Shaking introduces bubbles into the formula, which can be an awful thing for your floor.

After stirring your formula and putting it into the paint tray, have your brush or painter’s pad ready and start applying the formula to the surface. During the application, ensure that you are applying very thin layers of the formula as it plays a role in the formula’s drying. You need to avoid using lamb’s wool pads, as they tend to collect dirt with ease. During the application, make long and even strokes. Ensure that:

  • You avoid applying too much polyurethane on the surface; thin coats will give you a perfect finish.
  • Avoid repeated application to one spot to reduce the chances of formation of bubbles and other imperfections.

You cannot just start applying your formula from any position on the floor. Ensure that you begin the application process at the farthest corner from the entrance of your room. Starting from the most distant corner helps prevent instances where you step on your work before it dries. Even as you apply, try to work quickly, moving towards the door.

Once you have covered the entire room, allow your finish to dry. Usually, the manufacturer’s label on your products indicates the amount of time it takes for the finish to dry before you can apply the subsequent layers.


Observe your finished surface keenly and sand down any possible bubbles or uneven patches. Remember, sanding is after the surface is completely dry. Sanding helps with the removal of imperfections that might make your surface “ugly.” Use 220-grit sandpaper for the removal of blemishes. As you sand, ensure that you are doing it along the wood’s natural grain and not against the grain.

After removing the imperfection:

  1. Clean the surface using a piece of cloth.
  2. For water-based polyurethane, use a little soap and water for cleaning.
  3. Use mineral spirit for oil-based poly formula.
  • Step Four: Application of Second Coat of Polyurethane

If applying a polyurethane finish to a wooden floor, one layer does not do enough, so you need to add additional layers. For the extra layers, you need to thin the formula before use. Thinning helps reduce the chances of bubbles. Mix polyurethane and mineral spirit in the ratio of 10:1 respectively in a clean can and stir before pouring it into a paint tray. 

Follow the above step by applying a thin coat of thinned formula. During the application, you will notice some sections having thicker layers than the others. Use the same method you used for the initial application to ensure that you end up with a level finish.

Give your surface enough time to dry. It would be best to look at the manufacturer’s label for the drying time for a second layer.

As soon as your floor dries, you should even it out using an abrasive pad. Some of the pads you could use for this include steel wool or grade 0000. 

Follow the above step by cleaning the surface. Again, use the same procedure as the one during the initial application of the formula.

  • Step Five: The Final Coat of Polyurethane

For the final coat, ensure that you are using a polyurethane formula that is NOT thinned. Additionally, you must not clean or sand the coat. After application, leave your room and allow it to dry peacefully.

Allow your structure at least 24 hours to dry before walking over the surface. You can start replacing your furniture after 72 hours; however, give it at least 1 week for the best results. Give it more time before cleaning and putting rugs over the surface.

Reusable face mask for woodworkingThe Safety Measures When Using Polyurethane 

So, is polyurethane toxic? In most cases, it depends on the type of polyurethane that you are using. Therefore, you should read the manufacturer’s instructions to know how to handle the formula. Here are some of the general precautionary measures that you should pay close attention to while working with a polyurethane:

  • Oil-based polyurethane contains several dissolved chemicals, and these are evident during the dry and curing time because they produce a strong odor. Water-based poly products do not have a strong smell, but still, you mustn’t take chances. So try as much as possible to stay away from the surface when it is drying and curing.
  • Ensure that you are working in a properly ventilated room when applying the polyurethane formula to your surface. If not, ensure that you have a nose mask with approval for polyurethane application.
  • Oil-based polyurethane can catch fire when drying because it contains chemicals that evaporate as fumes. Therefore, ensure that there are no fire sources around your room. Items such as rugs used during the application of oil-based poly formula can also catch fire, so ensure that you dispose of them in the right way. Water-based systems are not inflammable. 


When applying polyurethane to your structure, there’s always one thing in the mind-the beautiful finish at the end of it all. However, sometimes, it can be frustrating to notice that your finish is taking extraordinarily long to dry, and I’d understand if you are starting to worry. However, here’s…

What to Do When Polyurethane Won’t Dry

Choose to dry the surface physically; some of the tools you can use to dry it include a heat lamp, heat gun, blow dryer, and a lot more. Heating is a tried and tested way of helping your poly finish to dry, and it should work well.

Are you having issues with the drying of your polyurethane finish? Did you find this article helpful to your quest to get the problems sorted? Kindly share your thoughts, opinions, suggestions, additions, and subtractions in the comment section below.

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Tyron Otieno

Tyron is an avid woodworker and writer. He founded this website to help other woodworkers, whether hobbyists or professionals by sharing his knowledge and experiencie after a decade of woodworking.