When you put polyurethane over a surface, the last thing you want is for the polyurethane to turn into a sticky mess. So how do you fix sticky polyurethane? Here is the answer to that.
To fix sticky polyurethane, you should expose the coating to heat using a heat lamp or hairdryer. The increased temperature around the polyurethane coating will speed up the evaporation of oils and moisture that are causing the polyurethane to remain sticky.
However, you should know that this fix is usually temporary. Even if you manage to dry the polyurethane, the coating will not be as strong or durable as it should since it didn’t dry properly.
The best way to fix sticky polyurethane is to wipe the polyurethane coating with a solvent and start painting from scratch. Why? Find out the reason for that and more in this post. So let’s dive in.
How Long Should Polyurethane Take To Dry?
Polyurethane takes between 2 and 48 hours to dry. On average, water-based polyurethane dries enough for light use and handling within 8 hours. Oil-based polyurethane will take up to 24 hours to dry enough for light use.
For re-coat, water-based polyurethane will take up to 3 hours to dry while oil-based polyurethane can take up to 12 hours before re-coat. You should know that the cure time of polyurethane is different from the dry time.
While the dry time refers to how long to wait before re-coating or touching the paint, the cure time refers to how long to wait before using the polyurethane. On average, water-based polyurethane takes 24 hours to cure while oil-based polyurethane takes 48-72 hours to cure.
The reason polyurethane takes longer to dry than regular paint is that polyurethane is a sealant. As such, the top coat is designed with several chemicals and resins to improve its durability, water resistance, and UV resistance. These chemicals and resins need time to react and harden enough to make the polyurethane coating strong.
Also, polyurethane is plastic in liquid form and it will take longer for the plastic to form and harden. So now that you know how long it takes polyurethane to dry, why does polyurethane remain sticky? Let’s take a closer look at that.
Related Read: How Long Does It Take Polyurethane To Dry?
Why Does Polyurethane Stay Sticky?
Polyurethane remains sticky because the topcoat is wet. The sticky texture of the top coat is because the solvent or paint thinner is trapped inside the coating. For the top coat to dry, the thinner has to be fully evaporated.
So, why doesn’t the thinner evaporate like it’s supposed to? The main reason for this is the inadequate dry time between coats. Usually, you’ll need 2-3 coats of polyurethane on a material to seal it. But you need to leave enough time for each coat of polyurethane to dry before you can lay the next coat.
If you don’t allow the first coat to dry enough, there will be solvent or paint thinner trapped inside the polyurethane coating. The trapped solvent will begin to bleed through the successive coats making the finish appear wet and sticky for several hours or days.
Another reason polyurethane won’t dry is humidity or moisture. This usually happens when you apply polyurethane in a wet or humid environment. After applying the polyurethane, the moisture in the atmosphere will settle on the polyurethane. When this happens, the top coat will get wet as the moisture content in the coating will be increased. This will lead to the polyurethane coating being sticky.
You can also have sticky polyurethane if you apply the polyurethane on a stained material or wood that has a lot of oily deposits. Mahogany, Bloodwood, and Rosewood amongst others have a high deposit of oils. So if you apply polyurethane directly on them, the stains and oils in the wood will bleed through the polyurethane coating causing it to turn sticky.
What To Do If Polyurethane Won’t Dry?
The best thing to do if polyurethane won’t dry after several hours is to wipe off the polyurethane coating with a solvent like turpentine or paint thinner.
Once the polyurethane is off, you should clean the material, apply a stain-blocking primer, and apply the polyurethane again. The reason for this is to ensure the polyurethane dries properly.
When polyurethane won’t dry or remains sticky, it’s usually due to improper surface preparation or not enough dry time between coats.
There is nothing you can do about both of these scenarios because you have already covered the improperly prepped surface and wet existing coat with more coats of polyurethane. So the best bet is to start from scratch.
When you have removed the polyurethane with a solvent, apply a stain-blocking primer like shellac on the material to prevent moisture and stains from bleeding through. Next, apply the polyurethane in light coats leaving enough time for each coat to dry. This will ensure a better result.
However, if you don’t want to start from scratch, there are a few hacks that you can try out:
- Dry the polyurethane manually using a hairdryer or heat lamp
- Open all windows, vents, and doors for improved circulation. This will get the polyurethane coating to dry quicker.
- Use a dehumidifier to get the excess moisture out of the room
- Apply Talcum powder on the polyurethane coating.
You should know that the hacks above are temporary fixes. They might get the polyurethane dry but it is usually for a couple of hours before the coating gets wet again.
Even if you manage to get the polyurethane dry using any of these hacks, the finish will not be as strong as it should be. It will also be quickly damaged by moisture. So it’s better just to start from scratch.
Should Polyurethane Be Sticky After It Dries?
Polyurethane shouldn’t be sticky after it has dried. Polyurethane should only be sticky for at most, the first 6 hours after the top coat was applied.
After the polyurethane has dried, the coating should become hard, non-porous, and usually glossy.
If your polyurethane coating remains sticky or wet several hours after application, it’s usually due to one or more of the reasons below.
5 Main Reasons Polyurethane is Sticky After It Dries
Here are 5 main reasons polyurethane is sticky:
1. Humidity Is More Than 50%
For the polyurethane to dry properly, the level of humidity or moisture in the atmosphere should be below 50%, preferably 40%. But if the humidity is high, it means that the moisture content in the air is much.
The moisture can settle on the polyurethane as it dries. When this happens, there will be more solvent in the paint coating causing it to become sticky or gummy.
2. The Polyurethane Was Applied in Cold or Moist Weather
Another reason your polyurethane turns sticky is cold or moist weather. When the weather is snowy, rainy, or wet, you should apply polyurethane because the weather during this time will be cold and moist. This will lead to increased moisture and a repetition of the first reason discussed earlier.
3. Thick Coats of Polyurethane Were Applied
A cliché of the painting world is the thicker the coats, the longer the dry time. Thicker coats of polyurethane equal more paint thinner.
More paint thinner equals a long process of evaporation and the longer the process of evaporation, the longer the dry time of the polyurethane. So to make your poly dry faster, apply light coats.
4. Not Enough Dry Time Between Coats
If you don’t allow the existing coats of polyurethane to get dry properly, then the successive coats applied will prevent proper evaporation of the first coat.
This will over time lead to moisture in the first coat bleeding through the successive coats. In simple terms, the underlying coat will cause water to affect the second coat causing it to take longer to dry.
5. The Polyurethane Isn’t Dry Yet
The last reason is a common one. Most people expect polyurethane to dry at the same time as regular latex or acrylic paint. So when the poly doesn’t dry within the first 1 hour, they think there is a problem. There isn’t. Polyurethane being a sealant is meant to take longer to dry and even longer to cure.
This is due to the increased levels of oils, chemicals, resins, and plastics in the paint coating. Oil-based polyurethane especially can take up to 12 hours to not be sticky.
To be sure this isn’t the problem, check the information inscribed on the polyurethane container to know how long the top coat should take to dry. If the polyurethane has exceeded that time frame, then you can look at other reasons.
So how can you know when polyurethane has dried? Let’s take a closer look at that.
How To Know When Polyurethane Is Dry?
The following signs will indicate when the polyurethane is dry:
- The texture will be hard and silky-smooth.
- The top layer will not be cool but warm when touched
- The top layer will be glossy
- The Polyurethane will no longer produce a strong smell
All these signs are good indicators for when the polyurethane is dry. But to be sure, you can try a personal experiment.
Try to dent the polyurethane coating with your finger. Push your finger or thumb into the polyurethane coating. If you notice an indent, then the polyurethane isn’t dry yet.
To know if the polyurethane has cured, put a few drops of water on the top layer for a few minutes. If you notice that the water is still there, it means the polyurethane has cured since cured polyurethane is usually water-resistant.
Related Read: How To Fix Yellow Polyurethane?
Overall, polyurethane is not meant to be sticky when dry. If the polyurethane turns sticky, there is something wrong either with the paint application or the environment.
As an expert tip, be sure to check your environment and remove moisture or dust before applying polyurethane. Also, always use a stain-blocking primer before applying polyurethane.