How Long Does Polyurethane Take to Dry?

If you are a woodworking enthusiast or a professional, it’s likely that you are going to use a polyurethane at some point. It could be on the table top or wooden floor. Fast-drying finishes like water-based polyurethane help, especially on short timelines. So, how long does polyurethane take to dry? If that’s the finish, you are using.

Well, an oil-based polyurethane requires 24 hours to dry while its water-based counterpart needs 6 hours to dry to touch or slight traffic that allows you to go ahead with the subsequent finishing processes like sanding.

Even so, it should be clear that there is a big difference between the drying time of polyurethane and the curing time; usually, it can take up to a month for it to cure depending on the prevailing weather conditions.

How do You Know if Polyurethane is Dry?

Much as there are several ways to tell whether a finished surface has dried, it’s quite straight and simple for the polyurethane.

An oil-based polyurethane, for example, is dry when you realize that it does not emit any odor and is not tacky. As for the water-based polyurethane, you will know it has dried when you touch it, and it does not feel cold, and you will notice some powder upon slight sanding.

How do You Make Polyurethane Dry Faster?

One of the simplest ways to speed up the drying time of your polyurethane finish is by applying very thin layers. Thin layers of any finish not necessarily polyurethane has a chance of drying faster compared to heavy coats.

Alternatively, if you have applied your polyurethane finish and you notice that it is taking longer to dry, then you can apply heat to it by the use of a blow dryer.

Note: You must map out how you want to go about your projects by predetermining things such as the number of coats that you need for your polyurethane application.

The Drying Time of an Oil Based Polyurethane 

Generally, the oil-based polyurethane products take a longer duration to dry compared to their water-based counterparts.

• For this type of polyurethane, you need to allow it up to 24 hours to dry following the application.
• After about 24-48 hours, you can step over the surface of the polyurethane finish but with your socks on. In this time, ensure that you don’t put on shoes or even walk on the surface with barefoot. It is also crucial that you keep your pets away from your working area. It is during this time that you can do subsequent finishing processes like sanding and addition of another finish if you desire.
• After 48 hours period, it’s safe to walk on the surface with your shoes on without inflicting any damages to the finish.
• After about for days, you can start moving back your furniture into the room in case the application of the polyurethane finish was on the floor.
• Do not allow your pets back into the room for at least another 2 weeks or so. It will let the finish to dry properly. That way, you will be limiting potential damages that may prove costly in the long run.
• It will take the finish up to 30 days to cure properly. After that time, you can start getting back all the coverings like rugs into the room.

The Drying Time of Water-Based Polyurethane

The water-based polyurethanes are the first drying ones.

• After just 6 hours following the application, you can walk on the finished surface. In this time, the floor should appear dry and not tacky at all. You should remember to have your socks on and not barefoot while walking over the surface.
• It is at this point that you can consider subsequent processes like sanding as well as the addition of a topcoat.
• After 24 hours, you can freely walk on the surface wearing your shoes
• 2 more days are enough until you can start getting back your furniture indoors
• Do not allow your pets into the room for at least another one week
• In 30 days, you can cover the floor with rags, etc.

The Difference Between Drying Time And Curing Time of Polyurethane

Most people confuse between drying and curing time of a wood finish like polyurethane. If you apply such a finish to your wooden floor, two phases are involved in the process. Drying is the duration allowed between two coats while curing is the duration after which your surface becomes ready for the use. 

The Drying of Polyurethane Finish

Drying is the very first phase towards your finish getting ready for use. Once you have applied your polyurethane finish on the floor of your room, for example, the solvent dries leaving the resin as the material that forms the protective layer which offers your wood the much-needed protection. 

The solvent that dries during the drying process could be water or oils that are available on different types of polyurethane finishes like the tung, linseed, and walnut oils. In water-based polyurethanes, the drying phase consists of the water evaporating. Water dries faster than oils that explain why water-based polyurethanes dry faster than the oil-based polyurethane.

The Curing of Polyurethane Finish

Curing is the next phase that follows the drying phase. During this time, your polyurethane finish starts to be hard with a plastic-like layer that will offer protection to your floor for several years to come.

As soon as the solvent present on the type of polyurethane that you have used dries out, the poly resin starts to react with the oxygen that is present in the air. During the reaction, the oxygen crosslinks with the polymer molecules to form a tri-dimensional matrix of the resin.  

Crosslinking refers to the process in which the molecular bonds are forged linking two polymer chains in one place. In our case, during the curing process, the polyurethane takes the role of a polymer molecule while oxygen takes the role of the molecule that forms the crosslink. If you apply many coats, the resins present in each coat will be crosslinked afterward, each layer will be crosslinked again. This sequence will form a single matrix that translates into a large molecule of the size of the room’s coating, which offers protection to the floor. Usually, this kind of reaction is slow, which is why we recommend that you give your finish up to one month to cure entirely.

How to Apply Polyurethane to Floor With No Bubbles

Adding a polyurethane finish to a wooden floor protects the surface from scratches, spills, foot traffic, and above all offers depth to the color of the wood. One thing that can ruin your entire is the formation of the bubbles in your finish which is usually a result of the agitation, faster application of the formula, and a thick finish. You might be new to finishing wood with polyurethane, but that should not worry you as it is possible to achieve a smooth surface with no bubbles.

Here are some of the steps that you need to follow to end up with a flawless polyurethane finish on your wooden floor:

Step One: Use mineral spirits to clean the surface of the floor to which you intend to apply the polyurethane. A rag alongside the mineral spirit would help in the removal of dust particles and debris.

Step Two: Stir your polyurethane to ensure that it mixes properly before proceeding to the next step.

Step Three: Pour the properly stirred polyurethane formula into a paint tray.

Step Four: Roll a synthetic paint roller inside the polyurethane formula so that it saturates with the finish.

Step Five: Start the application of your formula at the farthest point from the entrance of your room. Work swiftly from an end to the other, during this time, ensure that you apply thin and even polyurethane coats. You need to work back and forth while maintaining a wet edge. 

Do not overwork a similar spot as this will help minimize the chances of bubbling of the finish. Do this until you are sure that the entire floor has a polyurethane finish. Allow the finish some time to dry, 6 hours for water-based and 24 hours for oil-based polyurethane, afterwards; you can continue with the subsequent procedure.

Step Six: Use 220-grit sandpaper to sand the surface with the finish slightly but adequately. Sanding will help in smoothing out any possible bubbles as well as imperfections on the surface of the finish. Use 320- or 400-grit sandpaper for minor imperfections. 

Note: Sand in the direction of the wood grain

Step Seven: Dip a piece of rag or cotton cloth into the mineral spirit and use it to wipe the floor, cleaning all dust in the process.

Step Eight:

Mix the mineral spirit and polyurethane in the ratio of 1:10 respectively and stir. It will help in the thining of the polyurethane giving the bubbles enough time to pop and disappear. 

Step Nine: Apply the second layer of the poly allow it to dry. Follow the same procedure as in the first case. Do the third coat and don’t sand this time. The final coat would need 24 hours drying time before you can walk over it, allow it up to 72 hours after which you can start getting back your furniture into the room.

Note:

• Wipe spillage on the surface using mineral spirit as soon as it happens
• Work in a well-ventilated room by opening windows

Factors That Influences The Drying and Curing Time of Polyurethane

Different types of polyurethane formulas have different dry and curing time with the oil-based taking longer than their water-based counterparts to dry and cure. Even so, other factors will determine how fast your polyurethane fine takes to dry. These factors include:

• The Type of Wood

There are wood types that will take a little longer to dry when you apply polyurethane finish over them. Mostly, it is due to the chemicals present inside such woods because they make it hard for crosslinking to occur. Such wood types include a variety of aromatic cedar as well as the Rosewoods. 

• The Type of Polyurethane

We have spoken about this factor almost at every point in this article. Well, it doesn’t break any bone if we state it hear again. We have said before that oil-based polyurethane takes a longer time to dry compared to the water-based ones. For oil-based polyurethane formula, it takes roughly 24 hours for it to dry to touch. The water-based polyurethane, on the other hand, will take only 6 hours before it is ready for a second layer or sanding.

• Temperature and Humidity 

The drying and curing time of different polyurethane formulas that we have stated above are measure at the standard temperature of 70°F (21°C) and humidity levels of 70%. On a day where the temperatures are hotter and the air drier than these standard conditions, your polyurethane finish will dry even faster. The reverse happens for colder and more humid atmospheric conditions.

• Starting Surface

A raw and properly sanded wood surface quickly absorbs the first layer of the poly finish, making the dry time to be short. 

Safety Precaution Involving Polyurethane

Is polyurethane toxic? In most cases, you will find that polyurethane contains some toxins within its compounds. In such a case, we have put done some safety measures that you need to observe to avoid any chances of contamination or adverse health effects.

• You will notice that when the polyurethane finish is drying, it’s likely to emit some odor, these smells could contain Volatile Organic Compounds that might cause respiratory complications to the users. Water-based polyurethane has typically no odor; however, you still need to stay keen while handling these formulas. As soon as the finish cures completely, it becomes safe for human usage.
• If you can, ensure that you have minimal exposure to polyurethane products. The best thing that you can do during the application is to ensure that the room has proper ventilation.
• Oil-based polyurethane is highly flammable in its wet form. As it dries, this product emits some flammable fumes that can easily combust if they come into contact with a fire source. Therefore, try and keep fire sources around your working area. Also, avoid smoking during the application of polyurethane.

Conclusion

How long does polyurethane take to dry? 

We have come across this question multiple times which is why we would love to have it answered once and for all. Different polyurethane formulas have a varying dry time. For oil-based polyurethane, it takes 24 hours to dry. The water-based poly, on the other hand, requires just about 6 hours to dry to touch. Remember that these drying times are measured at a standard temperature and humidity of 21 degrees Celsius and 70% humidity.