Polyurethane is one of the best wood protections available on the market. However, the application is quite challenging.
In this post, we are going to look at how long it takes polyurethane to dry and some of the ways to make it dry faster.
How long does polyurethane take to dry?
Normally the polyurethane will take 24 hours to dry and be ready for the next coat. This is however subject to a few factors, Key among them the room temperature. In cold seasons it may take longer while in summer slightly shorter.
The other significant factor is the type of polyurethane.
How long does polyurethane take to dry between coats?
It goes without saying that most projects require at least two coats of finish. It is not recommended to apply more than two applications in a single day. As a result, knowing how long it should take to apply a second coat is critical.
If you’re using water-based polyurethane, wait at least two hours before applying your second coat, and limit yourself to two coats each day. However, temperature and humidity will have a significant impact on the time spent waiting between coats. With a humidity level under 60%, the best temperature for the fastest drying time should be between 60 and 90 degrees Fahrenheit.
Drying time of different types of polyurethane
Different polyurethane will dry at different rates as can be seen in the table below. Also notice that there is a difference between drying time and curing time for polyurethane. the discrepancies between the two will be addressed.
|Type of poly||Drying time||Safe to place objects||Fully cured|
|Water-based brushed||6hrs||36hrs||20 days|
|Water-based sprayed||2hrs||36hrs||20 days|
|Oil-based brushed||24hrs||4 days||30 days|
|Oil-based sprayed||6hrs||4 days||30 days|
Polyurethane Curing Time vs Drying Time
Polyurethane drying time
Dried polyurethane is not cured polyurethane. Drying is when the external coating of polyurethane hardens. So, how can you tell when the polyurethane has dried? dry polyurethane is not tacky and does not appear wet.
This state, however, does not dictate that the surface is ready for use. Too much pressure and wrinkles can damage this finish. Therefore, do not put the surface under heavy use when it is just dry.
Polyurethane Curing time
Curing, on the other hand, is when the polyurethane has completely hardened. Here, the oils in the polyurethane have been completely exposed to oxygen and have undergone a complete chemical reaction and hence “cured”.
Cured polyurethane, therefore, is the final, hardened finish. This final condition then allows you to exert hard use on the surface. Curing is a long process that could take from a day to almost a month.
How to speed up the drying time for polyurethane
There are a few things that can be done to speed up the drying time of polyurethane. One of the easiest to identify as per our table above is the method of application.
1. Atomizing polyurethane to speed up drying time and application.
The mode of applying poly greatly affects the dying time of poly. Take oil-based poly for example, if applied using a spraying system the atomized poly dries faster than when applied with a brush.
If you would like to know how to get started on spraying poly check out our guide for the best spray guns for polyurethane.
While spraying poly is a great way of speeding up its drying time it’s a little expensive to set up and may not be convenient for a one-time finish job. Here are other affordable ways to speed up poly
2. Thinning polyurethane to make the coat lighter.
The thickness of polyurethane affects how first it will dry. Thining your poly with mineral spirits can make it dry faster.
However, this is done at the compromise of the protective ability. The more you thin your poly the less protective and the more coats you will need to build.
As a guide when thinning poly always remember that most wipe-on polyurethane is just thinned 50/50 with mineral spirits. Try to keep the mineral spirits lower for better protection. Below is a video on how to thin poly.
3. Brush evenly with consistent thickness
Maintaining a consistent thickness ensures that the surface dries evenly. Runs, sags, and bumps are notoriously known to cause slow drying and curing.
Brushing any of these imperfections not only helps your poly dry more evenly faster but also lessens the task of sanding to a smooth surface before the next coat.
4. Warm the workshop
Warming your workshop can also help the poly dry faster. You can use a heater but make sure that the rugs and mineral spirits are wrapped in a bag and away from the heater to avoid fire outbreaks.
A blower may also be used but make sure the workshop is dust free lest dust particles settle in the yet-to-dry poly.
Factors that affect the drying and curing times of polyurethane.
1. Type of polyurethane.
It is crucial to note that there are many other subcategories in every water-based and oil-based polyurethane category.
Also, some manufacturers might include drying agents. Some add oil and probably other solvents. Therefore every component could affect the dry and cure time slightly, or it could force you to adjust your entire approach. The bottom line, water-based polyurethane dries faster than oil-based polyurethane.
2. Type of wood.
Some woods emit chemicals that prevent polyurethane’s crosslinking process, making them not dry entirely. For example, some aromatic cedars and Rosewoods.
3. Temperature and humidity.
The temperature affects the drying time of poly where hotter temperatures favor first drying. low humidity will also boost the drying time. if planning to apply poly you could take advantage of the weather to get faster finish-drying times.
4. Other factors
Other factors that may affect how fast your poly dries includes the thickness of the coat, the method of applying the poly, and the size of the workpiece.
For big furniture, the drying time might be longer than let’s say a bowl. Therefore your newly polyurethane floor may take up to 24hrs to dry in favorable conditions. Where else in similar conditions it only takes 12 hrs for a sizeable woodcarving coated with poly to dry.
When applying poly on large surfaces like wooden floors or large dining tables it’s better to apply by spraying or roller. The faster you finish applying your piece the faster it will initiate the drying process therefore a small brush may cause you more downtime. Don’t just use any roller use a special polyurethane roller.
Why You Shouldn’t Apply Polyurethane in Cold Weather
In the winter, you may find yourself wanting to apply polyurethane to your deck or other outdoor projects, but doing so in cold weather can actually do more harm than good.
Here are two reasons why you shouldn’t apply polyurethane in cold weather, and one way to get around it if you still want to use it in the wintertime.
Applying polyurethane in cold weather
In general, you should avoid applying polyurethane sealants when temperatures are below 60 degrees. If you’ve ever attempted to use a poly finish in a cooler environment, you likely run into poly during and curing issues.
This is because colder temperatures cause polyurethanes to dry slower, which can create bumps and ridges. The solution? Increase your temperature by using a heat gun or hairdryer for about five minutes before starting your application.
Once it’s warmed up, you should be able to smooth out any problems with ease. Just don’t forget that those same problems will return once it cools down again! Air conditioning by heating up your workspace is also a solution. But if you are not in a hurry the best option is waiting to apply on a warmer day
Conclusions; How long does Poly take to dry and how to improve
Poly may take up to a day to dry to touch but almost a month to cure completely. There are a few ways you could speed up the drying time of poly.
It’s always good practice to apply poly in hot weather to avoid slow drying and curing problems caused by cold weather.