Have you ever started a project only to realize that you’ve massively underestimated how long it would actually take to do?
This can be a real issue, if you are a professional then it can taint your reputation, and if you’re doing the job yourself you may find yourself caught in unpleasant weather or stuck in the middle of a job when you need to pick up the kids or make tea. Either way, it’s inconvenient and annoying.
So before you start any job, planning and preparation are key. This is no exception for any wood projects. Especially those involving polyurethane. So how long does polyurethane take to dry?
I think the first important thing to distinguish here is that drying and curing times are not the same thing. These can often get mistaken. Polyurethane will dry in anywhere between two to twenty-four hours. It will take around a month for it to cure.
Now, you may also be thinking that twenty-two hours is a large gap. What could possibly make the difference that some polyurethane dries in just 120 minutes but others take almost a full day? Well, it all depends on what kind of base your polyurethane has.
An oil base will usually need an average of eight hours to dry, whereas water-based it will be a lot closer to two hours.
Drying Vs Curing Time
Since there can be some confusion over drying and curing time, I thought I’d take the time to distinguish the difference between the two. Drying time refers to how long it takes before you can use another coat.
Curing time is how long until the wooden surface is actually ready for use.
If you’re wanting to start your second coat of polyurethane, you want to wait for it to stop being sticky and tacky. Once this has gone and it is dry to the touch, you can carry on.
When you’ve finished and the final coat has dried, you should try to avoid contact with the wood and not place anything heavy on it as it isn’t strong enough to support all the pressure.
Keep all liquids away from the wood to avoid them seeping through and ruining all your hard work. Think of the wood as ultra-sensitive until the polyurethane has cured.
So as we have previously discussed, different bases create different dry times. We will look into these further now.
Water-based polyurethane can dry as quickly as just one hour and usually after about three days, the surface becomes usable. Keep in mind though, that it will take around twenty-one days for the polyurethane to cure completely so you should still be careful during this time period.
Oil-based polyurethane usually takes about four hours to dry if you have a fast-drying formula. If you don’t you’re looking more at anywhere between one to two days for it to dry fully. Curing takes closer to thirty days with an oil base but is usually usable after around four days.
How Long Does It Take For Polyurethane To Dry On Different Surfaces?
Another thing to consider is that depending on what surface you are using polyurethane on, the dry time will chance. A lot of people don’t actually even realise this as most manufacureurs don’t even indicate it on their packaging.
It’s safe to say that most drying times on the packaging will be referring to a flat open surface – which will dry easily. Most furniture however, has curves, holes, carvings, and a variety of different shapes and patterns.
All of the above is going to effect how it dries, especially because the polyurethane can collect in these holes and create a thicker coating which will dry slower.
Then you also have to consider that a flat surface is going to have a fairly even airflow. If you’re using polyurethane on a chair for example, the airflow on the underside of the chair is not going to be the exact same as the top, or the legs, for example.
This will cause certain areas to dry quicker than others.
Hardwood floors are a lot flatter and so you’re likely to get fairly even coats which will dry a lot quicker.
Also since most hardwood floors are inside, a lot of the elements that can negatively impact the drying time can be either completely eliminated, or at the very least controlled. This means that it will dry fairly quickly.
Factors That Affect Polyurethane Drying/ How To Dry Quicker
There are a few different factors that will change how quickly polyurethane dries. We have already spoken about the base of your polyurethane, but lets look at a few other important factors.
Temperature And Humidity
It’s almost so obvious that it gets completely forgotten about, but of course the temperature or weather will influence the time it takes to dry.
The optimal temperature is around 70-77 degrees fahrenheit. Any lower than this and you may be adding a few extra hours, or depending on how much lower even a couple extra days.
So you’re going to want to keep an eye on the forecast to see when is best for you to pick a few days when the temperature is just right.
You may think that the hotter the day, the better for application but this is not always true. If it’s too hot it will dry too quickly and crack the outer surface.
This is actually worse than if you do it in the colder temperatures, because at least those just need a little extra time to fix. You’ll need to start over it starts cracking.
The humidity is also another factor to consider when checking the forecast as this also effects the drying time of polyurethane. You want about 50% humidity if you’re used a water-based product where as if you opt for the oil-based you’ll want about 70% humidity.
If it is too humid it will take the polyurethane to dry. Obviously you can’t really control the humidity and if youre doing projects in the summer it can seem a little impossible to plan around it.
In this instance, you’ll need to try and control the indoor humidity. You can do this sumind a humidifier, dehumidifier, or HVAC system.
When applying polyurethane you don’t really want the wood to get covered in dust or other substances, so it can be recommended that you keep your windows closed while coating the wood.
While this is true, the reality of it is that the polyurethanes that you’re about to use have really, really strong smells. This is especially true with oil-based polyurethanes. If you keep your windows closed, it’s going to smell the house out for a really long time. So personally I’d sacrifice the small amount of dust and pop the window open anyway.
Polyurethane does need good ventilation to dry quickly too. You are running the risk with the dust but you can always sand the coat down and reapply if this does happen too severely.
A fan is a great option for boosting extra ventilation and dispersing the odor.
When applying layers of polyurethanes I would always advise to use small thin coats, these will dry not only quicker but more evenly too. And you can always add more if you need it. Taking it back isn’t quite as easy.
If you coat the wood too thick, it’s going to take a really long time to dry, but do not try to speed the process along with the likes of a hairdryer as you’ll just damage your inner coat.
How You Apply Polyurethanes
Polyurethanes can be applied in a couple of different ways. You can wipe it, spray it or brush it on to wood.
Spray-on and wipe-on polyurethanes tend to dry fairly fast. They’ll dry quicker than if you use a roller or a brush. This is because you’ll unintentionally spead a much thinker layer if youre using a brush.
Polyurethane will dry a lot quicker on raw wood than it will on wood that already has a finish on it. Also, if you use water-based polyurethane over an oil-based finish it’s going to take a lot longer to dry, this works the other way around too.
If you have applied a finish, you’ll need to wait for it to cure too or the polyurethane will take twice as long to dry.
You’ll usually be able to tell when an oil-based polyurethane has dried because it will no longer smell. You’ll also notice that the sticky, tacky surface is dry. If your polyurethane is water-based, you’ll know its dried once the surface is no longer cold.
Once your polyurethane is dry you are able to begin your second coat.
So to save time, I would always recommend using raw wood. If you want to save yourself a little extra time again, you can always sand down the wood that your using.
When you decide to buy polyurethane you can get four different types of sheen; matte, satin, semi-gloss, or gloss.
Both semi-gloss and gloss will take longer to dry than a matte or satin sheen. However the margins of time are that small that I wouldn’t particularly let it make a major factor in your decision of which to use.
Formula Of The Finish
The most vital factor that will decide just how long your drying and curing process will take is the specific product that you choose to use.
If you purchase a fast-drying oil variant, it will dry considerably faster than regular oil-based finishes. You can also get fast-drying water-based options too and these will also cut the time it takes to dry and cure.
Frequently Asked Questions
Can You Speed Up Polyurethane Drying Time?
There are ways that you can speed up the drying time, but you want to use natural techniques such as creating extra ventilation or applying thinner coats. Adding heat through appliances such as hair-dryers can make the first layer cake and it can ruin the coat so I wouldn’t advise this.
Is 2 Coars Of Polyurethane Enough?
It depends on your purpose of the polyurethane to be honest. Two coats will protect your wood from contaminations and from moisture. Two coats isn’t likely to protect the wood from water damage though. For this you’ll need around four coats.
Can You Sleep In The House After Polyurethane?
I wouldn’t recommend it. Polyurethane can off-gass heavily for the first twenty four hours – even for the water-based kind. If you’ve used an oil-based type, this is even worse as it is highly toxic and can cause several health problems.
What Happens If You Recoat Polyurethane Too Soon?
If you do recoat too early you can end up with something called recoat lift where the underneath layer begins to wrinkle and lift off. If you have done this, don’t panic, all it means is that your going to have to start from scratch with the previous layer. It wont cause any major problems, its just a fairly annoying and time consuming fix.
Is It Safe To Use Polyurethane Indoors?
Most exterior polyurethanes can be used indoors fine, but I would always check the label. One thing I wouldn’t do though, is use interior polyurethanes outdoors. Because they are not designed for outdoors they don’t have the additives that are needed to protect the exterior finishes from UV rays.
How Long Until The Polyurethane Smell Goes Away?
The toxic smell of polyurethane usually takes around five to seven days to really start to decrease. You’ll also notice that the odor lingers slightly. This can happen for around three weeks or so in water-based products and around four to five weeks in oil-based products.
Is Polyurethane Flammable When Dry?
While dried polyurethane can be flammable, it is nowhere near as flammable as it is in its liquid state. When polyurethane dries the chemicals and solvents that make it highly flammable evaporate making a lot less lethal. The real trouble arrises in the liquid form because of its organic and chemical composition which is indeed highly flammable. When using polyurethane be sure to keep flames away from your workspace.
How Long Does Polyurethane Last On Wood?
Gloss oil-based varnishes can last ten to twenty years if looked after properly, so they can be worth the hassle it takes to fully coat the wood. Satin finishes probably wont last quite as long as the pigmentation and flattening agents tend to diable the driers.
Water-based coatings and paints will last around three to five years too.
Which Looks Better Oil-Based or Water-Based?
I suppose this can really come down to personal preference, but I believe that although it takes a bit longer to dry, oil-based polyurethane looks better to its deeper color and shine. Water-based polyurethanes tend to be a little duller.
So, it is quite clear that the question ‘how long does polyurethane take to dry?’ doesn’t have a one size fits all answer. There are loads of different variables that can change the exact answer, but as a general rule you’re looking at a minimum of a couple hours and a maximum of a day or two.
I would always advise to try and leave a minimum of at least 24-hours before the floor is subjected to footfall. More so because there really isn’t anything more heartbreaking than thinking you’re finally done, just to ruin it by trying to move on too quickly.
zThe last thing you want is for all of your hard work to go to waste and to have to start over.
One thing I would say is that due to all the contributing factors, if you’re planning on using polyurethane, plan it in advance. Check the weather to make sure the temperature and humidity is right for example. The more prepared you are, the better and quicker the job will be done.
Also, it is really important that throughout your time coating with polyurethane that you use the proper protective equipment to ensure that you do not come into contact with it. You do not want it anywhere near your mouth or eyes.