Polyurethane is generally considered to be the best in the market when it comes to wood finishing.
Whether this is flooring, furniture, or pretty much anything made with wood that needs a durable protecting finish.
Polyurethane is held in such a high regard because of how reliable, unbreakable, and sturdy it is, as well as the ease of accessibility it has.
However, when choosing to use polyurethane, there is a tricky question that needs to be asked; water based polyurethane or oil based polyurethane.
In spite of the fact that both of these finishes are labeled as polyurethane, there is a litany of differences that makes choosing between them a significant question to consider.
So read through this guide, so you can have the differences and distinctions clearly laid out, so you can make an informed decision.
What Are The Differences Between A Water Based And An Oil based Polyurethane Finish?
The best way to exemplify the difference between a water and an oil based polyurethane is to define both of them, so you can see what helps them stand apart from each other.
What Is A Water Based Polyurethane?
As you can guess from its name, a water based polyurethane will use water as the base that makes it up, this is the primary agent used in contrast to oil which, of course, is the primary agent for an oil based polyurethane.
It uses this water to hold the polyurethane solids which helps it do its job as a finish.
This is what gives water based polyurethane a milky appearance, but once it has dried it will look completely clear.
Historically a water based polyurethane would be seen as less durable than its oil based counterpart.
However, this has been proven untrue in the past decade with water based polyurethane manufacturers innovating the production process to make it just as durable as its oil based competition.
Because of this water based polyurethane has become a lot more popular in recent years and most professionals now use it because of its impressive durability.
While a water based polyurethane can be used on almost any woodwork masterpiece and will work well if applied properly, its most common use is for hardwood flooring.
A water based polyurethane is classified as wood raising, so it is recommended to apply subsequent coats if you want the smoothest finish possible.
This polyurethane has gained its popularity due to producing little odor, for its fast drying time, and for how easy it is to apply.
What Is An Oil Based Polyurethane?
In contrast to a water based polyurethane, oil based polyurethane will use mineral solvents or something similar like petroleum as a base for carrying polyurethane solids instead of water.
This is the original form of polyurethane and this is why it is preferred by a lot of more experienced woodworkers who are put off by how low quality water based polyurethane used to be.
Most oil based polyurethane appear to be a brown liquid that is noticeably thicker than water.
If you apply an oil based polyurethane correctly it will have an amber color once it has dried and this color will get darker over its lifetime.
If you look after the polyurethane it will only discolor gradually over the course of decades.
Being thicker than a water based polyurethane, oil based polyurethane is incredibly resistant to chemical and scratch damage which makes it a great choice for high-usage surfaces like countertops, tables and furniture.
Some woodworkers like it for how it enhances the natural appearance of a hardwood floor as well as its strong resistance to water damage as well as its versatility.
The Advantages And Disadvantages Of A Water Based Polyurethane
- It dries completely clear giving you the choice on if you want to tint it
- It is much easier to apply
- This polyurethane has a quick drying time
- It releases less VOCs and has a lesser odor when used
- This polyurethane is grain-rising which means it will require more than a single coat.
- Can be quite expensive depending on the quality
The Advantages And Disadvantages Of An Oil Based Polyurethane
- A lot of users are fans of the amber hue it creates on hardwood
- Incredibly durable
- Very resistant to scratches
- Does not require as many coats as a water based polyurethane
- Has a significantly noticeable smell when it is fresh
- Takes a much longer time to dry than water based polyurethane
So Which Is Better? Water Or Oil Based Polyurethane?
A lot of the descriptions so far have highlighted the positive qualities of each types of polyurethane and will have begun to give you an idea of which polyurethane is better in each area.
But to make the differences more apparent and to further emphasize which will be a better choice for you, we should go through how each polyurethane scores in each category of usefulness to see which comes out on top.
This process would be significantly quicker if we just had one single style of polyurethane, but there is of course a reason that water based polyurethane was developed as an alternative to the original oil based polyurethane.
So keep reading if you want to know all the details that separate these two wood finishes, so you can learn which will work best for what you need it for!
Water Against Oil - Color?
One of the most instantly noticeable differences between these different types of polyurethane is the color they are.
Water based polyurethane usually looks to be a milky white color while it is still in the can.
But once you begin to apply and thin it out the appearance will turn completely clear especially as it begins to dry.
On most wood bases the color will appear to be like a very pale maple unless of course on a white wood.
If it is on white paint it will have a slightly yellow hue, but it is not very noticeable but is worth considering.
Oil based polyurethane on the other hand is a distinctly brown color that once applied will give the surface it is on a noticeable darker shade and will dry to give a strong amber hue on hardwood.
This is seen as a positive by most users as it adds life and energy to more dull wood colors, however it is going to age over the years and begin to look darker and darker.
This sometimes comes as a surprise to amateurs so make sure you will be happy if it turns darker or will be willing to reapply.
So while both types of finish usually advertise as drying clear, this is usually only completely true for water based polyurethane.
Using a water based polyurethane with its less noticeable tone will also make it easier to add a tint if that is the level of control you want.
But are you looking for the natural coloring of an oil based polyurethane that will age after a while but can add a great highlight to your flooring.
Or do you prefer having almost complete control with a water based polyurethane that at default will dry crystal clear.
No polyurethane really wins in this category it is simply a matter of preference.
Water Against Oil - Durability?
This category has a clear champion, being the original oil based polyurethane that has been used for decades that have been developed to be as durable as possible.
While water based polyurethane used to be significantly worse than oil based in terms of durability, it is now at least not terrible in comparison.
So while there is still a stereotype that water based polyurethane will never be able to compare to the durability of oil based, manufacturers have been disproving this for years now.
Some much older water based polyurethane will only have a lifespan of about 6 or 7 years, but now they can last up to around 10 years.
On top of this they continue to get more and more resistant to scratching, as well as water and heat damage resistant.
However, oil based polyurethane is leagues more resistant to chemical damage with a lot of water based polyurethane becoming discolored if it comes into contact with some chemicals.
This could even be something as simple as pet urine. It will not damage the floor underneath it, but it can be an ugly result.
Sometimes it will revert to its natural appearance after a short period of time, but this is by no means guaranteed.
If you know that your finished surfaces will be having their durability tested regularly, oil based is the way to go.
Water Against Oil - Ease Of Application?
While the quality of final results is important, if you are not able to apply it easily and get good results there is no point.
This is why how easy a product is to apply is a significant factor worth considering.
When it comes to applying a water based polyurethane the best tool to use would be a simple synthetic bristled paintbrush, but if you are doing it on a floor, a roller will likely be more effective and efficient.
For an oil based polyurethane, it is preferable to use a natural bristled brush as it will be much more compatible with the oil based substance.
The animal hair they are made with will do better at holding the thicker texture instead of thinner synthetic bristles.
There are many other methods of application that can work based on oil based polyurethane like a spray method, using a lamb's wool applicator, a roller, and even aerosol.
You can also use the unique wipe-on method.
Oil based polyurethane has a much wider variety of methods of application, and you do not have to worry about it bubbling up easily.
While water based polyurethane is not super tricky to apply, oil based will give you a significantly higher number of choices.
Water Against Oil - How Many Coats Needed?
Just because oil based polyurethane can be applied with a wider variety of tool does not necessarily imply that it is easier to apply.
This is because we need to factor in the other aspects of applying a polyurethane finish.
One of these main factors is the number of coats that are needed for a satisfactory result.
With water based polyurethane being lighter and generally easier to spread, it also has the downside of needing a few more layers to get a proper protective layer.
However, this also means that you do not need to sand your polyurethane between coats.
As previously mentioned though, water based polyurethane will raise the wood grain and if this happens, you may need to sand between coats to smooth the layers.
This might require even more layers depending on how intense the effect is.
Since oil based polyurethane is so thick you will usually only need about 3 coats to get a satisfactory layer of protection.
Unfortunately between each of these layers you will need to sand the layers to discard any streaks, nibs, lint, or bubbles.
However, having this abrasive sanded layer will help your polyurethane layers adhere to each other easier.
Water Against Oil - How Long Does It Take To Dry?
This is quite a dependent category this is because while oil layers will take longer to dry, you will need fewer layers to get a satisfactory result.
However, because the drying time for water based polyurethane is so quick, you will need to do a massive amount of water based layers to have to even consider oil based polyurethane catching up with drying time.
While using polyurethane and getting a good amount of protection will take days to complete, using oil based can turn these days into weeks if you are not diligent.
If time is of the essence for you, water based is definitely the choice to make.
Water Against Oil - How Skilled Do You Have To Be To Use?
Considering the skill level needed is very important when choosing polyurethane, but unfortunately it is not an easy question to answer.
A factor that can make water based polyurethane harder to work with is because of the quick drying time, it can be quite difficult to spot mistakes before they have dried and become permanent.
However, some people disagree and think that oil based can be a lot more troublesome for how bothersome dust nibs can be, but they can at least be easily removed through sanding.
If you have become proficient and skilled in using polyurethane as a wood finish, you will likely prefer a water based polyurethane for how quickly it can get the job done, but to get to this skill point can take a considerable amount of effort.
For example, if you are not great at covering brush streaks, they can sometimes dry into a water based polyurethane and become permanent, but the more skilled you become, the less bothersome this factor is.
So while both methods have drawbacks, oil based is slightly easier to work with.
Water Against Oil - How Easy Is It To Clean?
A water based polyurethane is significantly easier to clean than an oil based polyurethane as all it needs to be cleaned is dish soap with water.
Sometimes it is possible to wash off your applicators just using water, but it is usually recommended to do more than this.
Soap will make sure that the stain is definitely off of your applicator just to ensure that there will be no excess.
Oil based polyurethane on the other hand is significantly harder to clean needing a lot of other products to clean up like mineral spirits, turpentine, as well as the standard water and dish soap to get rid of any traces.
This can be a very time-consuming process and if not done properly can permanently damage your tools.
This is another reason why professionals prefer working with water based as it almost always wins when it comes to saving time.
Water Against Oil - Toxicity?
This aspect is incredibly important but often completely overlooked.
The toxicity can cause a lot of problems if not properly considered so here we will assess the issues with toxicity in both water and oil based polyurethane.
The oil based alternative is more likely to contain a significant chemical content and the more chemicals it contains the more VOCs (volatile organic compounds) the polyurethane will release.
These VOCs are why air quality continues to decrease in recent years and this is part of the reason water based polyurethane gained so much traction as manufacturers were forced into making more of them as an alternative to the standard.
VOCs are also very unpopular as they are a carcinogenic and can lead to a significant number of illnesses and conditions like respiratory issues and can be particularly harmful to pets and children.
A lot of governments are aiming to limit the accessibility of products like oil based stains that release excessive VOCs which is why they are becoming less and less popular.
The VOCs in oil based polyurethane also releases a strong odor which is why respirators are needed when it is being applied.
This level of toxicity to people also spreads to the environment. Luckily once the polyurethane dries it no longer releases VOCs.
Oil based polyurethanes also contain more isocyanates which can also be significantly harmful.
There are some alternatives that have fewer isocyanates and therefore less VOCs , but these are not massively accessible yet.
Because of this water based polyurethanes are considered to be safer to work with.
So after looking at all these factors of varying levels of importance, which do you think is a better product overall?
Conclusion - Which Is Better? Water Or Oil Based Polyurethane
As you can tell from the large variety of factors that have been discussed, the preference between a water based or oil based polyurethane does not have a simple answer.
As it is with a lot of complex preferences, you will have to consider the projects which you will be working on and which polyurethane will be more fit for purpose.
Key considerations which should be made are the size you are finishing, the wood type, the time frame you are working with and the look you want after completion.
Let’s go through the two polyurethane types one last time to assess which works best in which situations.
Water Based Polyurethane Results
With the speed at which this polyurethane dries it is the better choice for large scale projects which you do not want to spend ages waiting for a finish to finally dry.
It will cost a little extra than oil based polyurethane, but it is also more accessible with how oil based polyurethanes are being produced and manufactured less and less.
However, if you have access to oil based, and you are not confident in your skill level, this fast dry time may be more of a disadvantage for your project.
But if you are looking to retain the original color of your hardwood, then water based is definitely a great choice as it will hardly change the appearance, especially in contrast to the drastic changes of an oil based finish.
Oil Based Polyurethane Results
This polyurethane was the top choice for the majority of recent history, but slowly its usefulness has been matched and overtaken by water based.
However, it still has a good variety of uses.
This product still remains the more durable choice and will need fewer coats to achieve this (however this is hardly a time saving feature with the increased drying time).
With how the color adds depth to the wood’s color it has a more distinct appearance, but this is not great if you want more customization.
This polyurethane is also a better budget choice but is getting harder to get your hands on.
However, you will need to be careful with the negative effects of the VOCs it inevitably produces.
Frequently Asked Questions
Which Type Of Polyurethane Is More Durable?
While it used to be that oil based polyurethane was leagues more durable than water based, they are now almost equal.
Both polyurethanes can last up to a decade with proper care, but over this time oil based will discolor while water based will not.
Oil based is slightly more scratch resistant and much more chemical resistant, however.
Can You Put A Water Based Polyurethane Over An Oil Based Polyurethane Stain?
Yes this is definitely possible. But it is recommended against doing this if the polyurethane underneath is old and peeling as the water polyurethane on top of it will then just have a very weak foundation.
Is Water Based Polyurethane Good?
Yes, it is now. It used to be a much lower quality than oil based because of its development starting decades later, but now it has had time to catch up it has many advantages over its predecessor.
It can last for years and is one of the best choices for hardwood floors.
Furthermore, it is much faster to apply making the job of polyurethane application much simpler for a water based user, and it also released far fewer VOCs which have a strong smell as well as being harmful to humans, pets, and the environment.
How Many Coats Of Polyurethane Are Needed For Good Results?
At least 3 coats will be needed for either type, but a water based will need maybe around 5 or 7 which will not be a difficult task with the speedier drying time.
Just keep in mind the amount of traffic the surface will be facing.
Should I Sand Between Layers Of Polyurethane?
You will need to do this for oil based polyurethane as it can very quickly get dust nibs and bubbles drying into it which should not have another layer of polyurethane above them.
The good time of this is a sanded polyurethane will be a great surface for the next layer to adhere to.
Can You Thin Polyurethane?
Yes, this will make brush marks less noticeable and make it level faster, but doing this to an already thin water based polyurethane could have bad results like effecting the durability.
How Long Should Polyurethane Take To Dry?
Water based takes about 4 or 6 hours while oil based will take 12 or up to 24.
Is Polyurethane Toxic To Humans?
Yes, especially oil based polyurethane, make sure to wear all the recommended protective equipment while applying and work in a well ventilated space!