Spar Urethane vs Polyurethane: Difference – Pros – Cons

Spar Urethane vs Polyurethane

We all know that furniture has to be protected especially wooden ones and if you leave it outdoors to stay all the time. Since wood is a living being it is prone to gain issues due to weather changes, so we can say that it is mandatory to protect it completely.

The question is which protection you should choose. The most popular ones are polyurethane and spar urethane, but it is essential to understand the difference and advantages/disadvantages of both of them before you make up your mind.

We are here to present you ways to differentiate these two wood protection products:

What’s the Difference Between Spar Urethane and Polyurethane?

Polyurethane coatings became popular in the middle of the 20th century. They come in liquid form, and the main idea and reason for their applying are to protect the wooden surface.

Have in mind that main ingredients that it features are nitrogen-based chemical amalgams, vegetable oil, mineral spirits, and isocyanates.

Nitrogen is vital because it will help you protect the finish from chipping, while isocyanates will create additional thickness.

Polyurethane coating features a wide array of chemicals that are affecting the environment due to emissions. Of course, it will protect your furniture so that it can resist the damage especially when it comes to outdoor weather conditions.

But it will create discoloration, which means that wood will become darker as time goes by.

On the other hand spar urethane is different than polyurethane, and even though it features several compounds, there are more differences than similarities — for instance, polyurethane stains and chips with less effective when compared with spar alternative.

It is also a better choice that will stand up with substances such as alcohol. On the other hand, spar urethane is stronger of the two, and it will coat square feet per gallon, while polyurethane will stick with more problem on the surfaces.

Polyurethane finish features a few downsides because it cures, sets and rises more slowly than spar urethane that could dry in a matter of minutes.

Both finish types come with a spray application. However, brushing spar urethane is a hardworking job because it tends to harden faster, and will produce as result visible brush lines

Therefore, the surface or wall has to be completely even if you want to add spar urethane. On the other hand, polyurethane should be sprayed after you finish the surface.

It will produce more significant shine which is the main reason for its popularity.

Which Urethane Is Better To Use?

We cannot say which one is better for your specific needs and requirements because it depends on various factors. The type and nature of your project will dictate which is the best choice for you.

Have in mind that spar urethane tends to be more expensive than polyurethane and its quality is less consistent depending on the brand, of course.

Polyurethane, on the other hand, has a greater tendency to promote ultraviolet light so it will discolor your furniture.

Pros And Cons Of Using Spar Urethane

Spar Urethane

The first thing that you should know about spar urethane is that it features low levels of odor and toxicity. Therefore, it is the best choice for your requirements in case that you have allergy issues or if you want to protect the environment altogether.

At the same time choosing this particular type of wood finish, is great because you will gain a long lasting solution but you have to maintain the furniture properly to get all these capabilities.

You will be able to use it both inside and outside, which is another reason for its popularity because it can withstand any weather conditions.

The main disadvantage of this particular type of coating is that paint won’t be as durable as oil-based polyurethane. At the same time, colors won’t match with the wood in all times.

Have in mind that when it comes to extreme heat conditions, water-based urethane is not that efficient.

Pros And Cons Of Using Polyurethane


The advantages of using polyurethane are also essential to consider especially if you want to determine which type is the best for your specific needs. It is better when it comes to durability, high-quality finishes, and longevity.

It can withstand harsh conditions such as immersive heat or cold, and due to its waterproof features, you will be able to protect your furniture against weather damage.

The disadvantages of using oil-based polyurethane are the high amount of toxicity that it contains due to harmful chemicals that will require more time to dry than water based.

At the same time, the odor can cause you harm which means that you have to let it dry in a highly ventilated area.

Sometimes it can create air bubbles during the finish, so that could mess up the entire coating since the removing of polyurethane from wood can be time-consuming and tricky.


Even though these two urethanes are similar, both of them feature unique qualities and features that will make them perfect products for your specific needs.

Of course, everything depends on what you want to use and where are you placing the pieces of furniture you wish to protect.

In case that you have pets or children, and lack of area that features excellent ventilation, you should avoid using oil-based coating such as polyurethane and choose instead spar that will provide you less toxicity and odor altogether.

Water-based coatings are a friendlier option for DIY enthusiasts that do not have a well-ventilated workshop where they can leave it to dry.

However, in case that you have a proper workspace, using polyurethane will provide you results with higher quality for less time especially when it comes to the aesthetical perspective of your finish.

But still, you should be extra careful on how many fumes you are breathing and try to take a break between coating, or wear a mask that will reduce the number of fumes that you’re inhaling during the project.

We hope that you understood the difference between these two types of urethanes, and if you have additional questions, you can ask them by leaving a comment in the section below.


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