What Is the Difference Between Spar Varnish and Spar Urethane?

Spar varnish and spar urethane are two popular wood finishes used for outdoor projects and marine applications. Understanding the differences between these two products is important when it comes to choosing the right finish for your project.

Spar Varnish

Spar varnish is a traditional wood finish that has been used for hundreds of years. It is made from a combination of natural resins, oils, and solvents. The ingredients are carefully selected to provide a durable, water-resistant finish that can withstand harsh weather conditions and UV rays.

Spar varnish is commonly used for outdoor furniture, decks, and boats. It provides a high-gloss finish that gives wood a warm, rich appearance. The natural ingredients used in spar varnish also help to protect the wood from drying out and cracking.

One of the key benefits of spar varnish is its ability to “breathe”. This means that the finish allows air and moisture to circulate freely, helping to prevent the wood from warping or splitting. However, this also means that spar varnish may need to be reapplied more frequently than other finishes, such as spar urethane.

Spar Urethane

Spar urethane is a modern wood finish that is made from synthetic resins and solvents. Unlike spar varnish,

it provides a much more durable and long-lasting finish, thanks to its high resistance to UV rays, water, and other environmental elements.

Spar urethane is commonly used for marine applications, as well as for outdoor furniture and decks. Unlike spar varnish, it provides a low-gloss finish that can range from satin to semi-gloss, giving wood a more natural appearance.

One of the key benefits of spar urethane is its long-lasting protection. This finish can last for several years without cracking, peeling, or fading, making it a popular choice for outdoor projects.

Differences between Spar Varnish and Spar Urethane:

Spar Varnish Vs Spar Urethane

While both spar varnish and spar urethane provide a protective finish for outdoor wood, there are several key differences between these two products.


When it comes to durability, spar urethane is the clear winner. This synthetic finish provides much better protection against UV rays, water, and other environmental elements, making it a more suitable choice for marine and outdoor applications.

UV Resistance

Spar urethane is highly resistant to UV rays, which can cause wood to fade or discolor over time. On the other hand, spar varnish provides less protection against UV rays, which can result in fading and discoloration.


Spar varnish is more flexible than spar urethane, which means that it is less likely to crack or peel when exposed to temperature changes or humidity fluctuations.


Spar varnish provides a high-gloss finish that gives wood a warm, rich appearance. Spar urethane, on the other hand, provides a low-gloss finish that ranges from satin to semi-gloss, giving wood a more natural appearance.


In terms of cost, spar varnish is usually less expensive than spar urethane. However, this difference in cost should be weighed against the longer-lasting protection and durability provided by spar urethane.


In conclusion, when it comes to choosing between spar varnish and spar urethane, it is important to consider the specific needs of your project. For projects that require long-lasting protection and durability, such as marine applications, spar urethane is the better choice. For projects that require a more flexible finish with a high-gloss appearance, such as outdoor furniture, spar varnish is a suitable option.

No matter which finish you choose, be sure to follow the manufacturer’s instructions carefully and take the time to prepare the wood surface properly before applying the finish. By doing so, you can ensure that your wood will be protected and look great for years to come.