Spar Varnish vs. Spar Urethane: What's the Difference?
By Harlon Moss & Janet White || Published on July 22, 2024
Spar varnish, traditionally made from natural resins, offers flexibility and UV protection for outdoor wood, while spar urethane, a synthetic product, provides enhanced durability and resistance to weather, UV light, and chemicals.
Key Differences
Spar varnish, originating from the shipbuilding industry, is formulated to protect wood in harsh marine environments. It is made from natural oils and resins, allowing it to expand and contract with the wood without cracking. This flexibility makes it ideal for surfaces exposed to moisture and temperature changes. On the other hand, spar urethane, a more modern invention, combines the protective qualities of traditional varnish with the added benefits of polyurethane, including better resistance to UV light, chemicals, and abrasions. Its synthetic base offers a tougher finish and can be either water-based or oil-based.
The application of spar varnish typically involves more layers and longer drying times, due to its natural composition. It imparts a warm, classic finish that enhances the wood's natural beauty. Spar urethane, however, is easier to apply, dries faster, and is available in various sheens, from matte to high gloss. This makes it a convenient choice for both DIY enthusiasts and professionals seeking efficiency without compromising on protection.
In terms of maintenance, spar varnish may require more frequent reapplication or touch-ups, especially in extremely harsh conditions, to maintain its protective properties and aesthetic appeal. Spar urethane's synthetic formula means it generally lasts longer before needing reapplication, making it a low-maintenance option for outdoor furniture, doors, and trim.
Environmental considerations also differ between the two finishes. Spar varnish, being derived from natural resins and oils, can be more environmentally friendly but may release more volatile organic compounds (VOCs) during application. Spar urethane formulas, especially the water-based versions, tend to emit fewer VOCs, making them a better choice for those concerned about indoor air quality and environmental impact.
While both products are designed for exterior use, the choice between spar varnish and spar urethane depends on the specific requirements of the project, including desired finish, durability needs, maintenance willingness, and environmental considerations.
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Comparison Chart
Base
Natural oils and resins
Synthetic, polyurethane-based
Durability
Good, with flexibility for wood movement
Excellent, with superior resistance to UV, chemicals, and abrasions
Application
More layers, longer drying times
Easier application, faster drying times
Finish
Warm, enhances wood's natural beauty
Available in various sheens, from matte to gloss
Maintenance
May require frequent reapplication
Generally longer-lasting, low maintenance
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Environmental Impact
Higher VOCs, more natural
Lower VOCs, especially water-based formulas
Ideal Use
Marine environments, outdoor furniture needing a natural look
Outdoor furniture, doors, trim requiring durability and low maintenance
Cost
Varies, often premium due to natural ingredients
Generally cost-effective, depending on formula
Spar Varnish and Spar Urethane Definitions
Spar Varnish
Requires more layers and longer drying times for application.
Restoring the outdoor bench with spar varnish took several days due to drying times.
Spar Urethane
A synthetic, polyurethane-based protective finish for outdoor wood.
Spar urethane was chosen for the patio furniture due to its UV resistance.
Spar Varnish
A protective finish made from natural resins, ideal for wood exposed to marine environments.
The boat's deck was coated with spar varnish to protect it from seawater.
Spar Urethane
Offers enhanced durability against weather, UV, and chemicals.
The wooden sign coated in spar urethane remained vibrant despite sun exposure.
Spar Varnish
Known for its flexibility, allowing wood to expand and contract.
Spar varnish was applied to the wooden bridge to withstand seasonal changes.
Spar Urethane
Available in various sheens, from matte to high gloss.
The homeowner selected a satin spar urethane to finish the outdoor kitchen cabinets.
Spar Varnish
Provides a warm, glossy finish that enhances wood's natural appearance.
The antique door's grain popped after a coat of spar varnish.
Spar Urethane
Low maintenance, with longer intervals between reapplications.
The front door's spar urethane finish has lasted for years without fading.
Spar Varnish
May need frequent reapplication in harsh conditions.
The garden gazebo's spar varnish finish is touched up annually to maintain its look.
Spar Urethane
Easier to apply and dries faster than traditional varnish.
The deck project was completed quickly thanks to spar urethane's fast drying time.
FAQs
How do spar varnish and spar urethane differ in application?
Spar varnish requires more layers and longer drying times, while spar urethane is easier to apply and dries faster.
Can both spar varnish and spar urethane be used outdoors?
Yes, both are designed for exterior use, providing protection against moisture, UV light, and temperature changes.
What is spar varnish?
Spar varnish is a protective finish made from natural oils and resins, designed to protect wood in moist and flexible conditions, such as marine environments.
What is spar urethane?
Spar urethane is a synthetic finish that combines the protective qualities of spar varnish with the durability of polyurethane, suitable for outdoor wood.
Do spar varnish and spar urethane have different finishes?
Yes, spar varnish tends to enhance the wood's natural beauty with a warm finish, while spar urethane is available in various sheens, including matte and gloss.
Which requires more maintenance, spar varnish or spar urethane?
Spar varnish may require more frequent reapplication or maintenance, especially in harsh conditions, compared to spar urethane.
What are the cost differences between spar varnish and spar urethane?
Spar varnish can be more expensive due to its natural ingredients, while spar urethane varies in price, often being more cost-effective, especially for water-based formulas.
Can spar varnish and spar urethane be used on indoor furniture?
While both can be used indoors, their formulations are specifically designed for outdoor use. For indoor furniture, products without UV protection might be more suitable.
Are spar varnish and spar urethane environmentally friendly?
Spar varnish, being natural, can be more environmentally friendly but emits more VOCs. Water-based spar urethane emits fewer VOCs, making it a better option for indoor air quality.
Can I use spar urethane over spar varnish?
Yes, but it's important to ensure the varnish is fully cured and properly prepared to ensure good adhesion of the urethane.
Which is more durable, spar varnish or spar urethane?
Spar urethane is generally more durable, with better resistance to UV light, chemicals, and abrasions.
How do I choose between spar varnish and spar urethane for my project?
Consider the project's specific needs, including the desired finish, durability requirements, maintenance willingness, and environmental considerations.
How do weather conditions affect the choice between spar varnish and spar urethane?
In harsher weather conditions, spar urethane's superior durability and UV resistance make it a better choice, while spar varnish is suitable for less extreme conditions where a natural finish is preferred.
How do I apply spar varnish or spar urethane to ensure the best protection?
Proper application involves cleaning the wood surface, applying multiple thin layers, and allowing adequate drying time between coats, with light sanding as necessary.
Can spar urethane be used over a previously varnished surface?
Yes, but the surface must be clean, dry, and lightly sanded to ensure proper adhesion of the urethane coating.
How does the choice between spar varnish and spar urethane affect the wood's appearance over time?
Spar varnish may yellow or darken slightly, enhancing the wood's natural look, while spar urethane tends to remain clearer, preserving the original wood color better.
What are the environmental considerations when disposing of spar varnish and spar urethane?
Both products require careful disposal according to local hazardous waste regulations due to their chemical content and potential environmental impact.
What safety precautions should be taken when applying spar varnish or spar urethane?
Use in a well-ventilated area, wear protective gloves and a mask to avoid inhaling fumes, and follow the manufacturer's safety instructions.
How does UV resistance compare between spar varnish and spar urethane?
Spar urethane generally offers superior UV resistance compared to spar varnish, making it better suited for areas with high sun exposure.
How long do spar varnish and spar urethane finishes last before needing reapplication?
The longevity of both finishes varies based on environmental exposure, but spar urethane typically lasts longer (several years) compared to spar varnish, which may need more frequent touch-ups or reapplication.
About Author
Written by
Harlon MossHarlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Co-written by
Janet WhiteJanet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
