Weathering Testing of Wood Coatings: Webinar Recap

Wood coatings often face harsh weather conditions, depending on the climate they are exposed to. Because of this, testing their durability before going to market is essential. For manufacturers, suppliers, and quality control teams, understanding how these coatings will perform over time is crucial.

Q-Lab's Technical Marketing team recently presented a webinar exploring both natural and accelerated weathering testing methods specifically designed for wood coatings, including insights from a landmark European study that shaped international testing standards still used today.

Natural Weathering Testing: Nothing Beats the Real Thing

Natural outdoor weatheringis always the true test of material durability, validating all laboratory test methods. Q-Lab operates three accredited natural outdoor exposure sites representing distinct climate zones: Florida (sub-tropical), Arizona (desert), and Ohio (northern industrial). While these provide real-world results and serve as a critical benchmark, standard outdoor tests can take months or years to produce meaningful data. 

Accelerating Natural Testing Results using the Q-TRAC Natural Sunlight Concentrator

Q-Lab's Q-TRAC Natural Sunlight Concentrator helps accelerate natural outdoor testing, providing fast and accurate results. This innovative system uses tracking mirrors to concentrate natural sunlight, delivering approximately 5× the UV irradiance of normal summer sunlight. 

The Q-TRAC can run multiple test cycles on wood coatings, including a soak/freeze/thaw procedure (referenced in ASTM D5722). In one comparison study, Q-TRAC testing with freeze-thaw cycles achieved in just 42 days what took 365 days of direct outdoor exposure, demonstrating both excellent correlation and acceleration.

Laboratory Weathering

When it comes to accelerated laboratory weathering, there are two primary exposure types:

• Xenon Arc Testing: Produces full-spectrum light matching natural sunlight but may be moisture-deficient, typically relying on water spray alone
• Fluorescent UV Testing: Focuses on the damaging shortwave UV spectrum. The UVA-340 lamp provides the best match to natural UV light, and hot condensation delivers the most realistic moisture conditions – critical for wood coating degradation.

Both offer a variety of strengths and weaknesses. Understanding the light source used in each can have a direct impact on the outcome of your testing program.

The Arwood Study

A significant development in wood coating weathering came from the Arwood Study, a collaborative effort involving 10 European research institutes and 4 industrial partners. Published in Coatings World in 2003, this research had a clear objective: determine an artificial accelerated weathering test suitable for wood coatings that would be cost-effective for small-to-medium-size companies, while providing accurate correlation to natural outdoor weathering.

Testing seven QUV cycles on six coating systems, researchers identified an optimized cycle that demonstrated approximately 10× acceleration in gloss and cracking behavior as compared to outdoor weathering.

The study provided a few key takeaways for researchers:

• UV fluorescent testing using UVA-340 lamps was proven to be a very effective method for evaluating wood coatings.
• Extended condensation cycles, combined with water spray to remove surface material, reproduce outdoor moisture attack.
• Special treatments such as freezing or soaking do not appear to significantly impact laboratory weathering.
• Three of the cycles tested showed the most rapid and realistic onset of cracking and gloss loss, and were ultimately selected by the test's authors.

This work was published as a European standard, EN 927-6 (2006), later adopted as an ISO standard, ISO 16053-2 (2024).

Ready to Start Testing?

Whether you need natural outdoor exposure, accelerated Q-TRAC results, or laboratory weathering using proven international standards, Q-Lab has the expertise to support your wood coating programs.
Watch the full webinar recording at Q-Lab.com/Webinars, or contact our team today.

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