Q-TRAC Natural Solar Concentrator Testing: Why Specimen Sizing Matters
Blog
Last Updated 2025
The Q-TRAC natural sunlight concentrator is a fast, powerful way to conduct accelerated weathering testing using actual sunlight instead of artificial light sources. The Q-TRAC system is useful for testing a range of products including coatings, high-temperature plastics, automotive materials, building materials, sealants, fluoropolymers, and geosynthetics. Correlation studies indicate that the Q-TRAC natural sunlight concentrator is particularly useful for testing coil coatings, powder coatings, automotive coatings, and plastics.
When you're investing in Q-TRAC natural sunlight concentrator testing, the size and shape of your specimens can make or break both your results and your budget. Here's what every customer should know to maximize their testing value.
Specimen Size Directly Impacts Cost of Test
Q-TRAC pricing is calculated by space occupied along the target board's length, typically measured in inches. This means that a simple sizing decision can double your testing costs. Here's how: if you submit specimens that are 5" long by 3" wide, you'll pay for 3" of test space. But if those same specimens are 6" long by 3" wide, they must be rotated 90° to fit —suddenly you're paying for 6" of test space for the exact same number of specimens.
That's why we suggest using specimens with dimensions no greater than 5.5" (14 cm) in order to get the most value out of your testing program. Any specimen with a length greater than 5.5" must be oriented along the target board's length dimension, ultimately increasing your costs.
Standardized Specimen Sizing
ASTM G90, a widely-referenced standard practice for concentrated natural sunlight testing, specifically requires that specimens meet target board dimensions and recommends thickness not exceed ½" (13 mm). The standard also emphasizes proper specimen mounting to ensure consistent exposure—which ties directly to the cooling requirements that make sizing so critical.
Proper Cooling = Reliable Results
The Q-TRAC delivers approximately 5× the UV radiation of Florida outdoor testing, which means that effective cooling is critical. Specimens are cooled by airflow across their faces, but this only works when they're properly sized and positioned.
For optimal cooling and consistent results, your specimens should have:
- Maximum thickness of preferably ½" (maximum 1") and
- Consistent thickness across all specimens in a test run to prevent thicker specimens from blocking the cooling of thinner ones
The Impacts of Improper Specimen Sizing
Using specimens that are too large can cause problems with your testing. Specimens thicker than 1" simply cannot be accommodated, as the Q-TRAC's air deflector can't open wide enough to provide adequate airflow. Mixed thicknesses create uneven cooling, where some specimens overheat while others receive proper temperature control. This inconsistency can compromise the results of you test program.
An Ideal Substrate Size for the Q-TRAC
If you're looking for substrates specifically designed for Q-TRAC testing, our 3" by 5" Q-PANEL substrates (designated with -35) are engineered to be the perfect size for the target board. They eliminate guesswork and ensure you get maximum exposure area at the most economical price point. Learn more about our line of aluminum and steel test substrates.
Maximize Your Testing Value
The Q-TRAC natural sunlight concentrator offers fast, powerful accelerated testing using real sunlight—making it particularly valuable for coil coatings, powder coatings, automotive materials, and other very durable outdoor materials. By following these simple sizing guidelines, you'll ensure consistent results while keeping costs under control.
Q-Lab has additional resources for customers looking to get the most out of their weathering testing program, including a webinars presented by Q-Lab's Testing Services Technical Director Mike Crewdson titled How to Get the Most Out of Your Weathering Testing Program, and Accelerated Outdoor Weathering.
Ready to get your testing program started? Contact our team today!