The Need for Accelerated Weathering Tester : Photo Stability of Products

Are the colors of your products stable under prolonged exposure to sunlight? Have you noticed that the colors of clothes or drinks fade after extended exposure to sunlight? These phenomena are due to a chemical mechanism called photodegradation. Ultraviolet rays from the sun break down the chemical bonds of chromophores, the light-absorbing substances in dyes, leading to bleaching.

Understanding Photodegradation

Photodegradation occurs when ultraviolet (UV) rays from the sun break down the chemical bonds in dyes, causing colors to fade. This process is particularly problematic for products exposed to sunlight for extended periods. The breakdown of chromophores results in the loss of color intensity, impacting the aesthetic and functional quality of the product.

Case Study: Interbev Philippines

Interbev Philippines, a manufacturer of non-carbonated energy sports drinks sold under the Cobra brand, faced issues with product shelf life due to photodegradation. As they considered exporting their products, they became concerned about the photo-stability of their drinks compared to competitors like Gatorade, a recognized leader in the industry. Interbev needed a reliable, repeatable accelerated test to compare their product's color fastness with the industry leader.

Solution: Q-SUN Accelerated Weathering Tester

To address this issue, Interbev utilized the Q-SUN xenon chamber for colorfastness testing. Preliminary tests showed that the Q-SUN was more effective than other methods. Three flavors of Interbev drinks (Berry Red, Lemon-Lime, and Orange) were compared with corresponding Gatorade flavors. After a 24 hour exposure in a QUV there was no visible change in color, however after 24 hours in a Q‐SUN, fading was obvious after the same 24 hour period. This indicates the color fade is from visual or infrared solar energy not present in the QUV.

Consequently, the Q‐SUN Xe‐3 was selected for the full comparison test. The test standard selected by the researchers is a modified AATCC TM 169. This is a commonly used colorfast test protocol and they liked using Window B/SL optical filters to simulate light through window glass, but they felt that the irradiance of 0.35W/m2 was insufficient to produce results fast enough. They opted for 0.68W/m2@340nm as the irradiance set‐point to produce faster results. The irradiance is continuous. Samples will be repositioned every four hours during office hours.

Four 40ml test samples were prepared for each of three flavors from the respective manufacturer. After each 24 hour exposure, one sample was removed from the Q‐SUN for a total exposure of 72 hours. One sample of each flavor was retained as an un‐exposed reference. At the end of the test, the samples were visually evaluated for photo‐stability and digital color measurements taken for each sample.


After the initial 24 hour exposure period, one sample of each product was removed for visual comparison with the retained reference sample. The remaining samples were subjected to another 24 hour exposure. After 24 hours of continuous light exposure, all samples displayed various degree of fading from their original color.

At 48 hours, differences can be seen in the durability of various Cobra and Gatorade products. The degradation of each product is uniquely different with different rates of degradation unique to the product.

The test was concluded after 72 hours and colors digitally evaluated with HunterLab Mini Scan XE Plus.


Accelerated weathering testing using the Q-SUN Xe-3 provides valuable insights into the photo-stability of products. Interbev's experience demonstrates the importance of such testing for maintaining product quality and competitiveness.

Are you concerned about the photo-stability of your products?

Q-SUN accelerated weathering testers can help you conduct reliable and repeatable tests to ensure your products withstand prolonged exposure to sunlight!

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