It was believed that a Q‐SUN xenon chamber would be more appropriate for this colorfast test and a preliminary 24 hours test verified this hypothesis. Three Interbev flavors were selected, Berry Red, Lemon‐Lime, and Orange and three comparable Gatorade flavors were selected for comparison. 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.