Location variations as an obstacle to light fade testing

The validity of lightfastness predictions based on standardized reference models that rely on a single testing environment was studied. The lightfastness of identical sample sets were evaluated for the same duration of sunlight exposure in five different locations around North America. The study showed that identical samples in different locations fade to differing degrees even when exposed to a consistent duration of irradiance. Furthermore, the relative fade rate was inconsistent from one sample type to another. Therefore, an accurate colorfastness prediction for a specific colorant must be, determined by testing that colorant under the actual use conditions and environment.