INHERENT VARIABILITY IN ACCELERATED WEATHERING DEVICES

Accelerated weathering tests have traditionally been assumed to be higly reproducible. This paper examines the within and between laboratory variability associated with commonly used accelerated weathering tests and devices. Examples of how variability can influence the interpretation of results are given. Much of this variability, which can be very large, is due to differences in the three primary stresses (light, water and temperature) within a single device and between seemingly identical devices.