Abstract: Prior to weathering test for samples, of example, plastic, fiber, or paint, the samples are exposed to ultraviolet ray radiation emitted from high pressure metal halide vapor discharge lamp at an energy level capable of deteriorating the samples in a short time, while maintaining the samples at a temperature which can not be a cause of the deterioration. According to the deterioration level, samples to be subjected to the weathering evaluation test are selected.

Abstract: A weather resistance tester comprising:(a) a U.V. radiation source,(b) a reflector,(c) a shield panel provided in the opening of the reflector and closing the opening for transmitting U.V. radiation therethrough and substantially blocking water vapor,(d) a sample support,(e) temperature adjusting device,(f) a compartment having accommodated therein the above elements (a)-(e),(g) a recycling duct provided with a heat exchanger and blower,(h) a humidifier and(i) a control device for giving operational instructions to maintain a sample on the sample support at a predetermined temperature while the lamp is on and to subject the sample to a condensation condition while the lamp is off.