This part of ISO 877 specifies a method for exposing plastics to concentrated solar radiation using reflecting concentrators to accelerate the weathering processes. The purpose is to assess property changes produced after specified stages of such exposures. General guidance concerning the scope of ISO 877 is given in ISO/DIS 877-1:2016, Clause 1. The reflecting concentrators used in these exposures are sometimes referred to as Fresnel reflectors because in cross-section the array of mirrors used to concentrate the solar radiation resembles the cross-section of a Fresnel lens. For additional information about solar concentrating exposures, including a partial list of standards in which they are specified, refer to the Bibliography.