ASTM G 90

1.1 Fresnel-reflecting concentrators using the sun as source are utilized in the accelerated outdoor exposure testing of nonmetallic materials. 1.2 This practice covers a procedure for performing accelerated outdoor exposure testing of nonmetallic materials using a Fresnel-reflector accelerated outdoor weathering test machine. The apparatus (see Fig. 1 and Fig. 2) and guidelines are described herein to minimize the variables encountered during outdoor accelerated exposure testing. 1.3 This practice does not specify the exposure conditions best suited for the materials to be tested but is limited to the method of obtaining, measuring, and controlling the procedures and certain conditions of the exposure. Sample preparation, test conditions, and evaluation of results are covered in existing methods or specifications for specific materials. 1.4 The Fresnel-reflector accelerated outdoor exposure test machines described may be suitable for the determination of the relative durability of materials exposed to sunlight, heat, and moisture, provided the mechanisms of chemical or physical change, or both, which control the rates of acceleration factors for the materials do not differ significantly. 1.5 This practice establishes uniform sample mounting and in-test maintenance procedures. Also included in the practice are standard provisions for maintenance of the machine and Fresnel-reflector mirrors to ensure cleanliness and durability. 1.6 This practice shall apply to specimens whose size meets the dimensions of the target board as described in 8.2. 1.7 For test machines currently in use, this practice may not apply to specimens exceeding 13 mm (<(hoch)1>/<(Index)2> in.) in thickness because cooling may be questionable. 1.8 Values stated in SI units are to be regarded as the standard. The inch-pound units in parentheses are provided for information only. 1.9 This standard does not purport to address all of the safety concerns ....(abbreviated)