the required end point in terms of

the required end point in terms of AATCC Fading Units, kilojoules per square meter of irradiance or reference specimen performance (that is, the reference specimen shows a color changeequal to Step 4 on the Gray Scale of Color Change).25. Machine Exposure for Lightfastness Classification 25.1 One-Step Method-Expose test specimens) simultaneously with a series of AATCC Blue Wool Lightfastness Standards or determine the number of AATCC Fading Units required to produce a color change in the test specimen equal to Step 4 on the Gray Scale for Color Change (see 44.10). 25.2 Two-Step Method-Proceed as directed in 25.1, except double the exposure area of the test specimens. After theb specimen has been exposed to a color change equal to Step 4 on the Gray Scalefor Color Change, remove the specimens from the test chamber and mask (cover) one-half of the exposed area and continue the exposure until the test specimen exhibits a color change equal to Step 3 onthe Gray Scale for Color Change (see 44.10). Option 3Xenon-Arc Lamp, Continuous Light, Black Panel OptionMachine Operating Conditions21i. Preparation 26.1 Prior tob of Test Apparatus running the test procedure, verify machine operation by using the following test protocol. To enhancethe repeatability of test results, install test apparatus in a room where temperature and relative humidity are controlled in accordance with the manufacturer's recommendations. 26.2 Check to see that the machine has been calibrated and maintained within the manufacturer's recommended calibration schedule interval. 26.3 Turn off all rack and specimen spray units, if applicable. 26.4 Set machine operating conditions as follows: Light source Xenon Continuous light-on Black Panel temperature 63士10C (145士20F) Chamber air temperature 43士20C (ll0士40F) Relative Humidity%30士5 Filter type See A3.3 Irradiance W/m2/nm (at 420nm) 1.10士0.03 W/m2 (at 300-400nm) 48士1 Water requirements (Input)