In the visual test, check the exposed test pieces against the test piece not exposed for discoloration degree and hardening of film. The degree of discoloration shall be evaluated using Table 5, using a discoloration gray scale( 17). For Pvc leather cloth which requires a special light resistance test, a 10 mm-thick polyether urethane foam stab(density 0.022) of the the test piece shall be attached to the back side of the test piece when the test piece is installea to the tester Table