The degree of discoloration of dyed fabrics irradiated by using the three kinds of 20-watt tubular type fluorescent lamps having different spectral irradiance distribution where the distance between the lamp and the samples was kept constant in order to give equal radiation energy (irradiance) to the samples was previously reported. In this research, the effect of the optical radiation on the discoloration of dyed fabrics under equal level of illuminance (500 lx) on samples using the three kinds of fluorescent lamps (D
65, W, NU) and the eight kinds of dyed fabrics was investigated. The following results were obtained.
(1) The order of discoloration degree was D
65>W>NU. On dyed fabric, differences in each mordant and each colorant especially were recognized.
(2) The discoloration reduction effect of the NU lamp compared to the D
65 lamp and W lamp was 33% and 9%, respectively.
(3) The discoloration reduction effect of the NU lamp compared to the D
65 was 18% for equal irradiance and 33% for illuminance. The equal irradiance condition was defined as changing the lamp in the museum and the equal illuminance condition corresponds to not only changing the lamp, but also keeping the illuminance equal.
(4) From this experiment, we found that the discoloration of dyed fabrics showed a closer relationship to the exposure dose of illuminance (lx·hr) than that of irradiance (W·hr).
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