ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 11, Number 3
JKCSEZ 11(3)
June 20, 1967 

Fading of Chlorantine Fast Red 5B (C.I. Direct Red 81) on cotton fabric exposed to carbon are light was examined. It was observed that the dye had anomaly in CF curve slope, while normal in CFG one. Auther considered that the reason for discrepancy of the one with the other curve slope might be appeared from Weber-Fechner law, and derived following equation Fv = [logCo - log(Co - CoFt/100)]×100/(logCo + b)where Ft; the proportion of dye faded after t hour exposure. Fv; the proportion of dye faded after t hour exposure, when a pattern is judged by visual method C0; initial dye concentration. b ; constant. also, the reason for increasing lightfastness with dye concentration was discussed on view of the above equation.