Improving light fastness of natural dye: photostabilisation of gardenia blue

The photofading behaviour of gardenia blue on cellulose was investigated. A contribution of auto‐oxidation and singlet oxygen to that fading was suggested. The inhibiting effect of phenyl ester ultraviolet absorbers towards the photofading of gardenia blue was examined on cellulose. It has been found that the presence of a simple ultraviolet absorber is not of particular value in improving the light fastness of natural dye. The introduction of a singlet oxygen quenching group into an ultraviolet absorber can, however, have an important effect. The nickel complex of 1‐benzoyloxynaphthalene‐3‐sulphonic acid was very effective in reducing the rate of photofading.