Fading of Azo Reactive Dyes by Perspiration and Light

The fastness of azo reactive dyes on cellulose in a combined perspiration and light test was investigated, and compared with the results obtained in a conventional light fastness test. Whereas reactive dyes containing an H- or K-acid azo chromophore performed better in the conventional fastness test, reactive dyes of the J- or gamma-type exhibited a higher fastness in the combined test. The results suggest that testing under combined perspiration and light conditions involves a photoreduction mechanism, but a photo-oxidation mechanism operates when dyed fabrics fade under light only