An evaluation of the effect of detergent, wash temperature and drying on the colourfastness of indigo and azo dyed cotton fabrics

English: An experimental study was carried out to evaluate the effect of detergent, wash temperature and drying on the colourfastness of indigo and azo dyed cotton fabric. After repeated laundering treatments (50 wash cycles) at wash water temperature of 40°C and 60°C, samples were laundered in a Launder-Ometer for 45 minutes in 200 ml of wash solution with 0,3g detergent, and line dried both indoors and outdoors in open air and extensive sunlight between 10:00 and 15:00. Colour loss was measured in daylight (D65/10), UV-light (Woolworths Storelight F11/10) and Tungsten (A/O), using spectraflash. Treated indigo and azo dyed cotton fabrics were subjected to colourfastness tests for washing, crocking, light and staining. In a colour transfer test where multifibre test strips were used, wool, polyester and nylon were the fibre types most severely affected by water without detergent (control) none of the dyes in both fabrics were transferred to fibres treated with the two brands of detergent. A correlation of the data by dye used shows that: • Colour loss increase with the number of wash cycles. • Indigo dyed cotton loose more colour than azo dyed cotton • Sunlight causes more colour loss • More colour loss is experienced at 60°C wash temperature • Detergents cause more colour loss than water without detergent • More staining to other fabrics take place without a detergent • More crocking takes place in the wet than the dry state.