Understanding and controlling dye transfer in the laundry process

Domestic dye release and dye transfer is an environmental problem that occurs every time a garment is washed. While it has been previously recognised, insufficient knowledge on types of dyes, mechanisms and wash settings exists to provide a significant decrease of dye transfer from clothes that make up an average consumer wash load. In particular, there is not currently a sustainable solution to reduce dye transfer from textiles. The research herein explored dye identification through Raman spectroscopy of a validated model wash load, mechanistic understanding of wash parameters, ionic strength and pH on both dye release and dye re-adsorption, and full wash testing to provide less dye transfer. It was found that reactive dyes predominantly make up a consumer wash load, and that high ionic strength and low pH increased the substantivity of the dye for the fibre. Cold washes and quick washes were beneficial for reducing dye transfer, with the duration of the wash proving to be the most significant factor. Acidified detergent provided benefits for the reduction of dye transfer from this model. Denim was also investigated as a specialty textile that is a known dye transfer donor. Analytical and supramolecular chemistry were used to understand the staining species. Wash parameters, pH, agitation and presence of detergent were studied for their effects on dye transfer. The staining species from denim was found to be a complex between indigo and cellulose oligomers. It was attracted most to wool fibres and after further investigation, was attracted most to arginine of the molecules tested, with which it formed a hydrogen bonded complex. This suggested compatibility between arginine and the staining species, which is likely anionic. Addition of arginine to wash loads reduced dye transfer from denim, as did acidified detergent.