Reviving of Cotton Dyeing by Saxon Blue: Application of Microwave Irradiation to Enhance Dyeing Performances

The present paper illustrates an unconventional but green exhaust dyeing process of cotton, in which the conventional reduction step of the indigo dyeing process is eliminated following the substitution of the insoluble indigo by the soluble indigo carmine. Indigo carmine can meet ecological requirements in terms of chemical consumption reduction, cleaner releases, and biodegradability. However, this dye produces unsatisfactory dyeing quality compared to indigo. In order to enhance dyeing quality, cotton samples were treated with Sera Fast GMX (a cationic agent) before they were dyed with indigo carmine. The influence of dyeing parameters (i.e., indigo carmine concentration, dyeing temperature, dyeing duration, and sodium carbonate concentration) on the evolution of the color strength (K/S) was studied. A response surface design was employed to optimize this unconventional dyeing process. The addition of salt to the dye bath appeared to improve both color strength and fastness properties. Finally, the effect of treating cationized cotton samples with microwave radiations was investigated. The results showed that exposure to microwave radiation for 5 min resulted in improvements in dyeing quality.