Dyeing of Lycra® fabrics with Indigo blue

Knitted lycra® fabric samples were dyed with indigo dye through an exhaust technique by controlling the ratio of sodium dithionite and sodium hydroxide concentrations in the dyebath solution. depending on ph different forms of the indigo existed and each one had different level of substantivity for lycra®. the non-ionic form like disperse dyes and ionic forms like acid dyes exhibited substantivity for lycra®. lycra® could be dyed in the acidic as well as alkaline ph regions,though the later caused degradation due to hydrolysis of lycra at higher ph values. the reflection spectra showed that absorption maximum for lycra® was at 610 nm. the rubbing and washing fastness were better while light was medium.