Extraction of Indigo from Some Isatis species and Dyeing Standardization Using Low-technology Methods

Abstract

Fresh leaves of four Isatis species culture form of I. tinctoria L and wild forms of I. buschiana Schischkin, I. candolleana Boiss. (endemic) and I. tinctoria L. subsp. corymbosa. (Boiss.) were used for indigo production. Dyes were extracted by fermentation and hot water application. The extracted dyes were optimized with different pH and reducing agents. Results showed that the dye from hot water application produced the desired dying quality at pH 11. Reducing agent concentrations had no significant effect on color quality. Dark blue and blue colors were obtained from I. tinctoria and I. candolleana extracts although I. tinctoria subsp. corymbosa and I. buschiana produced mostly yellow-gray colors. Light, dry and wet rubbing fastness values varied between 3 and 3/4 while washing fastness was between 2 and 4/5. The highest indigo amounts were determined spectrophotometrically as 4.19 mg/g and 2.53 mg/g in I. tinctoria and I. candolleana, respectively. Results also showed that harvesting season was important for indigo production and the highest indigo amount was observed in mid-June.

Keywords

• Isatisspp.
• woad
• indigo
• natural dye
• fermentation
• fastness
• spectrophotometry