Woo, Effect of Reducing Agent, Sodium Hydrosulfite on the Natural Indigo Dyeing of Silk Fabric, Korean J. Lee, A Study on the Dyeing Properties of Natural Indigo Complex Powder and Synthetic Indigo with Natural Fiber, J. Ryu, Natural Indigo Dyeing on Wool Fibers (I), J. Yoo, Color Character in Natural Indigo Dyeing: the Effect of Reducing Agent, Proceedings of KSDF 20th Anniversary International Conference of on Dyeing and Finishing, pp.126-127, EXCO, Daegu(Korea), March 13, 2009 Routte (Ed.), 'Redox potential, Reducing agents, Encyclopedia of Textile Finishing', Springer-Verlag, Berlin, Vol. Harvey, Green Chemistry Methods in Sulfur Dyeing:Application of Various Reducing d-Sugars and Analysis of Importance of Optimum Redox Potential, Environ. John, An indigo-reducing moderate thermophile from a woad vat, Clostridium isatidis sp. John, The mechanism of bacterial indigo reduction, Appl. John, Formation of Natural Indigo Derived from Woad (Isatis tinctoria L.) in Relation to Product Purity, J. Gangberger, Process balance and product quality in the production of natural indigo from Polygonum tinctorium Ait. Hill, An Improved Method for the Large-Scale Processing of Woad(Isatis tinctoria) for Possible Commercial Production of Woad Indigo, J. Marken, Electrochemical and sonoelectrochemical monitoring of indigo reduction by glucose, Dyes and Pigments, 76, 542-549(2008) Rys, Electrocatalytic Hydrogenation of Indigo Process Optimization and Scale-Up in a Flow Cell, J. All the colorfastness values were improved with the increase of color strength.

For both of ramie and silk fabrics, the colorfastness of washing and light was lower than that of rubbing. Indigo powder was obtained by drying the conventional niram paste in an oven at $50^12$ g/L of glucose concentration. Effect of reduction and dyeing conditions such as temperature and time of reduction/dyeing, and concentrations of glucose and calcium hydroxide on the dyeing process were explored. Dyeing process of the natural indigo powder onto ramie and silk fabrics was investigated by using glucose and calcium hydroxide as a reducing system.

Natural indigo