Color in Cloth Dyed with Natural Indigo and Synthetic Indigo

Color reflectance from the cloth dyed with natural indigo was quantitatively compared with that from the cloth dyed with synthetic indigo by the spectrophotometric method, and the results were analyzed by a CIELAB color system. The cause of the color difference between the clothes dyed with natural and synthetic indigo was attributed to the mode of dye dispersion in fiber resulted from the aggregation of dye molecules during the reduction process. The results are summarized as follows: 1) The color produced by natural indigo is bluer and brighter than color produced by synthetic indigo reduced by sodium hydrosulfite. 2) The color produced by synthetic indigo using zinc powder is more similar to the color of natural indigo than the color of synthetic indigo prepared with sodium hydrosulfite. 3) The chroma and hue of the cloth dyed with natural indigo are higher than the respective values of the cloth dyed with synthetic indigo reduced by sodium hydrosulfite when the clothes are dyed repeatedly. 4) The diffusion coefficient of synthetic indigo reduced by sodium hydrosulfite is higher than that of natural indigo, where the diffusion coefficient of synthetic indigo reduced by zinc powder is similar to that of natural indigo.