PREPARATION METHOD OF NATURAL INDIGO FROM POLYGOUM TINCTORLUM

摘要

PURPOSE: A method for preparing natural indigo pigment is provided to readily allow one other than an initiated expert to extract and ferment the pigment, mass-produce it, mass-dye with it, give good color, and enhance article quality. CONSTITUTION: The method comprises adding calcium hydroxide to natural indigo to extract indigo pigments, lyophilizing them to form powder of indigo pigments, adding calcium hydroxide or sodium hydroxide as an alkali agent and starches as fermenting nutrient to the powder, in order to make the water-soluble indigo pigment powder, and fermenting them. Thus, the obtained pigment shows good color. The natural indigo pigment is used to dye silk, ramie, hemp and cotton.