A chemical used in the process of indigo textile dyeing. Indigo is a vat dye, or an insoluble dye, which needs to be treated with a reducing agent to be rendered soluble. The process involves treating indigo with a reducing agent in a hot bath. The reducing agent removes excess oxygen from the solution, converting the indigo into a form known as leuco-indigo, which is colourless and soluble in water. The desired fabric is then dipped into the leuco-indigo solution. Some common reducing agents include sodium dithionite, hydroxyacetone, zinc, and natural sugars.