Indigo is a solid, insoluble, dark blue crystalline powder. It does not bind with the fabric at all nor does it chemically bonds with the fabric, it forms mechanical bond.

To make indigo soluble in the water it is necessary to reduce it, with the suitable reducing agent like bacteria, Zn, Sodium hydrosulfite etc. Once the indigo is reduced, it becomes colorless and water soluble. After the removal of oxygen (by reduction method), it then has a high affinity for cellulosic fiber. The reduced indigo dye easily enters the open spaces of the fiber and then the dyed fibers are exposed to air, due to which the dye molecules oxidizes back to their insoluble forms. The dye molecule gets trapped inside the fiber and colors the fabric permanently.

Indigo is used in for various purposes, for dyeing wood, cotton, leather and silk. The indigo application is safe for dyeing the silk.

Dyeing Silk by Indigo Hair dye:

Silk can be easily dyed using pure indigo hair dye with the help of following steps:

  1. The silk cloth is stretched with the help of embroidery hoop and then resist like wax or starch paste is applied to protect the design.
  2. The dye paste is prepared by mixing the indigo hair dye with water.
  3. The silk cloth is then reversed and the indigo dye is applied on the back side of the cloth.
  4. As the paste oxides, it changes color from dark green to dark purple-black. Different shades can be obtained by interrupting the oxidation by air, heat and light. Applying paste in sunlight gives the best results.