Indigo is a natural dye that produces a rich, blue-purple colour by the same name. Archaeological evidence suggest that this dye was produced as early as 2686 B.C. by ancient Egyptians using extract of woad and indigo plants. Despite its wide use, indigo is what is known as a fugitive dye, meaning it fades or discolours with exposure to light and repeated washing. You cannot completely set indigo dye. However, you can use a mordant immediately after dying or change the way that dyed products are handled to maximise colour retention.
Mix vinegar and water maintaining a ration of one to four parts.
Submerge dyed material in the mixture. Stir and leave the fabric to soak overnight.
Rinse the fabric in cool water and hang to dry.
Store indigo dyed fabrics in an airtight container or plastic bag that is waterproof.
Place the container in a dry, cool, shaded area such as a closet.
Wash fabrics in cold or cool water on delicate. Add a gentle detergent and 1 cup of vinegar to the wash water to reduce the alkalinity and help prevent dye loss.
Wash items in a lingerie bag or pillow case to reduce drum friction.