Indigo has been used to dye fabrics for at least 6000 years in civilizations all over the world. Indigo is derived from several species of plants and is non-toxic, colorfast, and sustainable. A single vat of indigo dye can be maintained for years and reused, simply adding new indigo and reducing agents as needed. Indigo is permanent on natural fibers (cotton, silk, wool, etc.) and rayon (a synthetic fiber derived from natural cellulose).

Indigo changes colors when exposed to oxygen in the air, going from yellow-green to dark blue