Indigo dyeing is a dyeing technique widely used for denim and jeans. After reducing indigo dye is absorbed into the fibers, it is oxidized by contacting with air to fix the vivid indigo color. In modern times, chemically synthesized indigo dye is mainstream, and the reduction and oxidation process is stable, allowing for uniform dyeing in a short time.

Indigo was first successfully synthesized on a laboratory scale in 1880 by German chemist Adolf von Bayer, and its chemical structure was elucidated in 1883. In 1897, BASF established commercial production technology, accelerating the transition to synthetic indigo.

The dye mainly remains on the surface of the fibers, so fading and creases occur with repeated wearing and washing, bringing contrasting changes to the appearance of the fabric. A major feature of indigo dyeing is that this aging process reveals depth and flavor according to each individual’s wearing conditions.