The color treasured by Japanese people

Ai (indigo) is a dye that is collected from the leaves of the Japanese indigo plant. Its deep, bright blue color has attracted people from the ancient times. Indigo dyeing has developed in various parts of the world; it is said that it was introduced from India to Japan through the Silk Road route. Although the timing is not clear, there are records of indigo plant cultivation from the 6th to 7th century. It was used only for aristrocrats or samurai at first. However, by about the 17th century, it had spread to the common people, and various household items were being dyed with indigo, including kimonos, hand towels, and bedding. Since indigo has antibacterial and insect repellent effects, and is also effective for preventing odors, Aizome clothing was appreciated as a remedy for skin trouble or eczema, while repelling insects. A British scholar who visited Japan in the 19th century when the country opened up was impressed by the color of indigo commonly seen around town and called it “Japan blue.”

Mixing indigo (left) and dyeing (right)

Indigo dye vat in which indigo is fermented

Although there are various methods to extract dye from indigo leaves, one that has become mainstream and has been handed down to the present day is the method in which leaves are fermented. Indigo leaves are dried and fermented to make “sukumo,” which contains a concentrated dye component, which will be mixed with lye, lime, and other substances in a vat and then fermented again. Currently, most sukumo is produced in Tokushima Prefecture in Shikoku, which is famously known as “Awa-ai” and yields high-quality color.

Tokyo Skytree in the color of “aijiro”

Aizome can create various shades of blue depending on the level of fermentation or the dyeing time, and each shade has a different name according to its slight color difference. There are various colors ranging from “aijiro (indigo white),” the lightest shade closest to white, to “noukon (navy blue),” the darkest shade closest to black, indicating how popular Aizome is in Japan. “Aijiro” was also used for the body of Tokyo Skytree, a new landmark in Tokyo.