- Japanese: 藍 (ai)
Indigo is a deep blue dye made from the leaves of the indigo plant. It was a very commonly and widely used dye in medieval and early modern Japan, and around the world. Tokushima han (Awa province, modern-day Tokushima prefecture) was the chief indigo-producing region in early modern Japan, and that most highly regarded for the quality of its product, though other regions are known for indigo production as well.
Indigo is a somewhat intensive crop, requiring fertilizer six times per season, and considerable labor, and is quite sensitive, or delicate. Poor handling can severely damage the quality of the crop. Once harvested, the leaves must be chopped and dried immediately, before they wither. Indigo processors known as aishi took the chopped dried leaves and mixed them with water, forming them into a mash which was allowed to ferment for several months, ideally under specific conditions of temperature, pressure, and moisture. The dye is formed as the leaves ferment; in order to obtain high quality dye, the leaves must be fermented neither too little nor too much. Once ready, the mash was then beaten and formed into balls or cubes known as aidama. It was in this form that they were then sold to dyers, typically based in Kyoto or Osaka.
Persicaria tinctoria (J: ai, tadeai), a plant native to East Asia, was used for indigo dyeing in China as early as the Western Zhou period (c. 1000 BCE), and was originally used in Japan as well, until the use of Indigofera tinctoria ("true indigo", J: komatsunagi) and or other plants of the Indigofera genus originally native to India spread into East Asia as it also spread into Europe. Ryukyuan indigo dyeing, meanwhile, traditionally used a different plant, Strobilenthes cusia (J: kitsunenomago), as was also used in Taiwan.
- Mark Ravina, Land and Lordship in Early Modern Japan, Stanford University Press (1999), 158-159.
- Ravina, 159.
- Gallery labels, "Churashima Textiles" exhibition, Shoto Museum, Tokyo, Sept 2019.