Natural Indigo Dyeing

Natural Indigo Dyeing, known as aizome in Japan, is a traditional technique that uses plant-derived indigo pigment to dye textiles. In Japan, the most commonly used plant has historically been tade-ai (Persicaria tinctoria), while Okinawa uses ryukyu-ai, and tropical regions such as India and Southeast Asia rely on indigo species like Indigofera tinctoria, commonly called Indian indigo. Each plant produces slightly different tones of blue due to differences in climate adaptation and pigment concentration. In Japan, the technique is thought to have been introduced from the continent during the Asuka or Nara period. By the Edo period, it had become deeply integrated into daily life, with the prevalence of indigo-coloured clothing leading foreign visitors to refer to it as “Japan Blue.”

Among the major indigo-producing plants, tade-ai and Indian indigo are botanically distinct. Tade-ai thrives in Japan’s temperate climate, while Indian indigo is better suited to hot, humid environments and contains a higher concentration of pigment, making it easier to achieve a strong and clear blue. In Japan, tade-ai is traditionally fermented and dried into a dye material known as sukumo, producing a deep, slightly reddish-blue hue. Indian indigo is often processed into solid cakes and yields a purer, brighter blue. These differences in source materials result in subtle variations in colour and texture of the dyed fabric.

The dyeing process relies on chemical reactions of reduction and oxidation. Because indigotin (the main blue pigment) is insoluble in water, it must be chemically reduced to a soluble form in the dye bath. Once absorbed into the fibres, it reoxidises upon exposure to air and becomes fixed to the fabric as a vibrant blue. Just after being removed from the dye bath, the fabric appears yellow-green or ochre, gradually turning blue as oxidation proceeds. Chemically reduced vats tend to produce brighter yellow-green tones upon removal, while traditional fermentation vats may yield more brownish shades at that stage.

The preparation of the dye bath, known as “building” the vat, can be carried out using either fermentation or chemical reduction methods. The fermentation method, deeply rooted in tradition, involves fermenting sukumo with natural ingredients like wood ash lye and rice bran to create a living vat maintained by microbial activity. This process requires significant time, attention, and expertise. The chemical reduction method uses reducing agents such as sodium hydrosulfite to quickly produce a stable and consistent vat, making it suitable for modern production environments.

At MITTAN, Indian indigo is primarily used in combination with the chemical reduction method. This ensures consistency in quality while maintaining the distinct character of natural indigo. In cases where deep colouration is desired, the fabric is dyed multiple times, producing layered, nuanced shades of blue. The finished appearance varies depending on the fibre type and the angle of light, resulting in textiles with subtle and dynamic expressions.

Over time, indigo-dyed garments soften and shift in tone through wear and washing. The colour gradually fades in areas that experience friction, adding depth and individuality. MITTAN values the historical significance of indigo dyeing and the evolving beauty that comes with time, continuing to incorporate this traditional technique into its work.