In Kyoto’s Nishijin district, indigo dyer Toshiyoshi Sumita runs his studio. At the age of 27, he succeeded his predecessor as head of Ai Ai Co., Ltd.. Using the traditional method of Awa Natural Lye-Fermentation Indigo Dyeing, he carefully dyes high-quality silk, bolt by bolt, over time—creating unparalleled shades of indigo that have drawn attention across the industry.

Called “Japan Blue,” indigo has been used in Japan for over 1,300 years since it was introduced during the Asuka period. Indigo encompasses not only the familiar navy blue but also a wide spectrum—48 shades ranging from pale blue-white to deep purples and near-black hues.

At Ai Ai, sukumo (indigo compost) produced in Awa (Tokushima Prefecture), where the tradition has continued for over 600 years, is used. This is fermented with oak ash lye and sake in the Awa Natural Lye-Fermentation method, focusing especially on dyeing silk, a fabric considered particularly difficult to work with.

In the past, Toshiyoshi worked alongside his late father and elderly mother, dividing the process among three people. With the heavy workload falling on his shoulders, he introduced rare dyeing machinery to this traditionally labor-intensive industry. This allowed him to dye four-bolt lengths instead of the previous limit of one, improving efficiency while continuing to dye silk with unmatched care and beauty.

The process begins with makitori, washing away impurities and evenly moistening the fabric while wringing. Next comes repeated washing to remove proteins and impurities from the silk before dyeing begins.

In dyeing, fabric is immersed in the fermented indigo vat, then oxidized in the air to develop color. Even when the studio is kept at a stable 25°C, subtle differences in fabric condition, air, humidity, or water temperature affect the final shade. The cloth must therefore be dyed evenly and carefully. Wrinkles, sweat, dust, or even a tiny bubble can cause unevenness—removing these is the dyer’s most critical focus.

After dyeing, the fabric is washed again and again. To achieve a typical indigo color, the process requires around 200 cycles of washing and wringing. The thoroughness of this work determines whether the indigo emerges flawless and uniform. Using the Awa Natural Lye-Fermentation technique, color clings to every silk fiber, producing long-lasting brilliance that synthetic dyes and inkjet printing cannot replicate.

After sufficient washing, the fabric is dried. Because the color appears darker when wet, the dyer must anticipate the final shade after drying and adjust the number of dyeing repetitions accordingly. It is said that three years of training are needed to master this judgment.

Even with some mechanization, genuine indigo requires countless cycles of dyeing and washing—taking at least six months before becoming a finished product. Shortcuts can reduce the time to one or two months, but the results are colors that fade easily, fail to achieve beauty, and cause problems decades later.

“When I inherited the business at 27, after my father’s death, I realized: careless work today becomes a problem in 10 or 20 years. To create kimono that can be worn by both mothers and daughters across generations, I must ensure colors don’t fade and garments endure. That is why I think always of the customer when I work,” says Sumita.

“Indigo dyeing on silk depends on five essentials: selecting fabric suited for dyeing, preparing the vat without chemicals, dyeing properly, repeating washing and wringing thoroughly, and fixing the color securely. Doing everything properly takes immense time, and the temptation to cut corners is always there. But if you endure, you create something truly good. With cheap products circulating widely, I choose to stand firm with genuine silk and true indigo. Even among dyers who claim devotion to materials, few take washing and wringing as seriously as I do.”

“There are no limits to the technical heights we can reach. My goal is to keep refining my craft while continuing, steadily and honestly, for the long term. I want to create works that let people experience indigo’s true depth and beauty, and make them think, ‘This is beautiful.’”

Through Sumita’s work, one can truly feel both the depth and the authenticity of genuine indigo dyeing.