Fermented Indigo (Sukumo)
The raw material for indigo dyeing, sukumo, is made by spreading harvested and dried indigo leaves (aiai) in a fermentation bed, sprinkling them with water, and mixing thoroughly to ferment.
Starting from the initial day called “Nesegomi”, the sukumo is created over more than 100 days through more than ten rounds of “Kirikkaeshi” (turning and mixing).
At the peak of fermentation, the center of the sukumo reaches about 70°C (158°F), and steam fills the entire fermentation bed, accompanied by a strong, pungent odor that can be overwhelming.
Careful observation using all the senses is essential to closely sense the state of fermentation. Although invisible to the human eye, the fermentation bed is full of a living microscopic world.
October – February: Making Sukumo (Nesegomi and Kirikaeshi)
Starting in October, dried indigo leaves (aiai) are spread out on a dirt floor called the fermentation bed (nedoko), sprinkled with water, and thoroughly mixed to expose them evenly to air. This initiates natural fermentation.
This first mixing process is called “Nesegomi.”
 "Nesegomi"
|
 "Sprinkling and mixing water on the dried indigo." |
 "Piling the indigo into a mound" |
 "One week after nesegomi (initial layering)" |
Afterward, while monitoring the fermentation progress, the pile of indigo leaves (aiai) is broken up once a week. Water is added as needed, and the mixture is stirred thoroughly to expose it evenly to air.
During this process, the inner and outer parts of the pile are swapped to ensure uniform fermentation.
This repeated task, starting from the second time onward, is called “Kirikkaeshi” (turning or mixing).。
 "Spraying" |
 "Kumade (A bear hand rake)" |
 "Pitchfork" |
 "Rake" |
 "Hane (A paddle for mixing fermented indigo)" |
Fermentation generates heat, and at its peak, the core temperature reaches 75°C (167°F).
The entire fermentation bed is filled with a thick steam of ammonia, producing a strong, pungent odor that can be overwhelming.
 "Bozu (Bundled fermented indigo)" |
 "Futon (Bedding)" |
Starting in October with a process called “Nesegomi” (laying down the indigo leaves), the sukumo is developed over more than 100 days and through more than ten rounds of “Kirikkaeshi” (turning and mixing).
By the end of February, the fermentation stabilizes, and the sukumo — the raw material for indigo dyeing — is completed.
Afterward, it undergoes surface packing and is further matured over approximately six more months.
 "Sukumo (Fermented indigo)" |
 "Rice straw bale packing" |
Watanabe's
2024 — This summer brought intense and prolonged heat, but thanks to the rain that fell at regular intervals, our indigo grew stronger than we ever expected.
Despite the exhaustion from the relentless heat and the challenges of sudden, heavy rainfall caused by linear rainbands, we worked together as a team and successfully harvested high-quality indigo leaves.
We offer our heartfelt thanks to everyone on the team and to all those who supported us.
 "Yoshino River" |