Sukumo - Polygonum tinctorum - Fermented Japanese Indigo

Pile of dark blue powder on a white background

Sukumo - Polygonum tinctorum - Fermented Japanese Indigo

$61.00

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Also known as composted Japanese indigo, traditional Japanese indigo leaf preparation.

Sukumo is the traditional Japanese preparation of indigo leaves, essential for creating a classic indigo fermentation vat. Freshly harvested leaves of Polygonum tinctorium are carefully composted over about four months, during which they are watered, turned, and aired until they transform into a rich, earthy, and fragrant (some would say smelly) mass of indigo matter.

Historical Note
The sukumo-making tradition has been practiced in Japan since at least the Heian period (794–1185), where it became central to the famous aizome (indigo dyeing) industry. Skilled sukumo makers are highly respected artisans, as the process requires patience, precision, and deep knowledge of fermentation. Sukumo production remains a rare and specialised craft.

Available in limited quantities.

Main dye compound: Indigotin
CI Natural Blue 1

Shading Tips

Produces classic aizome blues, from pale sky-blue to deep navy, depending on vat strength and immersion time
Layering multiple dips yields richer, darker tones
Overdye with yellows (weld, marigold, fustic) → vivid greens
With madder → purples and near-blacks

Recipe for 1 kilo of sukumo;

In a sizable container, combine 1 kg of Sukumo with 500 g of oak tree ash.
Add 10 liters of chlorine free hot water (70-80°C) to the mixture and use a stick to stir for 5 minutes.
During this process, the liquid will foam up, but its color will transition to brown.
Continue stirring the liquid daily for a week, and over time, the liquid will gradually shift towards a darker hue.
Once you observe large bubbles forming on the liquid's surface, it is ready for use in dyeing. The prepared liquid maintains its efficacy for up to six months.

For external use only. Not edible.
Keep away from children and pets.
Wear gloves and mask when handling powders.
Avoid inhalation of dust and contact with eyes.

Non-edible: For dyeing purposes only. Not for food, cosmetic, or medicinal use.

Handling: Wear gloves and protective clothing when working with wet or dry sukumo. Prolonged skin contact may cause irritation.

Dust: Avoid inhaling fine particles when handling dry sukumo. Use a dust mask or work in a ventilated space.

Eyes: Avoid contact with eyes. In case of contact, rinse thoroughly with clean water.

Storage: Keep in a cool, dry place, sealed to prevent mold and moisture damage. Store away from direct sunlight.

Environmental Care: Dispose of wastewater responsibly, following local environmental regulations. Do not discharge concentrated vats directly into drains or waterways.

Children & Pets: Keep out of reach at all times.