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PBJ Natural Indigo




ONLY A HANDFUL of indigo craftsmen, certified by the Japanese government, have mastered the natural indigo dyeing technique–prized in Japan as a cultural treasure–that makes the PBJ AI Series so unique. Natural indigo dye also requires a lengthy fermenting process with a low annual yield, which makes the dye a highly coveted material around the world.

For the AI jean, 100% cotton yarns are hand dipped into natural indigo dye made from indigo harvested in the Tokushima prefecture. Dipping the yarns repeatedly by hand allows the indigo to penetrate the core of the yarns, which is why natural indigo jeans retain their color so well. Most indigo dyed jeans use yarns that have not fully absorbed the dye; as a result, with moderate wear, these yarns will reveal their white centers. Natural indigo garments, on the other hand, retain their blue color longer and ultimately age more beautifully over time.

Below we’ve broken down the lifecycle of the AI Natural Indigo jean, whose incomparable texture and color never ceases to impress us, season after season.

Field to Fermentation



After seeding begins in March, by the time May comes around roots are mature enough to be transplanted from the greenhouse to the field where they grow beautifully.


Around July or August, the leaves are cut twice: first when they are almost 20" long, then, after a short period of regrowth, they are cut again. Usually the first clipping produces a more beautiful indigo color so the first and second cuttings are often combined.


Once harvested, the leaves are dried completely and separated from the stems since the stems do not produce any color. Everything is done manually so this step of the process is very labor-intensive.

Sukumo (すくも)

Leaves are fermented naturally for more than 3 months (90-100 days). This process produces the concentrate that contains the indigo colorant (called “sukumo” in Japanese). Fermentation must be carried out in humid conditions–the ideal temperature is around 140° Farenheit.

Washing to Weaving



The sukumo is placed in stone vats buried into the ground. Water, ash, as well as glucose and Japanese sake are added to fortify the dye. Artisans select vats with the right temperature and humidity.


Indigo color is extracted from the leaves by way of a four step soaking process: soaking, wringing, washing, and then wringing once more. For the Pure Blue Japan AI series, this process is repeated 12-14 times.


Winding of the yarns. (At this stage of the dyeing process, yarns are arranged into a loose wheel shape and as pictured above, they are winding effortlessly.)


Sorting yarns to prepare for weaving. For the AI series jean with a fabric width of 31.5 inches, there will be 2300 strings of yarn required for production.


Finally, weaving begins.


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