The Mill


Pure Blue Japan
AI-003 "Natural Indigo" 18oz Unsanforized Selvedge Denim

We’re excited to introduce the Pure Blue Japan AI-003, among the most incredible and rarest jeans we’ve ever had at Blue Owl. The fabric is woven through a painstakingly slow process on a single shuttle loom that has been custom modified. The result is a uneven and streaky denim that alternates between extreme slub and smooth uniformity. However, what is truly amazing about this jean is not just the fabric, but the natural indigo dye that capitalizes on generations of tradition to create one of the most beautiful colors in the world.

Indigo is one of the oldest plant dyes in existence, first brought to Japan approximately 1400 years ago. It originally was used by the Heian Imperial Court, but gained popularity during the Edo period when it became the dye of the common people. With widespread use many different designs and dyeing methods developed during this era.

During World War II the art was almost lost as the government required all agricultural land to be used for military purposes, prohibiting cultivation of the indigofera plant. Heisuke Sato, the most prominent indigo grower in Tokushima, continued his indigo cultivation in secret for many years despite the risk. The Japanese government has since recognized him for keeping the plant alive during the war. It is thanks to him this beautiful natural dye still exists in Japan. Today his grandson, Akihito Sato, continues his lineage as a 9th generation indigo craftsman, growing the plant and preparing the dye that is used for Pure Blue Japan’s AI-003 jeans.

Natural indigo is a unique dye that takes months to prepare. Compared to synthetic indigoes it creates a richer, deeper, more fascinating color which takes longer to fade. While the process is long and expensive, requiring years of experience, the color produced is well worth the costs.

Adhering to over 500 years of cultivation tradition, Sato oversees the entire production of the indigo, from the growing of the plants to the processing into usable dye. The process begins in the fall, when leaves are picked, chopped, and left in huge piles more than 60" high to ferment. Using water pumped from wells 80 meters underground, the piles are sprinkled, raked, and mixed every five days for three months, fermenting until mid December. At this point the indigo is water soluble, and ready for the dye bath. The fermented leaves are called “Sukumo”, and because they are alive with organisms, Sato says they must be treated with love to create a good color.

To prepare the dye bath the Sukumo is poured into clay vats filled with water and mixed with wood ash and lye. Lime and Sake are combined with other natural ingredients to finalize the mixture. It must be stirred several times per day to ensure fermentation. The peak of the dye is reached when bubbles begin to foam at the top of the solution. This is known as an “Indigo Blossom”, and means the dye is ready to be used.

Fabric that has been dipped in the dye will come out green, and must be exposed to air to oxidize into blue. The shade of blue after one dip will be very light, and the dipping process must be repeated many times to achieve darker colors. The time the fabric is dipped during the life of the dye, the pH balance of the solution, and temperature all have significant effect on the outcome, and the best results require years of skill and experience.

The indigo shades each have unique names based on the time the fabric is dyed and the number of repetitions. Kamenozoki is the lightest shade, almost white. Asagi is a very pale shade of blue. Hanada is reminiscent of a sky blue hue. Nokon is the deepest color. Each color is distinct, but can have a wide range of shades within it. The AI-003 uses one of the deepest dyes possible with natural indigo.

All of us at Blue Owl are honored to offer the culmination of hundreds of years of history and tradition in the AI-003 jean.