In Japan it’s called “aizome”. A dyeing process that uses the country’s native indigo plants, resulting in fabrics that possess a depth of colour and detail that mark them out as something special. As with most ancient crafts, aizome has been modernised and streamlined to a certain extent with the use of chemicals and complex machinery. But there are still a handful of artisans and workshops that are committed to the old ways, honed over generations. They combine natural ingredients and tend to their inky potion like a master vigneron or alchemist, or someone who is really into their sourdough starter.

Our friends at visvim, a legacy brand with a reputation for championing local textiles and techniques, handily break the process down for us. “Hakkō-date – the traditional method that aficionados believe gives the finished garment the best colouring and quality), which has been practiced in Japan since the Edo period – begins with the drying of the leaves of the Japanese indigo plant. These are then fermented to produce a substance called sukumo, the base for indigo dye.

“Next, lye (made from a mixture of wood ashes), alcohol, wheat gluten and lime are added to the sukumo and it is left to rest. The mixture needs to be stirred in the morning and evening. After three or four days, the fermentation process will have begun, at which point more lime is added in. When the fermentation has sufficiently progressed, more lye is added, then the rim of the vats is raised. After one week to 10 days, it will finally be ready to be used as a dye.”

From there, it’s all down to the experience and feel of the individual who is overseeing the job, an inexact science that makes aizome even more alluring. If you’ve seen a pair of jeans, a shirt or a chore jacket that’s been coloured using the original approach, you’ll immediately notice the shades of blue that run throughout the fibres. These will patinate and shift over time with wash and wear, almost like a living thing that ebbs and flows. It’s connected to its original environment in a way that few garments are.

Certain brands such as Blue Blue Japan – the clue is in the name – have made indigo a pillar of their designs, applying it to sashiko cotton tailoring, habutai silk shirts and even leather biker jackets. As mentioned, visvim knows its way around a fermenting vat. It also utilises a Japanese mud-dyeing technique – dorozome – that has been around for more than 1,000 years and produces unparalleled shades of brown and black. But that’s another story.

KAPITAL, OrSlow, Kaptain Sunshine and Beams Plus are all fellow Japanese brands with a deep appreciation for indigo. Even iconic European names such as Stone Island, whose approach to fabrication and colour development is legendary, owe something to the dedication and craft of those artisans in Tokushima and beyond. Those who were able to take a local plant, along with a handful of other ingredients, and create blue magic.