Building a Living Indigo Vat: Our First Fermentation Vat Session

Today Indigo Week moved from theory into practice as we gathered online to build our first indigo vat together.

After a week of exploring indigo through history, culture and traditional Japanese sukumo making, it felt fitting to finally roll up our sleeves and begin the process of creating colour ourselves.

The vat we built today was a fermentation vat.

Unlike quick reduction methods, fermentation vats rely on living biological processes to gradually create the conditions needed to reduce indigo. Rather than forcing a reaction, we are encouraging one. The vat becomes a small ecosystem, supported by warmth, food and careful observation.

For many participants, this was their first fermentation vat. Others joined with years of experience, curious to compare methods and deepen their understanding of how these living systems function.

One of the recurring themes throughout the session was patience.

Modern life often encourages us to expect immediate results, but fermentation vats work to their own timetable. Today was not about producing blue cloth within an hour. It was about creating the conditions that allow the vat to develop over the coming days and weeks.

As we mixed indigo, madder, wheat bran and alkaline ingredients together, conversations naturally emerged around water quality, vessel sizes, temperature control and scaling recipes for larger vats. Questions ranged from transporting vats and maintaining temperatures to the influence of household water chemistry and future upscaling possibilities.

One topic that generated particular discussion was temperature.

Fermentation vats are living systems, and like most living systems they have preferred conditions. Maintaining a stable temperature of around 28°C gives the microorganisms the best chance to thrive and begin the work of transforming the vat.

What I love about fermentation vats is that no two are ever quite the same.

Each vat reflects its environment, its ingredients, its temperature and the decisions of the person caring for it. The recipe may be identical, but the journey is always slightly different.

For those who made a vat alongside the session, the real learning begins now.

Over the coming days we'll watch the vat change, monitor its progress and learn to recognise the signs that fermentation is beginning to establish itself. Some vats will move quickly. Others will take their time. Both are entirely normal.

If you were unable to join us live, don't worry. The session recording is now available to watch, and the accompanying PDF handout can be accessed on the Academy platform in the Full membership Resource library. The PDF includes the full recipe, ingredient list, equipment recommendations and key notes from the session, making it easy to follow along and build your own vat at home.

Tomorrow we continue our exploration with the Organic Fruit Sugar Vat before moving on to the Mineral Vat later in the week.

By the end of Indigo Week, participants will have seen three very different approaches to indigo reduction and will hopefully have a clearer sense of which style of vat best suits their own practice.

For now, our fermentation vats are quietly beginning their work.

And we wait.