From Plant to Pigment

The Fascinating Process of Making Indigo

Unlike many natural dyes, which are typically extracted from bark, berries, or flowers, indigo requires a more intricate—and fascinating—process. One common misconception is that indigo dye comes from the plant’s flowers. While indigo flowers are pink, the coveted blue pigment comes from the plant’s leaves and stems.

From Plant to Pigment

Our process began with harvesting the indigo plants, but we did not cut them down entirely. Instead, we trimmed just a few feet from the top of each plant. This sustainable approach allows for multiple harvests throughout the growing season while leaving the plants healthy enough to produce seeds.

Once harvested, the plant material was packed into two large tubs and completely submerged in water. Chicken wire was secured over the top and weighed down with bricks to keep the plants underwater. This began the fermentation process, which took approximately two days, although timing can vary depending on temperature.

We knew the fermentation was ready when the liquid turned a distinctive “mermaid” blue-green. This dramatic color change signals that indicant, a compound found in the leaves, has broken down into indoxyl, the water-soluble precursor to indigo. At the same time, the plant material loses its bright green color and becomes dull and mushy—another indication that the pigment has been released.

A strong, somewhat unpleasant odor may also develop during fermentation. While it may not be particularly inviting, this is a completely normal part of the process.

Once fermentation was complete, the plant material was removed and the liquid was strained. Calcium hydroxide, commonly known as lime, was then added gradually while the mixture was stirred. This raised the pH to approximately 10–12, creating the conditions necessary for the next stage of the process.

The vat was then left undisturbed for several days, allowing the indigo pigment to settle to the bottom. Full sedimentation was reached when the liquid above the dye became a tea-like color. Most of the water was carefully scooped away, leaving behind the concentrated dye.

The remaining liquid was drained through a 25-micron filter set over a five-gallon bucket. This fine filtration captured the indigo pigment, a process that took approximately a day.

The collected dye was then washed with a vinegar-and-water solution and strained again. The vinegar wash helps neutralize the high alkalinity left behind by the lime and can help stabilize the indigo for storage. Another day was needed for the washed dye to fully strain.

Finally, the indigo paste was transferred into mason jars and stored in the refrigerator. In this wet form, indigo can be kept cold for future use or dried for long-term storage. Traditionally, indigo was sun-dried or gently heated and pressed into solid cakes. Today, a dehydrator provides a convenient alternative, slowly removing moisture to create a shelf-stable indigo powder that can be transported or rehydrated for future dyeing.

Because the plants can be harvested multiple times throughout the growing season, our efforts yielded an impressive sixteen 16-ounce jars of indigo dye.

Preparing the Indigo Vat

Making the pigment is only half of the process. Before indigo can be used to dye fabric, it must undergo another chemical transformation known as reduction.

In its normal state, indigo is insoluble in water. Reduction transforms the pigment into a soluble yellow-green form that can penetrate the fibers of a textile. To create our dye vat, we used a five-gallon bucket containing approximately four gallons of water, along with soluble lime and a RIT reducing agent. Traditional instructions often recommend a 1-2-3 ratio of indigo, lime, and reducing agent, but we adjusted our measurements by eye as the vat developed.

An immersion heater maintained the vat at approximately 110°F, while the pH was kept around 10–11. Once the indigo was fully reduced, the vat was ready for dyeing.

Creating Indigo Patterns

Different fibers require different conditions for successful indigo dyeing. Protein fibers such as silk, wool, and cashmere generally prefer a pH around 10, while cellulose fibers such as cotton can require a higher pH, closer to 12.

Before entering the vat, fabrics were soaked in water and then folded, tied, or partially dipped to create patterns. We experimented with techniques including folding, rubber banding, and controlled immersion.

Each piece remained in the vat for at least 30 seconds per dip. When the fabric first emerged, it was not blue at all. Instead, it appeared a brilliant neon yellow-green.

Then the magic happened.

As the fabric was exposed to air, oxidation transformed the yellow-green color into rich indigo blue. Watching this transformation happen in seconds is one of the most captivating parts of working with indigo.

Multiple dips are needed to build depth and intensity. Between each dip, the fabric must be given time to oxidize before returning to the vat. Unlike many dyes that are absorbed directly into the fibers, indigo is deposited onto the surface of the fiber through repeated cycles of dipping and oxidation.

The Final Wash

Once the desired color and depth were achieved, the fabric went through a final washing process to remove excess dye and neutralize the alkalinity left by the lime.

We found that a three-tub system worked best. The first tub contained water to remove excess dye and lime. The second was a vinegar-and-water bath to neutralize the remaining alkalinity. The final tub contained clean water to remove any remaining vinegar.

The fabric was then washed with a pH-neutral detergent to complete the process. After this final wash, the indigo no longer bled, leaving behind beautifully saturated and long-lasting color.

From harvesting the plants to watching yellow-green fabric transform into deep blue, making indigo is a process of patience, chemistry, observation, and a little bit of magic. What begins as an ordinary green plant ultimately produces one of the world’s most recognizable natural pigments—and every step along the way reveals something remarkable about the relationship between plants, chemistry, and craft.

Landscape Team August 2026