Maintaining and Troubleshooting an Organic Indigo Vat

Jacquard woven shibori, indigo dye
Jacquard woven shibori, indigo dye

The questions I receive most frequently about natural dyeing seems to center on  the indigo vat and its maintenance. Since 2011 I have been making and using organic indigo vats, an art and  skill that I learned from Michel Garcia.

My current vat began in a 5 gallon vessel over 2 years ago. I enlarged it to fill an 8 gallon vessel, and then last year I enlarged my vat again to fill a 30 gallon container. The increased size was needed because I was dyeing larger pieces of cloth.

my current indigo vat, 30 gallons
My 30 gallon indigo vat

The vat was made using henna as a reduction material. I chose to use this material because the slow release of sugars is good for a vat that will be maintained for a long time.  I add fructose after each use and additional henna when I need to boost the reduction. Lime (calcium hydroxide) is the alkaline.

The vat is used regularly and I achieve excellent color from the indigo.  The large size challenges me to solve problems as I encounter them. It would be tempting to discard a small vat that was not behaving well and begin again, but emptying this vat would require a great amount of effort. As a result I’ve learned a lot about maintaining the indigo vat.

An indigo vat is happiest when it is used on a daily basis. After each dyeing session I “feed” it with a bit of fructose, stir it to bring the un-reduced indigo and reduction materials up from the bottom, check the pH, and let it rest for a few hours before dyeing again.

Occasionally I run into problems that I need to solve. Recently I was away from home for several weeks. Before I left, the vat was dyeing rich, deep blues. The color of the vat was a golden bronze and there was a good healthy “metallic” sheen on the surface and plenty of bubbles.

surface of a healthy vat
Surface of a healthy vat

When I returned home the first thing I did was add lime to the vat.  When an indigo vat sits dormant for any amount of time it becomes more acidic and the pH goes down. I can test this with pH papers but a good visual indicator is to sprinkle some lime on top. If the lime is immediately “sucked” down into the vat – you can assume that the vat is in need of the lime. If the lime just sits on the surface, the pH is probably fine.

Next, I stirred the vat and waited for it to settle. The color of the vat looked good, as well as the surface. The vat was a clear gold color and there was a coppery sheen on top. But the first test sample resulted in barely any color at all!  That was a surprise, since I thought there was plenty of indigo in the vat. I thought I had also been “feeding” it with plenty of sugar. The vat had been used very heavily before I went away. I thought that possibly the indigo had finally been exhausted.

Before adding more indigo to the vat, I decided to add more sugar – a generous amount. Once added, the vat was stirred and I waited until the next day to do another test strip. It produced a  blue, though it was relatively light. I repeated the sugar-stir-rest and dyed again the next day. It was darker. I repeated the sequence again, and finally got back to a shade of blue similar to that which I had before going away.

dye test strips
Dye test strips

The lesson here is that before adding indigo to a vat, test it thoroughly for pH and reduction.  Although it “appeared” to be healthy, my vat was not reduced and the indigo wasn’t available to dye the fibers.

A Lesson About Dye Plants: Broom

Several years ago, as a novice dye gardener, I was perusing dye books to determine which plants I could grow here in the mountains of North Carolina, and I found a mention of the plant called broom. I had never grown it before and had never dyed with it, so I ordered two of the plants that were specified in the book: Cytisus scoparius, otherwise known as scotch broom. I had seen this plant growing along the roadsides in the west and knew that this plant was very invasive. Were all of those plants a potential source of great color?

After the plant had been in the ground for a year, I did more investigation and learned that scotch broom (Cytisus scoparius) was NOT the great dye plant I thought it might be. The one I should have planted was dyer’s broom, (Genista tinctoria). Other names for this dye plant are dyer’s greenwood or woad waxen. It has a long and distinguished history as a plant used for dyeing. In fact the word “tinctoria” is the latin word meaning “used for dyeing” and any plant that has “tinctoria” in its name has been traditionally used for dyeing. All dye plants, though, do not contain the word “tinctoria” in their name.

I ordered two dyer’s broom (Genista tinctoria)  plants and put them into the bed outside my studio next to to the scotch broom. When both plants were large enough I did some dyeing and compared the samples. I needed to see for myself what, if any,  difference there was in the two plants. There was clearly “no contest” in the results obtained The dyer’s broom dyed both wool and cotton in brilliant yellows and yellow greens. The color is  very similar to the one I get from weld plants. In fact both weld (Reseda luteola) and dyer’s broom (Genista tinctoria) contain luteolin, which gives a clear yellow that is extremely fast to washing and light. The scotch broom (Cytisus scorpius) gave me a very pale yellow or beige color.

The scotch broom (Cytisus scoparius) in my garden is blooming this spring for the last time. As soon as the flower “show” is over I plan to  remove it in order to make additional room for the dyer’s broom (Genista tinctoria).

Last year I was able to harvest enough of the dyer’s broom (genista tinctoria) for several projects and dry some of the shoots and leaves for later use. Genista tinctoria has earned a place in my garden. I still have a lot to learn from this plant, such as when is the best time to harvest for dyeing or drying and how to keep it pruned properly. I have learned to do more research about my plants and ALWAYS to pay attention and use their latin or scientific names.

Cytisus scoparius, left Genista tinctoria, right
Cytisus scoparius, left. Genista tinctoria, right

Experiments and Results

I am a weaver of textiles and a dyer. In the past I have used all types of chemical dyes to obtain desired results with my woven shibori fabrics. I live and work in the mountains of North Carolina near a small creek that flows into a river full of native trout. Our water comes from a shallow well and we have a septic system.  I have developed an an increased awareness of potential chemical pollution of these water sources and systems and have been inspired to begin a study of natural dyeing.

For the last 8 years I have been engaged in a learning adventure about natural colorants which I have found deeply satisfying. I have been exposed to great teachers: Michel Garcia of France and Joy Boutrup of Denmark. They are both scientists, and dyers, who have both helped me find a path which includes questioning and observing. Michel Garcia once stated in a class that it was more important to understand “why” than “how”. I have thought about this a great deal and always try to go beyond a recipe in order to understand the logic behind it.


I am an artist, not a scientist,  but have developed the skills to observe carefully and trust my own experiments. If I don’t know whether “X”  or “Y” process will work best, I do them both and record the results. My goal, as an artist, is to learn effective processes. I don’t always have a definitive scientific answer but I have learned to  observe objectively and be willing to change the way I work.

Each experiment brings a new insight and the realization of just how complex the field of natural dye is. My understanding of the fibers and interactions with dyes themselves has deepened, and I have a new respect for botany and chemistry.

I regularly carry out lightfastness tests, using the blue wool scale, an international standard to measure  the lightfastness of dyes. As a result of the tests, I have relegated some dyes to the back of my shelves some dyes from my shelf because they don’t perform well enough. When I go back and read old dye books, history usually confirms what I learned first hand.

My teaching and my work is now done entirely with natural dyes. Frequently students and colleagues contact me with questions, requesting further clarification of process, or needing encouragement. I try to answer those questions and at this point have decided to answer them in a more public format in the hope that the information might be of use to others. Hence the creation of this blog: Natural Dyes: Experiments and Results.

I don’t always have definitive answers. I know only what I have experienced and that knowledge is constantly evolving. I trust and depend on my teachers and colleagues who are using natural dyes and we have begun to study and question together. So I will share some of my own lessons from my own dye studio, my “kitchen of natural colors”, as we all learn together.

Your feedback is welcome and desired.

working in the window
Lightfast test “working” in the window