Indigo: Still Learning, and at last….. Indigo Fermentation

The indigo chapter of the book Joy Boutrup and I wrote, The Art and Science of Natural Dyes (Schiffer Press),  focuses on the use of quick reduction vats that use iron, henna or sugar, along with lime (calcium hydroxide) to reduce the indigo. Since the book was published I have been very interested to learn more about indigo fermentation. The concept seemed daunting and I was hesitant to begin.

Why did I want to make a fermentation vat? 

Initially, I thought that the indigo crocking issues that I described in the last post might be solved by making a vat that did not use large quantities of lime. 

The vats that use large quantities of lime (calcium hydroxide) also seemed to be presenting a challenge with “fading” issues. I had fabrics that were not exposed to direct light,  but the exposure to air itself seemed to make the indigo fade in a very unattractive manner. I consulted with another experienced indigo dyer who was having this same issue with her vats and we suspected that the amount of lime in the henna and sugar vats was part of the problem. Textiles dyed in an iron vat do not seem to exhibit this type of fading, despite the high volume of lime.

 

And finally, and maybe most importantly, fermentation seemed like the ultimate in understanding indigo. It’s the oldest, traditional process where bacteria is used to reduce the indigo.  I wanted to experience it.

At the end of last summer, I made the commitment to begin working with a fermentation vat. Hisako Sumi, a friend, colleague, and indigo dyer from Japan, has been encouraging and coaching me through the process. 

I began with a simple recipe for a fermentation vat that was published online by Cheryl Kolander of Aurora Silks. The vat was made with 

    • indigo pigment 
    • ground madder root, the source of fermentation 
    • soda ash, to achieve the correct pH 

It worked! It took several days of warm weather (or some applied heat) and patience. The blue dye from the vat was clear and strong. Thank you, Cheryl.

Since that first vat I have made and maintained many small (1 or 2 liter) experimental vats.  I have a 30 liter vat that I have using regularly for several months and am now preparing to make a 150 liter vat for use with larger textiles. 

The Indigo dye

A typical fermentation vat in Japan is made using sukumo. Sukumo is composted indigo (polygonum tinctorium) leaves. The sukumo is both the source of the indigo dye and the source of bacteria that results in fermentation of the vat. I do not have access to sukumo  although I still have plans to make a small batch of sukumo.  I have been using organic indigo pigment from Stoney Creek Colors for all of my fermentation vats. 

Alkalinity

Fermentation vats do not require the high alkalinity that is necessary for the quick reduction vats, which perform best at a pH near 12.0. The fermentation vats require a pH between 9 -10.  I have made many fermentation vats since that first one, experimenting with various alkaline sources: wood ash lye that I leached from hardwood ash, soda ash, potash, and very small amounts of lime (calcium hydroxide) or lye (sodium hydroxide) to control the pH.  I have monitored the pH carefully.  In the first few days, when fermentation is beginning, the pH will go down.  

pH papers were not accurate enough to discern the pH fluctuations. I invested in a good pH meter, which I calibrate regularly. Because of the relatively low pH, the vat is suitable for both cellulose and protein fibers without fear of damaging the textiles. 

Organic material for fermentation

I used a very finely ground madder root powder from Maiwa in my initial experiments. I’ve been told that the freshness of the plant material matters for purposes of fermentation. Madder root was traditionally been used as a source of bacterial fermentation. Indigo dyers typically used madder root that had already been used for dyeing red. Once the red dyes have been extracted, the plant material is still a viable source for fermentation. 

Other sources of material for organic fermentation that I have used include: wheat bran (cooked for a few minutes in a little water) and dried, ground indigofera tinctoria leaves, which are sold as a hair dye (also called “black henna”). I was given a woad ball and added that to one of my vat experiments and it definitely speeded up the fermentation/reduction.

Traditionally, in England, woad balls were “couched”  or composted in order to extract both pigment and provide bacteria for fermentation – much like sukumo. When indigofera tinctoria was introduced from India, woad was used more often to boost fermentation, as opposed to being the primary source of dye.

Hisako encouraged me to use indigo plants from my own garden to to increase the source of bacteria for the vat. I grow small amounts of persicaria tinctoria, indigofera suffruticosa, and isatis tinctoria in the garden.  After grinding the fresh plant material, forming the balls or patties, they are dried for storage and added when needed to boost the fermentation of the vat.  I assume that once the plant material breaks down in the vat, it is also a minor source of indigo pigment but this is speculation. 

Natural fermentation vats have changed how my dye studio smells – no longer the sweet sugar or plant smell of the quick reduction indigo vat – but now the odor of true fermentation and rotting plant material. I’ve quickly gotten used to it and it is now the smell of a successful vat, though my husband finds the smell very offensive and avoids coming into the studio!

Temperature

The ideal temperature for fermentation is between 80-90°F (27-32°C). Think of the rising of bread dough! Warm climates are the natural environment to make and maintain these vats. In my North Carolina mountain dye studio (with no heat) it is more of a challenge. In Japan, I saw many large indigo vats wrapped in electric blankets. I use heating pads around my small one-liter and two-liter vats and a bucket warmer (used to keep honey in a liquid form) for the larger vat. To prevent the vat from getting too warm, I use a temperature controlling outlet with a thermostat and probe.  

Maintaining the Vats

I have been keeping careful records of these vats, sampling on a regular basis and documenting and recording any additions. Keeping good records is key to my understanding and confidence! 

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Every few weeks the vats are “fed” with a small amount of cooked wheat bran or a small amount of indigo balls or patties. 

The quick 1,2,3 reduction vats using sugar, fruit, or plants have introduced many of us to non-chemical reduction processes and made it possible for us to dye with indigo on a regular basis. They are accessible,  easy to make, and can be ready within a few hours, thus making them ideal for workshops and experiments. These vats have taught us the principles of indigo reduction and dyeing and I am forever grateful to Michel Garcia for teaching us about them.

For the long-term serious dyer, I  believe that the fermentation vats are a viable alternative. They require more time and attention but I have been surprised at how well these vats have tolerated neglect when I am away from the studio – sometimes for several weeks. When I go away, I turn off any supplemental heat, cover them, and just let them be. When I return home, I check the pH and adjust if necessary. Then I dye a test sample. If the color is weaker than when I last tested, I will “feed” them, stir, add some heat and wait a day before test dyeing again.  

The fading issue seems to be solved with the use of fermentation vats. I can’t say that I have completely solved the crocking issue, though I think that yarns dyed with the fermentation vat are crocking less.  Maybe this is just the nature of indigo… 

Indigo and Crocking

At this time last year, The Art and Science of Natural Dyes (Schiffer Press) was published. Joy Boutrup, my co-author, and I submitted the completed manuscript almost two years ago. During these last 24 months I have been teaching, traveling, and continuing to work in the studio. We have heard from many of you and appreciate that dyers are actively using the book. I’ve tried to respond to the numerous questions and comments that have come my way. 

I continue to learn, and plan to publish a series of posts that will reflect some of the lessons from the dye studio that have revealed themselves in the last months. 

Today I want to share issues with indigo and crocking. 

A couple of years ago, I took up knitting…once again. I dyed yarns in my 30 gallon indigo vat reduced with henna. This vat has been dyeing well for approximately 3 years.  I came directly in contact (no joke) with the crocking issues of indigo. Crocking occurs when excess dye rubs off onto another textile or on the skin.  My knitting yarns had been dyed well, neutralized, finished by boiling and yet still they crocked. Because of the handling of the yarns, knitting reveals rubbing issues that are easier to ignore with other dyeing projects. 

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Testing for crocking is done by rubbing a small piece of white cotton 30x onto the textile.

This has started me on a long, involved exploration of indigo vats that has taken me in many directions. 

Indigo does not attach to the textile in the same manner as mordant dyes, so I think that some crocking is inevitable when dyeing with indigo but I wanted to see if we could decrease the amount of crocking on my yarns. 

I suspected that part of the problem was the high quantity of lime (calcium hydroxide) in the henna vat – or in any of the quick reduction vats. Joy also believed that the calcium binds to the indigo, making it more difficult to remove from the textile. 

The first thing we explored was a more thorough washing of the dyed textile.  Usually I finish all textile with a neutral detergent but a mild alkaline soap is particularly effective in removing excess dye. In order to be effective, the soap must be concentrated enough to foam up when heated. We soaked the indigo dyed textile in a mild “Ivory Soap” solution. We watched and saw that more of the excess indigo released from the textile in the soap solution than with a neutral detergent. The challenge when using soap is that it does not rinse out, leaving a fatty substance behind that would make mordanting and over-dyeing problematic. We used a heated Metaphos (phosphate) solution to remove the soap. But we saw no difference in the crocking after this treatment. 

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soaking water with detergent (left) and soap (right)

Next, we experimented with substituting lye (sodium hydroxide) for the lime (calcium hydroxide) in both henna and iron vats. Joy determined the amount the lye required, based on the molecular weight. We substituted 1.3 grams of lye (sodium hydroxide) for 1 gram of lime (calcium hydroxide). 

We often think of lime as being benign because it can be purchased it in the grocery store as “pickling lime” but it is a very strong alkaline and we need to be careful with both of these substances.

While teaching at Penland School of Crafts last summer, Joy and I made two 5 gallon vats with the class, using lye with  henna and iron as reduction agents. Initially these vats worked very well and there was an added benefit with the lye: no calcium sludge in the bottom of the vat.

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“Rubbing cloths” indicated by dotted lines. The henna vat made with lye resulted in excellent rub-fastness.

 The vats made with lye seemed to significantly decrease the amount of crocking but I did find the these vats more challenging to keep in reduction for long periods of time than those made with lime. The pH had to be watched more carefully, as the henna vat would go out of reduction when the pH went below 12 and required boosting with more alkaline.  I do believe there is potential to make these “lye” vats work well, but my own follow-up experiments were done with small 2 liter vats and I never scaled these vats up. The truth is, I got distracted by fermentation vats, which have long been on my own list to explore. 

In my next post I will share some of what I have learned about fermentation vats. 

Coming up: The North Carolina Arboretum will host the third Growing Color Symposium in Asheville March 11 & 12, 2020. Presenters include Sally Fox, Sara Bellos, Donna Hardy, Rowland Ricketts, Dede Styles, and myself. Rowland and I will teach a workshop on the indigo vat and Sarah Bellos will be able to update us on Stoney Creek Colors and their indigo harvest and extraction. Donna Hardy will also do a post symposium workshop at Cloth Fiber Workshop. Do come if you can! 

Update on The Book – The Art and Science of Natural Dye

Yesterday I received a phone call from Schiffer Publications – the publisher of Joy’s and my upcoming natural dye book. 

I am sorry to report that the release date, originally projected for the end of October, has been delayed until late January.

Why the delay? 

Schiffer is taking great pains to be sure that all color reproduction is exact and precise. The book is illustrated with photos of actual samples from my dye tests. Our goal was to share some of the hundreds of samples that I have done, comparing the use of different mordants, tannins, dye treatments, times in the dyebath, etc. Many of the variations are subtle – but the differences are important.

Careful color adjustments have been made to the digital images in Art & Science of Natural Dye to ensure that the dye colors  reproduce as accurately as possible through  the print process. Color proofs are  reviewed and compared to the actual dye samples as part of this process.

Yes, it will be delayed, but the color will be the best possible printed reproduction and I’m very happy about that. It’s good to be working with a publisher that really cares about these “small” details – they are really not small at all. Below is just a small hint of what will be included. 

I know that many of you have pre-ordered the book and are anxiously awaiting it. Joy and I  appreciate the vote of confidence and are sorry for the delay.

I can suggest a great thing to do while you’re waiting: 

Yesterday, on a long drive back home from New England, I finally had the chance to listen to a lecture given by Michel Garcia and available as a Maiwa Podcast. It’s title is Field Notes in the Color Garden, parts 1 & 2. It’s a long, wonderful, rambling lecture that Michel gave in 2015 and Maiwa uploaded as a podcast this year.  It has given me much to think about in regards to dye plants, resource books, investigation, and the human scale of natural dye. 

And keep dyeing!

It’s still less than a year since Joy and I turned in the manuscript and images to the publisher. My learning has not stopped and once the book is released, I look forward to sharing some of the things I’ve continued to work on and learn about since we sent the manuscript away.  “Stay tuned”.

Catharine

What We Call Things

While in Oaxaca, Mexico, a friend gave me a small bag of dried dye material. She had obtained it from dyers in the Teotitlan Valley. It was identified locally as “Mexican chamomile”. It was very aromatic and easy to believe that it was a type of chamomile, possibly related to dyer’s chamomile (Anthemis tinctoria), also known as know as golden marguerite.

I wanted to compare this “Mexican chamomile” with the chamomile I had at home. I had dried chamomile flowers from Maiwa and some whole plants from the end of the season in my garden. Both of them were Anthemis tinctoria.

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Dry and fresh dye materials

I dyed mordanted wool fabric with all three of these “chamomiles” and achieved very different results. Both of the known chamomile dyes produced in a soft, predictable yellow color while the Mexican “chamomile” produced in a much deeper, richer tone. When I completed lightfast tests on the three samples, the Mexican chamomile actually deepened in hue, which led me to believe that it contained a tannin. I guessed that it might not actually be chamomile.

chamomile
Fresh chamomile (Anthemis tinctoria), Maiwa dried chamomile flowers (Anthemis tinctoria), Mexican chamomile (Tagetes lucida)
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Lightfastness tests. Right side was exposed to direct sun for 3+ weeks.

After reporting these results to the friend who had given me the dye, she told me the plant had another local name: “pericon”. Once I knew this, it was easy to identify the plant in both Tintes y tintoreros de América by Ana Roquero and Plantes Tintóreas de Guatemala by Olga Reiche. Both of these are excellent dye books, written in Spanish.

The dye plant in question was Tagetes lucida, a type of marigold. The entire plant is used for dyeing, which explains the presence of tannin in the dye. The whole plant is likely to contain tannins while the flowers alone would not.

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Tagetes lucida,  Wikipedia photo

I have located sources of seed for this plant. The seed companies also refer to it as “Mexican tarragon”, “sweet smelling marigold”, and “Mexican mint marigold”. The leaves are a savory herb and can be used as a substitute for tarragon.

I bring all this up to emphasize the importance of using Latin names for our dye plants. Local names are only useful to local people. I understand that there is a great deal of emphasis on the use of local plants for dyeing but as we travel and meet dyers from other places it becomes important to talk about our process in a common, international language.

While in Mexico I took a workshop on plant taxonomy with Alejandro de Ávila at the Botanical Gardens in Oaxaca. I marvel at the incredible system of plant names that can be understood around the world and encourage dyers to get into the habit of using the Latin names for plants.

I will grow Tagetes lucida (or “Mexican chamomile”, or “pericon” or Mexican tarragon” or “sweet smelling marigold” or “Mexican mint marigold”) in my garden this year and think about the Teotitlan dyers who gather it wild and use in their weavings.

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Jacobo and Maria Luisa Mendoza, Teotitlan weavers and natural dyers in their home studio, with Rocio Mena Gutierrez

 

Book is out! & Teaching at Penland

 

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On the shelf at the Penland Supply Store – photo by Debra Frasier

Woven Shibori has been printed and is on the shelves of your favorite bookseller (also available at Amazon).  I had some of the first copies delivered to me while teaching natural dye with Joy Boutrup at Penland School of Crafts. It was a fitting place to receive the first books. Joy has helped me over the years to understand the chemistry of natural dyes, various finishing processes, and textiles in general. I could not have completed even the first version of Woven Shibori without her input.

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Catharine and Joy at Penland  –  photo by Robin Dreyer

I love teaching at Penland! The studios are beautiful, thoughtfully cared for, and well supplied.  Our students were fabulous and ready for whatever we brought to class. We focused on experiments, observations, and clarifications. The class worked with all natural fibers, and processes included dyeing, printing, and discharge. We were focused on WHY things happen rather than simply how they are done.

Every time I teach with Joy, I  walk away feeling that I’ve taken a  a class as well. We learn from each other as we solve problems, observe results, and identify the best practices for the studio.

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So here is one of the things that FINALLY became clear to me.

I’ve heard/read for years that if animal hide glue was added to the indigo vat, then it would be better for wool or other protein fiber. But WHY? That had never been explained. Did the glue coat the fiber in some way?

The organic sugar vats, that I learned to make from Michel Garcia, use sugars from fruit or plants to create the reduction. Lime (calcium hydroxide) provides the alkalinity.

The vat begins with a quick reduction that eventually becomes a fermentation vat. These vats require a very high pH (about 13-14) in order to start the reduction. If the pH is too low the vat will not reduce. But it does not need a high pH to stay in reduction or for dyeing. A pH of 10 is more suitable for dyeing wool, while cellulose fibers do better with a higher pH of 11. The vat will eventually get to a pH 10 as the sugars create lactic acid in the fermentation but this could take a long time. I’ve had vats take weeks to reach pH 10.

photo by Robin Dreyer
Indigo!  – photo by Robin Dreyer

The addition of dissolved animal hide glue (a protein) to the vat will gently lower the pH by absorbing some of the excess lime. The glue will precipitate to the bottom of the vat along with unreduced indigo and sugars. Joy also suggested using natural gelatin (another protein) as an alternative to the glue but we did not have a chance to try this.

It’s very important to insure that the vat is fully reduced before adding anything that will lower the pH. I would wait at least a few days after making the vat before doing this.

I’ve had dyers tell me that the addition of the glue does indeed improve the hand of wool fibers. How much glue? I’m not sure. We started by using a recommendation by Michelle Whipplinger  in her Natural Dye Instruction Booklet. She suggests using the equivalent of approximately 1%  fiber weight. The glue needs to be dissolved in water.  That seemed a reasonable place to start. The key is to watch the pH and observe with both the eye and the hand.

Woven Shibori and Teaching Natural Dyeing

The new edition of Woven Shibori, (Interweave Press) – with a focus on natural dyes – is at the printers right now and will be available by late June! It’s exciting to see the cover and the layout complete. I first wrote Woven Shibori in 2005 and it sold out several years ago. The book has introduced weavers to the concepts and specifics of weaving fabric with woven resist patterning. When the book was originally written I was using many different types of synthetic dyes and layering them in order to accomplish rich color surfaces.

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I have now been using natural dyes exclusively for 8 years. My challenge was to develop methods of resisting, mordanting, mordant discharging, and cross dyeing  to create unique fabrics that have all the elements I love: texture, color, woven structure, and always some surprises. The natural dye palette and processes not only rival, but I think surpass, the effects I was achieving with synthetic dyes.

Last week I taught a class on cotton printing with natural dyes at Cloth Fiber Workshop in Asheville. I was reminded once again why I teach and why I have written this book. It is gratifying to work with people who are curious, skilled (or not), and eager to learn more. The students in my classes keep pushing me to increase my own knowledge, to better understand what I do know, and to clarify my reasons for working with natural dye.

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Class photos from Cloth Fiber Workshop by Barbara Zaretsky

I would not be the dyer I am today without my own teachers and mentors. Michel Garcia of France and  Joy Boutrup of Denmark have been guiding influences. They are both curious and knowledgable and have inspired me to continue down this path. Michel and Joy are also generous teachers. None of us can do this by ourselves.

Although Woven Shibori includes lots of technical information about weaving fabrics for shibori, the dye information should be of interest to anyone who combines resist techniques with natural dye on their cloth.

 

Why I Switched from Synthetic to Natural Dyes

The Surface Design Association News Blog just published a piece I wrote on dyeing.  Here is the link. The transition from synthetic to natural dyes and ingredients took some time, a lot of thought, and some real determination. I have reached the point of no return…..

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Sodium hydrosulfite or thioruea dioxide was both the reduction agent for indigo/vat dyes and a discharge agent for fiber reactive dyes. Now I use plants and sugars to reduce the indigo vat and citric acid or lemon juice to discharge mordants.