More Notes on The Life of a Fermented Indigo Vat

Vat name: WEF (WEak Ferment)

Dates: June 2020-December 2022

The early months of the Covid pandemic proved to be the perfect time to delve deeper into fermented indigo vats. As I have discussed in earlier posts, I began making small (1 liter) sample vats and learning from them. Ultimately though, in order to really understand how the vats worked and dyed, I needed to commit to something larger. 

I built my first large (50-liter) fermented indigo vats in early 2019.

All the fermented vats were made using indigo pigment.   Wood ash lye or soda ash was added to provide the alkalinity.  They all  included combinations of spent madder root, dried Indigofera tinctoria leaves, and wheat bran to produce the fermentation which, in turn, produces the reduction.  

I frequently add small test vats to  larger ones as I build them. This “seeding” speeds up the reduction quite a lot, resulting in vats that are sometimes ready for dyeing after only 2-3 days, rather than the 10-12 days that would normally be required. 

These fermented vats were giving me good strong blue colors. Yet, I was also trying to understand and control a full range of light to dark shades of blue. I needed a weaker vat. Based on my experience with quick reduction vats, I decided to make an additional “weak” vat, by using only 2 grams of indigo per liter.

Note: when working with quick reduction vats, such as a fructose vat,  I can easily control the depth of color by making weak vats (1-2 grams/liter) vs. strong vats (5-8 grams per liter). This combination of both weak and strong vats is very helpful in creating shades from light to dark, and  when combing indigo with other dyes for greens, violets, etc. 

In addition to “numbering” my vats I also “name” them, using a title that is descriptive of the vat itself. This one was name WEF (Weak Ferment). Initially, it did NOT produce the anticipated pale color that I had hoped for. The color was actually quite strong, even though it contained what I considered only a small amount of indigo, compared to the other vats. From this, I concluded  that the reduction of the indigo in the fermented vat was much more efficient than in the quick reduction vats. 

In order to achieve the desired pale color from the vat I needed to deplete the indigo present.  Traditional vats typically give the palest of colors at the end of their life and this was very much in keeping with that strategy.

I began dyeing a LOT: large woven panels, cotton and linen clothing, etc. Because this vat was large (50 liters) it was easy to dye bigger pieces in this vat. I continued dyeing for a number of weeks, which turned into months. Still, the color remained deeper than I had hoped for. This was a lesson in patience.

Early in 2022, while working on The Studio Formulas Set for the Art and Science of Natural Dyes, a new recipe and color match project with Schiffer Publishing (more to follow about that later). The color samples in this project required careful control of my indigo blues (as well as all the other dyes). I was happy to find that my original “weak” fermented indigo vat (WEF) was finally dyeing beautiful pale blues, while my two other vats were still producing deeper blues. Access to both weak and strong vats was key to controlling the shades of blue.  

Six values of indigo produced for The Studio Formulas Set

Dyeing continued in the “WEF” vat on a regular basis for several more months whenever pale blue colors were required.

Each vat that I make is accompanied by its own small diary/notebook. In that book, I include all pertinent information, such as the original ingredients, dates, ph records, test samples, additions etc.  It is “the history” of that vat and an invaluable part of its life and maintenance. Regular maintenance always includes test sample dyeing, which is an excellent indicator of the health of the vat, as well as providing a record of the color that the vat is currently producing. 

In December, 2022 the WEF vat was finally depleted. It was producing no more blue color and resisted all attempts to revive it. After 30 months of use, the vat was consigned to the compost pile. 

The other two vats are still going strong today. One of them seems to be on its way to producing paler colors. 

Discharging of Indigo Dye

It is my belief that learning about natural dye takes a whole community of people who are willing to experiment, observe, and share. The sharing has been the most rewarding part of my own journey in natural dyeing. I have met many dyers, both in person and virtually, who are willing to be part of that communal knowledge base.

While my co-author,  Joy Boutrup, and I were preparing and writing The Art and Science of Natural Dyes, we experimented with potassium permanganate, a strong oxidizing agent that can be used to discharge indigo. It provides a unique approach to removing indigo dye. When combined with resist, such as “itajimi” clamps, wonderful resist patterning will result.  Changing the chemical treatment will result in a “permanganate brown” color. When the textile is pre-treated with a tannin, it is possible to achieve even darker brown colors juxtaposed with the indigo. All of these recipes/processes are included in the book. 

But direct application or printing with the potassium permanganate proved problematic. Any gum used to thicken the mixture rendered it chemically useless for discharge. In the book, we included a resist paste made with soy flour and lime (calcium hydroxide) in order to achieve some controlled resist printing effects. I had learned to make this paste while in China and found that the paste could be used as a resist for the potassium permanganate solution.  Unfortunately, the soy/lime paste, although effective, is harsh and very difficult to remove from the textile. 

After The Art and Science of Natural Dye was published, we received an email from Zoë Sheehan Saldana, an artist who has been using potassium permanganate. She experienced the same challenges when printing – but she solved the problem by thickening the potassium permanganate with a fine clay. The clay is inert and does not interfere with the chemical oxidation of the indigo.  Either bentonite or kaolin are suitable clays. These are the same types of fine clay that are used with the indigo resist paste. The printed application of the paste in her bandanas results in an even discharge and the printed patterns become pure white.

Use enough clay to achieve a suitable thickness for painting or printing with a screen. Varying the amount clay, as well as the application method, will result in hard lines or soft edges. When painted on, rather than printed, an uneven layer of the paste and the discharge can result.

Mix the paste in small batches, making only the amount that you think you will need.  The paste is most effective when used fresh, but if kept tightly covered it can last for a couple days.

Indigo discharge, using a painted application, by Amanda Thatch. taking advantage of the uneven thickness of paste that results from the brushed on application.

During this week of the United States holiday of Thanksgiving, I am grateful for the community of dyers and experimenters out there, who are willing to share and make our knowledge base stronger. Thank you. Happy Holidays!

Madder for the Indigo Vat

It is exciting to see such a passion for indigo these days, and especially the active exploration that is happening. With this also comes with a deeper understanding of indigo dyeing and process. 

Vats reduced with chemicals such as sodium hydrosulfite or thiourea dioxide used to be the norm when I first learned indigo dyeing in the 1970’s. But now, many dyers have abandoned those chemical reduction vats and are returning to more benign processes. They are now making quick-reduction vats that are reduced with sugar, fruit, plants, or iron – thanks to the teaching of Michel Garcia. Some are growing their own indigo to explore fresh leaf dyeing and pigment extraction. Others are making sukumo – a long process of composting persicaria tinctoria leaves – Thank you Debbie Ketchum Jirik for offering an online class this past fall. Recently, Stoney Creek Colors has introduced a natural, pre-reduced indigo. And more dyers than ever are now exploring vats that are reduced by fermentation.

Fermentation is the process that has captured my interest in recent years. The long-term committment seems to fit my own “stay at home” life right now. The lower pH is suitable for all fibers. Most of all, it’s been an interesting adventure. Something that once felt out-of-reach has now become my preferred process. 

The fermentation vat utilizes plant material to initiate and maintain an alkaline fermenting process, which causes the indigo to become soluble. During fermentation, plant material is broken down, creating bacteria. Lactic acid is produced, making it necessary to monitor the pH on a regular basis. 

Madder root is a common plant material used in a fermentation vat. There is a long history of its use in indigo vats. It is usually combined with wheat bran, which ferments readily. There are many recipes in old manuals for this Madder Vat.

From The Dyer’s Companion by Elijah Bemis (originally published in 1815, Dover Edition, 1973)

for a vat of 12 barrels (not sure what a “barrel” is)

  • 8 lbs potash
  • 5 lbs madder
  • 4 quarts wheat bran
  • 5 lbs indigo

When I first leaned of these vats made with madder, I struggled with the idea of using perfectly good madder root to reduce an indigo vat. But I have now come to understand that these vats were most likely made with “spent” or “used” madder. I remember Michel Garcia talking about how the “used” madder from professional dye studios in the past was sold to the indigo dyers after it had been used to produce red dye. Indigo dyers have no need for madder’s red colorants and thus nothing was wasted. 

So, I am dismayed each time I hear from someone who has made a fermented indigo vat using “new madder root”. “Spent” or “used” madder is every bit as effective as a fermentation booster as fresh or “unused” madder. 

Most of the madder I use in the studio is in the form of finely ground roots, though chopped roots would work as well. When my madder dyebath is finished, I strain the ground roots and dry them for later use in an indigo vat. It’s that simple! And nothing is wasted. 

Equal amounts, by weight, of “used” madder root on the left, and “new” madder root on the right. Most of the colorants have been removed from the madder in the dyeing process, leaving only the starches and sugars of the roots.

Plant materials, other than madder,  can be used in the fermentation vats. I frequently use dried indigofera leaves, as well as woad balls and have even begun a “hybrid “ vat using sukumo with indigo pigment. My most recent experiments have used both Dock root and Rhubarb root successfully. Madder, Dock and Rhubarb are all roots, all anthraquinones…..

The Surprise of Indirubin!

Why would a white plastic button turn purple from an indigo dyebath?

Indirubin is one the most curious components of indigo. It is sometimes referred to as the “red” of indigo. Indirubin only occurs in natural indigo and you will not find it in a synthetically produced pigment. Indirubin is valued for its medicinal applications.

Some dyers have been successful at manipulating the extraction and pH of indigo in order to reveal the mysterious purple/red color of indirubin on a textile. I have no real experience with this process.

At one point I did learn how to analyze an indigo pigment in order to determine the presence of indirubin. If indirubin is present, it is an indicator that the pigment is made from plants and not synthetically produced.  Natural indigo has varying amounts of indirubin. The process of analyzing uses solvents and chemicals so it is not something that I want to do on a regular basis. 

I purchase all of my indigo pigment from Stony Creek Colors, as I know that their indigo comes from plants (and, consequently, contains plenty of indirubin).

Now that I maintain several large “active” indigo vats, I will occasionally dye a ready made garment. A white linen blouse is not a good choice for wearing apparel in the dye studio, but one that has been dyed a rich indigo blue is perfect. 

After dyeing, just before the final rinse, I always boil an indigo dyed textile in order to remove any unattached dye. Cellulose is boiled vigorously with a small amount of neutral detergent for about 10 minutes. Wool and silk are brought to a near simmer and held at that temperature for the same amount of time. 

Once I started using indigo from Stony Creek I noticed that the water from the final boil was always tinted a purple hue. I assumed this was the indirubin that was being rinsed from the textile. Interestingly, I observed that the purple color in the boil water is temporary, and will disappear as the bath cools. 

Recently, I dyed some linen shirts that had plastic buttons. The buttons stayed white until the final boil. When the garment was removed from the boil bath, they had become purple. I have now learned that indirubin is less easily reduced and the undissolved indirubin will stain plastics and other petroleum derived materials. Some of the polyester threads used to sew the shirts are also tinted purple. 

Summer Arrowood, the chemist at Stony Creek Colors, tells me that all the plastic vessels in her lab are dyed purple from the indirubin!

Will these buttons remain purple after multiple washings? I don’t know. There is always more to observe and learn from the natural dye process.

Slow Process

Natural dye has never been a quick way to color my textiles. First there is the mordanting, then the extraction of plant/insect material – not to mention growing, gathering, or drying the plants. Did I mention collecting seed? And what about the weaving, where I actually make cloth from threads? 

These last 18 months at home have been a chance to dive in deeper (and slower) with some processes. Just before COVID came to our doors, a friend gave me a small jar of sourdough starter. So yes, I am one of those who has made sourdough bread every week for the last year and a half. What a gift – both sour dough starter and the time to use it!

It was my fermented indigo vats that gave me the courage to take on sourdough bread making. I thought that if I could keep indigo vats alive for a number of months, then I could certainly keep a sourdough starter going as well. That has proved to be true.

The first fermentation vat was started in July of 2019. It was a relatively small vat (20 liters) but I used it a great deal. A year later it was used it to “seed” a larger 50 liter vat. The success of this first experiment gave me the confidence to start two more 50 liter vats in 2020. All are still going strong. Over the last two years I have made many additional one-liter vats in order to test reduction material, alkalinity etc. That first large vat that I created in 2019, after being used heavily for over two years, is finally giving me lighter blues.

Now I am in the midst of another slow process – sukumo. Debbie Ketchum Jirik of Circle of Life Studios very generously took a group of zoom class participants through the entire process of small batch composting of indigo leaves based on the teaching and book of Awonoyoh. Every 3-4 days we logged in, watched the sukumo being lifted from its container and stirred by hand. Does it need water? Does it need heat? What does it smell like? Conversations were focused and interesting. Several class participants were also in the process of making their own sukumo along with Debbie. I am not so fortunate. I have to gather more seed, grow more plants, and dry more leaves before I will have enough plant material to do my own composting. 

This experience has given me a far greater appreciation of sukumo. I was recently gifted a significant amount of sukumo and had planned on making my own large sukumo vat. Now, understanding more of what sukumo is, I am experimenting with using smaller amounts of sukumo in combination with my fermented indigo pigment vats. When I told my Japanese colleague, Hisako Sumi, about this, she indicated that Japanese industrial production has used this approach since early in the early 20th century. There is even name for this hybrid: “warigate”. Yoshiko Wada translated this for me as  “WARI GATE” / “split vatting” and it was mostly done using synthetic indigo. 

I have made many small test vats, using varying amounts of sukumo, in addition to indigo pigment and other materials to boost fermentation. These test vats were ultimatley used to ‘seed” a larger vat. I now have my own 50 liter hybrid vat that combines sukumo with Stony Creek indigo pigment.

My latest “slow process” is vermiculture. I recently spent an afternoon with friends, sorting worms from castings and beginning my own worm “farm”. This is another of those long term, slow processes that bring me closer to the earth, and makes me appreciate the small miracles of watching things grow. And I know that this compost will feed my indigo plants.

But not everything must be slow….

Stony Creek Colors has just released information about their newest product: IndiGold. It is a pre-reduced liquid indigo, grown in Tennessee and designed to be used in combination with fructose and lime (calcium hydroxide). I have dyed with the earlier available pre-reduced indigo but I was never sure exactly what it was and didn’t want to use the reduction chemicals that were recommended. I stopped using that product a long time ago when Michel Garcia introduced us to the “quick reduction” vats made with sugar and lime. But there are some occasions, particularly when teaching a one-day workshop, that it is impossible to make a vat and dye with it on the same day. 

Stony Creek sent me a kit for test dyeing and I was amazed at how quickly the vat was reduced and dyeing to full strength. It took only minutes – not hours. Stony Creek Colors told me that they”skip the chemicals” and use an electric hydrogenation process plus an alkaline to reduce the indigo. There are no chemical reduction agents! I used the vat all day long and it was still in reduction the next day. 

This will not replace my slow, fermentation vats but it will make “quick” dyeing possible when needed. 

Once again, Stony Creek is changing how we think about indigo and its production. They are currently posting information through a Kickstarter Campaign to support this new venture.

The Life of an Indigo Vat

Over the years I have built, used, and discarded many indigo vats. Sometimes I have kept them going for a very long time. I have finally declared the 5 year old, 100 liter henna vat “done”. I have added indigo pigment, lime and additional henna to it many times and although it is still dyeing well, the space available for that dyeing (above the “sludge” at the bottom) has gotten very, very small. 

As many of you know, I have spent this last year at home getting to really know my fermented indigo vats. I have followed a rather strict protocol. Each vat began with a certain amount of indigo pigment, a source of alkalinity (soda ash or wood ash lye) and various plant based materials to begin and sustain the fermentation (wheat bran, madder root, dried indigofera leaves, etc.). Only small amounts of lime and bran have been added over the last year to sustain pH and fermentation. At no time have I added additional indigo.

Last May I was trying to achieve a wide range of blue shades from the very palest to very darkest. I was a bit dismayed to find that all of my vats were dyeing too dark to give me the pale shades I desired at the time.  I knew (in theory) that if used the vats enough, the indigo content of the vats would decrease but had no idea how long that would take, or how much dyeing I would need to do. No matter how much I dyed, it didn’t seem to happen.…

Now, a year after the vats were first made, I can see progress.

Indigo on cotton cloth: 1-15 ten-minute dips. May 2020

Indigo on cotton cloth, same vat: 1-24 ten-minute dips. February, 2021

Some observations:

This is a long process….

Two dips in May, 2020 gave the equivalent shade as 5 dips in February, 2021

The dark blue that was achieved from 12 dips in May, 2020 was not achieved, even after 24 dips in February 2021

The subtle differences in the darkest shades are difficult to discern from the photos – but they are there.

I now realize the value of having a number of vats: from old to new, weak to strong. It’s something I have heard Michel Garcia say on more than one occasion, but sometimes we just have to observe and learn the lessons on our own. 

This spring, I will not discard my weakening vats, but will add another vat for the strong, deep blues that I am currently needing to build up black colors on my woven cellulose fabrics. 

What Size is YOUR Indigo Vat?

I now have, and am actively using, three 50 liter (15 gallon) indigo vats, in addition to a 100 liter (30 gallon) henna vat. 

I am loving the size of the 50 liter vat! The vessel is tall and narrow. It’s just the right shape for a vat, with a relatively reduced surface area, and a great size for studio immersion dyeing. I have been dyeing samples, skeins of yarn, my own shibori work, and even clothing in those vats. 

Like most dyers, I began with what I then thought was a “large” 5 gallon vat. That is still the most practical size for teaching workshops and I am guessing that it’s the size/shape that many dyers start with – and most stay with. 

But, I don’t think it’s the best for studio work. IT’S TOO SMALL!  When working with natural indigo vats, whether they are fermentation vats or quick reduction vats, there is going to be a lot of ‘sludge” at the bottom of the vat. With some vats this can be up to 1/3, or more, of the total depth. If you keep the textiles above that sludge , it doesn’t leave much room for dyeing. I am afraid that many dyers might tend to let their textiles dip into that “wasteland” at the bottom, exposing the fibers to concentrated lime or plant material. As a result, the dyeing is not as good as it could be. 

A 50 liter/15 gallon liter vat is a much greater commitment than an 18 liter/ 5 gallon bucket, both in terms of financial investment and engagement.  Yet, it is so much more useful and the dyeing is so much better! It’s also harder to just “give up” on a larger vat. You get better at maintaining and problem solving.

This is the vessel that I use. It’s a hard, durable plastic. I place it on a wheeled dolly. Otherwise it’s too difficult to move. A heavy duty plant caddy works just fine. 

Sometimes I suspend samples and other small pieces from the top, using stainless hooks and wooden rods. 

I have experimented with several types of baskets, nets, etc. to hold my larger textiles and keep them away from the bottom of the vat. I have finally settled on using a large, mesh laundry bag. It fits the vessel nicely, is flexible, re-usable, completely contains the textiles, and prevents things from getting lost in the bottom. 

As I experiment with the fermentation vats, it becomes necessary to do a lot of dyeing. I am working on a long-term woven series, but regular dyeing has become increasingly important with my fermentation vats – and more possible, now that I am staying home.

I’ve taken some of my white or light colored clothing (too impractical to wear in the studio) and turned them into indigo dyed “dyeing clothes”. It took some courage to put a large linen tunic in the vat but I’ve been surprised at the even dyeing of even these larger,  constructed  pieces. I always do at least 3 long dips into the vat, which will assure that the dye “evens out”. I would never have attempted dyeing clothing in a 5 gallon vat.

Maintaining a good dyeing temperature is important, especially with the fermented vats. I have successfully used a band-type pail warmer and plugged it into a digital temperature controller. This has been keeping the vats at a regular temperature in my unheated studio. 

AND if you are going to make wood ash lye for a fermentation vat, this is the time of year to connect with friends who are burning wood. You will want to identify someone who burns only hard wood in an efficient wood stove. That will result in the best ash for making lye. 

A New Book from Dominque Cardon

Dominique Cardon, French researcher of natural dyes and author of the classic reference book, Natural Dyes: Sources Tradition, Technology and Science, has just provided dyers another important resource and insight into the natural dye process:  Workbook, Antoine Janot’s Colours

For several years, Cardon has been translating and publishing a series of books that document the work of 18th century French dyers. The 18th century was the classical period of wool dyeing in France. Last year, Des Couleurs pour les Lumières. Antoine Janot, Teinturier Occitan 1700-1778 was released, but only in French. This book was based on the original dye notebooks of Antoine Janot, a professional dyer from the Occitan region of the country.

Workbook, Antoine Janot’s Colours, which Dominique wrote in collaboration with her daughter Iris Brémaud, begins by providing background information on Janot and a description of the project. The most useful part of this small book to dyers is its practical nature.  It includes a full palette of Janot’s colors and their recipes along with process information. It is written in both French and English.

Both books are published by CNRS EDITIONS

The dyed colors are represented as visuals that were matched from actual wool samples from the original notebooks. Cardon used a color analyzer and the CIELAB system to accurately portray each hue. CIELAB is an international system that scientifically analyzes colors by using a system of coordinates to “map” them graphically and very precisely.

Descriptions of mordanting and dyeing include % weight of dye materials along with other additions that were made to the baths. In some cases, helpfully, an explanation of the WHY is included. 

Examples of green colors in the book which use indigo as a base.

Examples of mixed colors in the book that do not use indigo

The key to some of the color palette is a full gradation of indigo blues, from the very palest to very deep. Each blue has its own name such as “crow’s wing” (the very darkest) to “off-white blue” (the very palest). The CIELAB system allows an accurate visual description of each of these blues. 

Dominique Cardon, showing and discussing her research into the shades of indigo dyed wool at the TSA Symposium, 2014

These blue shades are critical to achieving greens, purples and greys.  Instructions for mixed colors designate which blue to start with. A full range of indigo blues, from lightest to darkest, is not an easy thing to accomplish. I have been working on that very thing consistently for the last months in my own studio, so it is especially meaningful to me right now.

Blue value tests done using different indigo vats in my own studio.
Indigo blues on woven cotton/linen from my own studio. This is a work in progress. The palest colors are the most challenging.

I have recently been doing color replication work for logwood purple using a combination of indigo and cochineal. A systematic approach to dyeing the initial indigo blues is a huge help in approaching this kind of color matching.

Attempt at matching logwood with a combination of indigo and cochineal (the cotton ties reveals which is which)

It is rare to be able to gain such a deep insight into a professional dyer’s process and results. Historical color descriptions, such as “wine soup”, “celadon green”, and “crimson” become more than just words on a page when colors are able to be seen accurately with the eye. 

For dyer’s looking for a deeper insight into the world of professional natural dye, this book is a treasure. 

I ordered my copy directly from France and it took several weeks to arrive.  According to Charlotte Kwon, the book will also soon be available from Maiwa.

Dyeing with Fresh Indigo Leaves

On some days it’s hard to believe how recently we traveled freely worldwide, meeting new people and experiencing new places. Three years ago I attended the natural dye symposium in Madagascar, where I first met Hisako Sumi who started me on my current journey of making and maintaining indigo fermentation vats. As I was harvesting Persicaria tinctoria leaves in the garden, I was reminded of the fresh leaf indigo dyeing that we saw being done in Madagascar. 

Many of us are growing indigo in our gardens right now and have likely had the pleasure of experimenting with fresh leaf indigo dyeing on silk.  It’s like magic to see the lovely turquoise color emerge from the cold leaf bath.

The indigo that grows in Madagascar is Indigofera erecta. It is a perennial in that climate and the leaves are harvested from the bushes as needed. The leaves were used to dye the raffia fibers directly. There was no vat or reduction. 

Yet, the dyers took this “cold” process one step further. The ambient temperature dyebath produced a lovely clear turquoise blue color on the raffia. When heat was applied, the color deepened and shifted.

This approach of heat application was new to me. When I inquired about it, both Hisako and Dominique Cardon indicated that they were both familiar with this phenomenon. Hisako sent me an image from a scientific report done by Dr. Kazuya Sasaki that documented the range of color that could be obtained from fresh leaf woad by increasing the temperature. Once armed with that information I was able to reproduce that range of color, nearly exactly, on silk and and on multi-fiber test strips, though the results were not precisely the same as those we saw in Madagascar. 

Indigo vat dyeing compared to fresh woad leaf dyeing of various fibers, at different temperatures.

I have always understood that the process of fresh leaf dyeing with indigo is primarily used on silk – a protein. Yet, the dyeing we witnessed in Madagascar was done on raffia. Why did this process work so well on raffia- a cellulose fiber? I posed the question to my colleague, Joy Boutrup. “Raffia is almost pure lignin” she said. Lignin is an organic polymer and has a strong affinity for dye. 

This week I repeated the tests with Polygonum tinctorium on silk broadcloth and raffia. I used a greater quantity of leaves this time – a blender full of leaves for a few small samples vs. less than 100 g. I puréed the leaves this time rather than chop them up. The “coldest” blue is a deeper shade but otherwise the results are very similar. I freely admit that I don’t understand, chemically, why the colors change with the temperature:

  • Are there other dyes attaching?
  • Has the indigo been transformed by the temperature? 

Maybe someone else can enlighten.

I have always suspected that the lightfastness of the fresh leaf indigo dye is not to the same level as the color obtained from a well reduced indigo vat. I will do lightfast tests on this range of color and report back in a later blog. 

Three years ago, the trip to Madagascar taught me about an approach to dyeing that I had never seen before –  truly one of the gems of travel. We may not be free to move around for now,  BUT other opportunities continue to present themselves on the web. One of the most exciting upcoming events is this year’s Textile Society of America Symposium: Hidden Stories: Human Lives.

Originally planned to be held in Boston this fall, Hidden Stories: Human Lives will now be live and completely online October 15-17. This biennial event brings together scholars, curators, and artists from all over the world who will present their original research in the form of organized panels and talks. Fee structures for the symposium have been completely re-vamped in order to make this event accessible to all – no matter where in the world you might be. Registration has just opened and you can see the full program here. In addition, You can also read about the keynote and plenary speakers. Hope to see you there!

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…