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! 

IMG_6802

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. 

IMG_2641

crocking indigo
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. 

soak and rinse water
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.

henna lye vat
“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! 

A New Use for Walnuts – The Indigo Vat

It’s black walnut season again in eastern United States – and soon the trees will be releasing their nuts and husks from the tree.

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This summer I had the pleasure of teaching, again, with Joy Boutrup at Penland School of Crafts. As always, when Joy and I spend time together, we begin investigating and learning more about the practice of natural dyeing. 

We were experimenting with “quick reduction” indigo vats and the used of lime (calcium hydroxide) vs. lye (sodium hydroxide) as the source of alkalinity in the vat. We made a vat that was reduced with henna (Lawsonia inermis). This is the vat that I commonly use in my studio. The sugars present in the henna reduces the indigo.  Joy was looking at the molecular formula of lawsone, (the active dye ingredient in henna) and noticed that it is very similar to juglone (the active dye ingredient in black walnut hulls) They are both oxidation dyes, which means that they will dye protein without the use of mordants. 

 

 

The question: Could black walnut hulls be used to reduce an indigo vat in the same way that henna does?

We tried a small test vat. When I test a new indigo vat I often make it in 1 quart mason jars. This allows me to test multiple ideas on a small scale, without risking large amounts of dye or other materials. These small vats give me enough information so that I can scale up to a larger volume at a later time. I used 4 grams of indigo, two walnut hulls, and about 10 grams of lime. 

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In June I had only whole frozen walnuts. I thawed them a bit, and covered them with water (no more than a quart, as this becomes the liquid for the vat).  As the walnut hulls softened more, I broke them up with my fingers and cooked them for a short time. The liquid was yellow. Joy cautioned against heating too much, which would turn the liquid brown as a result of oxidation. We wanted the oxidation to occur in the indigo vat.  So we stopped heating while the liquid was still very yellow. Next we strained the solid pieces out, and poured the liquid into the mason jar. We added the hydrated indigo and the lime.

 

Within a few hours we had a nicely reduced vat! I continued to dye test strips in the vat for a number of weeks. After a few days the color became lighter, but after the addition of supplemental organic materials (sugar, more walnut juice, cooked fruit juice etc.) the reduction improved and the blue color deepened as the indigo reduction improved. 

I  observed that after about 10 days the indigo blue got dull and the samples showed a wicking of a brown matter into the white cloth. Then, after about 30 days the color reverted to a clear blue again.  I described this to Joy.  She was not surprised and indicated that the juglone was by then inactive, having polymerized into a pigment that does not dye. Yet the sugars in the plant material continued to reduce the vat. 

drafts

I also tried adding puréed pieces of walnut hull to a test vat, but there was so much plant matter it made dyeing difficult – very messy. Thus, I now use only the liquid extraction. I have made several small vats since and they have all behaved consistently. 

When I collect this season’s walnuts I plan to scale up to a larger vat. 

In the spirit of understanding the plants that I use, this year I have planted a single henna bush in my garden. It will not winter over. It is not a local plant for me. I am thrilled to have discovered that walnuts,  a tree that grows locally in abundance,  can be used to reduce an indigo vat.