One Bath Acid Dyes – and “Textile Tattoos”

I have used one-bath acid dyes extensively in my own work, especially for cross-dyeing my handwoven fabrics that are constructed of both cotton and wool. The acid dyes attach only to the wool or other protein fiber. When combined with indigo, which attaches to both cellulose and protein fibers, very interesting combinations can be achieved. 

The “one-bath acid dyes” that Joy Boutrup and I discuss in The Art and Science of Natural Dyes include henna, madder, pomegranate, cochineal, lac, and rhubarb root. Since publishing the book, I have extended the palette with the addition of other dyes, mostly due to the help from Michel Garcia when he was here in my studio several years ago. 

Michel and I were discussing dyes that I might choose NOT to use because of their poor tolerance to light. Alkanet is one of those. A purple color is extracted from alkanet root by means of an alcohol extraction. The color is beautiful and enticing , but very fugitive. Michel indicated that the alcohol extraction does some damage to the dyestuff. 

The one-bath process extracts different dyes from the plant than from those that are obtained from using more traditional methods. While experimenting, we treated alkanet as a one bath acid dye (for protein fiber only) and a beautiful purplish brown color emerged that is quite fast to light. It’s a warm neutral color that I have not achieved using any other dye. 

Safflower petals are another dye source that he showed me can be used as a one-bath acid dye. A golden yellow is dyed onto wool or silk that is quite lightfast and requires no mordant. The safflower petals can still be used after the one-bath process to extract the traditional reds and pinks by altering the pH, though the red colors are still not fast to light. 

These discoveries energized my own work and as I went deeper,  I began noticing that many of the plant dyes that are used for the one-bath acid process have also been used as natural hair dyes: henna, madder, alkanet, dock, rhubarb root, cassia leaves (Cassia obovata, also referred to as “neutral” or “colorless” henna). These can all be used successfully for one-bath acid dyes and result in very lightfast colors. Dried Indigofera tinctoria leaves (“black henna”) are also used as a dye for hair and when combined with henna results in a very dark color. 

The application of henna as both a hair dye and as mehndi, (a temporary dye for the skin) is the same: finely ground plant material is mixed into a paste with water, acidified with lemon juice, and allowed to sit on the hair or skin for several hours. When the paste is washed away the color remains. These are considered non-permanent dyes for the skin and hair and may be repeated after the color fades. 

Acid dyes are very lightfast but are not as fast to washing. (This applies to both natural acid dyes and synthetic dyes.) If applied to the skin or hair, they will eventually be washed away.  BUT importantly, we don’t wash our woolen fabrics as aggressively or as often, thus the dyes are suitable for wool or silk textiles. 

I was curious to see if these dyes could be used for direct application to woolen fabrics. There is a Moroccan tradition of using finely ground henna leaf in this way on fabrics woven of wool and cotton. It is well documented in the book Die Farbe Henna / The Color of Henna Colour of Henna: Painted Textiles from Southern Morocco by Annette Korolnik-Andersch and Marcel Korolnik.

I made a paste of each of these dyes using finely ground plant material with a small amount of water. I acidified the paste with vinegar (citric acid would damage fabrics that contained cotton) and allowed it to sit overnight once applied to the textile. The colors are strong and clear, although some dyes spread more than others. They are not quite as deep as those dyed in a heated bath, though steaming the textiles will result in deeper colors. 

hand application of dye paste

I have observed that the freshness and quality of the dyes matter. Organic henna, used for hair and skin dye, resulted in a bright clear color while other henna powders that I have used produced duller colors. 

This approach has revealed to me one more way of understanding and using natural color and given me more opportunity to combining it with my own woven textiles. It has taught me more about plant categories, alternative applications, and the need to constantly be open to new ideas. 

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!

Lightfastness of Dyes – an Historical Perspective

A dear friend recently put a small booklet into my hands: Fast Dyeing and Dyes by James Morton.  It is the bound proceedings of a lecture that Morton delivered to the Royal Society of Arts in London, 1929. 

Morton’s father, Alexander Morton, founded the weaving company of Alexander Morton & Co, in England in the late 19th century.  The son, James was trained as a chemist and specialized in the use of permanent lightfast dyes for cellulose textiles. In the narrative, James recounts work that he  accomplished in 1903 to develop a palette of lightfast dyes for textiles. It was an interesting time in the development and use of textile dyes.  Up until the second half of the 19th century, natural plant and insect dyes were the source of all textile colors, but by the early 20th century chemical dyes were quickly replacing the natural dyes in industry. 

Morton’s company specialized in producing woven furnishing fabrics for curtains, carpets, upholstery and tapestries.  He spoke of observing one of the company’s tapestries in a store window display. After only a week’s time, the colors had faded dramatically. This led him to question the dyes they were using. He commandeered his family greenhouse (which had previously contained tomato plants) to set up a series of lightfastness tests. He tested fabrics from his own company as well as those from others. The results he described as “staggering”. Even deep shades of color applied to expensive fabrics became almost white after only a week’s time. He made detailed notes and documented each sample. 

After making these careful observations, his goal became one of identifying a few colors (produced by chemistry) that could be relied upon and that performed well. Morton believed that even a limited range of colors that would remain on the textile over time was far preferable to a large palette of color that would degrade quickly. The company trademark Soundour was born – a combination of the word “sun” and the Scottish word “dour” meaning stubborn or hard to move. He identified the Alizarines as “good friends” which kept their shades. This was a class of chemical dye, based on the synthetic manufacturing of alizarin, the primary red colorant in madder root.  In 1869 it was the first natural dye to be produced synthetically. Colors derived from minerals were acceptable as sources for light browns.  Indigo was deemed unsatisfactory for longevity on cellulose but Indanthrene vat dyes, new to the market, served as a good source of yellows, blues and greys. (These are the same vat dyes that I previously used in my own work.)

All the chosen chemical dyes were tested thoroughly, both in the greenhouse and on rooftops in India, where the sun was hot and intense and the humidity was high. The result was a carefully chosen palette of color that could be advertised as reliable and be priced accordingly – significantly higher priced than other fabrics on the market. The goal was to have colors that would last as long as the textile itself.

What strikes me about this story is the recognition of lightfastness being of value at a time when there was such excitement about the ability to easily produce almost any color through the use of the new “chemical” dyes. Morton changed the industry’s awareness of and approach to the use of synthetic dye color.  Interestingly, he stated that “Some manufacturers questioned the wisdom of raising the standards so high…”

I can’t help but see a parallel to today’s re-discovery and excitement about natural colors. That excitement often causes a “blind spot” when it comes to objectively looking at the longevity of some dyes. If the experience of making color is the singular goal then it doesn’t matter so much how long the color will ultimately last, but if there is a customer with an expectation that the color will last as long as the textile, then colorfastness is a different and critical matter. 

Professional natural dyers have made decisions over the centuries to provide customers with the best quality colors possible. The Dyer’s Handbook: Memoirs of an 18th -century Master Colourist, by Dominique Cardon makes the following statement about testing for “false” colors: “It is not enough for the dyer to have acquired knowledge on the drugs that are necessary to him and on their properties, and to have managed to employ them with success. He must also distinguish the fast colors from the false ones…”

All dyes fade – that’s a fact. And all textiles will deteriorate. My colleague, Joy Boutrup, says that acceptable fading of a dye results in a lighter version of the original hue while the integrity of the original color is maintained: a lighter indigo blue, a softer madder red etc. – not an “ugly beige color” that has no relationship to the original. And the ultimate goal is that the color last as long as the textile.

My own current study of “fast” and” fugitive” dyes on wool yarn: Indigo over-dyed with cochineal vs. logwood. Original colors (left) and after 3 weeks of direct sun exposure (right)
“Fast” and” fugitive” dyes: Cochineal vs. Brazilwood. Original colors (left) and after 3 weeks of direct sun exposure (right)

The Effect of pH on Yellow Dyes from the Garden

yellows on line

First of all, I know that my well water is acidic. It measures about pH 6.0 here in the mountains of North Carolina.  The water is ideal for most dyeing. There is no iron or other minerals that might dull the colors. The acidity is another issue. 

Most of the yellow dyes in my garden, or those that I might gather locally, are flavonoids. That means that they require a mordant in order to attach to the textile. No mordant means no yellow. It’s that simple. Some of the dyes may also contain some tannin or other colorants but the yellow is what we’re talking about here. 

Last summer Joy Boutrup and I taught a class together at Penland School of Crafts, located near my home in western North Carolina. A student in the class was especially interested in gathering local plants for use as a dye source. She struggled to get the locally gathered dyes to attach to her textiles, especially onto mordanted cotton. 

Joy had the answer-of course!

When the dye meets the mordant in a textile, an insoluble lake is formed. This lake is formed most readily in neutral or slightly alkaline conditions.

An alum mordant makes a very strong bond with wool but there is no chemical bond between cellulose and the mordant.  Instead, the mordant is deposited as an insoluble compound on the textile.

An additional issue is that many of our local plants are acidic. When the plants are boiled in our already acidic water, the pH of the dyebath becomes so low that the dye may struggle to attach to the mordant in the fiber. In fact, the mordant in the cotton can be damaged or even removed if the bath is acidic enough. This is exactly the reason why we don’t add an acid to a cochineal bath when dyeing cellulose. The mordant would be damaged and little dye attaches. 

The remedy: Add a small amount of chalk (calcium carbonate) to the dye bath to neutralize the acid that is present. This will do no damage to the dye or the textile. Chalk is not an alkaline but will neutralize an acid that is present. Within reason, there is no possibility of having too much chalk and any excess will simply precipitate in the bath and rinse out of the fabric

Since my own broom (Genista tinctoria) is currently in need of a serious trim, I began a series of flavonoid dye tests with that and then compared other dyes from my garden and environs. 

I used all fresh plants at 300% w.o.f. and dyed both wool and cotton. The wool was mordanted in alum. The cotton was mordanted using tannin plus alum and soda ash. After making the dye decoction, I divided the dye bath in two equal portions and added both wool and cotton to each bath.  Chalk was added to only one of the baths.

The results were quite surprising (but also very consistent) and made me realize that I have likely not been achieving the maximum amount of color from some of my local dyes. 

The plants I gathered and used were

    • Broom (Genista tinctoria)
    • Wild grape leaves
    • Apple leaves
    • Dyer’s Chamomile (Anthemis tinctoria). I used the flowers and after gathering a basket of the small flowers I tested the dye content in the entire plant. 
    • Staghorn sumac (Rhus typhena) . We often think of sumac as a good source of tannin but the leaves, according to Dominique Cardon, are also rich in flavonoids. 
    • Weld (Reseda luteola). This is my “go-to” yellow dye. I almost always use dried plants and I rarely add chalk with weld on cotton but frequently  add it to a wool bath. 

After boiling the plant material I recorded the pH of the decoction. The pH was measured again after the addition of chalk. Each dye bath was approximately 4 liters and I added about 1 TBS of chalk. 

The chalk will alter the appearance of the bath from transparent to cloudy and nearly opaque. 

weld in pot w/wo chalk
Weld baths: no chalk on left, chalk added on right

plant pH after boiling pH after addition of chalk
Dyer’s broom 

(Genista tinctoria)

5 6
Wild grape leaves 4 6
Apple leaves 5 6.5
Dyer’s chamomile (Anthemis tinctoria) (flowers) 4.5 6.5
Dyer’s chamomile (Anthemis tinctoria) (whole plant) 4.5 6.5
Staghorn sumac (Rhus typhena) 4 6
Weld (fresh plant) (Reseda luteola) 5.5 6.5
Weld (dried plant) 5.5 6.5

The samples below are wool. Individual samples on the left had chalk added to the bath. Those on the right did not.

In every case, I achieved  deeper and brighter yellows colors when the chalk was added to the fresh plant baths. The only exception was dried weld, which was used at 50% w.o.f. When dyeing with the fresh weld plants, deeper yellow hues resulted with the addition of chalk. When I used dried weld plants, the chalk made very little difference.  I asked Joy about this and she indicated that is was possible that some of the acids disappear in the drying process. It will require more tests and explorations to confirm this.

The cellulose samples are especially notable. The high acidity of some baths made without the chalk was enough to damage the mordant significantly. The grape leaves and the sumac, which were the most acidic, destroyed the mordant in the cellulose and only the tannins that are present in the leaf were able to attach and color the fabric. 

cellulose no chalk
Palette of color on cotton without the addition of  chalk.  Left to right: Chamomile flowers, broom, apple leaves, chamomile (whole plant), weld, sumac, grape leaves

cellulose with chalk
Palette of color on cotton with the use of chalk.  Left to right: Chamomile flowers, broom, apple leaves, chamomile (whole plant), weld, sumac, grape leaves

If your water is not acidic, or has calcium in it, then these tests may not be relevant but the addition of chalk will never harm the fiber or the dye and may release more color.

I recently found the following note that I had made during a class with Michel Garcia several years ago referring to grape leaves:

“If they are too sour they will dissolve part of the mordant.”       M. Garcia

 My own notes continue to say:

After boiling the grape leaves the solution of a pH 4 – too acidic – it will remove the mordants. Sumac will cause the same effect. Boiling breaks the bonds of the tannins and gallic acid is released. Add chalk to the bath to decrease the acidity of the dye bath – you cannot be in excess of chalk.

Sometimes we’re just not ready to absorb information the first time we hear it. This is exactly why I continue to question, keep notes, and actively test and observe. 

It’s summertime! Enjoy your yellow flavonoids!

Note: I purchase my chalk from a potter’s supply store. It is inexpensive and can be purchased in quantity. Potters refer to it a “whiting” and rarely refer to it as chalk or calcium carbonate. Do check the MSDS though, just to be sure. 

Upcoming: On July 13 I am presenting a Zoom webinar, entitled Colors from the Garden, as part of the John C. Campbell Folks School’s Appalachian Traditions Series. You can sign up here:

Indigo Dyeing During Covid-19 Isolation

These last months, a time when I would usually be traveling and teaching, I have found myself  immersed in studio and garden. We are healthy and thankful for that. 

I am also grateful for the extended time to spend learning more about indigo fermentation. Over these last months I have made dozens of small test vats in the quest to better understand how the vats work and how to maintain them. These small vats have given way to a three 50 liter vats that are healthy and dyeing beautifully.

All of my vats use indigo pigment from Stoney Creek Colors, plus organic material to produce fermentation and thus, reduction. 

As part of the experimentation and study, I have successfully made my own wood ash lye and worked with both soda ash and potash as alternatives. All of these sources of alkalinity work with these vats. I have almost eliminated the use of lime, except as an occasional addition to adjust the pH.

Lye
Samples from the 6 batches of lye made from wood ash, ranging from pH 11.5-13.2.

sample vats
Sample indigo vats. Some are wrapped in electric heating pads in order to stay warm.

Each of the small indigo test vats (mostly 1 liter) are designed and made to answer a single question such as:

  • How long does it take a vat to go into reduction?
  • Does fresh ground madder root behave the same as “spent” madder root?
  • What is the effect of applying heat? 
  • How much heat?
  • Can soda ash be substituted for wood ash lye?
  • Can potash be substituted for soda ash?
  • Will “seeding” a new vat with a small amount from an older, reduced vat speed up the reduction process?
  • What is the effect of additional indigo plant material when added to the vat?
    • ground woad balls
    • dried Persicaria tinctoria leaves
    • patties made from Indigofera suffruticosa leaves
  • Can I make a fermentation vat without adding indigo pigment? All the indigo would then come from the plant material that also causes the fermentation. 
  • Can I leave a vat unattended for a week? 2 weeks? 3 weeks? how long?
  • What is the best way to get the vat back into a healthy reduction after it has been ignored and the reduction is weak or non-existent?
  • What is the best way to make a weak vat for pale hues?
  • Can a fermentation vat be done successfully using synthetic pigment? – I was not successful at this!

Small samples are dyed daily in the sample vats and I monitor  both the pH and the temperature of the solution. I also take note of both the vat surface and its smell. Once I feel “confident” that I have learned the lessons that each experiment has to teach me, I add the small vat to one the large ones. This replenishes the volume and adds some organic material.

indigo vat comparsion (1)
alkali comparisons

Making the first “large” vat took courage and a leap of faith. I now feel ready to double the size.

Several years ago I began growing small amounts of indigo in my garden, simply to understand it. I knew it would never be practical to extract my own indigo pigment. Now I have found an important use for even the small amounts of those fresh indigo leaves as source material for indigo balls or dried leaves to be added to the fermentation vats. 

Earlier this month I “attended” a “Zoom” talk by Aboubakar Fofana in which he talked about his own indigo practice. It was hosted by Botanical Colors.  I think it is well worth you time and now available online.

The indigo research and opportunities to attend virtual lectures have become possible because of this focused time at home. Now, it’s time to go back to the loom and prepare some woven shibori textiles for dyeing!

indigo vat comparsion
Four different values of indigo dye from the fermentation vat.

woven shibori shawl, made and donated to Penland School of Crafts annual auction
Woven shibori shawl, made and donated to Penland School of Crafts annual auction

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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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.