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! 

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.

IMG_6046

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. 

IMG_5776

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. 

A Cautionary Tale: Indigo and Reducing Chemicals

The first indigo vats that I made in the 1970’s were reduced using sodium hydrosulfite. It was the only way I then knew to reduce the indigo. A few years later I began using thiourea dioxide as the reducing agent. I was never comfortable with these vats and, as a result, I never did much indigo dyeing. The vats smelled bad and I felt that I never truly understood them.

My current, and very positive, relationship with indigo began after meeting Michel Garcia in 2008. Michel introduced me to indigo vats that are reduced with natural materials: sugars, plants, or minerals. Since then I have worked hard to learn as much as I could about these vats, and have maintained them constantly in my studio. Indigo dyeing has become an integral part of my studio work and experimentations.

 

I know many dyers who use either sodium hydrosulfite (“hydro”) or thiourea dioxide (“thiox”) to reduce their vats. These chemicals work efficiently and predictably and can now understand why a dyer would make the choice to use them. But I’ve recently been asked about the safety of these reducing chemicals. This is not a question that I felt qualified to answer myself. I was with Joy Boutrup last week (we were teaching together in Iceland!) and I asked her to address this question.  

To paraphrase Joy:

Both sodium hydrosulfite and thiourea dioxide are sulfur based and will release hydrogen sulfide. This is what causes the bad smell and can affect human health when the gas is inhaled.  It can be irritating to the nose, throat, and airways and potentially paralyzing to breathing if inhaled in large quantities. Dyers with asthma should be especially cautious when using these reducing chemicals.

Both “hydro” and “thiox” also release sulfur dioxide, which is considered to be damaging to the brain. It is a chemical that has been used in photography and some photographers have suffered from long term exposure to this chemical. 

When using these chemicals dyeing must be done outdoors or in a very well ventilated area! Occasional dyeing using these types of vats may not result in noticeable effects but if you stand with your head over an indigo vat day after day, then serious breathing problems could result. Joy was recently consulted by a group in Denmark, who have been using these chemical vats for many years. Some of the dyers are experiencing a variety of health problems as a result of the exposure to the chemicals. She recommended that they begin using the natural/organic vats as an alternative. 

The other issue is disposal. The chemicals are very reductive and cannot just be thrown out. The reduction must be stopped before disposal but it’s not easy to keep the sulfur products from being reductive. Other chemicals can be used to stop the reduction but they are just as damaging. Some dyers simply keep their vat, adding additional indigo and reduction chemicals as necessary. Continuing to use the chemicals in the vat is preferable to uncontrolled disposal.

One another note: I have a friend who does production dyeing. She uses an indigo vat reduced with thiourea dioxide but was having trouble achieving pale blue colors. Dyers will often just do a quick 10-30 second dip in the vat to get light blues, but this doesn’t give the indigo time to penetrate the fiber. As a result, the dye is less fast to washing and crocking and is not likely to be even. I suggested that she try my approach to achieving pale blues: use only a small amount of indigo in the vat (1-2 grams per liter). 

When she told me that the small amount of indigo still resulted in a deep blue color, I did some tests myself using both “thiox” and sugar as reduction agents. 

I was surprised by the results. The organic sugar vat resulted in the pale blue color that I expected, while the vat reduced with the thiox was a very deep blue, although only a small amount of indigo had been use. 

Conclusion: the reduction chemicals will reduce the maximum amount of indigo, making it impossible to achieve the pale colors, while in the sugar vat, only part of the indigo is reduced at a time.  This is why a sugar or other natural vat can continue to be used over many days, weeks, or months. 

These reduction chemicals are used in industry and efficiently maximize the dye that can be applied to warps for blue jeans. But even industry has been concerned about the longterm effects of chemical reduction and disposal. Some industrial users have begun to use electrical reduction instead of chemicals for all vat dyes.  But artisan dyers are not industry…. The naturally reduced indigo vats are not only safer to use, but they allow us better control over our color and color mixing.

chemical vs sugar
Wool yarns were dyed in a vats, each made with 2 grams indigo/liter. Yarns had not been neutralized when this photo was taken.

Symplocos – A Plant Mordant

Symplocos is a plant species that accumulates alum mordant. It is one of number of plants that grows in acidic soil around the world, and thus is able to absorb available aluminum from the ground. Although different parts of the tree absorb alum, it has been determined that the fallen leaves have a high concentrations of alum and are the most sustainable source of mordant. By harvesting the fallen leaves, no damage is done to the tree. These leaves can be used as an alternative and highly effective source of mineral alum, while also imparting a pale yellow color to the fiber. 

One variety of symplocos is native to Indonesia and utilized by weavers and ikat dyers with when dyeing red with morinda (Morinda citrifolia) on cotton. The Bebali Foundation has been studying the mordant process for a number of years and has made symplocos available to dyers around the world, while supporting the local women who gather the leaves. Michel Garcia worked with the foundation to develop recipes for both protein and cellulose fibers. All of these recipes are available online at The Plant Mordant Project.

I have experimented with symplocos many times with great success. Recently I have been introduced to a variety of symplocos  (Sympolocos tinctoria)  that is native to the southeastern United States. It is described as a small tree or shrub, “deciduous or weakly evergreen”. It is also known as “horse sugar” or “sweetleaf” because horses are attracted to the sweet leaves of the plant. As I researched, I read that it grows in “very acidic soils”. It is sometimes described as a source of yellow dye, but nowhere did I read that it was a source of alum. 

Leigh Magar, a textile designer and dyer, brought me a handful of leaves last year that she collected at her home near Charleston, South Carolina. I proceeded to test the leaves as a source of mordant, comparing them to the symplocos that I have from the Bebali Foundation, and also to mineral alum. I ground the leaves and used Michel Garcia’s recipe. The results were very good. 

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Mordant only applied to wash-fast wool knit: 1.) no mordant, 2.) mineral alum mordant, 3.) Bebali symplocos mordant, 4.) South Carolina symplocos mordant
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Weld and madder dyes applied following 1.) no mordant, 2.) mineral alum mordant, 3.) Bebali symplocos, 4.) South Carolina symplocos
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South Carolina leaf on left, compared to the larger symplocos leaf from Bebali. Both leaves were ground fine before applying them to the textile.

Last month I was finally able to travel to Leigh’s home in South Carolina to see the plants myself and to gather some of the leaves. Our regional variety has leaves that are smaller than the Indonesian variety but they are shed in much the same way. The leaves yellow as they age and drop from the tree. They are easily gathered from the tree at this time. Leigh tells me that shedding seems to be more more prevalent in the spring, although the tree sheds its leaves all year long.  

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Older leaves yellow on the tree before falling to the ground

I am currently reading (and very much enjoying) Braiding Sweetgrass by Laura Wall Kimmerer. In the chapter entitled The Gift of Strawberries the author talks of wild strawberries as unexpected gifts received from the earth. Finding alum in a plant is very much like a gift – to be received gratefully – but not to be turned into a commodity. I will treasure this gift of alum and appreciate Leigh’s generosity in sharing it,  but it will not replace the mineral alum that I purchase from a supplier.

 

And a couple notes on our book: The Art and Science of Natural Dyes. First of all, I am very appreciative of the many notes and emails I have received from so many of you. It is exciting to both Joy and me that the book is finally out and truly being used. 

There is one important omission on pages 169 and 170. The mordants used for the photos of the dyed samples should cross reference mordants #1 – #5 (top to bottom), from the mordant mixing chart on p.150.

 

p 169 corretion

And about the spiral binding – we chose the binding very intentionally so that the book would open easily and stay open. The book is meant to be used, referred to, and likely to get stained, like a much used cookbook. Many of you have told me how much you love the binding but I have also heard from a few of you that pages can easily slip out of that spiral. A dyer in Australia showed me a perfect solution; she threaded a piece of cotton yarn through the binding, locking the pages in. I have now done this to my own book and would suggest that you do it to yours as well. 

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Madder Roots, Harvest, and Comparisons

For  a number of  years I have been using  madder (Rubia cordifolia) sourced from Maiwa (in Vancouver, BC almost exclusively for my dyeing. I particularly appreciate  the fact that it is finely ground so that I am usually able to just put the dye into the bath along with my textile. If dyeing yarn, however, I typically will  place the ground dye into a net bag  to keep small particles of madder from physically attaching to  the fibers.  

I once heard Michel Garcia speak about the fact that you can nearly double the yield from madder root if it is finely ground. It makes sense. More surface area means that it’s easier to extract the dye. 

Early last year I harvested about 5 pounds of madder roots (Rubia tinctorium) from my garden. The plants were started  from seed and they had been in the ground for about 5 years. I dug up the entire bed (about 4’ x 8’), pulled up the largest of the roots, leaving the smaller roots in place. I amended the soil, added some chalk, and the plants have continued to grow in the same location. My theory is that I can continue to harvest every few years by  leaving the roots in the same place and repeating the amendment process  We’ll see…

I cleaned and dried the roots. Some of the dyes are developed by in the drying process so that is important.  A few weeks later, I dug up another small patch.  With this second batch, it occurred to me that maybe I could grind up the roots before drying them. It was easy to chop up the fresh roots into small pieces with an old food processor that I have designated for studio use. Once chopped, the roots dried very easily on horizontal screens.

Last month, I was preparing a major piece for an exhibition and I wanted to use my own madder. The large, dried roots proved to be problematic. I wanted to grind them as fine as possible but was not sure how to proceed. 

I tried a mechanical corn grinder. It was a terrible experience! The grind was very coarse, the roots jammed in the grinder, and it was not at all successful. I tried the old food processor – not powerful enough to be effective.  I even tried grinding small amounts in a dye-designated coffee/spice grinder. It was better, but still not very good and it would have taken far too long since the capacity of the grinder was very small. 

I did some research, and finally decided to purchase  a powerful electric grinder that is recommended for medicinal herbs (roots) etc. It was amazing! First, I quickly broke the roots into smaller pieces by hand, which allowed me to pull out the “chaff” (the stem pieces with no dye). I put the smaller root pieces into the grinder and I had finely ground madder root in just two minutes!

I’ve learned a lot (of course). Madder root, even when dried completely, still has elements (sugars maybe?) that coated the bowl of the grinder with a layer of sticky madder. The bowl of the new grinder cannot be immersed in water so I had to work hard to clean it out. But the madder is all ground and the grinder is  now ready to grind my dried sumac leaves and some other tannins. 

In our book,  The Art and Science of Natural Dyes, Joy and I discuss and show examples of how a dyer sometimes has more control over the color when using madder roots rather than extracts.  The source (and type) of the roots is also a factor.  Madder contains many different dyes and the two different species contain different combinations. 

As  I began my tests for the exhibition piece, I did many samples and used madder roots from a variety of sources.  The woven shibori project utilized mordant printing with different strengths of aluminum acetate, ferrous acetate, and combinations of the two mordants. When Rubia tinctorium is used with iron mordants, it is possible to achieve distinct purple colors. The purples are not possible with Rubia cordifolia, as the dyes within the roots are different. I was very happy to observe that my own madder was the very best of all!

madder comparison cotton
Ground madder root @ 50% w.o.f. on cotton with mordant printing. Left to right: Rubia tinctorium from my garden, Rubia tinctorium from France, Rubia cordifolia from India (Maiwa). Note the purples achieved from the Rubia tinctorium with an iron mordant.

 

 

Garden Series: Madder, detail of finished piece
Garden Series: Madder, detail of finished piece

I am very encouraged to keep growing…and dyeing….

I have begun using my own copy of The Art and Science of Natural Dyes in the studio and in my teaching. No, I do not have all of those recipes committed to memory! I have found it very useful to add tabs to the book, making it easy to navigate and find exactly what I’m looking for.

book

Note: Maiwa now carries very finely ground Rubia tinctorium roots.

 

 

Where is YOUR Indigo Grown?

I first met Sarah Bellos of Stony Creek Colors in 2016 when she spoke at the Growing Color Symposium at the NC Arboretum in Asheville. She presented her vision for growing and extracting indigo in Tennessee. Her goal was to introduce natural indigo to the denim industry, which is currently a huge consumer of synthetic indigo (a serious source of environmental pollution). She was partnering with Tennessee farmers who had previously grown tobacco and planned to process indigo dye locally. 

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Air drying of traditional burley tobacco in TN
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Some Tennessee grown tobacco is cured by smoking with wood fire

I must admit that I was somewhat skeptical. The project seemed too big and too optimistic. I didn’t know anyone who had successfully grown indigo dye plants on the scale that she described.  Most dye plants are grown for commercial purposes in India or South America, where the price of labor is far less. Indigo was grown in the Southeast coastal regions of South Carolina and Georgia in the 17th and 18th centuries but, to my knowledge, has not been grown commercially in North America since that time.       

On a recent visit to Stony Creek near Nashville, TN I was very pleasantly surprised and now believe that they are truly on the way to something successful and very much needed. I’d like to tell you why I believe this. 

The first place visited was the “test farm”.  I had envisioned a small plot of Persicaria tinctoria but was amazed to find that the test farm was a densely planted, multiple acre farm tract where several strains of Persicaria tinctoria are growing next to the tropical varieties of indigo (Indigofera suffruticosa and Indigofera tinctoria). 

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Tropical indigo plants (Indigofera suffruticosa), harvested and continuing to grow in foreground, not yet harvested in background
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Sarah in the test field, where several varieties of indigo are grown
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Persicaria tinctoria, in bloom

Why grow so many different types of plants? Sarah and her staff are constantly asking questions and testing: Which varieties can be sown directly in the ground? Which need to be started in the greenhouse? Some strains bloom more readily than others (great for seed production but not so good for indigo production). Which plants can be dried for future extraction? What is the indigotin content vs. the biomass of the plants? Which can be harvested most efficiently?

I believe that the Stony Creek team is concluding that there is wisdom in growing more than one variety of indigo.  The farmers are currently growing many acres of indigo for pigment extraction. All farms are within a reasonable drive to the factory, as it is necessary to process the indigo leaves quickly.

The next stop was Stony Creek’s lab.  Walking in the door I saw that the dye chemist, Summer Arrowood, was pulling leaves from Persicaria tinctoria stems that had been harvested earlier that morning. She was weighing those leaves and recording the leaf-to-stem ratio. Next, individual bags of leaves (from very specific plants in very carefully identified locations at the test farm) were processed to extract the indigo pigment. I sensed that this was part of each day’s work at the lab. The leaves were soaked in hot water, the liquid was pumped into vessels for aeration, the paste was allowed to settle and then filtered. Several hours later, each batch of leaves had produced a small amount of indigo pigment. These were tested, labelled and stored for future reference. They report that their indigo contains 25-35% indigotin which is a very concentrated output. 

 

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Vessels for test extractions of pigment. Sarah is holding the piping used for introducing oxygen into the indigo extraction in order to precipitate the pigment.
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Filtering of test pigment
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Pigment extracted from test extractions
pigment samples
Each sample batch of pigment is carefully labeled for reference

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Yoshiko Wada, and Summer Arrowood, Stony Creek’s dye chemist, observing the results of TLC, (thin layer chromatography), used to determine whether indigo pigment samples that Yoshiko brought were natural or synthetic.
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Stony Creek is experimenting with extraction from dried plant material in order to extend the production season.

The production factory is located in a county-owned, former tobacco factory and leased by Stony Creek.  Here, 20,000 pounds of indigo plant material can be processed in a single batch. The factory is set up with modern equipment, carefully laid out, and efficient. Stony Creek precipitates indigo pigment without the use of lime (calcium hydroxide). When too much lime is used during the process, it will remain in the indigo pigment and skew the weight of any available indigotin. The extraction without lime is one of the reasons the pigment has such high levels of indigotin. The pigment paste is carefully filtered using processes that Stony Creek has developed specifically for indigo.  

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Truck trailers used for indigo harvest and initial steeping of plants.
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Water that has been collected from the root and heated in solar tanks is used for extracting the indigo.
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Stainless tanks are used for aerating the indigo. Stony Creek has recently installed two additional tanks.
settling tanks
Plastic tanks are used for settling of the indigo paste.
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All indigo paste settles to the very bottom of the tanks. The remainder is waste water, that is properly neutralized before discarding.

settle 2

How has Stony Creek come this far so quickly? Sarah Bellos has an academic background and experience in natural resources management and sustainable agriculture. She is a self-taught natural dyer; she and her sisters operated a dye business for several years under the name Artisan Natural Dyeworks. Stony Creek employs skilled and smart people, who know chemistry, plants, agriculture, and manufacturing. The farmers, who grow the indigo, are benefiting from a cash crop that has the potential to replace the tobacco that grew here for so long. Stony Creek is currently selling indigo paste to denim producers and they are able to test/replicate the warp dyeing process used by the denim industry in their lab. Sarah had a vision to produce natural indigo and they are making it a reality. 

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This chart says it all!

At a time when some of us are unsure if we are purchasing natural indigo or synthetic indigo (or a mix of both) Stony Creek is a beacon of light.  I have used their indigo and it is excellent. Of course I will purchase my indigo from them!  I will encourage other dyers to do the same.

Stony Creek is NOT yet set up for visitors. Right now, they need to focus on the work at hand and continue to develop their current products: indigo, black walnut paste extract (that really works!), and a madder extract paste (currently from Rubia tinctorium roots grown in India until their own roots are ready for harvest).  

After this year’s indigo harvest they plan to move the lab to the factory location and at some time in the future will be able to offer workshops onsite. I hope that you will consider helping to grow this promising endeavor by trying out their excellent indigo, and other extracts available for order online at their website. Other dye suppliers are also beginning to carry and sell Stony Creek Indigo.

The day we visited the factory, there was no indigo being processed. It had rained the day before and the indigo plants cannot be harvested when wet; this whole process is tied closely to the land. Before we left in the afternoon, the truck and trailer had left for the fields, ready to be loaded with indigo plants early the next morning.

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

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

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

Why the delay? 

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

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

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

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

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

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

And keep dyeing!

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

Catharine