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.

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. 

burley
Air drying of traditional burley tobacco in TN
smoking tobacco
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). 

tropical
Tropical indigo plants (Indigofera suffruticosa), harvested and continuing to grow in foreground, not yet harvested in background
IMG_3019
Sarah in the test field, where several varieties of indigo are grown
IMG_3020
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. 

 

test extractions2
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.
filter
Filtering of test pigment
test pigment
Pigment extracted from test extractions
pigment samples
Each sample batch of pigment is carefully labeled for reference

label

TLC
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.
drying
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.  

trucks
Truck trailers used for indigo harvest and initial steeping of plants.
solar
Water that has been collected from the root and heated in solar tanks is used for extracting the indigo.
Version 2
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.
settle 3
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. 

Version 2
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.

Indigo Harvest in Okinawa

A life of natural dyeing knows no bounds. Each year I am thrilled and delighted to increase my knowledge and understanding of dyes and process. 

This year, I was privileged to participate in the harvesting of indigo and the extraction of pigment on the island of Okinawa, Japan. 

The Okinawa farm has been producing indigo for many years, as evidenced by the large, round concert vessels imbedded in the ground. The vessels are used for extraction of pigment.  Smaller square vessels, also in the ground, are used for the storage of the indigo paste pigment. 

The indigo harvest and extraction is currently being done by a young couple, Takashi and Kitta Sawano. They have been extracting pigment here since 2012.  He is a dyer. She designs and makes beautiful, naturally dyed cotton garments in a studio located in northern Okinawa. The process of harvest and extraction requires many helping hands and there were a number of friends and artisans  who came to get their hands dirty and participate. 

The variety of indigo is Strobilanthes cusia. It looks similar to polygonum tinctorium but this variety requires a hotter climate and has a greater content of indigotin. Even the stems of the plants contain indigo. Eight different harvests are made during the summer season to extract pigment from all the indigo plants.

It was pouring rain the morning we arrived to harvest. I was given a small scythe and some white ropes. I felt somewhat prepared for the cutting and tying process since this is  the same approach that we used last summer when harvesting Polygonum tinctorium at Rowland Ricketts studio/farm. Everything else about the process was different, since Rowland uses his indigo to compost the leaves for sukumo.

The goal was to collect 400 kilos of indigo plant (leaves and stems). Each bundle was weighed and the weight of the wet leaves was taken into consideration. The plants were then tossed into one of the large round vessels that was already filled with water. A porous round tarp had been placed over the surface and the plants went on top of that. The indigo plants were weighted down with wire mesh, boards and rocks to ensure full immersion.  The plants were left to soak for the next 24 hours. 

On the next day, we observed that some fermentation was beginning and measured the pH. 

On the the third day, the fermentation was very active. The plant material was lifted out of the vessel (with the help of a small tractor).  Lime was added. The amount of lime was carefully calculated as too much lime will result in an inferior pigment.  The indigo extraction was aerated for 45 minutes using long rods with a small paddle affixed to the end. The shape of the vessel made this a very efficient operation.

 

 

The introduction of oxygen through aeration caused the indigo pigment to precipitate to the bottom of the vessel. Once the excess water was pumped off the surface, the paste pigment could be pumped into a storage container, where a more concentrated pigment will settle to the bottom over the next few weeks. 

I purchase  indigo for use in my own dye vats. Most of it has come from India but I am currently using indigo grown right here in the U.S. at Stoney Creek Colors.  This experience has given me a new appreciation and understanding of the cycle “grow, extract, dye” and a deep respect for those who participate in the entire process.  My thanks go to Hisako SUMI, who has participated in this indigo harvest for the last number of years and invited me to attend –  in the spirit of understanding and sharing. 

 

Indigo Dyeing: Time and Patience

Learning about indigo continues….

I often receive questions about indigo dye that fades very quickly on a textile. When I ask the dyer how long the textile was immersed in the vat the response is usually “1 or 2 minutes”. That is not enough time! Each immersion in the vat needs to be long enough to permit the indigo to penetrate into the fiber: at least 10-15 minutes. Otherwise the dye simply sits on the surface of the textile, making it susceptible to fading and rubbing off.

Recently, I completed a series of tests in which I experimented with much longer immersions in the vat. Immersion times in the vat ranged from 20 minutes to 20 hours. A longer dip encouraged more dye to penetrate the fibers. The results are worth observing and discussing. All samples were neutralized in a vinegar/water solution and “boiled” to finish and remove excess dye.

indigo and time
Indigo on cotton, silk, and wool, each with a single dip in the vat

The most common method of achieving dark colors with indigo is multiple successive dips in the vat and there are definitely some advantages to building color in this way. Any unevenness of the dye will level out as the textile is immersed multiple times. This is  especially important  when dyeing large textiles in a small vat. (This is the reason why larger vats are better suited when dyeing large textiles; allowing the dye to reach more of the textile surface)  If the vat is large enough that the textile can be immersed and exposed evenly to the dye, longer immersion times may be a practical approach.

multiple dips
Indigo on cotton, silk, and wool with multiple (1-6) 15 minute dips
time exposure 2
Fabric woven of wool and cotton yarns. After a single 20-minute immersion, the cotton fiber is darker. After 2 hours, both fibers are close to the same color. After 18 hours, the wool has absorbed a great deal more indigo while the cotton has maxed out. Multiple dips in the vat are required to achieve very dark blues on cotton.

My usual approach to dyeing textiles is using woven shibori. The textile is gathered with the woven “stitching” threads, making a compact “package”, and exposing the outside pleats of the textile to the dye uniformly.

indigo, dobby weave
Cotton, woven shibori, multiple indigo dips

Lately I have been experimenting with itajimi shibori (folded and clamped resists), where many layers of cloth might be folded multiple times. When using mordant dyes or fiber reactive dyes, the dye usually penetrates through the layers. When dyeing with indigo (10-20 minute immersions), the dye fails to penetrate beyond the outside layer and into the cloth within the folds, despite multiple immersions. When the immersion time was increased to 24 hours the dye penetrated ALL the layers – like magic. More time in the vat allowed complete penetration of dye throughout the textile.

 

Lightfast tests were performed on all samples dyed with extended times in the vat by exposing 1/2 of the samples to four weeks in a window with direct sunlight.

 

Note: When dyeing protein fibers, care must be taken with the pH of the vat, as the fibers can be damaged by long exposure if the pH is too high. Ideal pH for protein is 9.5-10. 

 



GrowingColor

The North Carolina Arboretum is hosting the second Growing Color Symposium on March 8, 2018. Michel Garcia will be our keynote speaker. Join us if you can!

How to Finish Indigo and a Natural Dye Book in the Works…

Last week I received several questions about how to finish textiles after dyeing with indigo. What now comes naturally to me, I realize, is not well understood by all dyers.

First, back to the dyeing: the textile should be dyed in long immersion baths (10-20 minutes). Without the long immersion, the dye will only sit on the surface of the textile and will not be lightfast.

Once the dyeing has been completed (and all the dye has oxidized) the textile must be neutralized. There is a great deal of alkalinity in the fibers from the calcium hydroxide (lime, calx) and that requires neutralization. Without this step, the textile will be vulnerable to damage. It will yellow over time and it won’t have a good hand.

IMG_0092

 

Many years ago, I made the assumption that only protein fibers needed to be neutralized. That is definitely NOT the case. All fibers must be neutralized!

Neutralization takes place in a water bath, to which a few “glugs’ of white vinegar (5% acetic acid) have been added. This is equivalent to about 1 tablespoon (10 ml.) per liter of water. Allow the textile to soak in the vinegar bath long enough for the acid to fully penetrate into the fiber (a few minutes to one hour, depending on the density of the textile). You can actually see the color brighten during this step.

indigo discharge 11
Silk, neutralized fabric on the left
indigo discharge 10
Cotton, neutralized fabric on left

Next, the textile must have all excess dye completely removed. The best way to do this is in a heated bath, to which a small amount of pH neutral detergent is added. Heating will cause the vat dye molecules in the fiber to combine into larger units, making them stronger, while also removing excess dye that has not attached to the fiber. Boil cellulose for about 10 minutes. Protein fibers can be heated to an appropriate temperature and maintained at that temperature for about 10 minutes. After this step a thorough rinsing should be performed. THAT’S HOW TO FINISH INDIGO!

Sample Set B

How did I come to understand all of this? I would still be wondering about much of it without my friend and colleague, Joy Boutrup. Joy is a Danish textile chemist, engineer and creative thinker. In an earlier post, I mentioned that we have taught together many times at Penland School of Crafts. Joy has helped me to understand process and the reasons behind the process. In its most recent issue, Fiber Art Now magazine has published a wonderful article about Joy, written by Lasse Antonsen.  I encourage you to read it here.

Version 2
Penland School of Crafts, NC

Joy and I are currently writing a book on natural dyeing! It will be a practical handbook for dyers, which not only explains HOW to dye but WHAT is happening in the process and WHY we might choose one process over another. Schiffer Publishing Co. will publish the book. Release date is targeted for late 2018.

Version 2
Joy, printing with indigo in the Penland studio

As I work through studio processes and words of explanation for the book, I realize how much I have learned from Joy’s deep understanding and perspective and I value her as a collaborator. Our book should help all of us to become better dyers.

How Much Indigo in the Vat?

As I learned to use organic indigo vats, I started with recipes from Michel Garcia: “one, two, three”. Michel talks about the vats in simple terms. It’s as easy as 1,2,3. This also represents the proportions of indigo, lime, and sugar that go into the vat:

  • 1 part indigo
  • 2 parts lime
  • 3 parts fructose sugar

It’s simple, right?

Not always.

I probably get more questions about making and maintaining an indigo vat than anything else. There are so many unknowns. It’s taken me a number of years to feel comfortable with those unknowns and to gain the confidence to solve problems with the vat.

I recently had several people ask me about the quantity of indigo in the vat. That’s an important question. Unless you know how much indigo, you can’t really determine how much sugar (or other reduction material) or how much lime.

I’ve watched Michel make vats with very small amounts of indigo and what I would consider very large amounts of indigo. What is the difference? Will you get a darker color from a vat with more indigo?

The answer is “yes” and “no”.

I made 3 small fructose vats with varying amounts of indigo

  • 2 grams indigo per liter of vat liquid volume
  • 5 grams indigo per liter of vat liquid volume
  • 8 grams indigo per liter of vat liquid volume

As you can see from the samples dyed the very next day, there was a great deal of difference in the colors produced from each vat. Even on day 3 there was significant difference. But one week later, the 3 shades of blue are much more similar. All of these samples represent only one 20-minute dip in the vat.

scan-545
Dye tests done with a single long dip in the three different vats

Why would you use 8 grams of indigo per liter instead of 2 when you can get a similar color from both these options? There is more indigo in the vat, which means more can be dyed over a longer period of time before additional indigo must be added. If I were doing a short-term vat for a small amount of dyeing, 2 grams of indigo per liter would probably be plenty.

The questions to ask are:

  • What  quantity of textiles will  be dyed in the vat?
  • How many people will be using the vat?
  • How long do you want to keep the vat?
  • How quickly to you need to get strong color from the vat?

The coloration of the reduced liquid in the 3 vats is different, indicating varying amounts of indigo in reduction. But the textile is only able to absorb so much dye at a time. We always build up color with multiple, long dips in the vat.

img_9825
Three indigo vats reduced with fructose: 8 grams, 5 grams, and 2 grams of indigo per liter

The other thing you can see through these glass jars is the amount of sediment at the bottom of the vat. The weakest vat has very little and it gets progressively deeper with the stronger vats. It’s important to keep our textile above this sediment when it’s dyeing.

I currently have a 30-liter vat that I have been using for over a year now. I’ve added indigo to it a couple of times, and of course plenty of reduction material and lime. The vat is still working well but over the months the sediment has gotten very deep, which has reduced my dyeing space so much that it’s time to make a new vat.

The “1,2,3.. ” proportions are guidelines and easy to measure if you’re using fructose. How many bananas or sweet potatoes do you need to reduce 10 grams of indigo? Take a good guess. Making small experimental vats in glass jars has taught me a great deal about how the vat works. We don’t always know but have to start somewhere.

Observe carefully. One must be patient with the indigo vat.