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. 

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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.

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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. 

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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
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Each sample batch of pigment is carefully labeled for reference

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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.
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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.
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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.

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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.

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.

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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.

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Indigo on cotton, silk, and wool with multiple (1-6) 15 minute dips
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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.

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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.

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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.

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Silk, neutralized fabric on the left
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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.

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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.

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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.

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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.

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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.

Indigo Reduction Materials

Michel Garcia has inspired and informed many of us in the use the organic indigo vats. He has given us a simple one, two, three (1:2:3) recipe that refers the proportions of indigo, lime (calcium hydroxide) and reduction material (often a sugar).

But nothing is ever as simple as 1:2:3! Dyers work hard to determine how to keep their vat active, when to add reduction material, when to add  lime, and how to best dye their textiles.

A key issue dyers must think about is the selection of the best reduction material that is also readily available. Michel commonly recommends the use of fructose or a fruit that is high in sugar, such as bananas. These high-sugar materials assure that the indigo vat will go into reduction quickly and successfully. I recently had a reader ask me if dextrose will work as well as fructose. I didn’t know, so I tried it. It was slower to reduce, but in the end resulted in colors very close to those obtained with fructose. On the other hand, cane sugar resulted in no reduction whatsoever.

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Vats were made with fructose and dextrose

In November I was in Oaxaca, Mexico for the 10th Intentional Shibori symposium, where Michel Garcia and I were both teaching workshops. Our time in Mexico proved to be another opportunity to realize how much more there is to learn about indigo vats.

One day, we were eating fresh oranges and Michel mentioned that we could use the orange rinds to reduce an indigo vat. I was surprised (and a bit skeptical) since I knew that oranges were acidic. It turns out that the orange juice is acidic but the rinds are full of pectin, which is an excellent reduction material.  We ate a lot of oranges, cooked the rinds, and used that juice to make our vat. Of course, it worked!

Further discussion of indigo vats in Michel’s class revealed that some vegetables can also be used to reduce the indigo vat: turnips, zucchini, etc. Some of these vegetables contain pectin as well as sugars.

I never really know something until I’ve tried it. In the last few weeks I have made nine small indigo vats using citrus skins and chopped vegetables. I made the vats in glass jars with 1 gram of indigo per liter of solution.  A great deal can be learned about an indigo vat when it’s made in a transparent container. I can see the color of the vat, the amount of un-reduced material at the bottom, and the speed (or slowness) at which the vats reduce. The use of the vat for dyeing is the ultimate test.

The “citrus series” was made with

  • Cooked orange rinds
  • Cooked lemon rinds
  • Commercially available ground orange peel
  • Commercially available pectin from the grocery story (additives included dextrose and fumaric acid)

When using fruit, I cooked the rinds from several small oranges or lemons in water and used that liquid as the basis of the vat. I used the 1:2:3 proportions (by weight) as a guideline for the commercially available orange peel and pectin (1 part indigo, 2 parts lime or calcium hydroxide, 3 parts reduction material).

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Samples dyed in the vat 1 day after making the vat and 9 days later. Reduction of the indigo vat is sometimes not complete for several days. The vat made with cooked lemon rinds never reduced well and continued to have a great deal of un-reduced material in the vat. All dying is a single dip in the vat.

The “vegetable series” was made with

  • Zucchini
  • Turnip
  • Carrot
  • Sweet potato
  • White potato

I used the equivalent of one medium sized vegetable per liter of vat liquid. The vegetables were chopped into small pieces and boiled for 15-30 minutes or until the vegetable matter was very soft. The liquid was then strained to make the vat.

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A vat in a pint size jar is enough for testing.
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The color of the bubbles on the surface of the vats is an indication of the reduction. The light colored bubbles of the white potato vat (back row, center) indicates the weakest reduction. This is confirmed by the color of the vat and the dyed color on the cloth.

Every vat worked to some degree. In the “citrus series” both the orange rind vats reduced first, the pectin vat was slow but after a week the color achieved matched the orange rind vats. The lemon rind was the weakest from the beginning and also has a great deal of unreduced material at the bottom. The white potato was the slowest of the vegetables to reduce and the resulting color continued to be the weakest.

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“Vegetable vats” after 24 hours and 5 days.

Some of these latest experiments were more successful than others but they were a huge revelation for me. There are indigo reduction materials everywhere! Some are better (and more available) than others. I can imagine a new use for the abundance of zucchini in the summer garden and I can use waste from my food kitchen to feed my indigo vat.

Several years ago I was doing indigo dyeing on the Island of St. John in the Virgin Islands. We harvested local Aloe Vera leaves as a reduction material. I later tried reducing a vat with Aloe Vera that was growing in a pot as a houseplant. The houseplant did not reduce the vat.

My studio doesn’t smell as sweet after cooking potatoes and turnips as when cooking orange rinds or bananas (neither does the vat), but it’s another valuable reminder of the complex world of natural dye and the resources at our fingers.

New Inspirations and Lessons

This summer took me to the Textile Center in Minneapolis, where I was invited to have a solo exhibition of naturally dyed textiles entitled Natural Dye: Experiments and Realizations.  The title pretty much sums up the way I work: testing, experimenting and finally bringing it all to a conclusion before beginning the next set of investigations.

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Natural Dyeing: Experiments and Investigations

The Textile Center in Minneapolis is a nucleus of textile energy. Also at the galleries this summer is The Power of Maya Women’s Artistry, a stunning collection of hooked rugs made by women in Guatemala using recycled cotton materials. Mary Anne Wise, the Wisconsin based rug designer who got this project started a few years ago, will be speaking at the Textile Center today, July 21, and a workshop will follow this weekend. The third exhibition on display is Naturally: A Natural Dye Invitational, which is a lively collection of eco-printed textiles done by members of the Minneapolis textile community.These exhibitions will remain in the galleries all summer.

Michel Garcia was at the Center last week as the  first Margaret Miller Artist-in-Residence, a residency named for the founding director of the Textile Center. Michel taught two fully enrolled classes: Color From Plants, A Natural Dye Workshop and Natural Indigo Dye Vat. I had the opportunity to sit in on a day of the natural dye workshop. It happened to be the day the class was working with cotton.

 

Over the last few years I have had several opportunities to learn from Michel  in both workshops and filming sessions with Natural Dye Workshop and Slow Fiber Studios. Each experience brings me a clearer understanding of process and I can never predict what I will learn.

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Michel is a philosopher as much as a dyer and chemist. He invites us to think about chemistry, process, and cultural ideas – all at the same time. It is stimulating, hard work to sift through all that he shares. One is not always ready to hear his messages. During this day, I began to get a glimpse of the way in which mordants may be affected (and damaged) by both acids and alkalines.

The next step for me, after being in a workshop with Michel, is always to go home, experiment, and really learn the lesson for myself. I have been trying to grasp the reasoning behind sequencing of dye colors with indigo. Years ago I learned to make greens and violets by dyeing indigo over yellow or red dyes. In 2011 I heard Michel Garcia state that the indigo should always be dyed first. Only then should the cloth be mordanted and dyed with another color. But I continued to work as I always had for a while – it’s sometimes difficult to un-learn what we think we know!

Over time I began observing that when indigo was dyed over a yellow or a red, the initial brilliant green or purple often becomes duller as the indigo dye is neutralized. If indigo is dyed first, and other colors dyed over the blue, the colors remain stable. WHY? Is the mordant damaged? Is the dye damaged? Is the alkalinity of the indigo vat the culprit? Is it the vinegar bath that is used for neutralizing the problem?  It’s a subtle difference but one that I was very aware of.

I made these observations on cotton, but does it hold true for all fibers?

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Cotton and ramie: the sample on the right definitely is a brighter green, when the indigo was dyed first, followed by tannin, mordant, and broom dyebath.

I wanted to test both protein and cellulose fibers that were mordanted. Instead of using indigo, I would simulate the alkalinity of an indigo vat by putting a similar amount of lime (calcium hydroxide) in water. As with indigo, I would also neutralize the cloth in vinegar after it had been in the lime bath. All samples were initially mordanted at the same time and dyed in the same dyebath. Sample #2 was dipped in an alkaline solution prior to dyeing. Sample #3 was dipped in the alkaline solution after dyeing.

from top to bottom

  • #1. Mordant, dye
  • #2. Mordant, dip in alkaline solution, neutralize in vinegar, dye
  • #3. Mordant, dye, dip in alkaline solution, neutralize

What I observed consistently on both cotton and silk is a lighter dye color after the mordanted fiber had been put in to the alkaline solution (sample #2), which would indicate that the mordant had been compromised. When the fiber was put into the alkaline solution after dyeing (sample #3) the final color was brighter than #2, but not as brilliant as #1. This brightening would be consistent with a calcium or chalk treatment of weld in the dyebath.

Wool was a slightly different story. In the past I have not observed there to be major color differences when layering colors with indigo on wool. Mordants attach to wool in a different way than on cellulose and even silk, which leaves the mordants less susceptible to damage by the alkalinity of the indigo bath.

from top to bottom

  • #1. Mordant, dye
  • #2. Mordant, dip in alkaline solution, neutralize in vinegar, dye
  • #3. Mordant, dye, dip in alkaline solution, neutralize

In the wool  samples, #2 was  nearly identical to #1. The alkaline treatment of the dye in #3 is consistent with the effect of pH and calcium on either of these dyes.

Conclusion: the mordant on cellulose and silk is very likely damaged by the alkalinity of the indigo vat. In my own practice, I had already shifted my sequence of colors when using indigo in combination with other dyes. Now I believe I understand more clearly why it is important. Cellulose and silk fibers, especially, should always be mordanted AFTER dyeing in indigo. Both the tannin and mordanting processes are acidic and will assure a thorough neutralization of the alkaline from the indigo. Although it may not be as important with wool, this same sequence may give the dyer more control over the final color.

Maintaining and Troubleshooting an Organic Indigo Vat

Jacquard woven shibori, indigo dye
Jacquard woven shibori, indigo dye

The questions I receive most frequently about natural dyeing seems to center on  the indigo vat and its maintenance. Since 2011 I have been making and using organic indigo vats, an art and  skill that I learned from Michel Garcia.

My current vat began in a 5 gallon vessel over 2 years ago. I enlarged it to fill an 8 gallon vessel, and then last year I enlarged my vat again to fill a 30 gallon container. The increased size was needed because I was dyeing larger pieces of cloth.

my current indigo vat, 30 gallons
My 30 gallon indigo vat

The vat was made using henna as a reduction material. I chose to use this material because the slow release of sugars is good for a vat that will be maintained for a long time.  I add fructose after each use and additional henna when I need to boost the reduction. Lime (calcium hydroxide) is the alkaline.

The vat is used regularly and I achieve excellent color from the indigo.  The large size challenges me to solve problems as I encounter them. It would be tempting to discard a small vat that was not behaving well and begin again, but emptying this vat would require a great amount of effort. As a result I’ve learned a lot about maintaining the indigo vat.

An indigo vat is happiest when it is used on a daily basis. After each dyeing session I “feed” it with a bit of fructose, stir it to bring the un-reduced indigo and reduction materials up from the bottom, check the pH, and let it rest for a few hours before dyeing again.

Occasionally I run into problems that I need to solve. Recently I was away from home for several weeks. Before I left, the vat was dyeing rich, deep blues. The color of the vat was a golden bronze and there was a good healthy “metallic” sheen on the surface and plenty of bubbles.

surface of a healthy vat
Surface of a healthy vat

When I returned home the first thing I did was add lime to the vat.  When an indigo vat sits dormant for any amount of time it becomes more acidic and the pH goes down. I can test this with pH papers but a good visual indicator is to sprinkle some lime on top. If the lime is immediately “sucked” down into the vat – you can assume that the vat is in need of the lime. If the lime just sits on the surface, the pH is probably fine.

Next, I stirred the vat and waited for it to settle. The color of the vat looked good, as well as the surface. The vat was a clear gold color and there was a coppery sheen on top. But the first test sample resulted in barely any color at all!  That was a surprise, since I thought there was plenty of indigo in the vat. I thought I had also been “feeding” it with plenty of sugar. The vat had been used very heavily before I went away. I thought that possibly the indigo had finally been exhausted.

Before adding more indigo to the vat, I decided to add more sugar – a generous amount. Once added, the vat was stirred and I waited until the next day to do another test strip. It produced a  blue, though it was relatively light. I repeated the sugar-stir-rest and dyed again the next day. It was darker. I repeated the sequence again, and finally got back to a shade of blue similar to that which I had before going away.

dye test strips
Dye test strips

The lesson here is that before adding indigo to a vat, test it thoroughly for pH and reduction.  Although it “appeared” to be healthy, my vat was not reduced and the indigo wasn’t available to dye the fibers.