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
sympolocos leaves
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
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). 

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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.
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.  

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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.
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. 

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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

It’s Goldenrod Season

I  have always enjoyed how the goldenrod grows and blooms alongside the purple asters – a beautiful combination of complimentary colors. Goldenrod (Solidago sp.) is a member of the aster family. There are many solidago species native to North America, and they can also be found in other parts of the world. 

Is goldenrod a good source of dye? Yes, but with reservations. 

Though it is not one of the “classical” dyes, and it’s lightfastness does not match that of weld, it was used as a locally available dye in North American and Europe. Dominique Cardon (Natural Dyes: Sources, Tradition, Technology, and Science) writes about goldenrod’s  historical use, along with weld and Persian berries, to dye the yellow hats the Jews were required to wear in the south of France in the 13th century. 

I’ve always read that goldenrod does NOT dry well for future use – so I never tried to dry it. I can accept the fact that some dyes deteriorate in the drying process. Black walnut hulls are a good example.

A couple years ago I was teaching a class here in Asheville, NC on dyes that could be sourced from the local food co-op. I used dried goldenrod plant material, as it is used medicinally. It resulted in very good color. So I began to wonder….. CAN A GOOD DYE BE OBTAINED FROM DRIED GOLDENROD? 

It’s one thing to read a statement about a plant – it’s another thing to know and understand that statement. I  had never tried to dry goldenrod. This year I finally got around to doing my own testing.

I gathered fresh goldenrod, and used that to dye aluminum mordanted wool, silk, and cotton. There are many yellow dyes in goldenrod and they may include quercitron, isoquercitron, kaempferol, astragalin, isorhamnetin. Since the dyes in goldenrod are primarily flavonols, a mordant is required. 

I  dried goldenrod from that same harvest. Plants were hung upside down in a dry space with plenty of air flow. Only the flowering heads were used as a source of dye. I was able to accurately determine the weight of the plant before and after drying. 300 grams of fresh goldenrod flowers resulted in 100 grams of dry flowers. 

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100 grams of dried flowers (left) and 300 grams fresh flowers (right)

I dyed with fresh goldenrod at 300% w.o.f, while the dried was used at 100% w.o.f. Because I knew the weight before and after drying, I was confident that I was using the same amount of dye, whether it was fresh or dry plant material.

The results: The dyes seem not to have suffered from the drying process. Careful drying is likely a key element. So yes, I will dry some goldenrod and I will complete lightfastness tests on all three fibers. The goldenrod will not replace the weld that I grow and dry each year, Weld will always be my primary yellow dye as that has proven to be the best, and most lightfast yellow dye. But it is good to know a bit more about the dyes from plants available in my neighborhood. 

goldenrod samples

Thus far I have used only the flower heads for dyeing. Maybe next year I’ll experiment with the stems and leaves from the entire plant. 

 

The Art and The Science of Natural Dyes by Catharine Ellis and Joy Boutrup, available in late fall, is now available for pre-order.

Are All Oak Galls Equal?

The short answer is “no” but here is the longer answer. 

I’ve used Aleppo galls (either ground or extract) for years as my preferred tannin.  They were recommended to me as being high in tannin and are readily available. Gall is a source of colorless, gallic tannin.  I’ve done many tests comparing the Aleppo gall to  tannins, such as sumac (from local leaves), myrobalan, tea, and many others but I had never compared different varieties of oak galls. 

First of all, what is an oak gall?  They are sometimes called “oak apples” and are small, round growths of plant tissue produced by the oak tree in response to the infestation and larvae of a wasp.  There are many different species of wasps as well as oak trees. As a result, the galls from each of these is different. The Aleppo gall nut (Quercus infectoria) is hard and dense but can be ground to produce fine particles.

A friend from Missouri gave me a jar of her local gall nuts. She lives in a forest of white oak (Quercus alba) and gathers the galls when they fall to the ground. These galls have a smoother surface than the Aleppo but are just as hard and dense. 

Recently I was in New England and was able to gather galls from the scarlet oak variety (Quercus cocinea). These are larger, very light in weight, and seemingly hollow. As a child, we referred to them as “puff balls”. 

 

I wanted to know something about the tannin quantity of these various galls and if they could be used interchangeably for dyeing applications.  They were applied to cotton fabric prior to  mordant and dye. I used each of the tannins at 10% weight of fiber, which is the standard amount I  use of gall nut extract.  

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1 gram of each gall source

The whole galls were ground with a small spice grinder, and further crushed using a mortar and pestle. Those from the White and Aleppo oaks broke down into fine granules, while the Scarlet oak variety was impossible to grind as fine, as the insides were truly “puffy” and “spongy”. Each of the ground gall varieties and the extract were put into warm water, using separate beakers for each, along with the cotton cloth.  They sat at room temperature for 1 hour before the mordant was applied. 

 

I took a portion of the samples with the tannin application and put them into a weak iron bath. When tannin and iron combine a dark grey or black will result. The shade of grey is an indication of the amount of tannin present. The Aleppo gall nuts, in either the ground or extract form, resulted in much deeper shades of grey than either the white or the red oak varieties. The large pieces from the scarlet oak resulted in a very uneven application of tannin. When the iron was applied, the surface was very splotchy and irregular. 

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TOP: Tannin only. Although the galls appear to have colorants,  an insignificant amount of color attached to the textile. MIDDLE: with weak iron applicaton.  BOTTOM: sample shows the uneven application of the scarlet oak gall.

The rest of the samples were then mordanted and subsequently dyed with both weld and madder. The amount of tannin has a direct effect on the amount of mordant that can attach to the textile, and the depth of dye color obtained is a direct reflection of the amount of mordant present. Based on the iron applications, I was surprised at the depth of the color obtained with all of the gall varieties. Although the dye color obtained from the white and scarlet oaks is lighter than the Aleppo, there is still significant color attached.

Scan
Comparison of various galls with madder and weld dye. Left to right: White oak gall, Scarlet oak gall, Aleppo oak gall, Aleppo extract

When using tannin prior to mordanting, it is likely that increasing the amount of gall from the white or scarlet oaks would increase the amount of mordant that attaches and thus the depth of dye color. 

Locally harvested galls, when available, are an opportunity to use the local resources and achieve acceptable results. 

The Art and The Science of Natural Dyes by Catharine Ellis and Joy Boutrup, available in late fall, is now available for pre-order.