I recently took on a small weaving commission that required the use of black wool yarn. For a brief moment I contemplated purchasing the wool in the required color and then decided that I could dye it. I was surprised at how easy it was to achieve a rich, deep black color on the wool using only indigo and madder.
It inspired me to continue my current series of color studies, woven in cotton and linen, with an in-depth exploration of black dyes.
Initially, I wanted to achieve all the black hues without the use of an iron mordant. My years of mixing hues with primary colors gave me the confidence to believe that I could mix a good black for cellulose using 3 primary colors: blue, red, and yellow. The key was going to be finding the correct proportions.
The first step was to build up a deep layer of indigo blue (usually 8-10 dips in the vat) followed by a mordant, and finally red and yellow dyes. That red could be madder or cochineal but I chose to use only madder, since that is what I am growing in the garden. My preferred yellow is weld. Each different combination results in a subtle variation. Some “blacks” are more purple, while others are a bit more green, or brown. I began using black walnut and cutch as a substitute for the madder and weld and sometimes added madder or weld to those. Each is a distinct hue, and definitely in the “black” family. I am confident of the lightfastness of these hues because of the primary dyes that have been used.
These multiple shades of black, put me in mind of the paintings in The Rothko Chapel in Houston, which is the site of a series of large large “black” canvases by the artist, Mark Rothko. These black canvases are painted with layers of crimson, alizarin, and black.
But no exploration of black would be complete without some experiments using tannin and iron. Instead of building up layers of primary colors, I soaked the textile in a gall nut tannin bath, followed by a short immersion in an iron bath. I wanted to use as little iron as possible, but still achieve a very dark shade. I decided that 3% weight of fiber would be the limit of the amount of iron I would use.
Most often, I use ferrous acetate instead of ferrous sulfate because it is less damaging to the fiber. Cellulose fibers are are somewhat tolerant of ferrous sulfate so I did experiments with both. That is where I was most surprised! Without exception, the ferrous acetate resulted in deeper colors than the same amount of ferrous sulfate.
Why? I wasn’t sure. So I consulted my colleague, Joy Boutrup, who always knows these things.
“I think the reason for the grey instead of black with iron sulfate is due to the higher acidity of the sulfate. The acetate is much less acidic. The tannin complex cannot form to the same degree as with acetate.”
The pH of my ferrous sulfate solution was 4. The ferrous acetate was pH 6. (My tap water is from a well and is a slightly acidic pH6.)
The grey and blacks achieved with the tannin and iron are quite one-dimensional compared with those that result from a mix of colors and not nearly as interesting, Yet they are likely a more economical approach to achieving black; the multiple indigo dips, mordanting, and over-dyeing takes considerably more time and materials than an immersion in a tannin and an iron bath.
Always observing always learning, here in the mountains of North Carolina…
Over the years I have built, used, and discarded many indigo vats. Sometimes I have kept them going for a very long time. I have finally declared the 5 year old, 100 liter henna vat “done”. I have added indigo pigment, lime and additional henna to it many times and although it is still dyeing well, the space available for that dyeing (above the “sludge” at the bottom) has gotten very, very small.
As many of you know, I have spent this last year at home getting to really know my fermented indigo vats. I have followed a rather strict protocol. Each vat began with a certain amount of indigo pigment, a source of alkalinity (soda ash or wood ash lye) and various plant based materials to begin and sustain the fermentation (wheat bran, madder root, dried indigofera leaves, etc.). Only small amounts of lime and bran have been added over the last year to sustain pH and fermentation. At no time have I added additional indigo.
Last May I was trying to achieve a wide range of blue shades from the very palest to very darkest. I was a bit dismayed to find that all of my vats were dyeing too dark to give me the pale shades I desired at the time. I knew (in theory) that if used the vats enough, the indigo content of the vats would decrease but had no idea how long that would take, or how much dyeing I would need to do. No matter how much I dyed, it didn’t seem to happen.…
Now, a year after the vats were first made, I can see progress.
Indigo on cotton cloth, same vat: 1-24 ten-minute dips. February, 2021
This is a long process….
Two dips in May, 2020 gave the equivalent shade as 5 dips in February, 2021
The dark blue that was achieved from 12 dips in May, 2020 was not achieved, even after 24 dips in February 2021
The subtle differences in the darkest shades are difficult to discern from the photos – but they are there.
I now realize the value of having a number of vats: from old to new, weak to strong. It’s something I have heard Michel Garcia say on more than one occasion, but sometimes we just have to observe and learn the lessons on our own.
This spring, I will not discard my weakening vats, but will add another vat for the strong, deep blues that I am currently needing to build up black colors on my woven cellulose fabrics.
I have used one-bath acid dyes extensively in my own work, especially for cross-dyeing my handwoven fabrics that are constructed of both cotton and wool. The acid dyes attach only to the wool or other protein fiber. When combined with indigo, which attaches to both cellulose and protein fibers, very interesting combinations can be achieved.
The “one-bath acid dyes” that Joy Boutrup and I discuss in The Art and Science of Natural Dyes include henna, madder, pomegranate, cochineal, lac, and rhubarb root. Since publishing the book, I have extended the palette with the addition of other dyes, mostly due to the help from Michel Garcia when he was here in my studio several years ago.
Michel and I were discussing dyes that I might choose NOT to use because of their poor tolerance to light. Alkanet is one of those. A purple color is extracted from alkanet root by means of an alcohol extraction. The color is beautiful and enticing , but very fugitive. Michel indicated that the alcohol extraction does some damage to the dyestuff.
The one-bath process extracts different dyes from the plant than from those that are obtained from using more traditional methods. While experimenting, we treated alkanet as a one bath acid dye (for protein fiber only) and a beautiful purplish brown color emerged that is quite fast to light. It’s a warm neutral color that I have not achieved using any other dye.
Safflower petals are another dye source that he showed me can be used as a one-bath acid dye. A golden yellow is dyed onto wool or silk that is quite lightfast and requires no mordant. The safflower petals can still be used after the one-bath process to extract the traditional reds and pinks by altering the pH, though the red colors are still not fast to light.
These discoveries energized my own work and as I went deeper, I began noticing that many of the plant dyes that are used for the one-bath acid process have also been used as natural hair dyes: henna, madder, alkanet, dock, rhubarb root, cassia leaves (Cassia obovata, also referred to as “neutral” or “colorless” henna). These can all be used successfully for one-bath acid dyes and result in very lightfast colors. Dried Indigofera tinctoria leaves (“black henna”) are also used as a dye for hair and when combined with henna results in a very dark color.
The application of henna as both a hair dye and as mehndi, (a temporary dye for the skin) is the same: finely ground plant material is mixed into a paste with water, acidified with lemon juice, and allowed to sit on the hair or skin for several hours. When the paste is washed away the color remains. These are considered non-permanent dyes for the skin and hair and may be repeated after the color fades.
Acid dyes are very lightfast but are not as fast to washing. (This applies to both natural acid dyes and synthetic dyes.) If applied to the skin or hair, they will eventually be washed away. BUT importantly, we don’t wash our woolen fabrics as aggressively or as often, thus the dyes are suitable for wool or silk textiles.
I was curious to see if these dyes could be used for direct application to woolen fabrics. There is a Moroccan tradition of using finely ground henna leaf in this way on fabrics woven of wool and cotton. It is well documented in the book Die Farbe Henna / The Color of Henna Colour of Henna: Painted Textiles from Southern Morocco by Annette Korolnik-Andersch and Marcel Korolnik.
I made a paste of each of these dyes using finely ground plant material with a small amount of water. I acidified the paste with vinegar (citric acid would damage fabrics that contained cotton) and allowed it to sit overnight once applied to the textile. The colors are strong and clear, although some dyes spread more than others. They are not quite as deep as those dyed in a heated bath, though steaming the textiles will result in deeper colors.
I have observed that the freshness and quality of the dyes matter. Organic henna, used for hair and skin dye, resulted in a bright clear color while other henna powders that I have used produced duller colors.
This approach has revealed to me one more way of understanding and using natural color and given me more opportunity to combining it with my own woven textiles. It has taught me more about plant categories, alternative applications, and the need to constantly be open to new ideas.
Dominique Cardon, French researcher of natural dyes and author of the classic reference book, Natural Dyes: Sources Tradition, Technology and Science, has just provided dyers another important resource and insight into the natural dye process: Workbook, Antoine Janot’s Colours
For several years, Cardon has been translating and publishing a series of books that document the work of 18th century French dyers. The 18th century was the classical period of wool dyeing in France. Last year, Des Couleurs pour les Lumières. Antoine Janot, Teinturier Occitan 1700-1778 was released, but only in French. This book was based on the original dye notebooks of Antoine Janot, a professional dyer from the Occitan region of the country.
Workbook, Antoine Janot’s Colours, which Dominique wrote in collaboration with her daughter Iris Brémaud, begins by providing background information on Janot and a description of the project. The most useful part of this small book to dyers is its practical nature. It includes a full palette of Janot’s colors and their recipes along with process information. It is written in both French and English.
The dyed colors are represented as visuals that were matched from actual wool samples from the original notebooks. Cardon used a color analyzer and the CIELAB system to accurately portray each hue. CIELAB is an international system that scientifically analyzes colors by using a system of coordinates to “map” them graphically and very precisely.
Descriptions of mordanting and dyeing include % weight of dye materials along with other additions that were made to the baths. In some cases, helpfully, an explanation of the WHY is included.
The key to some of the color palette is a full gradation of indigo blues, from the very palest to very deep. Each blue has its own name such as “crow’s wing” (the very darkest) to “off-white blue” (the very palest). The CIELAB system allows an accurate visual description of each of these blues.
These blue shades are critical to achieving greens, purples and greys. Instructions for mixed colors designate which blue to start with. A full range of indigo blues, from lightest to darkest, is not an easy thing to accomplish. I have been working on that very thing consistently for the last months in my own studio, so it is especially meaningful to me right now.
I have recently been doing color replication work for logwood purple using a combination of indigo and cochineal. A systematic approach to dyeing the initial indigo blues is a huge help in approaching this kind of color matching.
It is rare to be able to gain such a deep insight into a professional dyer’s process and results. Historical color descriptions, such as “wine soup”, “celadon green”, and “crimson” become more than just words on a page when colors are able to be seen accurately with the eye.
For dyer’s looking for a deeper insight into the world of professional natural dye, this book is a treasure.
I ordered my copy directly from France and it took several weeks to arrive. According to Charlotte Kwon, the book will also soon be available from Maiwa.
On some days it’s hard to believe how recently we traveled freely worldwide, meeting new people and experiencing new places. Three years ago I attended the natural dye symposium in Madagascar, where I first met Hisako Sumi who started me on my current journey of making and maintaining indigo fermentation vats. As I was harvesting Persicaria tinctoria leaves in the garden, I was reminded of the fresh leaf indigo dyeing that we saw being done in Madagascar.
Many of us are growing indigo in our gardens right now and have likely had the pleasure of experimenting with fresh leaf indigo dyeing on silk. It’s like magic to see the lovely turquoise color emerge from the cold leaf bath.
The indigo that grows in Madagascar is Indigofera erecta. It is a perennial in that climate and the leaves are harvested from the bushes as needed. The leaves were used to dye the raffia fibers directly. There was no vat or reduction.
Yet, the dyers took this “cold” process one step further. The ambient temperature dyebath produced a lovely clear turquoise blue color on the raffia. When heat was applied, the color deepened and shifted.
This approach of heat application was new to me. When I inquired about it, both Hisako and Dominique Cardon indicated that they were both familiar with this phenomenon. Hisako sent me an image from a scientific report done by Dr. Kazuya Sasaki that documented the range of color that could be obtained from fresh leaf woad by increasing the temperature. Once armed with that information I was able to reproduce that range of color, nearly exactly, on silk and and on multi-fiber test strips, though the results were not precisely the same as those we saw in Madagascar.
I have always understood that the process of fresh leaf dyeing with indigo is primarily used on silk – a protein. Yet, the dyeing we witnessed in Madagascar was done on raffia. Why did this process work so well on raffia- a cellulose fiber? I posed the question to my colleague, Joy Boutrup. “Raffia is almost pure lignin” she said. Lignin is an organic polymer and has a strong affinity for dye.
This week I repeated the tests with Polygonum tinctorium on silk broadcloth and raffia. I used a greater quantity of leaves this time – a blender full of leaves for a few small samples vs. less than 100 g. I puréed the leaves this time rather than chop them up. The “coldest” blue is a deeper shade but otherwise the results are very similar. I freely admit that I don’t understand, chemically, why the colors change with the temperature:
Are there other dyes attaching?
Has the indigo been transformed by the temperature?
Maybe someone else can enlighten.
I have always suspected that the lightfastness of the fresh leaf indigo dye is not to the same level as the color obtained from a well reduced indigo vat. I will do lightfast tests on this range of color and report back in a later blog.
Three years ago, the trip to Madagascar taught me about an approach to dyeing that I had never seen before – truly one of the gems of travel. We may not be free to move around for now, BUT other opportunities continue to present themselves on the web. One of the most exciting upcoming events is this year’s Textile Society of America Symposium: Hidden Stories: Human Lives.
Originally planned to be held in Boston this fall, Hidden Stories: Human Lives will now be live and completely online October 15-17. This biennial event brings together scholars, curators, and artists from all over the world who will present their original research in the form of organized panels and talks. Fee structures for the symposium have been completely re-vamped in order to make this event accessible to all – no matter where in the world you might be. Registration has just opened and you can see the full program here. In addition, You can also read about the keynote and plenary speakers. Hope to see you there!
First of all, I know that my well water is acidic. It measures about pH 6.0 here in the mountains of North Carolina.The water is ideal for most dyeing. There is no iron or other minerals that might dull the colors. The acidity is another issue.
Most of the yellow dyes in my garden, or those that I might gather locally, are flavonoids. That means that they require a mordant in order to attach to the textile. No mordant means no yellow. It’s that simple. Some of the dyes may also contain some tannin or other colorants but the yellow is what we’re talking about here.
Last summer Joy Boutrup and I taught a class together at Penland School of Crafts, located near my home in western North Carolina. A student in the class was especially interested in gathering local plants for use as a dye source. She struggled to get the locally gathered dyes to attach to her textiles, especially onto mordanted cotton.
Joy had the answer-of course!
When the dye meets the mordant in a textile, an insoluble lake is formed. This lake is formed most readily in neutral or slightly alkaline conditions.
An alum mordant makes a very strong bond with wool but there is no chemicalbond between cellulose and the mordant. Instead, the mordant is deposited as an insoluble compound on the textile.
An additional issue is that many of our local plants are acidic. When the plants are boiled in our already acidic water, the pH of the dyebath becomes so low that the dye may struggle to attach to the mordant in the fiber. In fact, the mordant in the cotton can be damaged or even removed if the bath is acidic enough. This is exactly the reason why we don’t add an acid to a cochineal bath when dyeing cellulose. The mordant would be damaged and little dye attaches.
The remedy: Add a small amount of chalk (calcium carbonate) to the dye bath to neutralize the acid that is present. This will do no damage to the dye or the textile. Chalk is not an alkaline but will neutralize an acid that is present. Within reason, there is no possibility of having too much chalk and any excess will simply precipitate in the bath and rinse out of the fabric
Since my own broom (Genista tinctoria) is currently in need of a serious trim, I began a series of flavonoid dye tests with that and then compared other dyes from my garden and environs.
Broom is currently blooming in front of my studio
Broom, with and without chalk
I used all fresh plants at 300% w.o.f. and dyed both wool and cotton. The wool was mordanted in alum. The cotton was mordanted using tannin plus alum and soda ash. After making the dye decoction, I divided the dye bath in two equal portions and added both wool and cotton to each bath.Chalk was added to only one of the baths.
The results were quite surprising (but also very consistent) and made me realize that I have likely not been achieving the maximum amount of color from some of my local dyes.
The plants I gathered and used were
Broom (Genista tinctoria)
Wild grape leaves
Dyer’s Chamomile (Anthemis tinctoria). I used the flowers and after gathering a basket of the small flowers I tested the dye content in the entire plant.
Staghorn sumac (Rhus typhena) . We often think of sumac as a good source of tannin but the leaves, according to Dominique Cardon, are also rich in flavonoids.
Weld (Reseda luteola). This is my “go-to” yellow dye. I almost always use dried plants and I rarely add chalk with weld on cotton but frequently add it to a wool bath.
After boiling the plant material I recorded the pH of the decoction. The pH was measured again after the addition of chalk. Each dye bath was approximately 4 liters and I added about 1 TBS of chalk.
The chalk will alter the appearance of the bath from transparent to cloudy and nearly opaque.
The samples below are wool. Individual samples on the left had chalk added to the bath. Those on the right did not.
Dyer’s chamomile, whole plant
Dyer’s chamomile flowers
Broom, with and without chalk
In every case, I achieved deeper and brighter yellows colors when the chalk was added to the fresh plant baths. The only exception was dried weld, which was used at 50% w.o.f. When dyeing with the fresh weld plants, deeper yellow hues resulted with the addition of chalk. When I used dried weld plants, the chalk made very little difference. I asked Joy about this and she indicated that is was possible that some of the acids disappear in the drying process. It will require more tests and explorations to confirm this.
The cellulose samples are especially notable. The high acidity of some baths made without the chalk was enough to damage the mordant significantly. The grape leaves and the sumac, which were the most acidic, destroyed the mordant in the cellulose and only the tannins that are present in the leaf were able to attach and color the fabric.
If your water is not acidic, or has calcium in it, then these tests may not be relevant but the addition of chalk will never harm the fiber or the dye and may release more color.
I recently found the following note that I had made during a class with Michel Garcia several years ago referring to grape leaves:
“If they are too sour they will dissolve part of the mordant.” M. Garcia
My own notes continue to say:
After boiling the grape leaves the solution of a pH 4 – too acidic – it will remove the mordants. Sumac will cause the same effect. Boiling breaks the bonds of the tannins and gallic acid is released. Add chalk to the bath to decrease the acidity of the dye bath – you cannot be in excess of chalk.
Sometimes we’re just not ready to absorb information the first time we hear it. This is exactly why I continue to question, keep notes, and actively test and observe.
It’s summertime! Enjoy your yellow flavonoids!
Note: I purchase my chalk from a potter’s supply store. It is inexpensive and can be purchased in quantity. Potters refer to it a “whiting” and rarely refer to it as chalk or calcium carbonate. Do check the MSDS though, just to be sure.
Upcoming: On July 13 I am presenting a Zoom webinar, entitled Colors from the Garden, as part of the John C. Campbell Folks School’s Appalachian Traditions Series. You can sign up here:
Cross dyeing: A method of coloring fabrics made from more than one kind of fiber. Each fiber in a fabric designed for cross–dyeing takes a specific dye in a different color or in variations of a color.
… The Fabric Dictionary
As a weaver, I often construct my own textiles before they are dyed. I choose warp yarns,weft yarns, and then make decisions about how they are going to be fit together. When a fabric is constructed using both protein and cellulose fibers, some dyes can be made to attach only to the wool. Direct dyes, such as black walnut husks, are a great example. When used on wool or silk, without the use of a mordant, those fibers will dye a deep brown, while any cotton used in the construction of the textile will only be lightly stained or absorb no dye at all.
This allows me to weave fabrics in white or natural, and then apply the color afterwards, using resists to incorporate design and create layers of color.
When indigo in used in combination with a direct dye, the cotton will only absorb the indigo blue.The protein fiber will absorb some of the indigo, but it is initially a much lighter blue. When overdyed with a direct dye, only the protein fibers will accept that direct dye.
This is an approach I have taken to dyeing my woven textiles for a number of years, ever since I was inspired by a Moroccan belt fabric that used acid dyes to achieve the effects of cross dyeing.
When I began working with natural dyes and wanted to do cross dyeing, I was initially limited to the use of direct dyes, such as black walnut husks, lichens or other dyes that did not require a mordant. Ifa mordant is used, both fibers will dye to some extent.Then Michel Garcia introduced me to the concept of one-bath dyeing.This is where tannins and acid are used to attach some dyes to a protein, while the cellulose fibers do not dye at all. In effect, the dyes behave like acid dyes. No mordant is required when applying dyes with this process.
Indigo dye on cotton and wool fabric. The cotton is a deep blue, while the wool is very light, although they were dyed in the same bath.
Top: black walnut dye only on wool and cotton. Bottom: indigo and black walnut on wool and cotton , with resists
Wool and cotton, dyed with indigo and alkanet
wool and cotton, dyed with indigo and madder
Fabric woven of cotton and wool. Clamped resist, indigo dyed.
Same fabric, overdyed with madder, using the one-bath acid dye approach
But not everyone is a weaver! Next month I will be teaching natural dyeing for knitters at the first Knitting Getaway at Shakerag Workshops . In preparation, I have been knitting samples that incorporate both wool and cotton. I have added resists, and dyed with combinations of indigo and one-bath acid dyes. This concept can also be applied to knitting yarns that incorporate both wool and cotton.
Knit samples, using wool and cotton yarns, and dyed with indigo, cochineal, and rhubarb root.
Yarn is made by plying linen and cashmere. Left: Indigo dye only, Right, indigo overdid with safflower petals.
It is challenging to identify commercially available fabrics for cross dyeing. I have had fabrics specially woven of wool and cotton for the class that I’ll be teaching at the 11th International Shibori Symposium in Nagoya, Japan. Space is still available in the workshop right now!
And on another exciting note: The Art and Science of Natural Dye will be published by Schiffer Publishers in the fall and is now available for pre-order from Schiffer or Amazon. In fact, I just finished the last of the copy edits today!
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.
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.
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?
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.
cotton dyed in weld
silk dyed in weld
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.
Wool, dyed in madder
Wool, dyed in cochineal
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.
I am a natural dyer but I also enjoy reading about and cooking food. I was recently perusing Michael Ruhlman’s book, Twenty: 20 Techniques, 100 Recipes. The first chapter is titled “THINK: Where Cooking Begins”. The author talks about the importance of thinking to the cook. I might say the same thing about the dye kitchen. Dyeing is not just about following a recipe, but thinking about and understanding the role of each of the ingredients.
Ruhlman recognizes that his list of techniques includes many that are also ingredients: salt, acid, sugar… One might say the same thing about our dye ingredients: mordant, acid, base, or dye plant… Awareness of what each ingredient contributes to the process is key to understanding how it fits into the larger picture of dyeing.
Let’s talk about mordants – alum specifically.
The alum we typically use in the dye studio is potassium aluminum sulfate [KAl(SO4)]. It is most likely made in a laboratory, is in powder or small crystal form, dissolves easily, and contains no contaminants such as iron.
Aluminum sulfate [Al2(SO4)3] is made by a different process and may be contaminated with small amounts or iron. The first dyeing I ever did utilized naturally occurring alum gathered from the ground surface – no telling how impure or contaminated it was.
We often shorten the name of our mordant to simply “alum” but there are many different types of alum and it may be best to use (and specify) potassium aluminum sulfate. I never purchase from a supplier who cannot provide material with that specific name.
Potassium aluminum sulfate bonds with the dyestuff and makes an insoluble lake INSIDE the fiber. Without this insoluble bond, the dye can wash out. This is why we don’t put dye, alum, and fiber in the same pot; inevitably some of the dye will bind with the alum in the bath OUTSIDE the fiber. That would be a waste of our dye and mordant.
The traditional approach to mordanting and dyeing is broken down into two steps. 1.) The alum is applied to the fiber. 2.) The fiber is dyed in a second bath, attaching the dye to the mordant and making the lake inside the fiber.
It’s important to get the mordant INSIDE the fiber. That is why we pre-wet and heat wool so that the scales will open up and the mordant goes inside. Otherwise we have ring dyeing, with the mordant and dye just sitting on the surface.
I have lately learned to dye silk using the Japanese approach of “middle mordanting” with Dr. Kazuki Yamazaki. The fiber is first dyed, then mordanted, and then re-immersed in the dye. This approach didn’t make a lot of sense to me until I experienced it and observed that it accomplished the same thing as pre-mordanting. The dye and mordant still go into the fiber and make the insoluble lake there. It’s a slower, quieter process which has the potential of building up layers of mordant and dye on the silk. This process is not suitable for wool.
Some things to THINK about:
Alum is acidic – a useful thing to remember.
Once a fiber is mordanted, it is always mordanted. The mordanted fiber can be dried and stored indefinitely.
The more dye there is, the more mordant is needed.
Alum can be removed with a stronger acid, such as citric acid.
I typically use my alum at 15% of the fiber weight but I always test a new source of mordant in order to be sure that the strength is the same. Test by mordanting, dyeing, and observing.
Potassium aluminum sulfate is an excellent mordant for protein fibers. I would take a different approach to mordanting cellulose.
When a dye lake is made OUTSIDE the fiber it results in an insoluble pigment.
When a dye lake is made INSIDE the fiber it results in an insoluble pigment.
How the mordant and dye are applied to the fiber is very important.
I am a weaver of textiles and a dyer. In the past I have used all types of chemical dyes to obtain desired results with my woven shibori fabrics. I live and work in the mountains of North Carolina near a small creek that flows into a river full of native trout. Our water comes from a shallow well and we have a septic system. I have developed an an increased awareness of potential chemical pollution of these water sources and systems and have been inspired to begin a study of natural dyeing.
For the last 8 years I have been engaged in a learning adventure about natural colorants which I have found deeply satisfying. I have been exposed to great teachers: Michel Garcia of France and Joy Boutrup of Denmark. They are both scientists, and dyers, who have both helped me find a path which includes questioning and observing. Michel Garcia once stated in a class that it was more important to understand “why” than “how”. I have thought about this a great deal and always try to go beyond a recipe in order to understand the logic behind it.
I am an artist, not a scientist, but have developed the skills to observe carefully and trust my own experiments. If I don’t know whether “X” or “Y” process will work best, I do them both and record the results. My goal, as an artist, is to learn effective processes. I don’t always have a definitive scientific answer but I have learned to observe objectively and be willing to change the way I work.
Each experiment brings a new insight and the realization of just how complex the field of natural dye is. My understanding of the fibers and interactions with dyes themselves has deepened, and I have a new respect for botany and chemistry.
I regularly carry out lightfastness tests, using the blue wool scale, an international standard to measure the lightfastness of dyes. As a result of the tests, I have relegated some dyes to the back of my shelves some dyes from my shelf because they don’t perform well enough. When I go back and read old dye books, history usually confirms what I learned first hand.
My teaching and my work is now done entirely with natural dyes. Frequently students and colleagues contact me with questions, requesting further clarification of process, or needing encouragement. I try to answer those questions and at this point have decided to answer them in a more public format in the hope that the information might be of use to others. Hence the creation of this blog: Natural Dyes: Experiments and Results.
I don’t always have definitive answers. I know only what I have experienced and that knowledge is constantly evolving. I trust and depend on my teachers and colleagues who are using natural dyes and we have begun to study and question together. So I will share some of my own lessons from my own dye studio, my “kitchen of natural colors”, as we all learn together.