Cross Dyeing with Natural Dyes

Cross dyeing: A method of coloring fabrics made from more than one kind of fiber. Each fiber in a fabric designed for crossdyeing 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.

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Wool, cotton, and silk yarns in the warp.

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.

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Belt from northern Morocco, woven in wool and cotton, dyed with acid dyes.

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. If a 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. 

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. 

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!

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Silk and rayon, dyed with indigo and rhubarb
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Linen and silk, dyed with indigo + cochineal rhubarb, madder, and madder.

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!

Art and Science of Natural DyesArt and Science of Natural Dyes back

 

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.

The importance of THINKING for a natural dyer

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.

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Alum (potassium aluminum sulfate) in powder form

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.

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Alum and dye in the same bath to make a lake. The dye has bonded with the alum and become an insoluble pigment.

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.

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Sappanwood (Caesalpinia sappan) on silk: the first dyeing before the “middle mordanting”
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Sappanwood (Caesalpinia sappan) on silk yarn after the “middle mordanting” and subsequent dyeing

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.
IMG_8355
Comparison of “middle mordant” and “pre-mordant” on silk. Weld (Reseda luteola) dye.

Experiments and Results

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.

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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.

Your feedback is welcome and desired.

working in the window
Lightfast test “working” in the window