Raise your hand if you’re crazy for indigo! Ok, what’s wrong with the rest of you? JUST KIDDING. But seriously, it’s been indigo-mania for a several years now (rightfully so), and the more I think about it, the more questions I have — some of which you guys have also asked me. So I asked natural dyer extraordinaire Kristine Vejar, owner of A Verb Keeping Warm and author of The Modern Natural Dyer, to set us straight on the difference between indigo and “indigo.” That is: natural (plant derived) indigo dye versus the synthetic lookalike more commonly used.

But first, a few answers to questions that are likely to come up in response to all of this:
– The gorgeous shawl above is Kristine’s Aranami (designed by Olga Buraya-Kefelian) knitted in Verb’s Flock yarn, dyed with natural indigo
– Verb sells a variety of natural indigo dyeing supplies, from dye stuffs to kits to classes
– We still have some of the gorgeous Verb kits for making an indigo-shibori and sashiko Stowe bag
– And yes, the indigo cowl kit we sell is dyed with natural indigo by Sincere Sheep

You can follow Kristine’s adventures on Instagram @avfkw, and take a peek into her crafting life here. Thanks so much for  this fantastic information, Kristine!

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There’s so much interest in natural dyeing these days, thanks to you and many others, and I think a lot of us believe that indigo falls under the heading of Natural Dyes, but not all indigo is natural, right? For instance, commercial denim is no longer (or very rarely) dyed with plant-based indigo.

Indigo pigment can be found in 700-800 different plants, although there are only about 10 plants that have enough indigo pigment in the leaves to warrant the labor-intensive process of separating the pigment from the leaves, making it available as a dye. Today, indigo dye, extracted from plants, can still be found, obtained and used. This is referred to as natural indigo pigment.

Originally, all dyes came from plants, minerals and a few insects. In the 1850s, scientists successfully synthesized color. With this shift arose the idea — and then eventually the reality — that color could be created on demand, and no longer need to be coaxed from nature. This began a major shift in color, farming, trade, dyes and dyeing. It was only a matter of time before indigo underwent the same scrutiny. Scientists took examples of indigo-bearing plants, began to be able to identify the molecular structure of the indigo plants, zero in on indigotin, the essence of indigo pigment, and recreate it in a lab, which is called synthetic indigo. I personally don’t consider this indigo because I think of indigo as a product made by and derived from a plant. The same type of process occurs in food. Take for example artificial flavoring, like strawberry. Scientists take a strawberry, break down the molecules that make up its smell and flavor, and then create a few of these molecules in a lab to mimic a strawberry. I would never call call this flavor a strawberry. Or describe the experience of tasting this flavor as eating a strawberry. When I eat a strawberry, I can taste the sun. There is texture, nuance in flavor from one berry to the next, and indescribable joy when tasting a strawberry — especially if the berry has been picked right off the plant. The same principle applies to natural indigo pigment; there are many small nuances in color, texture, smell and experience when working with it when it comes from the plant.

True, commercial denim is rarely found dyed with natural indigo. Most of it is dyed with synthetic indigo.

I’ve taken classes that have used (and I’ve also used) those little boxed indigo kits you can buy online and craft stores, with the powdered dye and whatnot. Is that natural or synthetic? Can you talk about the difference between stirring up a bucket of that and what you do — creating and tending a natural indigo vat?

The boxes of indigo I believe you are referring to — typically made by Jacquard — is synthetic indigo. It is not natural/derived from a plant.

To examine the nuances of working with synthetic indigo versus natural indigo, let’s first discuss the basics of how an indigo vat is made. For indigo to attach to cloth, it must be transformed into a soluble material. To do this, the dyebath must be alkaline (pH of 10) and all of the oxygen in the dyebath must be taken out. This is called reduction. To raise the alkalinity, lye, soda ash and/or limestone is used. To take the oxygen out of the vat, reducing agents are used. Chemicals such as sodium hydrosulphite or thiourea dioxide may be used to reduce a vat, as well as natural materials such as henna, dates, fructose and/or bacteria.

The first indigo vat I learned how to make was a vat made with natural indigo pigment, lye to raise the pH, and thiourea dioxide as the reducing agent. This vat needs to be heated. In my search to use a cool vat — so I would not need a heating implement and could widen my choices of surface design — I learned to swap thiourea dioxide with sodium hydrosulphite. This is the fastest method to reduce an indigo vat (about 20 minutes) and to start the dyeing process. As the indigo vat reduces, the color of the water changes from blue to green. The vat is ready to use when the vat is green, and when white yarn or fabric is dipped into the vat, emerges green, and then turns blue as oxygen touches the yarn or fabric. To dye using an indigo vat, yarn or fabric is dipped into the vat, left under the surface for about 5 minutes, lifted out of the vat, and left to hang for about 5 minutes. This process is repeated to acquire darker shades of blue. Every time fabric or yarn is dipped into the indigo vat, oxygen is introduced to the vat, and the pH goes down. So part of the learning curve of being an indigo dyer is how to bring the vat back into balance — high pH and removal of oxygen.

Since dyeing with indigo has a learning curve, and countless questions are always in play, I like to teach beginners how to reduce the vat with sodium hydrosulphite (referred to as a hydro vat), as it is easy to see and to learn about the changes occurring in the indigo vat. From there, we can work our way out to using natural reducing agents, like henna or fructose, which take longer to reduce — anywhere from 4 hours to ideally 24 hours. Instructions for creating a hydro vat and a henna vat can be found in my book, The Modern Natural Dyer.

In my studio, there are many different types of vats going at once. All have their own specific applications dependent upon the type of fiber being dyed, the depth of color desired, and the price-point at which something is being sold. When hydro vats are used, most times, we continue to use them for months, adding new indigo. When fructose vats are used, we dye through the indigo in the vat until there isn’t any indigo left, and then start a new vat. Ok, so then, there are our very special vats. As you can probably tell, I am in love with indigo. It was only a matter of time before I began to dig deeper into this process, surpassing the natural indigo pigment to work with the plant.

About five years ago, we grew our first indigo plant — a variety called Indigofera tinctoria which is commonly grown in India. It stayed about 2 feet tall for 5 years until it finally died. The Bay Area was just too cold and foggy. Rebecca Burgess at Fibershed began to grow a variety of indigo, then called Polygonum tinctoria and now referred to as Persicaria tinctoria, which is commonly grown in Japan. This plant grows very well in this area. She called upon Rowland Ricketts, an artist and professor who studied indigo in Japan, to help transform the plant into dye. Following the traditional Japanese method, the plant, once harvested, is dried and then composted. Rowland came to the Bay Area. A group of us gathered to build a special floor — as similar as possible to the surface used in Japan — to compost the indigo. Its unique structure aids in air circulation and drainage of water so the indigo, while being composted, does not rot. The composting process takes about 3 months. Once the composting was completed, a batch of the composted indigo also known as sukumo, was delivered to Verb. Using ash, we created our own lye water to use as the base of the indigo vat. So this provides the high pH necessary when making an indigo vat. And then, slowly over 2-3 weeks, we combined the sukumo with the ash water and wheat bran, encouraging fermentation. In this vat, bacteria is the reducing agent. We have two of this type of indigo vat. Currently, we grow Persicaria tinctoria at Verb and we have spent the last couple of years experimenting with the leaves in a number of ways to extract indigo and to make vats from this indigo. I find working so closely with the plant the most rewarding. There are greater nuances in color and in shades of color. Less dye is released when washing the yarn and fabric. I find it fascinating to think about the Earth, nature, and the intricacies of how it works, and how nature, plants and dye can be applied to my own work — in terms of dyed yarn and fabric as well as when I teach others to work with natural indigo.

So back to synthetic indigo for a moment. Since synthetic indigo has the same molecular structure as natural indigo, you must still follow the same steps as when working with natural indigo to create the vat. Typically the instructions that accompany synthetic (pre-reduced indigo) use lye or soda ash and thiourea dioxide or sodium hydrosulphite. The same dye process would also be followed: dipping in and out of the vat multiple times to achieve multiple shades of blue.

So with synthetic indigo, there really isn’t anything about it that is genuinely indigo — it’s really just blue dye in a color that mimics indigo.

Synthetic indigo does mimic natural indigo in that the molecular structures are the same. Like I described above: making a vat is pretty much the same, the dyeing process is the same, and the way in which the indigo will wear is the same. For example, crocking. Indigo dye and the process of dyeing is the act of creating a physical bond between dye and fiber. There isn’t a chemical bond. Also, the indigotin molecule is larger than most (if not all) other dyes. So this means that indigo eventually works its way out of the cloth. Sometimes crocking occurs right when you get a garment that has been dyed with indigotin (natural or synthetic) because it can be difficult to remove the extra pigment — that which has not bonded — from the cloth. Many times, it takes actual physical pressure to remove the excess indigo. This is why you may see a tag that comes with your jeans that alerts you to the fact that your hands or legs may turn blue when first wearing your jeans. Then no matter what, with sustained pressure to areas in a garment, the indigo will work its way out of the cloth, which is why the fabric over the knee region of your jeans eventually becomes light blue or white. Historically, if a dark, uniform shade of indigo was desired, the cloth or garment would be re-dipped in the indigo vat over the course of its life. So it can be very hard to differentiate between synthetic indigo (some may refer to it as fake) and real indigo, unless you know the dye house and can see the nuances between the blue created by synthetic indigo and the blue created by natural indigo.

I place synthetic indigo in the same camp as other synthetic dyes — like acid and chemical dyes — which have a wide array of blues to choose from and are much easier to use. But why go through all the steps of reducing an indigo vat and the labor-intensive process of dyeing if the indigo is synthetic? If you are going to go through all the same steps, use natural indigo pigment, support an indigo farmer, and embrace the relationship with the plant, process, and depth and nuance of blues that can only be created using natural pigment.

And for those of us who might be using the boxed kit (or any other kind of indigo dyestuff) at home, what do we need to know about tending to and especially disposing of the dye bath when we’re done with it?

If you are using thiourea dioxide or sodium hydrosulphite to reduce an indigo vat, you can either mix oxygen — by taking a spoon or a stick and whisking air into the vat — or let the vat sit overnight and the vat will turn to blue, and can then be disposed of. The high pH is not a problem — if anything it will help clear your pipes. If you still feel worried, you can always neutralize the water by adding lemon juice (an acid). If you are on a septic system, call your local septic system company, let them know what type of alkaline and reduction agent you are using, and ask for their advice.

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PREVIOUSLY in What I Know About: Dress forms (with Liesl Gibson)

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