Today we are going to explore the basics of how to dye with indigo. Dyeing with indigo is very different from other natural dyes. This is due to the fact that indigo extract powder is insoluble in water. In order to facilitate the bonding of the dye to the yarn or fabric, it is necessary to create a vat. In this introductory post to indigo dyeing, I will share the vat method I use with you. We will explore further vat options in a different post.
Since creating a vat is a more complex process, I don’t recommend dyeing with indigo for complete beginners. If you are only starting out with natural dyeing, you can have a look at this blogpost where I share a detailed step by step approach using onion skins.
History & Sources of Indigo
Indigo has been used as a dye for centuries. The word indigo reflects the fact that India was the main supplier of indigo to Europe, already in the Greco-Roman era. It was considered a luxury product, also known as blue gold. Not only was it used for dyeing wool and cloth but also as a pigment for painting, medicinal and cosmetic purposes.
Indigo is probably the most popular dyestuff due to its use for the production of denim fabric for blue jeans. It can either be derived from the leaves of certain plants from the Indigofera genus or produced synthetically.
There are several plants which contain indigo molecules. The most popular one is called Indigofera tinctoria which is also called true indigo. Isatis tinctoria, also known as woad, and Polygonum tinctorum (dyer’s knotweed) also contain indigo molecules but in lower concentrations. Mollusks, like the Murex sea snail are a natural source of indigo as well.
The first chemical synthesis of indigo dates back to 1882. Today, there are different viable routes established for the synthetic production of indigo.
Indigo Vat Basics
In order to make the indigo molecule water soluble, it has to be chemically reduced. The reduction converts the indigo into white indigo or leuco indigo. When you take the yarn or fabric out of the dye bath, the white indigo reacts with the oxygen in the air and reverts back to indigo.
In order to facilitate the reduction from indigo to indigo white, the dye solution has to be alkaline. Furthermore, the oxygen has to be removed from the liquid.
How to Dye with Indigo: List of Materials
|Undyed skein(s) of yarn or fabric|
You can experiment with the amount of dye material you use. Less dyestuff results in a lighter color and more dyestuff yields darker shades.
|Washing Soda (Na2CO3)||source of alkali|
|Sodium Hydrosulphite (Na2S2O4)||reducing agent|
|Heat source||cooking plate or stove|
|Pot||You can use an old pot or acquire one just for natural dyeing purposes.|
|Bucket or Washing Pan||To scour and wash the yarn/fabric and to put the yarn/fabric into when it comes out of the dye bath|
|Salad Spinner |
(or Spin Dryer)
|To remove any excess water from the skeins/fabric|
|Drying Rack||To hang up the dyed skeins/fabric directly after the dyeing process to let them develop their final color|
|pH paper||To check the pH of the vat|
|Teaspoon, Tablespoon||wooden or stainless steel|
|Tie||To secure the yarn and avoid tangling. You have to use something that is stable in warm water and doesn’t give off any color. I usually use some kind of natural package cord.|
|Dish Soap||Whatever you have on hand. This is used to scour and wash the yarn.|
|Wool Laundry Detergent|
Precautions: Don’t use the same pots and utensils for natural dyeing that you use for food preparation. Always wear gloves. Creating the vat and the dyeing process itself should be done in a well ventilated area. I often use a cooking plate that I put on my patio.
Dyeing Yarn with Indigo: Instructions
1. Prepping the Yarn
Use the tie to segment the yarn in at least four different sections. This will help to prevent tangling. Make sure to not make the ties too firm. Otherwise these spots will take less dye which will be visible in the finished skein.
The yarn has to be completely soaked if you want to achieve an even color distribution throughout the skein. To do so, I place the yarn in a bucket filled with lukewarm water and a little bit of dish soap. Then I let it sit for at least a couple hours, ideally overnight so that the wool is completely wet. Gently wring it out before putting it in the dye bath.
Note: When dyeing with indigo, mordanting the yarn or fabric beforehand is not required!
3. Creating the Vat
Like I mentioned before, there are different possibilities to create a vat. In order to not make this post too complex, I will share the method I use with you which is the hydrosulphite vat method. And we will explore further options in a future post.
- The water should be kept at a temperature of about 50°C (122°F). The pH value should be at 9-10. Check the pH regularly throughout the dyeing process and add a teaspoon of washing soda (Na2CO3) to bring it back up, if necessary.
- In order to keep as much oxygen out of the dye bath as possible, the vat should not be agitated. You also have to make sure to avoid dripping of water from the yarn or fabric into the vat.
Dissolve 4 tsp. washing soda in 5 tbsp. of boiling water. After it is slightly cooled, add 2 tsp. indigo and mix. Let it stand for 30 minutes.
In the meantime, put water in your dye pot and heat to 50°C (122°F). Add 3 tsp. sodium hydrosulphite and 1 tsp. washing soda and mix gently. Slowly add the indigo/washing soda mixture and keep the temperature constant. You will have to wait at least 30 to 45 minutes until the color of the dye bath changes from blue to a green/yellow. Sometimes this can be hard to see, you can use a spoon to check the color more easily.
If the vat starts to turn blue again, add some more sodium hydrosulphite.
Discarding the vat afterwards: If your dyeing process is complete, stir the vat really well to add air and exhaust any remaining sodium hydrosulphite.
4. Dyeing Process
Carefully place the yarn or fabric in the vat, trying to create as little air bubbles as possible. You can leave the fiber in the vat between 5 and 20 minutes. The longer the fiber sits in the dye bath, the more intense the color will be.
Remove the yarn or fabric carefully, trying to prevent the creation of air bubbles. If you want to create an even color result, quickly put the yarn or fabric in a bucket filled with water. This will help to remove any pieces of undissolved indigo.
Hang the yarn or fabric on a drying rack. The exposure to the oxygen in the air will convert the white indigo back to the blue indigo. You will immediately see the transformation of the colorway. Wait at least 20 minutes. If you are not satisfied with the color result, you can redip the skein or fabric into the dye bath.
The next step is washing out the excess dye. Firstly, take the bucket and fill it with lukewarm water. Then add a little bit of dish soap. Gently place the yarn or fabric into the soapy water. Squeeze gently so that any excess dye can come out. Secondly, wash the yarn or fabric very carefully under some running, lukewarm water. Then fill the bucket with water and a mild wool detergent. Put the yarn or fabric in and let it sit for a couple of minutes up to a few hours. Afterwards, wash it under some running water again. Repeat these last two steps until the water runs clear and try to use as little water as possible.
There are several ways to get the yarn to dry quickly. You can simple wring it out gently and hang it to dry on a drying rack. Especially on a hot summer day, this works really well.
You can also use a salad spinner or spin dryer to get out the excess water.
Tips for Dyeing Yarn with Indigo
- Take your time
I feel like I am repeating myself but it simply is true for natural dyeing in general: It is a slow process and you cannot rush it. Creating a vat requires time and I recommend you block at least 2.5 hours if you are dyeing with indigo.
- Have enough yarn or fabric on hand
If you have gone through the elaborate process of creating the vat, you should make the best use out of it and dye as much yarn (or fabric) as possible in this dye session. The example of 2 tsp. indigo used above will be enough to dye at least six 100 g skeins of yarn into light to medium blue colorways.
- Mordanting is not necessary
If you are dyeing with indigo, you don’t have to mordant the yarn or fabric beforehand. It is a substantive dye which means it adheres to the substrate (in this case the yarn or fabric) directly.
- Prepare a large enough drying area
In order to allow the colors to fully develop, the skeins or fabric need to be hung up after the dyeing process before washing them. Make sure you have enough room to hang each skein separately.
- Keep a clean work surface
Using gloves is something I always recommend when it comes to natural dyeing. In this case, it is especially important since you are working chemicals. In addition, you should wear safety glasses as well as long sleeved clothing.