Wednesday, August 14, 2013

Natural Dyes - Indigo

The Maiwa Guide to Natural Dyes
What they are and how to use them



Natural indigo is obtained from indigo bearing plants, the most significant one being indigofera tinctoria. This shrub grows wild and is cultivated in tropical areas throughout the world.

The plant produces a colourless glucose based-substance called indican which is a precursor to indigo dye. When the plant matter is fermented an enzyme is produced which, together with oxygen, facilitates the transformation of indican to indigotin (the dyeing component of indigo).

Synthetic indigo was first created in 1880 by Adolph von Bayer. It is chemically identical to natural indigo (but without the additional elements from the plants and the extraction process). Synthetic indigo can be made more cheaply than natural indigo, is more uniform in its concentration and dyes more evenly. Yet many artisans attribute a character and depth to natural indigo which is lacking in the synthetic version. The discerning eyes of a textile collectors also favour natural indigo.

Indigotin (indigo powder) is insoluble in water. To use it for dyeing it must be chemically reduced to a water soluble form known as indigo white. When fiber is added to an indigo vat (which is an amber or yellowish-green colour) and then removed, a molecular combination occurs. The indigo white oxidizes back to the insoluble blue form, where it remains in relative permanence.

The same recipes that are used for indigo may be used for woad. Simply substitute woad powder for indigo powder.

White scarves are the perfect starting point for a blue project.

Recipe for Vatted Indigo

Lye-Thiourea Vat and Lye-Hydros Vat

This is the easiest recipe. Maiwa chooses thiourea for it’s studio as it has a longer shelf-life and keeps well. The thiourea vat is more forgiving than some of the other vats. This recipe is designed to dye approximately 1 pound (450 g) of cotton, silk, hemp, ramie, rayon, or linen a medium blue (or 2 pounds of fibre (900 g) a light blue). The same amount of indigo will dye twice as much wool to the same intensity.

This recipe can be doubled, halved, or made in any size so long as the proportions are kept constant.

Supplies Needed:
- indigo
- thiourea dioxide or sodium hydrosulphite (sodium hydrosulphite cannot be shipped in the post)
- lye (sodium or potassium hydroxide)
- synthrapol soap and soda ash (for cotton)
- orvus paste and vinegar (for wool and silk).

Equipment Needed:
- A large bucket or plastic garbage can
- quart wide mouth mason jar
- quart pot (stainless steel, enamel, or pyrex),
- measuring spoons
- wooden rod or stick for stirring
- rubber gloves.

Some notes before beginning
  • Although synthetic and natural indigo are chemically identical, less synthetic indigo is usually needed in a recipe because it has a higher concentration of indigotin.
  • Indigo dyeing is rewarding; but it does require proper instruction, experience, commitment, and comprehension of what is going on in the indigo vat.
  • Deep shades of indigo are best produced by successive dippings in a weak to moderate bath rather than by making a strong bath.
  • Fabric preparation or scouring is vital. It is paramount that the fibre be free from grease, wax, pectic substances, and oil.
  • If attempting to overdye with indigo, use indigo last as indigo can be stripped out by other processes.
  • Indigo can dye all natural fibres and give shades from the palest blue to an almost purple black. The colour achieved depends on the type of vat, the level of indigotin, and the number of dips.
  • There are many types of indigo vat that have been developed throughout the ages. Each has advantages and disadvantages and every dyer develops a preference. There is the zinc-lime vat, the ferrous sulfate vat, and a whole range of natural fermentation vats.
Scour the cloth. 
See our full instructions here:

Proper scouring is absolutely essential to good dyeing. Improperly scoured items do not dye level, the dye does not penetrate well and the dyed item will have poor rubfastness.

Scour test. One piece of fabric torn in two. Left no scouring.
Right scoured.

Preparation of Stock Solution

Caution: a mask should be worn to avoid inhaling any powders; especially lye, thiourea dioxide, or sodium hydrosulfite.

1. Fill a quart size wide mouth mason jar with hot water. Dissolve 1 to 1.5 teaspoons of lye.
2. Add 2 teaspoons of fine synthetic indigo powder, or 2 - 4 teaspoons finely ground natural indigo and stir for 2 minutes.(if you have natural indigo in lumps use a mortar and pestle to grind it to a fine powder before adding.)
3. Add 1 teaspoon of thiourea dioxide or  2 teaspoons of sodium hydrosulfite and stir for about a minute.

If reduction of the indigo starts properly, the colour of the surface of the liquid should change to a purplish violet with at coppery sheen. Place a lid on the jar and set aside in a warm room (or place in a pan of warm water) for about 60 minutes. The solution will change from an opaque blue to a translucent brown-yellow as it reduces. Check the stock solution to see if it is ready by dribbling some solution on the side of a white cup. Note the change from clear yellow to opaque blue as the indigo is reintroduced to the oxygen in the air. At this point the stock solution may be used or kept up to a week. If kept longer the solution may need to be revived. Heat gently to about 50°C (120°F)  and add some more reducing agent (thiourea or hydrosulfite) and stir well.

Tips
  • If the stock does not reduce after 60 minutes it may do so if left overnight.
  • The solution does not have to be absolutely clear. A cloudy solution usually means the indigo was not ground finely enough.
  • Be careful not to heat the stock solution above 140°F (60°C).  Indigo in its reduced form will be destroyed by excessive heat.


Preparing indigo in Laos.

Preparation of the Vat

1. Put 5 gallons of hot water 110-140°F (45 - 60°C), in a plastic pail or garbage can.

2. Add 1/8 teaspoon of lye into the water and stir until dissolved. This makes the vat slightly alkaline so that the reduced indigo from the stock solution does not re oxidize when added.

3. Add 1/2 teaspoon of detergent (Synthrapol or Ivory liquid). This will help the indigo penetrate the fiber and will break up oxidized indigo on the surface of the vat.

4. Add 1 teaspoon of thiourea dioxide or 2 teaspoons of sodium hydrodulfite and stir gently until dissolved. Cover the vat and allow it to reduce for about 15 minutes.

5. Carefully lower the jar of stock solution into the vat and pour out the contents (avoid pouring from above as this adds oxygen). Use all the stock solution for cotton or half for the same weight of wool.

6. Stir gently and allow 30-60 minutes for the vat to turn yellowish green.



Dyeing

Wool should be wetted out prior to dyeing. Cotton, linen and silk may be added either wet or dry for different effects.

1. Add the fabric to the vat carefully, avoid splashing.

2. Wearing rubber gloves, work the fabric through the vat gently, allowing 10 - 30 minutes for this first dip.

3. Squeeze the fiber out underneath the surface as much as possible and gently lift out of the vat. Open the fiber to allow the air to get at the fibre. The colour change from yellow to blue never ceases to fascinate dyers and observers.

4. The fibre may be redipped any number of times to achieve the desired shade. Allow 30 minutes of oxidation (avoid hanging in direct sun) before redipping.

5. If a pale clear shade of blue is desired, reduce the immersion  time to about 1 minute. Have a basin of warm water ready and when you take the fibre out of the indigo vat place immediately in the water for 30 - 60 minutes.

6. After the final dip allow the fibre to oxydize 24 hours before rinsing and washing.

7. Final washing is very important to neutralize the pH. Rinse very thoroughly. Wash with a gentle pH neutral soap. Rinse well and dry. Silk and wool benefit from an additional rinse with a small amount of vinegar and water before drying.

Indigo adire oniko a traditional patterning from Africa.


Disposal or Storage

When the indigo vat is exhausted it will loose it’s greeny-yellow shade and cloth dipped into the vat will no longer hold a blue colour after washing. At this point the thiourea (or  hydrosulphite) is spent. The vat now is chemically inactive but still has a high pH. It may also still contain indigo. The pH can be brought back down through the addition of vinegar and the vat can be disposed of by pouring down the household drain.

If the vat is not exhausted it cannot be disposed of this way. There are two options, continue dying to exhaust the vat or let it exhaust itself by standing over time.

If storage space is available, consider storing the vat. A vat may still contains valuable indigo (or woad). An exhausted vat may be revived through the addition of small amounts of thiourea (or  hydrosulphite) and indigo (or woad). A completely exhausted vat may be also be reactivated through heating and the addition of a second batch of stock solution.

This information is also in our Indigo and Woad Datasheet.

Next up - Organic Indigo Vats.




The Maiwa Guide to Natural Dyes



6 comments:

  1. Hi. I wonder if you can help. Please.
    This weekend I made a dye bath from indigo plant.
    I placed in a 1/2 gallon canning jar about 1 lb of leaves and the rest water.
    i submerged the jar in a pot of water at about 160-170 degrees for 4 hours.
    i then strained the leaves and added a tblesoon of baking soda.
    Then for about 15 minutes I poured the bath from one bowl to another .
    Then I added a tablespoon of Spectralite ( thiourea dioxide).
    After that I added my pieces of silk organza for about 1/2 hour. Gently pushing around
    every so often.
    What I got was a lovely shade of cool green-I guess I didn't have enough leaves to make blue.
    When I began to iron it the color disappeared. The heat caused it to go back to its natural color.
    I stopped ironing immediatey and still have some of the fabric left.
    My question is this:
    Is there any way I can make the silk I have left color fast and is there
    anything I can do in the future to hold the color?
    Help!
    Frustrated in NYC

    ReplyDelete
    Replies
    1. Hi there,

      It sounds like you are trying to both extract indigo from the leaves and dye with it. This is a fairly complex process and there are many variables. There are different species of indigo bearing plants. Indigo plants grown in cooler climates may not develop enough indigotin to dye with. If you got green then you are probably getting some colour from the plant matter - rather than the indigo.

      Generally a natural extraction involves fermentation of the leaf compost in water (2 - 3 days) and then removal of the plant matter from the water, then oxidization of the water (through vigorous stirring or whisking). Once the water is oxidized a blue precipitate (indigo) should form. All these steps require experience to know when they are complete.

      Our instructions should give you confidence to dye with indigo powder, but, sorry, we do not extract indigo from plants ourselves and we have no skill in this area.

      Delete
    2. Hi,
      I work with natural indigo quite a bit, and your extraction temperature is too hot if you were working with Japanese indigo. You will have denatured some of the enzymes vital to the process. Keep the temperature closer to 100-120F and a four hour extraction should be sufficient to give a light color to fabric, if there is indigo in the plants you used. The extraction should develop an antifreeze green color and a coppery sheen if there is any appreciable indigo content. Good luck!

      Delete
  2. ello! I just stumbled across your site. It is so wonderful! So many things to learn. Thank you for being her for everyone.

    I have a question. I have just ordered several indigo fabrics, hand blocked and dyed in India, and have purchased from a reputable source, so the fabric was handled well. I have also ordered other hand blocked, natural dyed fabric of different colors from the same source. I am going to make garments using different colored fabrics together, and was wondering how to care for them and how to minimize color bleeding. I don’t mind fading so much, as some of the colors running together. The indigo running is fine, but there is a green fabric in particular that I am worried will run into the other fabrics. Do you have a solution for washing the fabric first to set the dye? I have been told by the seller that salt works wonderfully, but I would love your input. I believe the fabric has been properly handled, and finally washed to minimize leaching, but I want to be confident, as the garments I am making will be for sale.

    Any help is appreciated, or if you could point me to a place on your site or any place on the net that discusses the care of a final garment, I would be so very grateful. Thank you!

    ReplyDelete
  3. Hi there,

    I purchased your indigo kit and started my first vat recently. I have a few questions.
    I made mine in a large plastic pail with lid. It seemed to reduce and dye well the first time around. Then I left it for a day or so. When I checked it again it had turned a deep blue.
    I tried adding some thiourea dioxide to reduce it but nothing happened.
    It wasn't exactly warm anymore, and I understand it helps to reheat it?
    How do you do so when its in a plastic vessel?
    I ended up pouring it into an enamel pot and reheating it on the stove. Probably the pouring introduces too much oxygen? I have tried adding thiourea dioxide again and no change.
    Also the enamel pot had some exposed metal/ rust on the bottom that I cleaned up as best I could before using. Could this also affect the vat?

    Thank you!

    ReplyDelete
  4. Also, at what point should I add Lye/soda ash? Or both thiourea dioxide and lye?

    ReplyDelete

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