Natural Dyes - About The Organic Indigo Vat

by - Monday, August 19, 2013

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

These organic vats were originally developed by French dye chemist and botanist, Michel Garcia. Michel has been teaching and lecturing at the Maiwa Textile Symposium since 2009. He has worked with Maiwa in India as a dye specialist, most notably at the 2011 Maiwa Masterclass. Michel and Maiwa founder Charllotte Kwon meet on a regular basis to conduct natural dye research, explore recipes and test procedures. Together they are always looking for techniques that give the most exquisite colours - made to outlast the fibres they adorn.

Let's consider each of these three things ...


Natural indigo is obtained through a non-toxic fermentation of the indigo plant. It is an extract derived from plants. Depending on the variety of indigo available locally, some artisans will make a dye vat directly from the plant leaves. When buying indigo extract, it may be purchased as lumps (which require grinding) or as a fine powder.

Indigo being extracted from plants in south India.

Indigo in paste form being cut into squares.
Dried indigo. Sometimes called a cake or rock.

A Reducing Agent 

 In many parts of the world chemicals are used to quickly prepare an indigo vat. Sodium hydrosulfite or thiourea dioxide are both commonly used as reducing agents.

A reducing agent removes the oxygen from a solution. In doing this, the reducing agent also takes the oxygen from the indigo molecule. With the oxygen removed, indigo becomes soluble in water at room temperature.

 A reducing agent is necessary to make an indigo solution. Without it the powdered indigo is suspended in water but not actually dissolved.

 What is the difference between a suspension and a solution? A fish is suspended in the ocean. But salt is dissolved in the ocean.

A fish. Suspended - but not dissolved.

You can see the fish (which remains distinct) you cannot see the salt (which has dissolved by being broken down into separate components). Many natural substances will behave as reducing agents. These absorb oxygen and are known as antioxidants. In the indigo vat we can use natural sugars from fruits, medicinal plants, and even other dye-plants, as reducing agents.

Some fruits that make excellent reducing agents.

A Base 

Chemically speaking, a base is the opposite of an acid. A base is a substance that will allow the action of any reducing agent. Some bases are rather unpleasant; for example ammonia and caustic soda, while others are weak; such as soda ash and potassium carbonate. Weak bases are not very toxic - but by themselves they are inefficient.

The recommended base for an indigo vat is ordinary lime (calcium hydroxide) also known as “calx” or hydrated lime. Do not confuse it with “quick lime” (calcium oxide) which is much more corrosive, or chalk (calcium carbonate) which will not work. Ordinary lime is available at Maiwa or at a building supply store.

Calcium hydroxide, ordinary lime, hydrated lime, calx
- many names for the same thing.
The recommended base for the organic indigo vat.

About these Indigo Vats 

We suggest that you take the recipes that follow only as a guide. Adapt them to use materials that are plentiful and inexpensive where you are located. As with all natural dye recipes you may find yourself adjusting amounts to suit your particular dyeing situation. These vats give the best results when made the day before you dye with them.

Hydrating Indigo

Indigo powder always needs to be hydrated before being added to your vat. Sometimes alcohol is used to do this, but we have found a quick and efficient way to hydrate your indigo with marbles.

Simply fill a strong plastic container 2/3 full of marbles or smooth, round stones. Add indigo powder and cover the marbles with warm water. Shake vigorously for one minute. The indigo is now hydrated. Pour the hydrated indigo into the vat while using the lid to keep the marbles in the jar. Swirl a little bit of water in the jar to wash the rest of the indigo out and into your vat.

Dyeing with a Basket

When using an organic vat, rather than filtering the liquid you may use a basket to keep the yarns or cloth away from the sediment. This is particularly important with the ferrous vat as the iron may cause dots or stains. Stir the vat, wait for the sediment to settle, then use a basket.


The proper pH is 9 - 9.5 for wool and 11-11.5 for cotton. You may test the pH of the vat with a test strip. If it is too low carefully add some more lime. If it is too high, then add some more fruit juice and wait a little, the pH will decrease.

The addition of more fruit juice from time to time is recommended to keep the vat reduced. Remember, the action of dyeing will introduce oxygen into the vat.

Some fruits are more acidic than others. If using very acidic fruit add more lime at the beginning until the pH is correct.


The first shades obtained from your vat will be strongest. You will increase the depth of shades by dipping more times. For very pale shades it is best to make a vat with less indigo and dip more often than to dip once in a stronger vat.

Exhausted Vats and Revived Vats 

These vats may be revived until the amount of sediment becomes problematic. There is an art to reviving an indigo vat (check the pH, adjust, bring it up to temperature) and it can be satisfying to do so, but at some point it will be necessary to abandon the vat and make a fresh start.


If whisked, lime will very quickly absorb the carbonic acid of the air (CO2) and be neutralized. The lime will then be transformed into calcium carbonate (chalk or limestone) a non-toxic substance which can be poured down domestic drains. Both liquid and sediment of these vats may be used as compost.


Mixing two organic reducing agents, such as henna and fructose, gives a strong indigo vat.
Michel Garcia suggests that individuals do their own experiments. Clear glass pots of about one liter make excellent test vats. Try different combinations or experiment with local plants and fruits.

Up next - The Fruit Vat recipe.

The Maiwa Guide to Natural Dyes

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  1. i particularly enjoyed the fish and salt definition!

    1. Hah, so have I. And i must take this opportunity to say how much I've enjoyed your books. Thank you for sharing your stories and knowledge.

  2. Does anyone know if this will work with synthetic indigo? I have a supply of this I would like to use up before ordering some natural indigo.

  3. Re: Anna Carlson - The chemistry of the organic vat provides the necessary environment to reduce the indigo to its soluble form. As such the organic vat will work with either synthetic or natural indigo. But the organic vat, when used with natural indigo, permits the entire process to be as natural as possible.

  4. Today I made my first attempt at an indigo vat. I ordered the indigo through your online site. I used the 'Ferrous Vat' recipe on the information sheet you sent with the indigo. It appeared that I should almost boil the water first. For a 15 -20 litre vat I assumed that I should have that much water in the pot. [I read later that it could be easier to make a starter solution]. So I followed the instructions, hydrating the powdered indigo with marbles in a plastic container, adding the ingredients as recommended. In the recipe it wasn't clear if I should boil 15 -20 ltrs; if I should stir the mixture, if I should remove it from the heat before I added the dry ingredients.. In the intro to the recipe it states that the '1,2,3' vat is a cold vat. Does that mean you can dye with it once the liquid cools? I intend to use the indigo vat for dying paper, rather than cloth. The water was a very pale blue for the first hour or so. There was a very subtle 'flower effect' on the surface. I dipped the paper & got a pale grey sludgy effect on some pieces, no colour at all on some, & rust coloured effects on others. Later the surface of the vat was rust coloured. I haven't tried dipping any more paper. Do you have any idea what I've done wrong, please? I'm very disappointed.

  5. I sent an enquiry a few minutes ago & have another question about the ingredients for the 'Ferrous Vat' for indigo: is garden lime the same as the lime you recommend for the indigo vat? I can't seem to get a handle on it via on line searching - I got some garden lime from a friend to use in this recipe - perhaps that's what I've done wrong? thanks. Cher

  6. Garden Lime is calcium carbonate - different to the Lime used in Indigo vats. The lime for indigo vats is calcium hydroxide Ca(OH)2. Other names for this lime is calx or slated lime. I think you will have success if you change your lime. Please be aware that an indigo vat is ready to use when there has been a good reduction in the vat and this can take some time in an organic natural vat. The tell tale signs of it being ready is that there is a metallic sheen to the top layer (maybe bubbles) on the surface of the vat and the blue indigo particles underneath have changed to a reddish or greenish colour. Dip a scrap of white cloth or white paper for half a minute or so and when it is brought out to the air it should magically shift to blue. Boiling the ferrous vat is not recommended, though encouraging reduction with a little heat (warming up) can move it along faster.

    1. Thank you so very much for your response - I will attempt to find the elusive Ca(OH)2. I did a dip on the 2nd day in the 'failed 1st attempt' vat & got some beautiful results - copper & gold & bronze fragments adhering to the paper on a copper background. I'm going to keep it a while & see how it develops! But I am looking forward to a lovely rich dark indigo! Thanks again. Cher

  7. Hello,
    I am interested in using fresh indigo leaves instead of the powder and I was wondering what type of ratio to use with fructose and lime when using fresh leaves.
    Also, do I need to treat them ahead or let them sit?

  8. I made a henna vat with 24 grams of indigo and found it worked well, but too strong for subtle overdyes of my eco prints. Is there a way to weaken the color? Bet you never had that question before?

  9. We do agree with India Flint! The fish and salt definition, couldn´t be more exemplifying! With your permission we always use this comparison in our workshops. Congratulations for all your work! We read you carefully from Spain!

  10. Such a perfect pdf. It has so many layers of information in it.
    I am so eager to start dyeing indigo organically.

    But one thought. You write of using a basket when trying to avoid sediment and stains. I have that problem when dying grey with organic dyes. And the idea of a basket is brilliant.
    But what type of basket would be useful?

    /Anna from Sweden

    1. Hi Anna, I am using a colander in my vat as a basket because it has a 'foot' on it to keep it away from the sediment at the bottom.

      Rara Matthews

  11. hello! I was wondering if it was possible to use soda ash with pears as the reduction agent? or is it only possible with lime?

  12. Has anyone tried to use organic vat methods with fresh leaf indigo. We used 1k of polygonum tinctorium with ferrous and fructose. Waited 24 hours, it looked reduced, but gave little color

    1. Had read in past of experiments did with mini vats, fructose,henna, mineral (Fe) and they said could mix all but the mineral with the fruit/fructose. They did alkalizer (lime) with iron. Am looking at alternatives for lime (like ash water...). Lynn

  13. Does it matter if use Calcium hydroxide or potassium or sodium ??
    Also wonder if adjusting the vat for dying silk or wool is different than for cottons and other plant fibers? Thank you

  14. Why or how does fruit sugar (fructose) act as a reducing agent in an indigo dyeing vat?

  15. How shoud I handle the washing proses after i finished dying silk in indigo dye?
    Shoud I youse sope? Regular hand sope make white stains on the fabric . What kind of soap shoud i use. Thanks for answering.


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