You've purchased seed, sown, potted up, planted on, fed and watered the results are in - you've successfully grown bushels of tender green indigo ( Persicaria Tinctoria)
The choices of what you do with your plants are plentiful. 'Happazome", raw leaf dyeing, salt leaf dyeing.
For this article the focus is to procure your own beautiful deep blue indigo pigment, with which to create your own vat, ink, paint or chalks and crayons, employing the hydro method of soaking the plants to release the pigment.
You will need;
Calcium hydroxide also known as; builders lime, picking lime or Calx for this article will be referred to as Lime, which is readily available on Amazon at food grade.
N. B. It is paramount when using Lime you add lime to liquid and not visa versa.
2 x storage containers for your indigo
1 mixing bowl
1 whisk ( optional)
1 x teaspoon
A dust mask. Super important when dealing with calcium hydroxide powder form
Fine muslin or cotton cloth to fit your sieve
Piece of silk to line sieve or coffee filter.
Check indigo pigment is present. Simply pluck the top leaves and crush into a ball of juicy green in the palm of your hand. Within 5 mins - 10 mins the sap from the leaves will turn from green to blue as it comes into contact with your personal ph and air. For a less messy alternative simply pinch the tips of your indigo or crinkle a leaf and the colour will show up after 30 mins or so.
With the color test rendering blue the alchemy can begin.
Ensure your plants are weed free before harvest, any other material other than the indigo itself can alter pigment results, even inhibit the indigo pigment from truly dropping out. Cut plants leaving a good 6" for regrowth and any new tender shoots. This advice is for those of you with shorter and cooler summer months. I've talked about this and shared the information in instastories.@bailiwickblue "Indigo Alchemy"
Place plant material into a large vessels, size of which will largely depend on your harvest. Most use storage containers.
Pack the indigo down, but don't crush, fill vessel with water to cover branches and weight the plants beneath the surface of the water.
Use whatever you have available, in my case its ice-cream containers filled with water to weight down branches and leaves.
In the hydros method, the plant releases Indican into the water, Indican separates into two parts, sugar, and indoxyl. The reaction occurs within 3-5 days depending on the outdoor temperature, the warmer the day the quicker the reaction.
Over the next three days inspect the surface water. Pigment will be seen collecting on the surface and around items used to weight down the plant matter, in a purple blue sheen. The water will become a luminous turquoise green thru teal colour.
While we mostly talk visuals, there is also an important note to make regarding the "Ready" aroma; a high sweet smell with a lower warm green undernote, many of you are already aware, however, for the new indigo growers in the crowd it is an important factor to be aware off because indigo gone to far is no-ones friend.
YES sometimes plastic bottles as weights.
Once you have a visual confirmed by the aroma remove all plant material, and screen the liquid through a fine muslin cloth or cotton into the second clean vessel to remove any tiny pieces of indigo debris.
Now the indoxyl is released and ready for the aeration process with an increased ph. Altering the ph and incorporating oxygen captures the indigotin, the indigo pigment with which we dye.
Gloves and Masks ON please! Lime is caustic so protection is definitely required.
Create a slurry, taking up a small amount of the freshly screened indigo liquid, I recommend 100 ml to start, add a teaspoon of lime, and blend in well. Increase the amount of lime gradually, until the consistency is that of maple syrup. Increase the amount of liquid if needs be.
By taking the time to make this syrup, it will ensure the lime is 100% effective once applied to the main vessel of indigo liquid and will leave little to no residue in the form of lumps within the pigment.
Alternatively, you can also use Lime putty, though this is less frequently found at the hardware store but from specialists. This then removes the dust element from the equation. I sieve lime putty to break it down into rice sized particles to blend it into the liquid.
You will notice an instant change in colour as the lime acts to capture indigotin available in the liquid.
For 100 Litres of indigo liquid, 2 tblspn ( maybe 2.5 ) should be prepared and blended prior to commencing aeration. Err on using less, not more lime, ( Just as Meis van de Rohe said "Less is more") as this will alter the purity of the indigo pigment at the final stage.
Start aeration by slowly adding lime to the main vessel. Using a whisk or passing liquid back and forth between the two vessels using a bucket or bowl ( I find this works best - even as an owner of a submersible pump!) It usually takes circa 20-30 mins to work roughly 100-120 litres) You may think this is hard labor, in actuality its magical watching the pigment change color.
Slowly add "lime syrup" as you aerate. The colour will change and foam will appear. Keep aerating and adding lime little by little between rotations of the liquid. at 20 mins you should have a good indication of whether you need to add and make more lime dilute.
There should be no foaming, at this stage, only white bubbles which snap and pop quickly on the surface of a now indigo blue liquid. Within the liquid you should see the movement of dark blue particles billowing cloud like as you stop your aeration process.
If this is the case. Down tools! The indigo will need a good 24 hours to settle to the bottom of the vessel. You've had your work out, time for a cuppa.
Time to screen off the supernatant which will be yellow or pale bluey green, depending on how much lime you decided to add. Remember less lime gives a much cleaner indigo. More lime a faster process. More lime will give you the colour below, this is not necessarily a good thing to have super defined separation.
Gently remove the excess liquid above the indigo pigment and set aside. Pour out the pigment. Add water to half the volume of water used in the alchemy process, this is to rinse and remove the odour of the lime. Allow the pigment to settle once more.
The second drop out will be quicker, it is best to allow 12-24 hours for the pigment to totally drop out.
The surplus lime'd water should be treated with either white vinegar or citric acid crystals and brought down to a ph of 7 before disposal. If you are growing madder you can drop the ph to 6 / 6.5 dilute with water and feed to your madder plants.
Line your sieve, with cotton, silk or coffee filter paper.
Screen off as much water as possible from the top of the pigment, pour out the pigment into the lined sieve. Give the pigment 1-6 hours to sit on a vessel for the excess water within the paste to drop out completely. You can transfer your paste to dry further into a lined basket or tray.
Place out of direct sunlight and leave to dry at room temperature.
Once completely dry, it's time to grind and hydrate your very own small batch indigo and set to work on your very own "Sustainable Indigo vat".
For further reading and inspiration on how to use Persicaria Tinctoria a.k.a indigo plant, please take a moment to check out these wonderful ladies on instagram and via their websites.
@dogwooddyer Liz Spencer Dogwooddyer
@dreambird.studio Iris Sullivan Daire DreamBirdStudio
@indigobluefields Luisa Uribe www.indigobluefields.com
@naturesrainbowhitchin Susan Dye & Ashley Walker www.naturesrainbow.co.uk
@seaspellfiber Brittany Boles SeaSpellFiber
Brittany Is also the founder and creator of Facebook page "Indigo Extraction Pigment Method" which is brimming with information and shares so much good and good information you will not be alone in your quest for knowledge and meeting like-minded souls.
Back to Harvest tomorrow, first an early night
Fantastic!! Thank you so much for the step by step details. I am off to give it a go this weekend. What is the approximate yield of pigment from weight of fresh leaves? I only have a few plants!
George, you are a star. Thank you for mentioning me in your blog and for sharing your process with us! Xx