Friday, 9 December 2016

Two Different Ways to Process Indigo Leaves.

Look at this wonderful square pile of blue indigo leaves.  Gorgeous.

The leaves were harvested throughout the summer when the sun was out and stripped off the stems and dried in the sun. (Many thanks to the strippers who lent a hand.)


Now, the trees are almost bare in the valley, the angle of the sun is low and the mountains are heading into a cold sleep.

In just three days the pile of indigo has already started to ferment. If you stuff your hand in deep enough it is warming up. It should reach 60 degrees Celsius and maintain that temperature for 100 days.

The leaves were lightly wet (Just enough so that when you squeeze hard barely a drip escapes.) and tossed for an hour or so to evenly distribute the dampness.

Yamazaki san, Yoshi kun, Ishii san, Eliot kun helped get the room and the leaves ready.

We peppered salt around the leaf pile to keep any potential indigo eating villains at bay, rubbed ourselves with a few pinches to purify any invisible tenacious baddies,  took  few sips of sake to help with inner purification and keep off the crisp sweater-penetrating gusts and solemn December sun and lit some incense sticks to sanctify the occasion.

We wrapped and blanketed on some rice straw mats to keep the heat and moisture in.

This method is more complex than my usual technique of fermenting the leaves and making indigo balls. From this past spring I have two more indigo fields just below the house. Yamasaki and Ishii sans share the work and the produced indigo paste. Two more indigo producer/dyers in Fujino! This has been my goal for over 15 years and it is finally happening! 100 years from now an indigo culture may still exist in this solitary village.

The leaf pile needs to be tossed and dampened on a regular basis for 120 days. I will keep you posted on the progress.

Another process to extract indigo pigment:

One problem with growing indigo is dealing with cloudy and rainy weather. The leaves should be dried to crisp as soon as possible after harvesting. Sometimes it is impossible and the indigo grows taller and taller. The leaves pass their prime and the pigment content decreases. (Sob sob....)

This summer past was particularly cloudy. We managed three full harvests but could have squeezed in a fourth had the weather cooperated. Instead of crying in my beer I cut (with the help of workshop cutters) the indigo leaves, left them on the stems and submerged them in a stainless bathtub for four days to leach the pigment out. I kept them in large onion bags to make the job easier and neater.

This simple technique is the perfect solution to what to do with a few huge indigo fields with thin leaves and not much strength left in the sun and not much pigment in the leaves.

After four days it gets rather stinky. (Just below gag-reflex intensity.) The leaf bags get taken out and placed above the blue liquid to drip all the excess back in the bath.

A cup of calcium hydroxide. (slaked lime) is hydrated and poured in.

At first we used bamboo rakes to whip oxygen was exhausting and then I remembered my old cement mixer in the barn!


The whipped liquid is left and the indigo pigment sediment settles to the bottom.  The clear liquid is then scooped off. The muddy bottom sludge is filtered through a few layers of cotton and then scooped into a container and left to dry in the sun.

This can now be used as regular indigo powder in a hydro-sulphate reduced indigo vat. It is a lot simpler than the three or four month slow fermentation technique. Not as sexy and involved. It is considered the Indian way of doing it although in Okinawa they use the same technique.


  1. omg! blue gold. Hard work, time and the weather for the joy of heavenly blue.

  2. I just planted out my Japanese indigo seedlings this afternoon - seed from last year's single plant. I'm not planning to ferment them though - too close to the neighbours for that.

    1. agh.... what is a little ammonia smell amongst neighbours.....

  3. Hi Bryan. When do you sow your indigo seeds please? I have some that I must sow but will need to adjust for our southern hemisphere seasons of course!

    1. Hi Carol san, Just as it starts to warm up, no fear of frost you can plant them.
      Need some more I can send you some.


  4. holala I wanna stay there!! :-) you know we are using this second method here too...and no cement mixer but a old washing machine pump, really efficient and even resting :-)

  5. Hello from France! I have indigo seeds and was wondering when to start planting- i live in the mountains (it is about 20 degrees farenheit!) - so, i guess i should wait... but i am very excited to try them...! (Indigofera tinctoria and japanese indigo-Persicaria tinctoria)... Thanks!

    1. Please wait until it is warm and there is no chance of frost!

  6. The days before power tools...I guess power tools could be considered sexy!