Following Making Homemade Indigo Paste (Precipitated Indigo), Part 1, we continue the process of making our own indigo material.
In the previous stage, harvested Japanese indigo was finely chopped, placed in a barrel and submerged in water.
This time, the soaked leaves are strained out, slaked lime is added, and the liquid is agitated so that the blue pigment can settle.
Changes between the first and third days
The first photograph shows the Japanese indigo after one day in water.
▼ Japanese indigo on the first day of soaking
The next photograph shows the condition on the third day.
The leaves have broken down further, and the water has begun to show a blue tint.
▼ Japanese indigo on the third day, with the water turning blue
Compared with the previous year, we are testing a longer soaking time and chopping the plants before placing them in water.
We will also observe how these two changes affect the precipitated indigo obtained at the end.
Straining out the soaked indigo leaves
Once the soaking stage has progressed, the leaves and stems are strained out of the barrel.
The liquid that remains after removing the plant material is used in the next stage.
▼ Straining the soaked Japanese indigo leaves from the liquid
Adding slaked lime and agitating the liquid
Slaked lime is added to the strained liquid, which is then agitated thoroughly so that air is incorporated.
As air enters the liquid, the blue pigment begins to form.
▼ Thoroughly agitating the liquid after adding slaked lime
※ Handling slaked lime
When using slaked lime, wear gloves and a mask and avoid breathing the powder or getting it on the skin or in the eyes.
A Japanese-language conference paper from the Japan Society of Home Economics, Study of precipitated indigo formation from Japanese indigo and its dyeing conditions, also examines differences caused by soaking time and agitation conditions.
Allowing the blue pigment to settle into indigo paste
After agitation, the liquid is left undisturbed so that the blue pigment can settle at the bottom of the vessel.
The water-rich material is precipitated indigo. After the clear upper liquid is removed and the remaining material becomes thick and paste-like, Hitotsuya calls it indigo paste.
▼ Indigo paste after the pigment has settled and excess water has been removed
Drying the indigo paste into solid indigo cakes
When the indigo paste is dried completely, it becomes a solid indigo cake.
Crushing the dried cake into powder makes it easier to weigh and store.
▼ A completely dried indigo cake crushed into powder
Why does it dye ash blue every year?
Every year, cloth dyed with my homemade indigo paste turns out more ash blue than deep navy.
I like this colour, so it is satisfying in its own way, although there are times when I would like a deeper shade.
Is the cause in the way the indigo paste is made? Or could it be related to how the plants are grown, the harvest timing, soaking time, agitation method or dyeing conditions?
The dyeing process using a dried indigo cake is introduced in our Japanese-language article Dyeing with indigo paste, precipitated indigo and dried indigo cakes in a hydrosulfite vat.
More study will be needed to obtain a deeper indigo colour from our homemade material.
By recording the working conditions and the resulting colour each year, we will continue to examine the differences little by little.
For the full method, see our Japanese-language guide How to make precipitated indigo, indigo paste and dried indigo cakes.