How to Make Precipitated Indigo (Indigo Paste and Indigo Cakes), Part 1 | From Fermenting Indigo Leaves to Adding Slaked Lime

This year again, we are making precipitated indigo, indigo paste and dried indigo cakes from Japanese indigo grown at the Hitotsuya（ひとつ屋） Dye Plant Farm.

This year, we would also like to use the material for something beyond dyeing and develop a product that feels distinctly Hitotsuya. First, however, let us begin making the precipitated indigo.

The complete method is explained in our Japanese-language guide How to make precipitated indigo, indigo paste and dried indigo cakes.

The work can also be seen in our YouTube video on making precipitated indigo.

The process of making precipitated indigo

▼ First-cut Japanese indigo leaves are picked, placed in a barrel with water and left in the summer heat to ferment.

First-cut Japanese indigo leaves placed in a barrel with water for fermentation

▼ The container is covered and left in the summer heat: day 1.

Japanese indigo leaves fermenting in a covered barrel on day 1

▼ Day 2.

Japanese indigo leaves fermenting in water on day 2

▼ Day 3. When the leaves and liquid reach this condition, slaked lime is added.

Japanese indigo leaves and liquid on day 3 before adding slaked lime

▼ A good indigo-blue colour has developed. The liquid will now be agitated vigorously to incorporate air.

Indigo liquid showing a strong blue colour before vigorous agitation

That is all for today. In the next article, Making Homemade Indigo Paste (Precipitated Indigo), Part 2, we leave the pigment to settle and then collect it.