When you dye indigo, you are literally taking the indigo pigment away from küpe onto the fabric. The küpe is not infinite. So, when you dye a lot, you need to add new indigo pigment to it so it has enough pigments inside.
You do not add just the indigo pigment itself, but you make a stammküpe, which is a mix of indigo pigment, eisensulfate and kalk and warm water. Janina has experimented a lot with the ratio, and the current ratio we used is:
200g indigo + 2L warm water
1kg eisensulfate + 3L warm water
1kg Kalk + 5L warm water
First, weigh each of the materials and mix in warm (~50 degrees) water. Then add eisensulfate mix to indigo and mix it well.
Then mix in the kalk mix. It suddenly changes the consistency and becomes very thick, shiny indigo-purple liquid. when you mix it, you see the blue green color inside. very beautiful material.
