Indigo is a pigment obtained from the processing of different plants, depending on the world area. For example in Europe from Isatis tinctoria or Woad, in Far East from Persicaria tinctoria (or Polygonum tinctorium), in South America from Indigofera suffruticosa. The main indigo producing country has long been India, where was and still is worked Indigofera tinctoria.
The manufacturing process of this pigment is fascinating and involves the fermentation of the plant in big tanks to allow the extraction of the coloring principle, which will then precipitate as a pigment, due to an oxidation process. It is actually the fact that its color displays following the oxidation, which induced to its use in centuries, because it ensures its stability along time.
Indigo which Nila Colori uses for this watercolor comes from India.
Colouring agent: Indigotin
C.I.: NB 1