In this video, you see dyed yarns with the Nile that are coming out of the color cauldron. It is noteworthy that the yarns do not become completely blue when it comes out of the cauldron, but when the yarns are exited from the cauldron and are placed in the vicinity of air and oxygen, their color change in blue. But the important thing is to have a skillful dye experience to know when it comes to removing whipped yarns from the cup when it comes to the desired blue color. If a dying person is a beginner, he may not be able to obtain the desired blue. Diligence with Neil is, by the same simplicity, very difficult to do with many mysteries that the discovery of secrets is only possible based on experience.
In fact, the use of the Nile in dyeing is very old and its origin is Indian. But the point that has left many of the formulas and gestures still remain unidentified in dyeing or formula
The discovery of a particular type of plant is that in the past knowing dyeing techniques were inherited and familial, and nobody prepared the steps or techniques of it and did not teach others, this caused many of them would disappear when the dyer died.
Today, the situation is getting better and with a little searching and studying specialized books and talking with renowners and pioneers you can get good information but still the basic point is having experience in this way.