When we apply Acrylic and oil technique , we not allowed to use water at all as a medium to mixed with the colors . They have their own medium. Mostly we painting on canvas, and the brushes and medium we can buy easly at Art store.
Traditional Chinese Painting and Sumi-e, almost have a same technigue , mostly use black ink . it could be from the rub one or from the botol. Mostly no chemical on it / somehow their have colors powder also. Mostly organic. The paper from bamboo fiber and very thin.
Water color did not use the real black color, the dark color mostly came from combination from another dark colors . Use a lot of water to make a light color and transparency is the character of this technigue.