Scientific American 26, 22.12.1860
The stalks of the Chinese sorgho contain a coloring matter possessing great tinctorial power. It is prepared by fermenting the stalks of the plant from which the juice has been expressed. At the expiration of fifteen days the coloring matter is developed, and it gives a beautiful brown or red color to the stalks. They are fried to stop the dermentation, and then ground to a fine powder, which is treated with water. This removes a small solution of caustic soda or potassa. The base is neutralized by sulphuric acid, and the carmine is soon deposited under the form of light flakes. The red of teh sorgho is soluble in alcohol, the alkalies and feeble acids. It answers very well for dyeing silk and wool, and it appears to resist the action of light.