Take and wash one pound of green spinach thoroughly in water, then squeeze it through a piece of muslin until perfectly dry, then put six spoonfuls of cold water in it, and let it stand, then remove it to a very small bowl, and gradually cook six hours. Empty the water gradually, be careful not to disturb the bottom, and do this until you find a thick green spinach coloring. Put a little bit of soda as big as a large pin's head and dissolve well, and put this in a small bottle, and it will keep for a fortnight or three weeks.