To Write in various Colors with the same Pen and Ink.

Scientific American 31, 24.4.1847

Take a sheet of paper and wet some parts of it with a solution of subcarbonate of potas, which must be diluted with water so as not to appear on the paper when dry. Wet some other parts with diluted muriatic acid, or with juice of lemons. Some other parts may be wet with a diluted solution of alum; and others with an infusion of nutgalls (water in which bruised or pulverized nutgalls have been steeped.) None of these preparations must be so strong as to color the paper.—When these are dry, take some finely powder. ed sulphate of iron, and rub it lightly on some parts of the paper, that have been wet with the subcarbonate of potas and infusion of galls. Then with the juice of violets, or of the leaves of red cabbage, write on the paper as usual with a pen. The ink is of itself a faint purple; where the paper was wet with acid, the writing will be a bright red; on the subcarbonate of potas, it will take a beautiful green; on the alum it will be brown; on the subcarbonate of potash that was rubbed with powdered sulphate of iron, it will be deep yellow; and oft the infusion of galls that was rubbed with powder, it will be black. The juice of violets will take a brilliant yellow on the alkali if it be very strong. The juice of violets or red cabbage may be kept a long time by means of the addition of a few drops of alcohol; or the leaves may be dried by the fire, and thus may be kept ready for use; and it is only requisite to steep them in hot water, in order to prepare the ink at any time.