Luminous Ink
“Luminous ink that will shine in the dark.—To half an ounce of essential oil of cinnamon, in a phial, add half a drachm of phosphorus. Cork the phial slightly, and set it, or suspend it near a fire, where the heat may be nearly equal to boiling; continue the heat four or five hours, shaking the phial frequently, but cautiously lest any of the oil should escape, or come in contact with atmospheric air, in which case it would take fire. The cork should be set sufficiently tight to exclude atmospheric air, but not so as to prevent the escape of any vapour that might be produced by excess of heat. The phial may be afterward removed from the fire and suffered to cool. With this phosphorised oil, any letters may be written on paper, and if carried into a dark room, will appear very bright, resembling fire. The phial should be kept corked close, except when used.“
A Select Collection of Valuable and Curious Arts and Interesting Experiments, 1826.
