Carbon Ink
Genuine Indian ink rubbed down with good black ink until it will flow easily from a pen. This ink resists chlorine, and oxalic acid. acids, of rain, or of the elements in general, and the liquid is thus adapted for marking signs, labels, or tags which are liable to exposure. To bring out the letters in relief, immerse the zinc tag in a weak acid for a few moments. The writing is not attacked while the metal is dissolved away.