The soft brown lettering shown at left was made with iron gall ink. The improbable ingredients in this substance included ball-shaped growths created by insect infestation of oak trees, and ferrous sulphate, or copperas, an iron salt made by evaporating water from ferrous earths. These nutlike galls were ground and soaked, and the liquid extract was then mixed with earth and gum arabic to create a murky broth that served as ink. Back