Iron gall ink is primarily made from tannin (most often extracted from galls), vitriol (iron sulfate), gum, and water. Because iron gall ink is indelible, it was the ink of choice for documentation from the late Middle Ages to the middle of the twentieth

Iron gall ink is primarily made from tannin (most often extracted from galls), vitriol (iron sulfate), gum, and water. Because iron gall ink is indelible, it was the ink of choice for documentation from the late Middle Ages to the middle of the twentieth century. Iron gall ink was also easily made; the ingredients were inexpensive and readily available. Good quality iron gall ink was also stable in light. It was very popular with artists as a drawing ink, used with quill, reed pen or brush. The coloring strength of iron gall ink was high and it had, depending on its manufacture, a deep blue-black, velvety tone.