Iron gall ink pleading from the New York City Mayor's Court, circa 1700. (Courtesy of Geof Huth)Monis, Judah, 1683–1764. Biblical texts in Hebrew, circa 1740s? (Courtesy of Harvard University Archives, HUG 1580.7)n.an indelible ink once commonly used for writing and drawingEusman 1998, http://www.knaw.nl/ecpa/ink/html/ink.htmlIron 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.
Iron gall inks came into widespread use by the ninth century. Such inks are acidic and can cause the underlying paper to deteriorate. They are black when fresh, but the acidic reaction with paper often turns the ink brown over time.