Iron- or Oak-Gall Ink
Bibliographic descriptions of Medieval and Renaissance manuscripts always indicate whether they are written on vellum (calf-skin) or parchment (sheep- or goatskin) or paper. Such distinctions are direct measures of the cost of producing the document, and that can suggest the scribe's or customer's estimate of the document's contents' worth, as well. Nevertheless, those bibliographic descriptions rarely need to specify the nature of the ink used because, from Roman times until the early Twentieth Century, only one basic formula for manuscript ink usually was used by anyone who wrote.
"But who would have thought that the ink used to fill Leonardo da Vinci's notebooks, or to complete line drawings and paintings of Dürer, Rembrandt and Vincent van Gogh, not to mention the score sheets of Bach's heavenly music, were all derived from an excrescent growth on oak trees caused by parasitic wasps? Oak galls, found especially on the Aleppo [Syria] oak Quercus tincturia, were the raw stuff of human letters for hundreds of years." (Mark Cocker, "Westminster Hall from an Acorn," Review of William Bryant Logan, Oak: The Frame of Civilization [NY: Norton, 2006] in The Times Literary Supplement 1/13/06: 6).
Oak galls were boiled with pure fresh water to leach out their corrosive gallic and tannic acid, which was intended to help the ink "bite" or eat into the parchment or paper surface. The partially evaporated oak gall mixture was mixed with "copperas" (iron sulfate), which also produced sulfuric acid, and lamp black or burned wool, and gum from evergreens. The resulting mixture was viscous enough to cling to the sliced end of a quill pen, and to hold the nearly vertical surface of scribe's parchment or paper without running.
Lamentably, it was discovered only after several centuries had passed that the iron sulfate, gallic acid, and tannic acid used in preparing oak gall ink would gradually react with trace metallic elements in papyrus, tanned animal skins, or paper, and this reaction would gradually burn away the substrate beneath the ink. This leaves not black ink on the page, but a tracery of empty space where the letters and punctuation had been. When the ink was used to draw images rather than to trace words, the effects could be more widespread, as in the ink sketches of Rembrandt. As early as 1898, a Vatican librarian called an international conference to warn librarians about the impending loss of irreplaceable manuscripts of incalculable value due to this little-understood chemical reaction. Since then, archive conservators and conservation librarians have undertaken innumerable efforts to stabilize or rescue vulnerable documents.
Investigators who inspect old books and MSS must be alert to detect traces of ink corrosion and to record this as part of the document's description. The specific pages on which damage occurs, as well as the kind and extent of the damage, should be indicated as succinctly as possible. If the document appears to be in danger of disintegrating, immediate steps must be taken to conserve it, if possible, and the Special Collections librarian should be notified at once.
See the Library of Congress Web site, "Corrosive Media: Iron Gall Ink Corrosion," for more resources.