The Characteristics and Preparation of Gall Inks
by Madame Elizabeth de Nevell
Despite the highly corrosive properties that caused iron gall ink to pass out of widespread use by the early twentieth century, it is arguably the most important ink in Western history. Known by the Romans and widely used after the late Middle Ages, iron gall ink is not easily erased, and this property made it an obvious choice for record keeping of any sort. Libraries and archives around the world hold a vast number of manuscripts collections ranging from Leonardo da Vinci's notebooks, early drafts of the American Constitution, and music compositions such as J.S. Bach all executed in iron gall ink.(Karnes)
The word ink derives from the Latin word encaustum, meaning, "burnt in". Actually a dye, and not a suspension of pigments, gall inks rely on Tannic acid for coloring and were extremely popular in the Middle Ages. The gallic and tannic acids in the ink and the oxidation which would occur to them actually caused the lettering to eat into the surface of the page.
Large concentrations of naturally occurring tannic acid can be found in the "gallnuts" that are sometimes produced in oak trees. Gallnuts (see picture at left) are a swelling on the surface that is produced when an insect stings the tree while laying eggs. The tree then reacts by concentrating tannic and gallic acids, which are poisonous to the insect, around the point of the sting. The small swelling in the surface protects the tree from further damage. These galls can then be harvested, soaked in water and mixed with iron salts to produce a fine ink.(Brown, 57, 73) Various other sources such as pomegranate rinds, horse chestnuts, hemlock and pine bark, can be used, but they will yield less durable green toned ink, rather than the characteristic blue black of high quality iron gall inks. (Karnes)
Many methods of producing gall inks have been left to us over the years, passed down by monasteries, scriptoriums, and families. "A Medieval Home Companion" gives the following recipe for oak gall ink:
"A Book Containing Divers Sorts of Hands", by John de Beau Chesne and M. John Baildon, published in 1571 offers us the following recipe for "instant" ink.
Batch #1 - October 14, 2002
Gall inks are very light when first applied. Many recipes from late medieval English texts recommend burning a bit of parchment or paper and adding the soot to the oak gall ink to make it more readable (Thompson. p. 84). The tannic acid of the galls, when mixed with iron salts, produces a dye that becomes even blacker as it oxidizes on exposure to air. Over a great amount of time the ferrous ink produced by the iron salts will occasionally fade to the familiar red brown color found in many western manuscripts of the period. Copper salts, which were sometimes used, will fade to a gray-green color.(Brown, 73)
In principle, deterioration of foundation materials by ferrogallic ink is largely a result of the action of the inks consisting of iron of diverse other transition metal ions, such as copper or zinc. The support material suffers an extensive gradual decline in its natural properties which in the end makes its further use as an information medium impossible. As early as about 100 years ago the head of the Vatican Library, F. Ehrle, worried about the problem of ink damage and warned of the impending destruction of numerous documents and manuscripts. The conference he called to St. Gall in 1898 was the starting point for the systematic and scientific research for an explanation of the causes of this degenerative process.
The reasons for this destruction are not fully understood yet, although numerous theories have been proposed to explain the degradation of papyrus, paper and parchment objects. The desire to conserve these items necessitates the development of effective treatment methods, which can only be possible after determination of the chemical causes for deterioration. (Banik)
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