Ferro-tannic inks

Ingredients

gall-nuts, rind of pomegranate, Terminalia, myrtle, tamarisk, carob, ferrous sulfate

Preparation Steps

Original Recipe Text

The production relies on the reaction between metal salts and tannins. Tannins are typically extracted via hydrolysis from sources such as gall-nuts (swelling growths caused by insects of the cynipidae family), pomegranate rind, or the fruits of plants like Terminalia, myrtle, tamarisk, or carob (p. 6). A brownish solution is obtained as a simple tannic ink, but a dark black ink requires the addition of a metal salt, usually ferrous sulfate. The proportion between the two ingredients is critical; an excess of metal salt causes oxidative degradation of the paper support, sometimes leading to perforation (p. 6, 9).

Evidence

"The principle of their production is based on the reaction between metal salts and tannins: the tannins were usually extracted from gall-nuts... to obtain a dark black ink a metal salt, usually ferrous sulfate, has to be added. The chemical reaction between the two ingredients resulted in a more or less dark precipitate"

Remarks

This type of ink is part of a five-group classification identified in northern Nigerian and other sub-Saharan African manuscripts (p. 6). The study notes that the presence of acidic inks like these is a primary driver of chemical degradation in African manuscript collections (p. 9).