Iron gall ink - Manufacture of ink
Elmer Eusman (1998)
Crushed or ground galls were mixed with vitriol and gum Arabic in liquid. The solution was filtered if needed. This method would yield a minimum of pure gallic acid but, since the iron also reacts with gallotannic acid directly, it would still produce a strongly colored ink. The ingredients could also be mixed dry, which would produce ink the moment water was added to it. This powder would make for a perfect traveling ink, created only as needed to avoid the opportunity for mold growth. A transportable ink could also be prepared by drying the made iron gall ink, and resolubalizing for later use by adding water.
Galls were treated in different ways to make iron gall ink. The following procedures were used to not only extract the tannin (gallotannic acid) from the galls but also to increase the amount of gallic acid.
Boiling crushed or ground galls in water (wine, beer, etc.) extracted most of the gallotannic acid and gallic acid from the galls. Addition of an acid (vinegar, hydrochloric acid) also serves to increase the percentage of the gallic acid.
Fermenting the crushed galls by soaking them in water in a warm place produced the highest yield of pure gallic acid. The mold reacted with the glucose in gallotannic acid and hydrolyzed it to form gallic acid. Various sources mention that fermentation for ten days should be long enough to allow a complete transition of gallotannic acid to gallic acid.
After the tannic acid was obtained, it could be mixed with vitriol and gum Arabic. Other ingredients could also be used to modify the characteristics of the ink:
Natural and synthetic dyes increased visibility of a freshly prepared ink (logwood, indigo, aniline dyes).
Rain water, beer or wine used in place of standing or pumped water sources produced fewer impurities.
Pomegranate rind, walnut husks, and various tree barks could be added for extra tannin.
Vinegar or other acids mitigated the premature precipitation of the ink complex Sugar, honey or gum created a more brilliant and slow-drying ink.
Carbolic acid, vinegar, alcohol, cloves, different salts or alum slowed mold growth.
Brandy protected against freezing.
Some of these ingredients are used in the ink recipes presented in How to make your own ink. A source for some of the harder to find materials, such as galls and iron sulfate, is also provided on that page.