Making iron gall ink

By Abigail Bainbridge

Last week the graduate book students learned how to make iron gall ink, a common writing ink from the Middle Ages through the 20th century. It's only made from a few relatively inexpensive ingredients but if made in the wrong proportions it can cause a lot of damage to paper or parchment substrates.

The ingredients (in order of the pictures below) are tannic acid, most commonly from oak galls; ferrous sulfate, known historically as copperas or green vitriol; and gum arabic, a gum from the acacia tree that acts as the binder and modifies the flow of the ink. Other ingredients such as dyes, other sources of tannins, etc., might be added as well, and there are hundreds of historic recipes.

A couple different methods of extracting gallotanic acid from the galls can be employed; we crushed them and heated them in water. A couple students also tried crushing and just soaking for a couple days to compare the resulting inks.

The extract is a warm brown color, and as soon as the ferrous sulphate (which normally goes yellow in water) is added, the solution turns dark brown/blue black.

Then we added a little ground gum arabic, and tried out the ink with some pens. We watched the lines in the image below get darker over a couple minutes (they were all made with the same ink) as the ink oxidized, and plans were made to experiment with aging marks made on paper with different recipes to see how the proportions and method of extracting the gallotanic acid would affect the stability of the ink!