The Problem With Sepia Inks

Iron gall inks are made from certain kinds of bugs plant plant lay eggs in. The stems and leaves of oak trees responds by producing this giant gall which has a huge amount of tannic acid. Tannic acid is what makes tea that dark color And so they would use the um, uh, these galls and mix them with iron salts to create beautiful ink. But over time it would oxidize into this deep dark Sort of brown black color That we associate with really old drawings Um, and it is slightly Corrosive and that's the problem if you're ink was too acidic. It will in time destroy your book Oh, dear So this drives, um Museum conservators