What gall!
Iron gall ink is one of the most historically ubiquitous plant-based pigments. The black-brown ink has been used for centuries due in part to the ease of producing it. “Galls” are growths that develop from the leaf buds of trees – commonly oak – after a gall wasp lays her eggs. A chemical reaction occurs during the development and feeding of the gall wasp larvae, creating the hard gall to protect the larvae as they grow. While recipes for iron gall ink vary, key ingredients include galls, iron sulfate, water, and gum arabic.