Oak galls have been used to make ink for well over a millennium.

This ink was made from the galls of Texas live oaks (Quercus fusiformis). The “gall” is the site at which a wasp has lain its egg. In response to this intruder, the oak creates a ball of tannin rich flesh around the site to protect itself. Once the wasp has hatched, the gall remains, providing an highly contrasted source of pigments for artist and scholars throughout the centuries.

Water can be used to leech out the tannins, gum arabic to thicken the mixture, and clove and alcohol to preserve it. Iron sulfate can be added to obtain the classic blue-black color, but I prefer it without.