Fermented pokeberry ink with a stick pen:
Recently I've been trying to identify berries that I see around the area. Pokeweed is common, including a large plant growing on the side of my house. The bamboo-like stalks grow very tall. As a kid, stick-in-hand, it was always great fun to have at a large patch of the plant. A swung stick slices through the thick stalks like a machete, and a 10-year-old could make quick work of a thousand weeds in a few short minutes.
Dark purple berries grow on the plant, however they are apparently dangerously poisonous. However! Juice from the berries can be made into temporary ink. Fermentation makes the ink permanent. Click here for more details about making the ink.