Make your own writing ink with ordinary household tea.
To make 4 floz/115ml
4fl oz/115ml boiling water
5 tea bags
1 teaspoon gum arabic
In a medium-size bowl, pour the boiling water over the tea bags, stir in the gum arabic and steep until cool. Then squeeze the tea bags hard to get out all the tannic acid. You can use the ink with a paintbrush, quill pen or any other type of writing implement.