Combine tobacco leaves and water in a pot.
Add the vinegar and salt.
Heat to just below boiling and simmer for at least 2 hours. Stir occasionally.
When mixture gets to your desired color (you can test this by dipping paper into the pot) remove from heat and let cool.
Into a heat resistant container (I use an old Chemex) place a coffee filter into the funnel and filter the ink solution. You may need to sieve the mixture first if you have particularly large plant matter.
Add gum arabic: For each 60 mL of ink, use roughly 10 drops of gum arabic. Add more for a viscous solution and less for a more fluid solution.
To preserve mixture, add a few drops of wintergreen oil into each container.