Science-backed iron gall ink tips

Based on the number of recipes out there, it seems like any ol' method will do when it comes to making iron gall ink; however, my first attempt was terrible. In reading the conservation research, these are the most important factors for getting black ink.

• Hot water extraction works well for gallotannins (around 75°C).
• Boiling can work but may not always give the best results as it may breakdown the important PGG and HGG compounds.
• Room temperature (long soak) gave variable results for different researchers.
• I was not able to find up-to-date research supporting fermentation as an extraction method; however, long room-temperature extraction (8 days) was considered acceptable in one study.