Yes, iron gall inks are acidic and best not used on regular paper. But they last pretty well on vellum (eg Book of Kells, https://en.wikipedia.org/wiki/Book_of_

Yes, iron gall inks are acidic and best not used on regular paper. But they last pretty well on vellum (eg Book of Kells, https://en.wikipedia.org/wiki/Book_of_Kells https://en.wikipedia.org/wiki/Book_of_Kells, on which all the lettering is done with iron gall inks) Lots of interesting discussion here: https://www.fountainpennetwork.com/forum/topic/226717-archival-qualities-of-iron-gall-inks/ https://www.fountainpennetwork.com/forum/topic/226717-archiv...