My former post (#20) may have veered off a bit from the original thread's topic, but it's still related. This bottle of Akkerman #10 Ijzer-Galnoten blauw/zwart ink had gone bad, with heavy black staining in both the ink reservoir & the filling chamber. After the cleaning steps I described in the previous post, the totally clean bottle is used to dispense my pen flushing solution.
As to how to properly store Iron-Gall ink: -- keep it in a cool dark place
-- inspect the ink frequently
-- try to use up the iron gall ink as soon as possible (my rule is about three years tops).
That said , I still have an 8+ yr. old MB Midnight Blue that I'm loath to part with. It's still OK