[NullInvictus]

Notably Diamine’s Registrar Ink and Rohrer & Klingner’s Eisen-Gallus-Tinte inks are relatively easy brands of iron gall ink to acquire and the modern formulas are less harsh and useable in fountain pens.

They’re nice in that they’re naturally waterproof inks. They’re a bit on the dry side though in terms of flow.