Platinum Classic: Citrus Black Ink

Citrus black is a permanent dark yellow-green ink that darkens as it dries. This ink is waterproof, lightfast, flows well, and dries well.

Platinum Citrus Black is a modern iron gall ink, which means it’s permanent (and becomes even more permanent as it darkens with time). If you leave this to dry in cheap steel nibs, it may corrode them (iron gall inks are acidic), but it’s perfectly safe for normal use.