Platinum’s pigment blue (from their "Classic" line) is a permanent blue fountain pen ink. This ink is waterproof, lightfast, flows well, and dries well.
This is a pigment ink, which means that if you leave this to dry in your pen, you’ll have a less-than-ideal afternoon when you go to clean it (it’s possible, just takes time). Perfectly safe for normal use, just flush your pens with tap water when changing inks.
