I think I've stumbled upon an ink mix. Basically I had a Hero 336 filled with Pelikan 4001 Brilliant Black recently, and once the ink ran out, I just filled it again with 'Herlitz' (It's a cheap ink I keep in office). Here's the result: And it shades! It goes from blue to black depending on the amount of ink laid down on paper. Suddenly the flow has increased tremendously compared to the dry 4001. There's a nice color change on drying, when written it's a dark blue, when dry it's a blue-black. The scan shows it 'bluer' than it looks, but that may be dependent on the lighting conditions. Now I'm not sure if the combination is safe, but I think the pen's cheap enough to be disposable (I hope I don't end up doing that however).