Okay so I know this sounds strange (or normal for those who have been in the hobby for long enough), but I've received a lot of information regarding pigmented inks which have ended up being quite confusing.
The main source of confusion is in its behaviour on paper.
I've seen glowing reviews of inks such as Sailor nano inks, Montblanc Permanent Inks and Platinum Carbon ink, but then I've got some more confusing (not contradictory) information regarding the pigmented inks from Rohrer & Klingner regarding their behaviour on paper:
There is also confusion coming from my own experience: Speedball India ink (don't worry, I used it with a dip pen, no fountain pens were used) spread everywhere, feathered, and bled quite a bit, even on high quality paper such as Clairfontaine, and even cartridge paper. I could only be *salvaged* when I went to dilute it, and only ended up behaving when I had made it a 6:1 water:ink solution, producing a very sad, light grey. Rohrer & Klingner Sepia Calligraphy ink ended up misbehaving too, though it was slightly better than the Speedball.
May I please get some clarification on why this is?