I really like to draw with my fountain pens, it is a pleasure, the flow, line variation etc is very nice and gives a lot of possibilities.
The problem is that after the drawing is done I like to use watercolors, at that point the chosen ink is of great importance.
I tried everything, noodles, carbon, indian ink for fountain pens etc.
All those inks are waterproof, but not as good as indian ink. Indian ink is the best waterproof ink you will find, extremely black and with an special sheen.
Everyone in the forum discourages to use indian ink in fountain pens, but I couldn't resist trying it.
I bought a carbon pen, that is intended to use with carbon ink and filled it with indian ink.
Here are my findings.
Used with indian ink the flow is ok and does not clog
The cap is very airtight and the pen can be used without cleaning for at least two weeks
If the ink is not extremely dry, it can be cleaned with a mix of ammonia and water with no problem
I find it is a very good solution to use indian ink, at least with the carbon fountain pen.
I wouldn't recommend to use indian ink on fountain pens, but if you need it for your art work and you don't mind to do some maintenance and clean the pen often, it is a good option in my experience.
Any one has any other experiences or any other options????