Thank you for sharing your result with Koh-i-Noor drawing ink, I see I have to get my hands on a bottle.
I'm on a hunt for the perfect waterproof black ink myself so I am trying everything I can get my hands on
.
(I would love to find an ink that can be used in fountain pens too, I love Pilot Iroshizuku Take-sumi and R+K Leipziger Schwarz but sadly they are not waterproof. I have heard the Higgins Calligraphy Ink can be used in fps? I want to try some of the waterproof Noodler's inks too.)
For dip pens I am currently using the R+K Antique Drawing Ink - I wouldn't recommend it, it's a fickle ink, very watery, clings to everything, yet it is not waterproof....
I received a bottle of rotring drawing ink yesterday (23ml - they are all that small), I have read&seen contradicting things about it's waterproofness online so I am waiting a full 48 hours before trying to smudge it with water... I am not expecting anything, I initially got it because I have heard that the bottles are great way to transport ink "on the go".
Anyway, I have found this link which shows the waterproofness of some other, maybe lesser known inks (some of these might be easier to get in Europe, sorry) which I found very interesting and hope some of you may find too:
http://blog.ywana.fr/2015/03/26/lencre-de-chine-tests-qualitatifs/First blotch is pure ink, second is waterproofness after drying overnight, third is an ink wash.