(This is a guest post by Tony. Whereabouts unknown.)
In my opinion, every fountain pen user should have at least one waterproof black ink in their collection (yes even you person-who-never-ever-uses-black-ink). Unfortunately, by last count there are approximately 137 different black fountain pen inks currently on the market that claim to be waterproof. Some are more waterproof than others. Some have additional properties over and above their waterproof-ness that you may or may not want. Toss in terms like "eternal", "bulletproof", "nano-pigment", along with a host of others and it becomes almost impossible to decide which one best suits your needs[1].
You could go out and buy samples of every single one and test them, but that takes time and money which could be better spent elsewhere. Wouldn't it be much more convenient if someone else did all that legwork for you? Well today is your lucky day: Brad has graciously allowed me some space on his web log to be that someone.
For this article I have assembled 17 common and readily-available waterproof black inks. The list is limited to inks I had on hand or could easily acquire (with my own money, thanks Brad) from site sponsor Vanness Pens. That said, I feel like this sample covers enough of the bases to be both useful and not overwhelming. I am also including three permanent black inks that are not for fountain pens to serve as a "control group". Each ink will be tested on 6 different types of paper known to be fountain pen friendly. For the best balance of presenting the inks' color properties I have decided to use a glass nib pen and a cotton swab[2]. Once the ink has been put to the page, I'll allow it to dry completely, take a "before" picture, and then submerge the sheet of paper in a basin of water for 5 minutes. Finally, after removal from the bath each page will air dry and have an "after" picture taken.