For my first black ink I wanted an extremely dark shade of black so after much research I decided to go with Noodler's Heart of Darkness or HOD as it is also known. Though there are darker blacks, Heart of Darkness is black enough for me and considering it is a generally well-behaved ink, I consider it a keeper. And it better well be, because I got the big 4.5oz bottle.
The 4.5oz bottle costs $19 and comes with a Platinum Preppy F nib fountain pen, converted to an eyedropper. The price per milliliter comes to $0.14 which is pretty good considering the free pen. Some people discredit the Preppy, claiming it is a cheap and worthless pen. Personally I like it because it is easy to fill up with ink, being an eyedropper, and the capacity is huge. It is also a wet and smooth writer. Its only flaw is that the F nib is not fine enough for how wet this pen writes.
One disadvantage of the 4.5oz bottles from Noodler's, and one that I didn't consider before I bought it, is that it's very hard to fill a non-eyedropper pen from it. I filled my Lamy AL-Star with the piston converter and it was difficult because of the very narrow diameter of the bottle neck.
Being a very black ink, Heart of Darkness is also extremely saturated. Interestingly enough, the Preppy lays a line that's as dark as a black hole but as you can see from the q-tip swabs, when applied to a larger surface, it looks lighter. There's no shading to speak of and that's how I like it. If it had any shading I wouldn't consider it a deep black.
I'm not a big paper buff so I tend to use cheap paper. As a result, this ink tends to bleed through significantly, to the extent that the reverse side sometimes becomes unusable. On very cheap paper there's also some feathering but not nearly enough to cause major issues. Now of course, with the Preppy which tends to write very wet, if I don't lift the nib quickly from the paper, the ink will feather a lot more.
HOD flows very nicely through the Preppy. On the paper I usually use it dries up very quickly, within a couple of seconds.
So far, this is the most water resistant ink I possess and in fact it is classified as "bulletproof", meaning that is is resistant to a whole plethora of chemicals that forgers might use to alter documents. This also means that it is totally waterproof. You can see from the sample that I've submerged it under running water for over a minute and nary an atom of this ink has been dislodged from the paper. The paper will dissolve under water long before the ink. If you want to write archival stuff, this is an excellent ink for it.
Noodler's Heart of Darkness may not be the best black ink out there but it's good enough for my needs. A good, bulletproof black ink should be in any fountain pen lover's arsenal. My bottle will last me a while and when it's over I might go with the same ink.
Here are two samples written on photocopier paper and a Staples journal with off-white paper, respectively.