Same here; some accidents with punctured cans in a backpack (coated fabric, watertight) led to loss of some notes written with normal blue ink. The stuff with with "Pelikan Fount India" (the archival ink they sell at the local shop) just went from "looks like laser-printed" to "looked like normal black fountain pen ink". No issues in a EF Kakuno. When dry, needs soaking/washing to un-stick much more severely than normal blue Lamy ink. Still fine for using more than once a week.

Ever tried Noodler's Bulletproof inks?

https://www.jetpens.com/blog/Noodler-s-Fountain-Pen-Inks-A-C...

I have Walnut in an Edison Collier and Dark Matter in an Eco at the moment. Walnut is "bulletproof."

Noodler's Ink Dark Matter is not. It is, however, a recreation of the official ink of the Manhattan Project. The ink wizard behind Noodler's was sent a bottle of the original Manhattan Project ink, and he chemically analyzed it, and reproduced it as closely as he could manage with modern components. Scientists and clerks were required to us it so any materials could be traced back to the project. The bottle has a picture of Oppenheimer on it.

Bottles of 54th Massachusetts and Heart of Darkness lurk in my closet waiting to come round in the rotation.

Avoid Baystate Blue!

Counterpoint: BSB is my favorite ink

Why?

It has a reputation of staining everything and notoriously difficult to clean out of some pens.

Baystate Blue also seems to be a cursed ink. It's not a matter of if you drop that bottle, but a matter of when.

It's a vibrant blue and is an archival ink. Cannot remove it and it's impossible to miss when you stain something with it. It'll stain your fingers for days.

If you drop it on a rug, or countertop or spill some while filling or cleaning a pen it's a major pain to clean up, if you can even clean it up.

It also has a reputation for staining the ink reservoir of your pen and if you have a fancy demonstrator to show off the ink you'll only ever see blue and none of the fun colors you're using.

Which is why Noodler's Ink issues a free fountain pen (The Charlie) with the 4.5 oz. eyedropper bottle. You can use that, or you dedicate an inexpensive pen, like a TWSBI Eco or a Pilot Metropolitan to the ink. (Many do this.)

My favorite fountain pen inks, especially ones that stand up to watercolors:

Platinum Carbon Black, Rohrer & Klingner sketchINK, and any of the De Atramentis Document Inks.

Noodler's ink is fun (especially the Lexington Grey) but not very water resistant in my experience.

Many of the bulletproof Noodler's Ink inks will "move" in water, but the stuff that is soaked into the paper is absolutely bonded to the cellulose. This means your writing will remain clearly legible. Some of the bulletproof inks do not budge at all once dry.

The thing about them, however, is they are all dye-based inks, so they're generally safe for all modern fountain pens.

The sketchINK series is a pigment-based ink, if memory serves, so better for dip or brush pens. Platinum Carbon Black is a bit special. It's a nano-pigment black ink. Will not budge, and works well in fountain pens. I also hear great things about the Document Inks.

One of these days I'll pick up a few bottles of the different Document inks (which are designed to be mixed with each other). For black ink, though, my heart belongs to Noodler's Ink Heart of Darkness, followed by Dark Matter.

Rohrer & Klingner iron gall inks (Salix and Scabiosa) are on my list as well... one day.