I use a syringe to refill cartridges from whatever bottle of ink I want to use. The cartridges can be reused many many times.

edit: lol, if I had reloaded the page before commenting, I would have seen all of these people saying the same thing!

> edit: [...]

Every time fountain pens come up on HN I'm amazed how active the discussion gets.

I mean, how important is the pen as a tool to human history? The pen is one of the most important human inventions and the fountain pen is by far the coolest version of it :P

I am similarly surprised at the number of technical people who prefer one or more of the following:

* Fountain pens * Mechanical watches * Cars with clutches

Most pens either ship with or will work with a piston converter. You don't need to mod a pen just to use inks other than those available in compatible cartridges.

E.g.,

https://duckduckgo.com/?t=ffab&q=fountain+pen+piston+convert...

A lot of people just reuse empty cartridges a few times by refilling them with a blunt tip syringe (sold by most online pen/ink shops), using whatever ink they want.

It is far easier to get a blunt nosed syringe for $0.10 (not sharpened for medical use) and use it to quickly and cleanly refill cartridges with whatever ink you want.

For a video visualization of how this works, Brian Goulet (who runs a popular fountain pen YouTube channel) published a tutorial on cartridge cleaning and refills: https://youtu.be/QloRQWHe5Gk?t=301

Isn't it even EASIER to get a converter?