Got around to turning a cartridge fountain pen into an eye dropper pen. This is my first attempt, and so far, no leaks.............
So, did you fill an old cartridge with ink via the eye dropper, or did you just fill the end of the pen with ink via the eye dropper?
I didn't have an eye dropper, so I used that plastic bottle with a needle tip. Basically, you need an o-ring and silicone grease to seal the threads. No cartridge needed as the whole barrel of the pen is full of ink. This guide shows how with pics............ https://www.jetpens.com/blog/Pilot-Petit1-Fountain-Pen-Eyedropper-Conversion-Tutorial/pt/427
I bought a refillable thingy on Amazon a few years ago that fits into cartridge fountain pens. It was just a few bucks. I haven't tried it yet since I haven't used up the cartridge that came in the pen I bought.