It’s a popular question: Can I refill a fountain pen cartridge? The answer is a firm yes! You can, and you should.
You need very little in the way of materials:
This method makes use of a blunt-end syringe in order to refill the cartridge. This is necessary because the hole at the end of the cartridge is quite thin and fountain pen ink is quite viscous so refilling through any other means (eye dropper for example) is not possible.
The first thing you need to do before doing any of this is to inspect the cartridge you plan on refilling. Look for any visible cracks or wear. It’s unlikely you’ll find anything, but in the case that you do you’ll want toss the cartridge and use another.