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Every fountain pen needs a way to hold ink, and the method a pen uses shapes almost everything about owning it. It decides how much ink you carry, how easy it is to switch colors, how often you refill and whether you can use bottled ink at all. Pen makers use five main systems today: cartridges, converters, piston fillers, vacuum fillers and spring loaded pistons. This guide explains each one using real pens as examples, so you can choose the system that fits the way you write.
Cartridges: the simple start
A cartridge is a small sealed tube of ink. You push it onto the back of the nib section, the seal breaks and ink flows. When it runs dry, you pull it out and push in a new one. Nothing could be easier, and that is why most first fountain pens use them.
The Platinum Preppy is a classic example. Platinum describes it as a colorful, transparent pen where you can change the ink color simply by changing the cartridge, and its refill cartridge is listed as SPSQ-400. Its cap also uses Platinum's Slip & Seal mechanism, which the company says keeps the ink from drying out for a year with the cap closed. Read our full look at the Platinum Preppy for more.
Good for: beginners, travel and anyone who wants zero mess. Trade off: you are limited to the ink colors sold in that brand's cartridge format, and cartridges hold less ink than most built in systems.
Converters: bottled ink in a cartridge pen
A converter is a small refillable reservoir shaped like a cartridge. It fits into the same socket, but it has its own mechanism, usually a twisting piston, for drawing ink up from a bottle. In other words, it converts a cartridge pen into a bottle filled pen.
TWSBI's Traditional Converter is a typical design. TWSBI describes it as a traditional twist converter with a standard international top fitting, made to hold more ink than a typical converter. The important word there is fitting, so always check that a converter is listed as compatible with your pen before you buy it.
Good for: people who like cartridges for travel but want bottled ink at home. Trade off: filling from a bottle takes a minute longer than snapping in a fresh cartridge.
Piston fillers: the barrel is the tank
In a piston filler, the pen's barrel is the ink reservoir. A seal on a rod runs inside the barrel, and turning a knob at the end of the pen moves it up and down. Dip the nib in ink, turn the knob and the piston draws ink into the barrel. Because there is no separate cartridge or converter, a piston pen holds much more ink.
The TWSBI ECO is the friendliest example. TWSBI sums up filling it as unscrew the end cap, dip into ink and screw the end cap back. A step up is the TWSBI Diamond 580ALR, which TWSBI says holds about 30% more ink than its earlier 530 model. The Diamond 580 also has all detachable parts, so owners can take the pen apart and put it back together for cleaning and maintenance.
Good for: heavy writers, ink lovers and students taking long notes. Trade off: you need a bottle to refill, so a piston pen is less convenient if you run dry away from home.
Vacuum fillers: the biggest gulp
A vacuum filler works differently. Instead of turning a knob several times, you work a plunger rod in a single stroke while the nib sits in the ink, and the barrel fills.
The TWSBI Vac700R is the best known modern vacuum filler. TWSBI describes it simply: pull up, push down and your ink is filled. The pen also has an ink shut off valve. Closing it seals the barrel away from the nib, which TWSBI says makes the pen easy to carry without spills, and TWSBI notes the pen now delivers even more consistent ink flow when the valve is opened.
Good for: people who want maximum capacity and like the ritual of filling. Trade off: the valve has to be opened before long writing sessions, which takes a little getting used to.
Spring loaded pistons: one press
A newer design uses a spring to return the piston. Instead of turning a knob, you press a plunger down with the nib in the ink and let go. The spring pulls the piston back and ink is drawn in. The TWSBI GO uses this system, which TWSBI calls a spring loaded piston filling mechanism: simply press down and release.
Good for: anyone who wants bottled ink with the least fuss. Trade off: it is a newer, simpler mechanism, so it suits everyday writing more than collecting.
Which system should you choose?
- Brand new to fountain pens: start with a cartridge pen. You will learn how a nib feels without worrying about bottles.
- You love trying ink colors: pick a piston filler. A clear barrel shows off the ink and you can refill in seconds.
- You write for hours: a vacuum filler or a large piston pen means fewer refills.
- You want both: buy a cartridge pen that accepts a converter, and use whichever suits the day.
Filling tips for any system
Submerge the nib fully when you fill from a bottle. Once the pen is full, wipe the nib and section with a soft cloth. If you change ink colors, flush the pen with clean water until it runs clear. Keep the cap on when you are not writing, and store pens nib up when you carry them in a bag.
Paper matters too. Fountain pen ink is wetter than ballpoint ink, so smooth, heavier paper gives the cleanest lines. For more pens beyond TWSBI and Platinum, see our roundup of the best fountain pens.
For more desk tools we love, browse our desk and EDC picks.
