How Do Fountain Pens Work?

Fountain Pen 101: Part Two

Fountain pens are both elegantly simple in their principle and amazingly complex in their engineering. My goal in this video is to explain to you in detail all the different parts of a fountain pen, different filling mechanisms used, and how these all can influence how a fountain pen functions so you can better understanding the benefits and tradeoffs of different pen designs. This is the second video in our Fountain Pen 101 series, so if you missed the introduction to what a fountain pen is, check out the first video we made.

How fountain pens work

Fountain pens are all essentially the same in their basic function: they have an ink reservoir in some form or another inside the body of the pen. Ink flows through an ink channel inside a part of the pen that’s mostly unseen called the feed, and that ink flows down the feed through the grip of the pen to the nib, the metal part that you probably recognize as the defining characteristic of a fountain pen.

As you write, ink travels through a small slit cut in the nib and gathers at the tip which makes contact with the paper. The ink absorbs into the paper and the capillary action of this whole process allows the ink to flow continually as you write until it’s time to refill the pen.

Pilot Custom 74 fountain pen in blue uncapped on a desk

Parts of a fountain pen

Let’s cover some some basic terminology of a fountain pen that’ll help you understand better how they work, specifically the main parts of a pen.

Most fountain pens have a removable cap, usually with screw threads, and come apart into two main pieces: the cap, and the body. With normal writing, you’ll cap and uncap the pen, and you won’t need to break it down further until you clean or fill them. When you write you can either leave the pen uncapped, or post the cap onto the back of the pen if you like (not all pens have postable caps).

Infographic showing labeled parts of a fountain pen

The body of the pen is where most of the action happens. There are two main components here: the grip section, where you hold the pen while writing, and the barrel, which houses your reservoir of ink. Some pens have a barrel you can remove so you can access the ink reservoir inside, other pens house the ink directly in the barrel of the pen so it’s not removable; more on that when we get to the different filling mechanisms.

Infographic showing labeled parts of a fountain pen barrel


Parts of the Grip Section


The nib is the single-most defining feature of a fountain pen, and chances are even if you’ve never used one or even knew that it was called a nib, you’ve probably seen it used in artwork or icons as it’s so synonymous with fine writing.

Nibs are made of very specific metals, usually a high grade stainless steel or gold alloy. The tipping on a nib is often a super-hard wearing precious metal that’s designed to last decades of everyday writing. How the tipping is shaped and ground can give you a wide variety of line widths and writing feel.

Infographic labeling the parts of a fountain pen nib



The feed is the backbone of the fountain pen, crucial for both delivering ink from the reservoir to the nib, but also allowing air to replace that ink in the reservoir in perfect balance. Most of the feed is hidden inside the grip section of the pen, and you might see just the underside of it beneath the nib.

The design of feeds can vary greatly from one pen to another but they all perform the same function. The ink channel of a feed that facilitates the capillary action is incredibly precise, so some basic regular maintenance such as flushing your pen with lukewarm water once a month or in between ink color changes helps to keep your feed flowing as it was designed.

Infographic of labeled parts of a fountain pen feed



The grip of the pen is the part of the pen you’ll touch the most, as it’s what you hold when you write. The shape, size, and material of the grip varies greatly from one pen to another, and you’ll find you’ll gain a personal preference for some over others as you write more and more. What’s most important is that it’s something comfortable to you.

Some pens have a removable barrel with threads on the grip section that allow it to screw into the pen body, and allow removable ink reservoirs like cartridges or converters to attach onto the post located on the back of the feed inside the grip.

Infographic of labeled parts of a fountain pen section


Parts of the Cap

Pen caps vary in style but usually have a few common components. The lip/opening is the open end of the cap where the grip of the pen goes in when you’re capping it. Most fountain pens will have screw-threaded caps, and this is where you’ll see the threads inside the cap.

Infographic with labeled parts of a fountain pen cap


Some pens have centerbands to reinforce the opening of the cap, as this is often where pens have the most pressure put onto them. Many manufacturers use centerbands for reinforcing the cap threads as well as a design element, writing the name of the manufacturer or pen model or some other aesthetic element.


Most fountain pens have clips, and they can vary a lot in design. There’s usually a balance of function and form that these clips serve, helping hold the pen in your pocket as well as keeping them from rolling off your writing surface.


You’ve probably not heard of this term, but a finial is basically the end of a pen, either on the cap or barrel. This is often a place you’ll see manufacturer logos or design elements, especially as the finial on the cap is visible when in your pocket.

Insert (optional)

Some pens have inserts inside the cap specifically made to seal up the nib, so that water doesn’t evaporate from the ink as it sits in the pen over long periods of time.

For even more details on the parts of a fountain pen, you can check out our Anatomy of a Fountain Pen page.

Filling a fountain pen from an ink bottle

Filling and cleaning your pen

One of the most intimidating aspects of fountain pens is the filling and cleaning, but I promise it’s not all that scary. It’s actually one of the more personal and enjoyable aspects of fountain pen use once you get over the fear of it, but it does take some getting used to. You’ll get some ink on your fingers and maybe your desk and that’s okay, it all washes off.

While I’ll save the deeper details of filling and cleaning pens for other videos more dedicated to the subject, I want to at least give you an understanding of the main different types of filling mechanisms found in modern fountain pens.


Filling mechanisms

Fountain pens are amazing because of the fact the ink flows so freely through it, however, that freer flowing ink does mean the pen empties quicker than other types of pens. This means that as you use your fountain pens more and more, the particular type of filling mechanism will start to matter to you more as you’ll be interacting with it on a fairly regular basis and you’ll develop your own personal preferences.

The most popular filling mechanism in modern fountain pens is the cartridge/converter. They’re often more economical to produce so many of your starter fountain pens will have this filling type.


An ink cartridge is a small, disposable, sealed plastic reservoir that holds fountain pen ink. Some pen brands use their own proprietary style, though many use a standard international (short or long) size cartridge.

A cartridge-style fountain pen is filled by inserting one of these prefilled ink cartridges onto the back of the grip section. Its main advantage is convenience, though usually has a higher usage cost and more limited ink selection. Most cartridges hold enough ink to write several dozens of full pages of writing before needing to be replaced.

A blue fountain pen with parts separated on a white background

Pictured: LAMY safari fountain pen with an ink cartridge


The vast majority of pens that take cartridges will also accept a converter. A converter is a detachable, refillable ink reservoir that allows you to “convert” a pen designed for ink cartridges to one that can be filled with bottled ink. This alone is a huge benefit as there are many exciting inks that are only available in bottle form, and you also pay a lot less for bottled ink by volume, compared to cartridges. Fountain pens that have this converter option are often referred to as Cartridge/Converter pens.

Another added benefit to converters is that they’re replaceable, so if it gets damaged or stops working, you can get a new one pretty easily without needing any specialized knowledge, parts, or repairs. They do generally last a long time though. They’ll hold close to the same volume of ink as most cartridges, just know that not all pens that accept converters have them included with the pen, so make sure when you’re shopping you pay attention to whether a converter is included or an add-on purchase.

A pink fountain pen with a converter on a white background

Pictured: Sailor Pro Gear Slim fountain pen with a converter


Eyedropper fountain pens utilize the entire barrel as a reservoir for ink. Ink is filled directly into the barrel, allowing for some of the highest ink capacity of any style of pen. This can be done with a medicinal style eyedropper, hence the name, or a similar item like an ink syringe. Some pens are designed from the manufacturer to fill as eyedropper-only, meaning they do not accept a cartridge or converter, but most “eyedropper” pens are done as a conversion from a cartridge/converter design as sort of a “hack”. You get a large ink capacity, but sometimes there’s more of a risk of ink leaking or “burping” out of the feed, so this is a “use at your own risk” hack for many pens.

Filling a fountain pen with ink via eyedropper

Pictured: Diplomat Nexus fountain pen being filled via eyedropper


The piston-filler is a type of filling system that uses a retracting plunger inside the sealed pen barrel to draw ink into the pen. A piston filling mechanism has a similar design to a converter, except it utilizes the entire body of the pen to hold a larger volume of ink. Piston pens will usually hold significantly more ink than cartridge/converters, so they’re a favorite among many fountain pen users who write for long sessions. Piston pens can be a little less convenient when it comes time to clean it out or maintain and repair if needed.

A piston fountain pen on a white background

Pictured: TWSBI 580ALR fountain pen with a built-in internal piston mechanism


Vacuum-filling pens have a push-style piston that uses vacuum-pressure to fill the large pen body with ink. They seal the ink chamber when closed, making it more ideal for travel without risk of the ink leaking. These are some of the coolest designed filling mechanisms in my opinion, though there aren’t as many made with this style and they’re the most time consuming to clean.

Pilot Custom 823 vacuum fountain pen on a white background

Pictured: Pilot Custom 823 fountain pen with a vacuum-filling mechanism


I know that was a lot, and you’ll probably want to watch this video through a few times to make sure you got it all. But you’re starting to get a really solid foundation here, and I promise this is the hardest part, just grasping all these new terms and specific parts of the pens. Hang in there with me, if you can get these basics down, I promise you’re not very far from really starting to appreciate and enjoy fountain pens.

There will be more to come in the rest of the Fountain Pen 101 series, specifically how to clean and maintain your pens, more detail about nibs, and how to hold and actually write with your pens. In the meantime, you can check out the rest of our blog here for more great fountain pen education and fine writing products, and we have thousands of fountain pen videos on our YouTube channel.

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