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How Does a Fountain Pen Work

How Does a Fountain Pen Work?


​How Does a Fountain Pen Work?

​With numerous types and brands of pens available on the market, the fountain pen is the oldest writing utensil that is still in use today. Making the ​switch to a fountain pen can sometimes be tricky. ​In this article, we'll explain in full detail the intricacies of how fountain pens work.

The short answer is a fountain pen uses capillary action to allow ink to pass through the ​pen. The ink flows from an internal reservoir through the feed structure to the nib using capillary action, or the movement of liquid in narrow spaces without the use of gravity. ​Its distinct nib design, a feed structure, and ink reservoir distinguish it from other writing ​instruments.

The combination of capillary action and the pen’s heavier weight require minimal pressure to transfer ink to paper, making the fountain pen ideal for those who write extensively in their personal ​or professional life.

Disassembled Pilot Metropolitan

​Disassembled Pilot Metropolitan, courtesy of Author

Capillary Action

​A fountain pen is a unique writing utensil that uses capillary action, a phenomenon first record by Leonardo da Vinci in 1490. The most familiar example of the capillary effect, also known as capillary motion or the capillary effect, is water spreading across a paper towel. As the physics behind a functioning fountain pen, capillary action regulates the flow of ink from an internal reservoir through a feed structure to the nib. Unlike other types of pens, like the ballpoint, that involve pressure from the fingers and hand to write, the fountain pen needs only to touch the page to promote ink flow.  

​Fountain Pen Nibs

​The nib, the most identifiable feature of the fountain pen, is the metal tip connected to the feed structure that manages the release of ink. Some nibs attach to the feed to make a single unit, known as the “nib and feed” or the nib collar. The nib and feed link to the ink reservoir inside the grip, which is the part of the pen held in the hand while writing. The nib and feed separate from the grip for complete cleaning or replacement. A clean nib and feed are necessary for capillary action to facilitate ink flow.

Anatomy of a Nib

The anatomy of the nib of a fountain pen. Photograph and diagram by Francis Finch, 2016. 

Several features contribute to the nib’s efficiency. On the surface, the tines are vertical grooves strengthened with a metal alloy, iridium, to maintain the shape and stability of the nib. Between the tines, a breather hole and a narrow passage called the ink slit work together to keep an even stream of ink to the tip of the nib. As the ink flows from the ink reservoir, the breather hole allows air to flow back inside the pen. The air that returns to the ink reservoir maintains the pen’s internal pressure and regulates the flow of ink from the nib to the page. Nibs vary in size, shape, and material, and they allow the user to customize the fountain pen to his/her personal writing style.

Fountain Pen Nib Sizes


​A photograph showing the various sizes of fountain pen nibs. Pictured from left to right: Pelikan M1000, Montblanc Meisterstuck, Parker Duofold Centennial, Waterman Carene, Pilot Custom Heritage 912, and the Lamy Dialog 3. Photograph by Ilkin Santak, April 3, 2018.

​​​​Nibs come in varying thicknesses: Extra Fine (EF), Fine (F), Medium (M), and Broad (B). Nibs on Japanese fountain pens have thinner tips than Western fountain pens because Asian characters are more intricate than the Western alphabet. Larger nibs are better for those with broader strokes in their handwriting because they transfer more ink to the page. This makes a smoother writing experience, but the ink can feather on low-quality paper. Smaller nibs are better for those with thinner, delicate strokes in their handwriting because they have lower ink output. They make slender lines similar to a gel or ballpoint pen on both high and low-quality paper.

Fountain Pen Nib Types 

​Types of Fountain Pen Nibs

Broad Nibs

  • ​Flat Edge
  • ​Inflexible
  • ​Thick vertical; thin horizontal

​Pointed Nibs

  • ​Rounded tip makes uniform lines
  • ​More pressure on downward stroke makes thicker lines

​​Calligraphy Nibs

  • ​Combination of both broad and pointed nib
  • ​Measured in millimeters
  • ​Have flat edge with rounded corners

Music Nibs

  • Designed for writing music
  • Flat edge with rounded corners similar to calligraphy nib
  • Two ink slits and three tines for more ink flow

There are multiple types of fountain pen nibs that vary in shape which alter the thickness of written lines when changing the direction of a stroke. Broad nibs, also known as a broad-edge or chisel-edged nibs, are an older design with a flat edge that creates thick vertical lines and thin horizontal lines. They have no flexibility regardless of the pressure used when writing.  

Pointed nibs have rounded tips that create uniform lines despite a change in the direction or angle. Applying pressure on a downward stroke separates the tines, releasing more ink into the ink slit and creating thicker written lines.

Calligraphy nibs, also known as stub nibs or italic nibs, have characteristics of both broad and pointed nibs that improve the appearance of your handwriting. Stub nibs measure in millimeters, with the popular sizes ranging between 0.9 mm and 1.5 mm. A 1.1 mm is similar to a fine tip nib, but a 1.5 mm makes thicker lines than a broad nib. They are smaller than a broad nib, but their chiseled edge with rounded corners glides along the page and creates thicker lines with vertical strokes.  

Like the calligraphy nib, the music nib is also a hybrid of the broad and pointed nibs. A broad nib with smooth edges that glides across the page, the shape of the music nib gives the writer more versatility in the strokes. Its rotation at a 90 degree angle serves the functional purpose to make the wider horizontal lines and thinner vertical lines. Holding the music nib at a high angle on the page creates the strokes necessary for recording music. Most music nibs have two ink slits and three tines to allow for more ink flow, and the feed is specifically designed to fit the nib.

Fountain Pen Nib Material

​Modern fountain pen nibs made of metal, most commonly steel or gold. Gold nibs are more pliable than steel, and they increase wettability, which is the process in which a liquid adheres to a solid. Softer gold nibs decrease surface tensions between the tip and the page, increasing the thickness of the lines by allowing ink to flow more freely. Sturdier metal alloys, such as tungsten, iridium, or osmium, strengthen the tip of the nib, but microscopic imperfections in these coated tips cause scratchiness or skipping.

How Does a Fountain Pen Work - Pilot Metropolitan Nib

​Steel nib of a Pilot Metropolitan, courtesy of Author

Nib Flexibility

Applying pressure can change the thickness of lines, but nibs were not made to withstand significant force. Pressing down on the nib during writing can damage or break the nib. Semi-flexible nibs allow the writer to use pressure to create thicker lines. Vintage fountain pens, formerly used in classroom handwriting lessons, had more flexible nibs, but modern fountain pens have stiffer nibs with little line variation.


​Fountain Pen Feed

​The feed is a rubber or a plastic tube that connects the reservoir to the ink slit that delivers ink to the nib using capillary action. The feed also allows air back inside the ink reservoir to prevent leakage. Fins, the grooves inside the grip, catch excess ink from traveling to the nib, reducing ink blotting. Many modern designs house the feed inside of the grip, hiding it from the naked eye.  

How to Fill a Fountain Pen

The fountain pen ink reservoir stores liquid or water-based ink that moves through the feed to the nib. Ink reservoirs vary in design, but they fall into two main categories that are refillable through cartridges or bottled ink. Disposable ink cartridges come pre-filled with ink, but they can be recharged with bottled ink when cleaned properly. Converters use a twisting or a pressure mechanism to pull ink from the bottle into the reservoir. Some cartridges and converters are proprietary for a specific type of pen. Manufacturer’s website and user manuals provide information on which cartridges and converters fit specific fountain pens.

How does a fountain pen work cartridge converter comparison

Comparison image of ink cartridge and converter for a Pilot Metropolitan. Photograph courtesy of the author

Fountain pens with an ink bladder, or an ink sac, fill with bottled ink when pressure is applied and released. Some ink reservoirs are built-in to the design of the pen, which have mechanisms that use low pressure to refill the ink reservoir. Fountain pens without a cartridge, converter, or a sac store ink in the barrel of the pen, sealed with an o-ring or silicone grease to avoid leaking.  


​Comparison image of cartridge/converter filling systems and built-in systems. From top to bottom: Parker Jotter, Parker Vector, Parker Frontier, and Parker “51.”, Courtesy of Fountain Pen Network

Bottled Fountain Pen Ink

Using bottled ink is more cost-effective and better for the environment. A fountain pen ink bottle refills an ink reservoir many times, making the cost per milliliter much less than purchasing disposable ink cartridges. Only use bottled ink specifically designed for fountain pens when refilling the ink reservoir. These dye-based, non-corrosive, and particle-free inks move more freely through the feed to the nib. Other pigmented or carbon inks have binding agents that clog the nib and feed.


​Photograph of Pelikan 4001 Brilliant Black bottled ink. Photograph courtesy of the author.

Many fountain pen owners mix bottled inks to create unique colors. Some inks have chemical reactions to each other, changing the pH level and altering the intended color. Do not mix an alcohol-based ink with a non-alcohol based ink; they are insoluble, and the ink mixture will coagulate and clog the feed.

​For more detailed information on inking or charging a fountain pen, read our article:
“​How to Put Ink in a Fountain Pen

Fountain Pen Benefits

The parts of a fountain pen all work together through capillary action to maintain a constant flow of ink without leakage. Fountain pens require maintenance, which will help your fountain pen last for years. They may have more upfront costs, but fountain pens are cheaper than disposable pens over time, and they produce less plastic waste.

There are many benefits to writing with a fountain pen compared to a disposable pen. Fountain pens require minimal effort to write so that you can use them for longer periods of time. Disposable ballpoint, gel, and rollerball pens require pressure to produce ink flow, which leads to ballpoint pen tenosynovitis, colloquially known as “writer’s cramp.” Continuous pressure on the fingers and palms contributes to Carpal Tunnel Syndrome, a painful condition that may require medical treatment or surgery to correct. To learn more about how fountain pens compare to ballpoint pens, please read our article ​entitled "Fountain Pens vs Ballpoint Pens."

Writing is an activity that encompasses both my personal and professional life, so having a quality pen relates directly to my productivity. I used disposable pens for years, suffering from aches and pains in my fingers. As a creature of habit, I was initially hesitant to invest in a fountain pen, but my reluctance was completely unwarranted. My hands ached less after a few days of daily use of my fountain pen and writing became a much more comfortable experience.

The monetary investment also influenced my fountain pen’s importance to me. Disposable pens were so readily available to me that I took them for granted; if I lost one, I could always replace it with another. The care and maintenance that I invest in my fountain pen make it even more valuable, so I always know its location and condition. Even if you are not a professional writer, using a fountain pen can improve the health of your hands and give you a reliable writing utensil that can enhance your daily life.


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