What's inside a pen

Pen Anatomy 101

Ever wonder how a pen works? You've come to the "write" place. Knowing your pen anatomy is key to troubleshooting any issues that may occur during a lifetime of writing. Let's say you contact the manufacturer for some assistance with a problem - your pen is leaking. To help diagnose the problem, the service representative might ask, "where is the ink leaking from?" Instead of grasping for the part name, you confidently describe the pen and the issue becomes clear to the service representative. A simple solution is reached quickly and without having to ship the pen back.

True, not all warranty issues will be an easy fix. However, an experienced fountain pen enthusiast can troubleshoot simple issues that may arise. As you'll see in the diagram below, the pen is not a complicated tool like your modern smartphone.

Fountain Pen - Cartridge Fill


The nib is the heart of the fountain pen and the fulcrum of the writing experience. The imprint will tell you important details, such as the manufacturer and metal content of the nib. Gold nibs are struck with 14kt, 18kt or 21kt to designate the amount of gold content. A 14kt nib will have 58.5% pure gold and will often read "14kt <585>." A stainless steel nib will not have such a hallmark. Most nibs will have an engraving of the point size - EF for extra fine, F for fine, M for medium and so on. Sometimes, the nib size is engraved on the side of the nib or imprinted on the feed (Like the Aurora Optima or 88).

If your nib feels scratchy or skips while writing, you may have a nib alignment issue. To visually spot this issue, use a loupe or magnifying glass to examine the tipping material. From the front view, the tipping material should look like a sphere split in half. If both sides of the sphere don't match up, then the nib is out of alignment. Experienced fountain pen users that adjust and tune their own nibs can easily remedy the problem. If you have trouble using your pen and spot this problem, contact the shop, the respective manufacturer or a professional nib repair specialist (lovingly called a "nibmeister").

The slit of the nib carries ink from the feed's ink channel to the tipping material. Looking at the nib top-down, the width of the slit should taper from its start point at the breather hole all the way to the tipping material. Although most do, some nibs do not have a breather hole.


The feed controls the flow of ink from the main reservoir (supplied by a cartridge refill, converter, piston-mechanism, etc.) to the nib by capillary action. Feeds are designed to keep a steady stream of ink while you are writing and prevent the pen from leaking when you are not. The moment you touch nib to paper, the feed is channeling more ink to supply each stroke.


A fountain pen's section contains all the functional components, including the nib and feed. It is also the part that is usually gripped while writing. The housing is usually screwed into the section. The nib and feed are friction-fit into the housing. The fit should be snug to prevent any accidental leakage.


The pen barrel is like the "handle" of a pen. Inside, it contains the ink reservoir, like an ink cartridge, converter, or piston-fill mechanism, etc.


The cap keeps your pen from drying out and protects the nib while not in use. Sometime's called a "lid," the cap can either screw-on, snap-on, twist-lock, or magnetically attach. Most caps have a functional pocket clip that attaches to a thin piece of fabric and prevents the pen from rolling off a desk.


The cartridge is a plastic-walled ink capsule. It usually narrows at one end, where the mouth (or nipple) can be pierced by the back-end of the feed. Although cartridges are designed to be disposable, some opt to clean out and refill them using a blunt needle syringe.

Fountain Pen - Converter


A converter is like an empty cartridge that can refill itself using the screw-activated piston mechanism. The suction created by the piston moving from the front-end of the converter to the back will draw up the ink. Please note there are different types of converters that operate by pulling, pressing, squeezing or turning the mechanism.

Fountain Pen - Piston Fill


The piston-fill fountain pen operates similar to a converter. Instead of twisting the knob of the converter, you activate the internal piston by twisting the blind cap at the end of the pen barrel. The advantage of this type of pen is a larger ink capacity over cartridge/converter type pens.

Fountain Pen - Eyedropper


Eyedropper-fill fountain pens utilize the entire volume of the barrel, unencumbered by the presence of an internal filling mechanism. To fill, remove the section from the barrel and use an eyedropper to transfer ink from a bottle to the pen. It would be advisable to apply 100% pure silicone grease to the section threads to ensure a leak-proof seal.
Certain eyedropper pens like the Opus 88 feature a shut-off valve that helps seal-off the ink in the barrel from accessing the feed. This feature prevents the pen from leaking due to temperature or air pressure changes.

Fountain Pen - Vacuum Fill

Vacuum Fill:

The one-stroke filing mechanism operates using air pressure built by the movement of the piston rod. To fill, unscrew the blind cap and pull the piston back to extend the rod away from the barrel. Then, fully submerge the nib into a bottle of ink and press down on the blind cap all the way. Once the piston head reaches the forward end of the barrel, the internal pressure is released and a vacuum sends ink up into the barrel of the pen. Screwing the blind cap back in will activate the shut-off valve and seal-off the ink reservoir from the feed.

Ballpoint Pen Anatomy

Ballpoint Pen:

The ballpoint pen mode utilizes a replaceable ink cartridge designed for a retractable mechanism. Most ballpoint pens can be separated at one junction of the pen. To access the refill, the writer must find how the pen can be taken apart. It is best to follow the manufacturer's directions, which are usually included in the pen packaging. If not, you will probably find a video online.

Most ballpoint pens include a spring to provide tension for the retraction mechanism. Make sure to keep the spring when changing the refill of the pen.

Ballpoint pen retraction mechanisms vary. You might twist, slide, push, or click a part of the pen to activate the mechanism.

Rollerball Pen Anatomy

Rollerball Pen:

Rollerball pens are similar to ballpoint pens in that they use a replaceable ink cartridge. The main difference is the ink style. Where ballpoint pens use a paste ink that resists drying-out, the rollerball cartridge is liquid- or gel-based. The result is a smoother, richer, more fluid line. Since liquid ink tends to dry out and evaporate, most rollerball pens have a cap to keep the ink fresh.

Rollerball pens might also accept other types of refills like felt-tip, fine liner, or ballpoint type ink cartridges. Rollerball pens can be disassembled much like a cartridge/converter fountain pen. They are designed to have the section unscrewed from the barrel to access the refill.

Mechanical Pencil

Mechanical Pencil:

Mechanical pencils hold a stick of graphite lead at the tip of the pencil. Most have a click- or twist-action mechanism to propel the lead forward when the tip starts to wear down. A small cone-shaped shield protects the lead from accidental breakage.

Mechanical pencils are offered in different lead diameter sizes. Please note that only one lead size is compatible with your mechanical pencil. For example, a 0.7mm mechanical pencil can only accept 0.7mm leads. Petite erasers may also be attached to the pencil. Some erasers include a small needle to help clear lead jams at the tip.

Fountain Pen University

Welcome to our library of all our fountain pen knowledge. Get started by educating yourself in the basics here:

How to use a fountain pen - a beginner's guide

What is inside of a pen?

Ever wonder how a pen works? You've come to the "write" place. Get familiar with the anatomy of your pen using this helpful illustrated guide.

Explore the anatomy of a fountain pen.

How to use a fountain pen

What makes writing with a fountain pen such a fun and rewarding experience? We'll take you step-by-step so you can fully enjoy the pleasure of putting nib to paper.

See how to write with a fountain pen

How to fill a fountain pen

Inking your fountain pen should be easy and mess-free. We show you how.

Step-by-step fountain pen filling instructions

How to write with a fountain pen

Take your handwriting to the next level while using your fountain pen.

Learn how to write with a fountain pen.

How to Clean a Fountain Pen

Keep your nibs writing smoothly with our tips, tricks, and methods to clean fountain pens.

Here are the best practices in cleaning fountain pens.

Cartridge Converter Compatibility

Pen refills can be a little tricky. Make sure you're ordering the correct replacement cartridges using our handy reference.

Find the cartridge/converter compatibility chart here.

Best Pens For Lefties

Don't leave out the lefties! We discuss how a left-handed person can make the best use of fountain pens.

See the best pens (that don't smudge) for lefties here.

Fountain Pen Troubleshooting

Get that ink flowing again with these time-tested tips to troubleshoot your fountain pen.

Find out how to fix your fountain pen here.


All of your burning fountain pen questions answered here.

Browse our responses to frequently asked questions about pens here.

Customer Reviews

See which pens other writers are raving about.

Browse over 6,000 reviews on the Goldspot Pens website here.

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