Fountain Pen Design

Function, Development, Construction and Fabrication

6.1 Captivating Cap

A Bit of History

Photo 1 — Early Quill Holder

To fully appreciate the history of an event or item, one needs to reminisce on the time before it all started, what brought it to existence and why did it remain. Understanding the cap, I start with a historical view as shown in photo 1 depicting a quill holder. Its function was to store the quills and to keep the inky bits away so that they would not soil the scene.

Photo 2 shows a cropped painting titled “Still Life with writing implements” painted by Cristoforo Munari around 1685. Somewhat in the centre, above the red box, you can see a tin with a perforated lid and two quills standing in it. One could expect that there is some soft material in the container, preventing the tip from damage.

Photo 2 — Italian Desk 1685

Moreover, I would like to draw your attention to the three holes in the lid. Assuming that in proper use this lid would be closed the drying of the ink was reduced.  Then the quills would be passed through one hole each which would keep them separated, hence, they would not stain each other and were easy to be picked up.

In the right dark bottom corner, a sander is lying on its side. By mistake, it’s a common belief that it is actually beach sand which was used for drying, in fact, it is gum sandrac made from the sap of a North African citrus tree; see Patricia Lovett website for details.

In the front of the red box, you see a penknife (for shaping the tip of the quill). Is it from this application where the “pen knife” received its name? (A native English speaker friend told me, it is. In German, this style of knife we call it Taschenmesser = pocket knife) Right to the penknife, the red stick in the foreground looks like seal wax and on the left of the knife is the stamp for the seal.

It appears that at the time, protection of the nib-tip and the drying of ink was of not much of a concern. I wonder, did they ever make caps for dip-nibs providing these functions in those days, 1685? It would appear pretty obvious, however, in 1952, when I was writing with a nib and holder, they still had not been around.

Photo 3 — Cap for Dip Nib

And here I found one, needless to say: “On the internet”. Photo 3 shows the outer protection part and even an inner cap for the reduction of the dry out. It comes with the Tachikawa Comic Pen Nib Holder Model 40. I am almost certain that there have been forerunners of this design idea, however, this one was the first I saw.

Photo 4 — Desk Pen

The pen holder in photo 4 demonstrates the next step of evolution towards the cap. Over and above the function of storing the pen, it also offers the protection of the nib and facilitates the picking up. From the picture, I cannot tell whether it also reduced dry out, but with the pen resting in the nib downward position in a presumably slightly sealed tube, it surely would prolong the drying.


Today, the cap is an essential, integral part of a fountain pen. Its functions are to protect the nib and feed from damage, and to prevent the ink from bleeding out into any wettable material the nib touches. Some caps incorporate an additional component, the inner cap, which seals the nib and thus slows down evaporation and the drying of the ink on the nib, which helps to maintain the pen’s readiness for writing.

For a uniform appearance, the cap is often made from the same material as the barrel. Usually, the cap can be stuck onto the end of the barrel, which elongates the pen, known as posting. Some writers, in particular those who like to hold the fountain pen further back, prefer this arrangement for reasons of balance and comfort.

The Components of a Cap

If there is anything typical about caps, I have chosen the one in photo 5 because it shows all the components.  During my recent reading, I found that people call the same components by different names. “What’s in a name? A rose does smell as sweet by any other name!” However, since we don’t deal with roses here, I have shown and named the parts for consistency in this chapter on the cap. It is a transparent cap of a Pelikan fountain pen, obviously.

There is the main part, the body of the cap (1), showing the inner thread (2). The metal enforcement ring (3) at the lower end absorbs any radial forces caused by misalignment when joining the cap and pen. Most screw-on caps have such a metal ring often adorned with the company logo to absorb the widening forces caused by the tightening of the thread, which can be high enough to crack a cap made from plastic.  In this example, the metal ring does not help much because the thread is further in, away from the ring.

Photo 5 — Components of a Cap

You can notice a thicker section (4) at the upper end for strengthening (and tool design) and several veins, which engage with the longitudinal grooves on the inner cap (5). They prevent the cap and inner cap from rotating relative to each other during assembly and when screwing the cap on or off.

Note, the open end of the inner cap is blunt, which indicates that the seal is formed with a flat area on the grip-section, a good construction but more about that later. The finial with the logo (6) comes off, it is put on later;  I guess the photographer placed it at this central position to give it importance.

The clip (8) is attached with a metal ring, called the clip screw (7) by engaging with the thread on the top end of the inner cap which secures the inner cap and the clip (8) to the cap body (1). As a final step, the finial (6) is joined to the inner cap which assures alignment with the clip since the clip does not appear to have any alignment features to lock it in a particular position with the cap.

Photo 6 — Inner Cap with Leaf Spring

Slide-on, slip-on or clip-on caps often include a spring of some shape, which holds the cap to the grip section. See photo 6 showing one of the better constructions.

This type of construction may provide some ease of operation to some fountain pen users, but for the task it performs.  It is quite elaborate (complicated) when compared with the simplicity of the design shown in photo 5 which is used in a screw-on cap.

I discuss the various styles at length on a separate page on the Fountain Pen Cap – The Inner Cap.


After this brief journey into history and general introduction, let’s look at the ingeneering aspects of the cap’s construction.  They are subdivided under several headings:

Cap Mechanics and Physics
The Inner Cap
The Clip
• The well-designed Cap … have to think about that a bit longer… or, after you have learned all about caps, show me what your thoughts are.

Above all: Enjoy!


Amadeus W.

09 January 2019

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