Fountain Pen Design

Function, Development, Construction and Fabrication

3 Simply Inks

During my early days of fiddling around with fountain pens (1978), I took ink as something given, just like air, gravity or life. One does not question it but some recognise it as an essential part of existence.

Concerning the ink’s chemistry, I found out that it had not changed since the 1920s or so. That’s another reason for not to worry about it but to respect it and leave it alone.
When something remains unchanged for such a long time, it must be good. Another reason? At school or later university, chemistry had not been my favourite subject, more so, it didn’t interest me the slightest but I got by and passed, just.

However, when I calibrated my test and measuring methods for the function of fountain pens, I stumbled more frequently at unexplainable idiosyncrasies; fluctuations where I did not expect them, or they occurred in unpredictable variations. Inevitably the question arose: “Was the ink responsible for these variations?” Believe you me, I surely didn’t like the sound of this question. It smelled of chemistry.

Setting up Ink Testing

After my first five-litre container of ink had emptied and I had started a new one, all previous test results had shifted in the same direction, sensible as well as the irregulars included. This aroused my suspicion that not all inks are the same. The easiest way of exploring this notion was to take samples out of several containers from the storeroom and compare them, not through chemical analysis but by applying a simple capillary test which would be much more relevant to my field of application.

From a local industrial glassblower, I acquired a bundle of glass tubes with inner diameters of 0.3, 0.4 and 0.5mm, about 100mm long. In order to find a ballpark figure, I measured the capillary rise with distilled water first and compared the results with the calculated values.

In the 0.5mm tubes, the water would rise between 50mm and 60mm, tightly distributed around the calculated value of 56mm.  Of course, the smaller diameters gave higher readings but with a wider spread. Since the distribution of results proved to be wider and had not increased proportionally with the higher reading, I assumed impurities inside the capillary; they were much more difficult to clean.

How does one clean the inside of a 0.5mm capillary?  I had already learned that consistent, thorough cleanliness of all equipment was of utmost importance. Therefore, I heat-treated the tubes at 800ºC in our toolmakers’ steel hardening oven. Then I pumped medical alcohol through the capillary to wash out the carbonised debris. A consecutive heat treatment dried out the alcohol for sure. Now I was sure there had not been any residue left inside, which could have affected the test results.

Then I measured the different inks, first of our supplier, the range of results of our ink was distributed around a mean value of 52mm it showed a variation of ±10mm or ±20%. It included the 56mm value of water. This means the total variation from the lowest to the highest value was 20mm or 40%, which had a huge influence on any test result when the ink was involved. In order to achieve sensible, useful test results, I knew then that I had to brew my own ink with a variation of less than 4%, if not better.

Inks of other manufacturers and brands recorded a mean value of 45mm and a variation of ±15mm (30-60mm = 66.7%!). It also revealed that the inks of the world had a lower surface tension.  Since the relationship between surface tension and capillarity is directly reverse proportional, the lower the surface tension, the higher the capillary rise.  Applied to a fountain pen, the lower the surface tension, the wetter, runnier the pen writes.

Such ink is more readily absorbed by photocopy paper, in “normal” writing paper it wicks in more thus spreads more thus leaves a wider trace.  It also dries faster, on paper as well as on the nib, the latter is a disadvantage which needs to be rectified through an extra-tight inner cap. More about this in the chapter Inner Cap.

As much as these findings fascinated me, I did not follow this path any further. It was too hypothetical. What I really needed to know at this point was, whether these variations were within the range a fountain pen could compensate for and still perform reliably. This marked the beginning of my interest in ink.

I had learned a lot about the behaviour of ink, not only ours but also the inks of other manufacturers. The variation of data was quite significant, but at the time I assumed that they all had valid reasons for their choices.


Still, following from the above, I improved my capillary measurement technique, acquired a surface tension measurement apparatus, a simple chromatography tester and a box of paper strips for pH value measurements. The latter proved very silly because all strips ended up being blue.  I had tried to avoid using an electric pH meter because they were difficult to clean and tune and quite expensive.

Even though, I had to beg the budgeting so that they would approve the purchase. I didn’t bother measuring viscosity because I knew already that ink was mainly water, therefore, I expected viscosity to vary only within a range so minimal to have any noteworthy impact on fountain pen function.

Ink in a Fountain Pen

Subsequently, I tested the inks in several fountain pens from various brands and noted that the laboratory ink tests correlated with the tests performed previously with the fountain pens in a practical situation. This time I assured that the fountain pens of one brand were filled with the ink of this brand all from the same bottle.

The tests performed were:

1.)    The time it took the fountain pen to start writing after the pen had been emptied with blotting paper and a new cartridge was inserted. (I had filled the cartridge with a syringe.) The test results were the time it took and the distance the nib moved over the paper before a line was written.

2.)    Measuring the holding capacity of the feed, by increasing the air volume in the cartridge so that ink was pushed into the feed without any usage of the ink for writing. The increase of air volume was achieved by raising the ambient temperature (in a laboratory oven). Measured was the temperature at which a drop fell off the nib. (Temperature difference and expansion of air are proportional)

3.)    Continuity and consistency of ink flow during writing on the circle writing machine, photo 1, further down.  This was a qualitative test.

4.)    Drop-test, where the fountain pen was dropped vertically, nib down, from a certain height (The test rig stopped the fall before the nib hit the platform!). The test rig was described previously, on page Initial Dry Start. Measured was the number of “drops” before the pen spat.

In summarising, when trialling the ink in the various pen tests, the results correlated sensibly with the characteristics of the different inks measured during the previous ink tests. This indicated that the two types of tests (ink-as-it-is test and ink-in-pen test) agreed with each other, which was absolutely crucial to be verified. Only now the development of the fountain pen components could start because this evidence provided me with an understanding of the ink-material relationship.

I realised that the ink’s consistency could increase the fountain pen’s performance and reliability, significantly.  I had learned to what extent the variation in the properties of the ink affected the function of a fountain pen.  This was a further incentive for my curiosity in ink.

Ink on Paper

Ink not only moves in fountain pens but also on paper. And papers come in a wide variation. Therefore, when measuring ink characteristics, I made use of chemical filter paper, which is guaranteed in porosity, chemical neutrality and certain surface quality.


Photo 1 — Circle writing Machine

For writing tests, as a norm, there was a paper used in the well-known circle-writing machine, a standard instrument found in every pen manufacturer’s laboratory and quality assurance rooms. Originally, it was designed for testing ball-pen refills and fibre pens. I added some variations so it could hold fountain pens.

In order to obtain some measurable information on ink’s behaviour on paper, I developed two more devices.

Ink Penetration on Paper

The first test was for the measurement of ink penetration speed on paper.  Under the lens of my stereo microscope on a microscope slide, I laid a 2mm wide filter paper strip where I had drawn two pencil lines, 10mm apart. While one end of the strip was dipped into the ink for a specific length for consistent absorption, I measured the time it took for the ink to progress from one mark to the other.

Ink Drying

The second test was for measuring the drying time when I applied a specific size drop on my standard filter paper from 10mm height. The drying time I determined by timing the change of reflection; wet ink has a much higher light reflection than dry. I noticed that an ordinary eyedropper was not accurate enough since the drop size varies too much with the ink’s surface characteristics, a variation I wanted to avoid.  Since a drop of water/ink is approximately 0.05ml, a long 0.5ml glass pipette with graduation worked quite well.


The test methods had to be fine-tuned so to obtain consistent results and determine the method’s tolerance deviation. Then one could decide whether and to what degree the variation of test results was caused by the tested material or by the test procedure itself.

I considered this task achieved after test results became predictable to some degree and correlated sensibly. All these tests were performed under constant temperature and humidity conditions. That’s why colleagues visit me on hot summer’s days more frequently and meetings were held here. In those days, even the boss had no air-conditioning in his office.

Variations of Ink

Focusing on our ink, I compared the measurements of subsequent deliveries from our ink supplier and found variations of the surface tension of ±12%, capillary action at ±8% and penetration speed of up to ±12%. The drying time would not vary much at all, and the pH value was almost constant, it ranged from 6 to 6.5, which means slightly acidic.

At that time, I considered these variations considerable, however, the question about their significance on the workings of a fountain pen I could not answer. Therefore, the best person to ask was our ink manufacturer who had reliably and constantly supplied our ink for decades, as I had been affirmed by purchasing.  I will write about this in the next chapter about the Making of Ink.


Amadeus W.

29 July 2014

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