Fountain Pen Design

Function, Development, Construction and Fabrication

04 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 its chemistry ink 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. Another reason? Chemistry had not been my favourite subject at school or university. I got by and passed.

Only later, after I had improved my testing and measuring methods for the function of fountain pens I arrived more frequently at idiosyncrasies; fluctuations where I did not expect them or they occurred in unpredictable variations.

Setting up Ink Testing

When my first container of ink had emptied and I had started a new one, the irregularities of all test results had all shifted in the same direction. This aroused my suspicion that inks aren’t inks at all. And the easiest way of finding out was to compare samples taken from many bottles and apply a simple capillary test.

From a local industrial glassblower, I acquired a bundle of glass tubes with inner diameters of 0.3mm, 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 showed 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 to clean the inside of a 0.5mm capillary?  I had already learned that consistent, sorrow cleanliness of all equipment was of utmost importance. Therefore, I had heat treated the tubes at 800º C in our toolmakers’ steel hardening oven to make sure there had not been any residue left inside, which could have affected the results.


Then I measured the different inks, first of our supplier and later those of other manufacturers. The range of results of our ink included the 56mm value of water and with a mean value of 52mm it showed a variation of ± 5mm.

Inks of other manufacturers and brands recorded a mean value at 45mm and a variation of ±15mm. It also revealed that the inks of the world had a lower surface tension (directly proportional to the risen height).

I did not follow this path any further. What I really I needed to know at this point was, whether the parameters are within a range for a fountain pen to 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 chromatograph and paper strips for pH value measurements. 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 results of the ink tests correlated with the tests performed with the fountain pens in a practical situation.

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.
  2. Measuring the holding capacity of the feed, as the air volume in the cartridge was increased and more ink was pushed into the feed without any usage of the ink
  3. Continuity and consistency of ink flow during writing
  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!).

In summarising it indicated that the behaviour of the ink in the various pen tests correlated sensibly with the characteristics of the different inks measured during the ink testing. This indicated that the two kinds of tests agreed with each other, which was absolutely crucial. Only now the development of the fountain pen components could start because it provided me with the understanding of the ink-material relationship.

I realised that the ink’s consistency would increase the fountain pen’s performance and reliability, significantly. I had learned to what degree the characteristics of the ink impacted on a fountain pen’s function. This was the beginning of 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, I referred to chemical filter paper, which is guaranteed in porosity, chemical neutrality and certain a surface quality.

DirectindustryFor 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. I used a 2mm wide filter paper strip where I had drawn two pencil lines, 20mm apart, laying horizontally on a microscope slice. Then I measured the time it took for the ink to progress from one mark to the other while one end of the strip was dipped into the ink for a specific length for consistent absorption.

Ink Drying

This test was for measuring the drying time where I applied a specific size drop on standard paper and timed 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 0.5ml glass pipette with graduation worked well.


The test methods had to be fine-tuned to obtain consistent results together with the method’s deviation. Then one could determine the degree the variation of test results referred to the tested material and which were caused by the test procedure itself.

The task was achieved when test results became somewhat predictable and correlated sensibly. All these tests were performed under constant temperature and humidity condition.

Variation 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.

Making Ink

When I contacted our supplier, they were quite reserved about informing me of their product, it was almost like saying: “No one has ever asked us these questions. Who are you to challenge us?” It almost felt like blasphemy.  I was told that they had been in the writing ink business for generations and a magician could have not been more secretive.

Luckily, the guys from dye manufacturers were much more open. Quite jovial, they informed me that writing ink would just be like dirty drinking water. It would be simply water containing about two percent dye, preservative and detergent and the worst being black with about five percent dye.

Then they were silent, like saying: “That’s all the information you need. You can go now.” I had not even got comfortable in my chair and the coffee was still too hot to drink. They had a laugh about my long face.

But they duly listened when I told them a few details about my calamities and findings and were quite happy to enlighten me in areas where I had expressed my uncertainty.

Sometimes, I played a bit dumb to gauge how much they knew about fountain pen ink. Once I had realised that their information backed up my findings, I trusted their advice.  I had to because I am not a chemist, after all.

They were the chemists and got quite excited when I related the physical characteristics of the ink with the function of fountain pens. And of course, we went into the magical field of speculation, researchers’ playground, the place where new ideas grow.


Two weeks later, much better equipped, I approached my hesitant ink manufacturer again.  This time, backed by the support of my findings and concrete data, I confronted them more astutely. Soon I realised that they had no idea what I was on about.

Once challenged and before losing face too much, they showed me their pH­‑meter, and they proudly took me to the place where they shovelled some kind of salt into 50-gallon drums, mixed it with a propeller on a long rod driven by an electric drill … their ink manufacturing plant. I was not impressed.

With the help of my friends from the dye manufacturing company, I began to make my own ink. After that, the results of my fountain pen testing showed less variation and therefore were more meaningful.

Just out of interest, I investigated tap water with my ink test methods and found that the changes of tap water accounted for of about a third of the variations I had measured with the ink.

The comparison of water samples with the most extensive variation were those taken on Monday morning after the water had been resting in the pipes for two days and those taken at evenings, which were the most stable.  During summer the morning-evening variations were larger than during the colder parts of the year.

In order to reduce the water’s impact, I used distilled water, initially, but realised later that boiling had enough calming effect for making ink of consistent enough quality.

Components of Ink

As you heard in my adventures with the dye chemists in 1978, fountain pen inks were considered as being mainly “like dirty water”, they are mostly water with small amounts of different additives, which give them colour, physical and paper adhesive characteristics. Since the most crucial ingredient is the dye, I would like to spend a bit more time on it and tell you the result of my studies.

Dyes have been around for some time, and there are many types, but here I only want to elaborate on dyes for fountain pen inks.  Ink dyes are coloured substances, which have the ability to compound with, meaning to adhere to paper.

This is not the result of a chemical reaction, but the dye and the paper fibre are held together by the attraction of adhesion. Adhesion describes the bonding between molecules of different materials.

Ink dye is dissolved in water. The water is the transport agent, which moves the dye inside the fountain pen, disperses it on the paper where it evaporates. At that time, the bond with the paper fibre is established.

In contrast, pigments are insoluble, they remain in suspension and have no affinity to the substrate (paper). Both dyes and pigments appear to the eye to possess a particular colour because they absorb most colours of the light spectrum and reflect only the wavelengths of the colour of their appearance.

Acetic Acid

Ink dyes we used thirty years ago belonged to the group of basic (high pH) dyes.  Their pH value is compensated by adding acetic acid  (as used in vinegar) at a very low concentration. Inks are generally slightly acidic, which causes the mildly pungent smell of the ink.  It assists the uptake of the dye onto the paper fibres and improves the stability of the ink and its colour.

If you want your ink to stain your paper more (have a more vibrant colour), add a few drops of that stuff. You will need to experiment because the type of paper has a considerable impact, in some cases, it can blot through.

Acetic acid is one of the oldest chemicals and was used already in alchemy. Before wine had not been treated chemically to the degree as it is today, it occurred naturally, especially in stored dry wines and was found as the clear crystals deposited either on the cork or at the bottom of the wine bottle.  Beside other acids, they are formed from tartaric acid (link to Wikipedia).

In German, it is known as Weinstein meaning wine-stone.  At about the concentration of domestic vinegar acetic acid has a pH of 2.4, thus quite acidic.

It is hygroscopic, which means it absorbs water from the environment, which unfortunately causes, at high humidity, ink to smudge again. Acid is also the reason why ink forms crystals when it dries out. Therefore, it is quite safe, just to add small amounts of water to the ink to dissolve them.

Recently, I was informed that non-ionic dyes (pH neutral) have become available, which are soluble in water.  This eliminates the need for adding acetic acid. However, I assume that another kind of acid will take over the task of improving the ink absorption into the paper.

Ethylene glycol

… or glycerine I added to effect the drying characteristic of ink.  And as I will elaborate in the chapter about the feed, the flow of the ink is mainly determined by the design of the feed and its physical properties and the physical characteristics of the ink but less its viscosity.  More about that, later.


… reduce the surface tension of fluids, and it is believed it is used in ink to increase its flow, and no doubt it would do that. I invite you to a test but use a fountain pen that you can miss. Just add the smallest amount of detergent (one grain of washing powder to a cartridge) into your ink.  It will end in a disaster, and your fountain pen may never work again.

The wettability of fountain pen components carrying ink is critical, though it is achieved by other means, which I will describe in the chapter on  Feeds made of Plastic.


… or other mild fungicides prevent mould from growing in ink. Therefore don’t drink ink; you could experience minor effects of poisoning (after about ten litres) and staining of your teeth.

Drying of Ink

For some time, I left my ink studies alone, but when I was developing the inner cap for my first fountain pen, I opened the ink books again. I realised how vital a certain degree of airtightness was, how difficult it was to obtain and maintain. I will talk about this in detail in the chapter The Cap (in process).

In order to reduce the susceptibility to drying while the ink was inside and on the pen, I asked myself, if there was an opportunity to reduce the ink’s drying time without affecting any other characteristic. Initially, this question sounds contradicting because when the ink hits the paper, you want it to dry as quickly as possible.

During the speculations mentioned above about ethylene glycol, I learned about organic, large molecule materials that have a strong dipole character. They are commonly used at the dry-cleaners such as ethanol, ethylene glycol, and glycerol. In that order, they also increase the viscosity (resistance to flow) when added to water but only at higher concentrations.

Amongst other conditions, evaporation depends on the size of a liquid’s molecules. Small ones puff off fast, bigger ones more slowly. Molecules can have opposite electric polarity at either end.  For some reason, such dipole molecules don’t like water, and eventually, they all meet at the water surface, sit tightly next to each other and create a molecule thick film.

I added gradually tiny amounts of ethylene glycol to the ink and recorded the drying times.  At some point, the drying time increased, spontaneously.  Concerning the fountain pen, adding ethylene glycol significantly prolonged the drying of ink at the air-exposed areas at the nib and feed.

And what effect did this have on the drying time on paper?

Sometimes, luck favours the sedulous, “Glück folgt dem Tüchtigen” as we say in Germany. Once the ink hits the paper it disperses quickly along all the fibres in reach, and the surface it covers is about 10 000 times than those air-exposed areas on a fountain pen, as mentioned before.

Therefore there are not enough large molecules present to act as a barrier and the ink (the water) can dry as quickly as before. Once I knew that I developed the optimum percentage of the additive, which makes a fountain pen less susceptible to drying out.

And mind you, drying of ink not only depends on evaporation but also on the ink absorption of the paper, which is highly influenced by the type and quality of the paper, which is another field of ancient alchemy, in which I have not entered, yet.


Thank you for reading ever so patiently. While writing the last few paragraphs, I felt the steady rising of your burning, inevitable question. After knowing all the things about ink flowing in a fountain pen and on paper, you want me to tell you what the perfect ink is?

The Perfect Ink

One could philosophise on this topic extensively, considering the function of the fountain pen, the ink’s behaviour on paper and what qualities the writer might perceive as desirable.

But as much as sitting on a mountaintop (or in a laboratory) can be a revealing exercise, alas, ultimately it may culminate in the insight that only God is perfect and even trying to approach perfection could arise his anger.

Nevertheless, eventually, all the logical and deductive reasoning will come to a sudden end when it does not correlate with the writer’s opinion and expectation.

All my research had come up with, was a kind of ink, which was manufactured to narrow standards and due to its chemical composition possessed specific physical characteristics, which supported the reliable writing of a fountain pen.

Was it perfect? Is it still perfect? I don’t know; I can say: It fulfilled all the requirements that I posted on it thereby facilitating the development of a fountain pen’s inner components.  And for sure, new demands will arise from the market or technology, then further action will be asked for.

What do Writers want?

This question is asked so quickly but to arrive at a few narrow, perhaps simple answers is quite a struggle, if not impossible. Writers’ needs and expectations differ widely. Writing is writing? By no means.

The dilemma is that for transforming needs into technical data and solutions, they must be specified.  Components can be designed without the knowledge of every detail but eventually, all the Ts must be crossed, and all the Is dotted.  Otherwise, they can’t be manufactured.

Let me summarise my collections of the recent finding in papers about ink, fountain pens, and discussion groups.  Here are some typical demands, critiques or facts on ink as expressed by the fountain pen enthusiasts.

Ink is smooth flowing

Good ink is sometimes characterised as smooth flowing. I would guess that this describes the quality of the fountain pen nib rather than the ink. What would be the opposite? Intermittent or inconsistent flow? This is undoubtedly caused by the fountain pen and not the ink.

Ink is dry (flowing?)

I have heard this expression often enough to find it intriguing, if not confusing when attempting to make technical sense out of this expression.  Once physical data are attached to it, one could respond in a technical way for its compensation if so desired.

Being an artistic (passionate) ingeneer, I find myself sucked into this web of opinion.  Firstly, dry ink means different things to different people.  It has been described as slow flowing (from the pen), as slow drying on the nib and fast drying on paper and exhibiting a rough or scratchy or not lubricated feel when the nib moves across the paper.

Since test parameters are missing I cannot suggest indisputable answers.  Most likely the various characteristics of dryness have different causes.  Slow flow from the pen may have something to do with the feed or nib design.  Slow drying on the nib and fast drying on paper suggests the presence of a surfactant in the ink.  A scratchy feel of the nib likely is caused by an improper adjustment of the tines, bad writing habits or the kind of paper.

Rounding up, the mentioned dryness has not much to do with the ink but rather the overall perception of the writing experience, towards which, many parameters contribute, in particular, the writer’s opinion.

Ink looks washed out

Characteristics named as washed out or its opposite, deep, one could call the degree of colour saturation, which has to do with the dye and dye concentration as well as the dispersion on/in the paper.  This may not be a quality criterion as the washed out appearance can be a desired choice of the ink manufacturer.  I have read comments of writers who enjoy the washed out look.

Some inks agree better with paper

Some inks agree better with certain papers than with others. The expression better can be quite personal, and I am not sure what the measuring criteria for such a characterisation could be. I would suggest that all components, which make up paper can be the causes of different behaviour.  Let’s start: the fibre material, the fibre size, the bonding material, the coating of the paper or paper fibre with certain surface active chemicals.

In the writing industry, as I mentioned before, we employed standardised paper for testing, as it has been used in a circle or infinity figure writing machine (see the upper part of this article). I would like to bet that almost every writing implement developed on this planet was optimised on that paper.

Of course, in the alchemy of ink production, everyone adds a few extra spices. This could be the cause of some inks performing differently from paper to paper. However, the concentration of chemicals in ink is so minute (dirty water), instead, I tend to blame the paper for the variations than the pens.

Even inks of the same brand behave differently

Having heard this question, I ask: “In what situation? In the fountain pen or on paper?” Using an old dip nib and holder provides a quick answer. If the ink line shows only variations on various paper types, then it’s the paper.  Alternatively, when a selection of samples of the ink of the same brand behave differently on the same paper, it’s the ink, obviously.

If the inks are from the same brand but of different colour or type (permanent/ regular) I would agree, “they would behave differently” …they would need to differ because of their different composition.

Nevertheless, any conscientious and reliable manufacturer would try to minimise such variations. If they happen within the same colour and type of ink, then I would suggest, the ink manufacturer has done a shoddy job. Finally, I would like you to consider that it is also a matter of degree when assessing something to be the same or at what stage is it different.  I ask: Is it measurable?

If the above dip-nib-and-holder test does not show any variation, then that different behaviour is caused by the fountain pen. Here, I would like to say: “Inks and pens are tuned to each other. It’s a fickle business, believe you me … been there, done it.”

Some fountain pens can compensate for variations of the ink’s characteristics better than others.  Primarily, it comes down to the feed, the size of the cartridge and the nib/feed/ink interface.  If one parameter of the equation is altered, it is highly possible the result would change, too. I have seen it.

For the ink the company offered at the time, blue, black, red and green, I made sure that the feed could compensate for the different characteristics without noticeable differences in appearance and writing behaviour. That’s my promise to you.

What colours should I use (or avoid)?

During my time as pen ingeneer, I used blue ink as a standard and optimisation criterion for component designs.  Other colours I tested later to ensure that the pen works with them. Blue ink was chosen because it was the most widely preferred. This information was based on the quantities of ink the company sold.


… has the lowest solid content, green and red some more, culminating with black, which has the highest. Using blue should result in (almost) maintenance free proper performance of the pen while inks with a high solid content (not only the dye but all the other additives) such as red, dark green and worst of all black would need cleaning every now and then.

Most important is: use your fountain pen. The more you write, the more you keep solid matter moving.

If your pen has plastic components that can be exposed to the ink, such as the front of the section or the inside of the cap, the intense colours such as red (it has the highest acidity) can stain the plastic permanently but should not affect the function of the fountain pen.

Black blacks

… (Indian ink) clog up the capillaries of the feed, and some irresponsible makers add surface reactant chemicals to the ink to prevent the clogging. That throws over the whole ink-flow regulating-mechanism of the feed. You will not be very happy.

If you want to use such ink, use a drafting pen with a tubular tip, they are designed for such applications.  Those with cartridges and feed clog up over night, even with the cap put on tightly.  The old nibs with a small reservoir attached to them work well and are easy to clean.  During my drafting time, as an ingeneering student in the sixties (how long ago was that?), after work, we rinsed the nibs in water and stuck stainless steel needles in the tube.

Good tubular nibs have a rounded, polished tungsten carbide tip and they even write reasonably well.  The expression of character is in the shape of the line, rather than the added dynamics in line width such a nib can provide.

Bright colours

… when written with broad nibbed pens, can appear blurry or blotchy because broad nibs need more ink per length of writing line. Bright colours have more solids in them; therefore, the flow can be reduced due to the capillary function of the feed.

By the way, I just learned (2016) that by some writers, irregularity (blotchiness) is considered an added feature of the character of writing.

Lighter colours

… develop their full richness on the paper and after drying because then the activity of the acetic acid is more noticeable. On top of that, the water in ink acts as a thinner and the wet ink appears pale.  Once the ink is absorbed by the paper and the water has dispersed and evaporated the colour appears denser.

Special inks

If you want to use iron gall inks, I learned that insiders use one called ESSRI … Ecclesiastic Stationary Supplies Registrar Ink.  It has been tested for not destroying your fountain pen, as long as the fountain pen is flushed, let’s say twice a year.  Other iron gall inks have been known to eat your pen’s interior away.  Still, if you want to use such ink only occasionally and for invisible inks, I would recommend using a dip nib on a holder.

Do I have to use the same brand of ink as the pen?

By now, this question is almost redundant (you know by now). However, allow me to state the obvious to free you of all doubt. The ink, feed, and nib tribunal are finely tuned to provide the writer with a reliable, satisfying pen performance. Once you have experienced this, you would not want to go for another brand.

Those, who see writing with ink as art, would respond like a painter to a change of paint or an old-time photographer to a change in film brand or photographic paper. Why would you want to?

As a clear answer: Yes you can, there may some consequences reducing, or at least changing the quality of writing performance.

When do pens need to be cleaned?

The only legitimate reason for cleaning or emptying a pen is when you decide not to use the pen for an extended period of time, which may be the case for fountain pen collectors. And obviously, when you change the colour. Otherwise, your pen should run maintenance free, unless the cap is not tight or something else is broken causing excessive drying of the ink.

If there is a need for cleaning, only use clean water, lukewarm works better.

When do I need to throw ink away?

If you detected a broken seal on your ink-bottle, observe whether there are stain marks on the side walls, inside the glass bottle. If yes, only water has evaporated since all the other components have a higher evaporation point.

Most likely, the characteristics of the ink have changed, and it may not work in your fountain pen and clog it up more easily. You can add (boiled, filtered) water up to the level of the stain marks inside the ink bottle.

After ink has remained unmoved for several years, you may find mould floating on top or stuck inside the lid. This is very uncommon. Even if the ink would be contaminated with some organic matter, the anti-fungal component should prevent mould from occurring. Even though, if it has moulded, I would not use it.

Again, after some time, you may notice grease puddles on the ink surface. They are caused by the large molecule components having separated out of the mixture.  Just shake the bottle, and they will disappear, no reason to discard the ink.

Do fountain pen inks vary in their flow characteristics?

Yes, they do.  If you swap inks in a given fountain pen, then the physical characteristics of the ink influence its flow through the feed, the way it flows out of the nib and its distribution and absorption on paper.

If the flow varies between batches of the same colour and manufacturer, I would have a serious talk with your vendor, or change brand.

If an ink is recognisably thick such as drafting ink, I recommend: don’t use it in your fountain pen.

What is the Perfect Ink?

Still, after all, which has been said, I can’t tell you, …only what it means to me: It is an ink with narrow performance characteristics, the ink, which helped me to design and fine-tune the fountain pen components I developed. Thus, it is the ink, which fits perfectly with this pen and all the subsequent fountain pens using the same components.

For a dedicated or aspiring fountain pen user it is worth trying out what works best for you; find your preferred combination of fountain pen, your choice of paper and ink.

What counts, ultimately: “Does the appearance of your written product fulfil your expectations?” If yes, then you have found your perfect ink, your perfect match.


Amadeus W.

29 July 2014

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