Fountain Pen Design

Function, Development, Construction and Fabrication

Simply Inks

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

Concerning its chemistry, I had been told that ink had not changed since the 1920s or so. That’s another reason why to not worry about it, but rather to respect it and leave it alone.

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

Ink Testing

I noticed that my first 5-litre container of ink had emptied and I had started a new one all my 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 laboratory supplier, I acquired a bundle of quartz glass tubes with inner diameters of 0.3mm, 0.4 and 0.5mm, about 100mm long. In order to find a standard 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 range of distribution had not increased proportionally with the higher reading, I assumed impurities inside the capillary.

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 samples of our ink.  The mean value was 52mm with a variation of ±5mm.  Inks of other manufacturers and brands showed a mean value at about 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 was, whether the parameters are within a working range.

Testing in Fountain Pens

Subsequently, I tested the inks in several fountain pens from various brands and noted that the laboratory results correlated with the tests performed in a practical situation.

The tests performed were:

1. time to starting to write, after the pen had been emptied with blotting paper and a new cartridge was inserted.

2.  an ambient pressure test measuring the decreasing holding capacity of the feed, as the air volume in the cartridge, increased

3.  continuation and consistency of ink flow during writing

4.  drop test, where I dropped fountain pens from a certain height

The behaviour of the pens in the various tests correlated sensibly with the material testing of the inks.  The comparison of those inks, which I had used in multiple tests, with the results in the tubes, provided a considerable correlation.  I had realised to what degree the characteristics of the ink impacted on a fountain pen’s function.  This was the beginning of my curiosity in ink.

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 effect on fountain pen function.

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 surface quality.

DirectindustryFor writing tests, there is a standard paper used in the well-known circle-writing machine, a standard instrument found in every pen manufacturer’s laboratory and quality assurance rooms.  As it comes, it is designed to test ball-pen refills and fibre pens.  I added some variations so it can 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, where I measured the time between two marks on 2 millimetres wide filter paper strip, while one end of the strip was dipped into the ink for a specific length.

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 eyedropper was not accurate enough since the drop size depends on the ink’s characteristics.


The various test methods had to be fine-tuned in order to obtain consistent results. They were compared and optimised so that all results correlated sensibly, in an expectable way.  All these tests were performed under constant temperature and humidity condition.

I 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.

After that, I focused on our ink. I compared the measurements of one delivery to another and found the variation of the surface tension of ±12%, capillary action at ±8% and penetration rate of up to ±12%. The drying speed would not vary much at all, and the pH value was almost constant, it ranged from 6 to 6.5, which means slightly acidic.

This told me that the influence of ink consistency on fountain pen performance must be significant thus the reduction of its parameters’ variation would increase the fountain pen’s reliability.

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, one of the leading dye manufacturers (BASF) was just across the River Rhine, and those guys were much more helpful. Quite jovially they informed me that writing ink is “just like dirty water”. It’s mainly water, the blue ink containing about two percent dye, preservative and surfactants (detergent) and the ‘worst’ being black ink with about five percent.

They laughed about my long face. But they began to respect me a bit more after I had told them a few details about my calamities and were quite happy to enlighten me in areas where I had expressed my uncertainty.

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

They were 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 samples accounted for of about a third of the differences, which I had measured with the ink.

Water samples taken on Monday morning, after the water had been resting in the pipes for two days, showed the most extensive variation from the mean values.  Samples collected at evenings were the most constant. During summer the morning variations were the largest.  During the colder parts of the year, the evening values stayed within the error range of my devices.

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 before, fountain pen inks are 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 force 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, and then 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 as 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 fibres of the paper 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 substantial impact, in some cases, it can blot through.

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 of the feed.


… 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, 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) but only at higher concentrations.


Amongst other conditions, evaporation depends on the size of a liquid’s molecules. Small once puff off fast, bigger once 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 that stuff to ink observing its drying time.  At some point, the drying time increased, spontaneously.  Concerning the fountain pen, it significantly prolonged the drying of ink at the air exposed areas at the nib and feed.

And what effect does 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, the dipole molecules spread out over a larger area, and there are not enough available to act as a barrier.  Thus, the ink (the water) can dry as quickly as before. Once you know that you can develop the optimum percentage of the additive, which makes you 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 philosophy on this topic extensively, considering the function of the fountain pen, the ink’s behaviour on paper and what qualities the client might or should perceive as desirable.

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

Nevertheless, eventually, all the logical, deductive reasoning will come to an end when it does not correlate with the users’ opinion and expectation.

All my research has come up with, is a kind of ink, which is manufactured to narrow standards and due to its chemical composition possesses specific physical characteristics, which supports the reliable writing of a fountain pen.

Is it perfect? I don’t know; I can say: It fulfilled all the requirements I had posted on it. If new demands arise from the market or advances in technology, then further action may be asked for.

What Clients want

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

The dilemma is that transforming needs into technical solutions, they must be specified.  Any component can be designed without the knowledge of every detail, all the Ts must be crossed, and all the Is dotted.

Let me summarise 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 client.

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 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 most likely is caused by an improper adjustment of the tines or bad writing habits.

Rounding up I would like to say that 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 such 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.

Some inks agree better with paper

Some inks agree better with some papers than with others. The expression better can be quite personal, and I am not sure what the criteria of measurement could be for this. I would suggest that it is in the coating of the paper, bonding agent or paper fibre, with which certain surface active chemicals can deal better than with others.

In the writing industry, as I mentioned before, we use a standardised paper, produced for a circle or infinity figure writing machine (see the upper part of this article). I would like to bet that almost every quality writing implement developed on this planet was optimised for 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 on different papers different than others. The concentration of chemicals in ink is so minute (dirty water), instead, I tend to blame the paper for the variation than the pen.

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 variations on various paper types, then it’s the paper. If the inks are from the same brand but different colours or types (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 of ink, then I would suggest, the ink manufacturer does 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 and what is 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 interface.  If one parameter of the equation is changed, it is highly possible the result is different. I have seen it.

For the ink we 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 writing behaviour. That’s my promise to you.

What colours should I use (or avoid)?

Fountain pens are designed and optimised by using blue ink. Other colours are tested later to ensure that the pen works with them to a satisfactory degree. Blue ink is chosen because it is the most widely preferred by users, based on the quantities of ink we sold in various colours.


… 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 black and other inks with a high solid content (not dye but all the other additives) such as red and dark green 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, 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.  The old ones, which are fed with an eyedropper are quite good.  Those with cartridges and feed clog up always.  During my drafting time, in the sixties, we washed the nibs daily and stuck stainless steel needles in the tube over night.

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

Bright colours

… in broad nibbed pens are blurry or blotchy because broad nibbed pens need more ink per length of writing line. Bright colours have more solids in them; therefore, the flow is 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.  After drying the activity of the acetic acid is more noticeable. On top of that, the water in ink acts as a thinner for the appearance of the ink colour.  The colour appears denser once it is absorbed by the paper and the water has dispersed and evaporated.

Special inks

If you want to use iron gall inks, insiders use one called ESSRI by insiders … Ecclesiastic Stationary Supplies Registrar Ink.  It has been tested and as long as the fountain pen is flushed, let’s say twice a year.  Still, if you want to use it 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 good pen performance. Once you have experienced this, you would not want to go for another brand.

Those, who see writing with ink as an art, respond like a painter to a change of paint or an old-time photographer to a change in film brand or print paper material. 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. Another, if you want to change colour. Otherwise, your pen should run maintenance free, unless the cap is not tight or something else is broken causing subsequent 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.

This would change the characteristics of the ink, and it may not work in your fountain pen and clog it up more easily. You can add 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 to the lid. This is very uncommon for inks. Even if the ink would be contaminated with some organic matter, the anti-fungal component should prevent mould from occurring. Even though, if it does, I would not use it.

If the ink has been sitting in the bottle for 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 pen, then the physical characteristics of the ink influence the flow of ink inside the fountain pen, 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 you are looking for a fast-flowing ink, you will need to perform some trial and error experimenting, because the amount of ink coming out of your fountain pen depends on the three essentials, namely: ink AND feed and nib.

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 to my pen.

As a dedicated fountain pen user, which many people with fountain pens are or may want to become, it is worth trying out what works best for you and finding “Your preferred combination of fountain pen and your choice of paper and ink.”

What counts is the character of the writing instrument and what your written product looks like on paper.  Does it fulfil your expectation? If yes, then you have found your perfect ink, your perfect match.


Amadeus W.

29 July 2014

Continue reading about how nibs work on Nippy Nibs
go to Content

▲  top


2 thoughts on “Simply Inks

  1. Acetic acid concentrated or otherwise is a liquid, not a crystal at room temperature. The solid derived from wines is tartaric acid, iirc.

    I’ve been trying to formulate some inks from dye molecules. My pH testing suggests they are already slightly acidic i.e. pH 4-5 range and adding acid would in some cases alter the colors of the dyes. Many dyes are used for this purpose as pH indicators.


  2. I have read all entries twice already and I’d like to say I really appreciate your time and efforts to explain the fountain pen physics in such detail. It’s exciting and precious content!

    I would like to ask a question which has bothered me for some time. Every now and then a topic of ‘dry’ inks appears on the fountain pen forums ( I admit I myself prefer to use such inks mainly because of their behaviour on lesser quality paper: less feathering, minimal show-through and well defined thinner lines. This usually comes at the price of somehow restricted flow and you may need to use so-called wet pens. I assume that the main factor is the use of less surfactants but I can’t really find a definitive confirmation and not sure what is happening exactly in terms of physics. Do you think you could explain?


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s