Penexchange

Topic: Function of a fountain pen
Startbeitrag
Author: Sammy

Hello dear filler friends
I stumbled over this forum a few days ago.
Sifting through I read a few assumptions why pens sometimes don’t write right, or why they leak.
As the production of writing equipment is a part of my job (ball point pens, pencils, pencil extensions, fountain pens, and much more) and as I helped develop ink pen systems, I know that some of the assumptions are wrong.
That’s why I wrote up a short essay on the function system of a fountain pen, a few main problems and their solutions:

For a (good) functioning pen, you need (good) ink. Without it the best fountain pen won’t work. That is why I put ink at the beginning of my essay.

Every ink type, brand, color, has its own properties. These differ in the quality of the used ingredients and in the quality of the production. There are also great differences in the consistency of the ink. Besides that, the coarse ingredients need to be fine and not lumpy. These lumps can congest the ink feed.

The ink feed is the heart piece of a pen, as it bridges the gap between the ink cartridge and the converter or nib. The right amount of ink from the cartridge to the nib is essential. At the same time the right amount of air needs to be let into the cartridge.

The principle of the ink feed is based on the capillary reaction. It sucks the ink out of the cartridge. That is why you can write upside down for a longer time using a fountain pen, than you can using a ball point pen. If the feed lets too much air into the cartridge, the ink is sucked out without resistance and the pen drips.

If the feed lets too little air into the cartridge, the suction of the capillary does not suffice and this leads to interruptions in writing or even to a total stand-still of ink flow. This can be fixed by turning the converter farther in to balance the under-pressure of the cartridge. This is a short term solution that does not fix the core of the problem. Of course it can also be that the air hole of the feed is full of ink and dries, which narrows the flow passage of the air channel. This also leads to writing interruptions.

When the capillary channel gets too narrow, not enough ink can flow through and this again leads to writing interruptions. When it is too large, the suction strength is reduced and this leads to the same effect. There is also a big difference in the material choice for the ink feed. The two most common materials are hard rubber and plastic. The feed made of hard rubber is the first choice, but also the more expensive one. Hard rubber is pressed, so a fine forming such as a capillary channel is not possible. Therefore each must be made separately in a difficult process. (Modern CNC machines do this work today, but still need several minutes per part.) The cheaper solution is the plastic feed, where each part takes mere seconds to make. The exact shaping of the capillary channel is no big problem. Also a larger amount of plastic feeds is produced at once.

The hard rubber feed, on the other hand, has better surface material than the plastic feed. It is much better for the capillary effect. This difference can best be explained by the lotus effect. Here the ink pearls off the surface, and cannot stick. The surface itself is not wetted. This deficiency is often met with a wetter. Herein lays the problem: the wetter is washed off by the ink after a while, and the writing quality weakens.
For the hard rubber feed, no wetter is needed, and a constant writing quality is guaranteed. As long as two factors are obeyed: The constant quality and texture of the ink, as described earlier. And the good position of the nib and no deformation of it.

Another function of the ink feed (not by all) is the collecting of the ink. The more the ink cartridge gets empty, the larger the air bubble in the cartridge gets. This bubble can play a role in the leakage of the pen. The bubble expands in higher temperature or air pressure differences, or may decrease. If it gets warmer or the air pressure sinks (e.g. in an airplane), the bubble expands and ink flows out. This ink is saved in the nib section until it is used up (through writing) or the temperature sinks again resp. the air pressure rises, so the bubble decreases again and sucks the ink back in.

The nib also plays a vital role hereby. It also bases on the capillary function. If the nib is bent, the function of the capillaries is disrupted. Another possibility is that a bent nib no longer lies on the feed and the transmission of ink from the feed to the nib is interrupted. The nib might not lie on the feed from the very beginning.

By the way: the capillary channel of the feed ends at the hole in the nib. The nib, depending on its surface, can have a better or worse wetting, which influences the writing quality.
Another important point is the width of the nib. A fine nib needs a lot less ink than an extra wide nib does. This stands in a not unimportant connection to the amount of ink the capillaries of the feed transport. This again stands in connection to the size of the air channel. The ink consistency should also be kept in mind.

This leads one to the conclusion that only a perfect harmony of the single components results in perfect writing.

Concluding I want to assure you that slight malfunctions of one component do not necessarily result in a complete malfunction of the pen. This only happens when severe malfunctions appear. In my description of possible pen failures I assumed the worst cases possible.

These experiences and results derive from my cooperation in designing ink feeds. I can therefore not guarantee for completeness.

I hope you like what you read.
Many greetings

Sammy

Answer_01
Author: DanielH

Hello Sammy,

Thanks for the overview! Just recently I wondered where I could check out how a fountain pen actually works.

Maybe a few words on the wetter, as ideas of a chemist…

Plastic has a hydrophobic surface. This is due to the molecules, plastic is made of. In chemistry you differ between hydrophilic and hydrophobic molecules. Some molecules are both. Such molecules have a hydrophobic and a fat-phobic end. (They look like little sticks.) A classic example for such a molecule are all detergents, so all washing active substances such as soap. Their job is to get fat out of textures, and this is how it works: If you have a piece of cloth with fat stains on it, and you lay it in a detergent solution, then the detergent molecules orient themselves so their hydrophobic ends show towards the fat stain, and the hydrophilic ends show towards the water. The fat stain, which is taken alone hydrophobic, is capsulated with a hydro friendly shell and can thus be washed away better.
This should also work in a plastic feed. Its surface has similar attributes as fat, it is hydrophobic. If you put detergent on it the hydrophobic ends of the molecules will settle on the plastic and you get a surface that is made of hydrophilic ends of the molecules and can transport the ink better.
What kind of solution could you use as wetter? Probably the companies have their special mixtures that stick to the feed as long as possible. But generally speaking Tintenkuli’s wetter solution should work, as well.


…
…

@Sammy: Could you tell me what at what price level ebonite (hard rubber) feeds are used, and how you recognizes them?

Answer_02
Author: yoda


Hello
Thanks for all the information all of you, I am going to print it out and save it. You hardly ever get information like this, this compact.

To your question Daniel: I don’t think it is only a matter of price level. I can only say for sure that cheap pens have plastic feeds but you cannot say the same vice versa.

As far as I know, Montblanc only uses plastic feeds. Delta and Omas only use hard rubber feeds. (as far as I know). There are companies that think hard rubber is the worse choice, as the fine structure cannot be cut out so well. I like hard rubber feeds. But who knows, maybe someone will come along tomorrow and tell me Delta doesn’t use ebonite feeds and I was mistaken. I don’t know how to recognize them either, but I’d sure like to know.

Greetings
Hugo

Answer_03
Author: Sammy

I don’t know which wetter is used. I only helped in constructing the feed.

I know Omas pens have ebonite feeds, but I don’t know i fit counts for their whole product line.
Paragon gets feed of a different producer, because the old ones were so popular. The new Paragons definitely have hard rubber feeds

I don’t know how you tell the difference. Though I think plastic shines more than hard rubber. Maybe you could try smelling it. Hard rubber smells like sulphur.
Also, a good store should know these things about the products they sell.

About the price level, I go along with Yoda. I don’t think you can differ between hard rubber and plastic by that.

You also have to consider that the development and production of feeds is very expensive. Not many companies in Germany do that. Only two or three companies in all of Germany make hard rubber feeds. That is probably why even renowned companies choose the plastic feeds.
Greetings Sammy

Answer_04
Author: Tenryu

Doesn’t hard rubber have the disadvantage that it is brittle and the feed can break more easily?
I wonder if there really is a practical difference. I own a few Pelikans of different price levels, that are all made of plastic ink feeds and none of them have a bad ink flow (not even after many years of use).

Answer_05
Author: Sammy


A feed made of hard rubber is definitely more flexible than a plastic one. Anyway, the mechanical burden of a feed is very small.


P.S Hard rubber is also a kind of plastic.

Hard rubber has been used longer than plastic. The feeds alone are not the only point, as I wrote above. If all other parts work well then it won’t make that much of a difference what is used as a feed.

Greetings Sammy

Answer_06
Author: DanielH

About the smell of ebonite: I noticed that it has a certain smell with the corpus of my Cleo Ebonite (where the feed is supposed to be made of ebonite, as well, though it has a very fine lamellae) I discussed this with Sokko once, who also owns an ebonite from Cleo, and he couldn’t detect the smell. But I would say that ebonite looks matte when not polished. Anything else could probably be detected with an infra-red spectroscope but for that you do need special equipment.

Answer_07
Author: G-H-L

You actually don’t need special equipment. At least not when the ink feed is made of the same material as pipe mouth pieces.

Pipe mouth pieces have a softer bite than e.g. acrylic mouth pieces. This kind of test is hardly possible with pens.

If you leave a pipe open or in the bright sunlight, the ebonite mouth piece turns brown or grey. This can only be removed by polishing it.

Greetings
Gerhard

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