An alternative look at ink wetness

[InesF]

On 2/4/2022 at 4:11 PM, dipper said:

Hydrostatic pressure in the nib slit, and in the ink under the nib tip, is slightly lower than atmospheric pressure. That pressure difference is what limits how far the ink can pull itself out onto the paper.

At the edges of the nib/paper contact patch the narrow space between nib and paper curves upwards and widens. (We are looking at small fractions of a millimetre here.) At the edges of the nib the ink meniscus  becomes less tightly curved, and so the ink cannot pull itself any further against atmospheric pressure. (line width measurement.)

+1 👍

Thank you! Once again, you found the right words. I tried to explain it my way, with a drawing (page 7, Nov 14th, 2021) and with a way weaker explanation.

 

On 2/4/2022 at 4:11 PM, dipper said:

So potentially A ) and B ) above may cancel each other out, giving a pen that writes equally wet with inks of different surface tensions?

... but only if the area under the touching nib causes the same "sucking" force as the bubble causes a "holding back" force.

 

From my experiments I learned, that paper can pull out the ink by the wick effect. In all cases, the absorbent paper caused more ink to be delivered than the "ink friendly" paper did. The surprise was in the hp inkjet photo paper that pulled out crazy amounts of ink (3 to 5 times more) by its capillary cavity structure. And the pens delivered happily. For all three paper types, pen and ink were the same, so was the "bubble" force and the surface under the tip.

 

The concept for explaining a fountain pens wetness needs some more complex considerations.

To say it with The Witcher: "Hmmmm" 🧟‍♀️

[LizEF]

Warning!  I have 68 pictures of 18 feeds. I'm not sure they're all interesting.  I won't get around to cropping them tonight, so I suspect they won't get posted until Monday.  I'll have to make a "feeds" album...

[txomsy]

I think it would be interesting to see them, at least to have them available somewhere for reference. Maybe a separate thread for feeds might be useful so feed info can be easily located, but I ain't sure, maybe here they'd fit best.

[dipper]

On 2/5/2022 at 4:51 PM, InesF said:

From my experiments I learned, that paper can pull out the ink by the wick effect. In all cases, the absorbent paper caused more ink to be delivered than the "ink friendly" paper

....so we could see the total wetness of a given ink,pen,paper combination as the sum of two components:

 

1) The amount of ink absorbed into the paper during the brief fraction of a second that the pen nib & the associated ink meniscus "wet patch" is passing over a point on the paper top surface.

 

2) The amount of ink left behind on top of the paper at the instant that the trailing edge of the nib and ink meniscus crosses over a point on the paper top surface, and the nib moves away from that point.

 

After the nib has moved on, leaving behind ink in the paper = 1) above, and ink on the paper = 2) above, the ink "on top" can continue to soak into the paper, but that does not change the total amount of ink that the pen has left behind.

 

Now components 1) and 2) cannot be separated in any experiments or ink reviews. They both happen together, and we can see only the total end result.

 

But we can separate them in our thinking......?

We may even give them names....? 

 

As a starter:

Component 1) must involve a fundamental property of the ink+paper combination. If the pen is not flow-limited then its only role is determining the time period for absorption, set by nib tip size and speed of movement.

 

Component 2) must involve a separate fundamental wetness property of the full combination of ink+paper+pen. (Without the absorbed component 1 being counted.)

 

Any ideas for names for wetness components 1) and 2) above?

 

Scientist / philosophers sometimes name things before knowing if they even exist, just so the subjects can be discussed. "Dark Matter", "Dark Energy", "Phlogiston", "The Aether", etc. (Though "the aether" has been dropped by modern mainstream science and has moved into Minecraft, apparently.)

[Karmachanic]

30 minutes ago, dipper said:

Phlogiston

 

Flowgiston, surely.

[LizEF]

37 minutes ago, dipper said:

After the nib has moved on, leaving behind ink in the paper = 1) above, and ink on the paper = 2) above, the ink "on top" can continue to soak into the paper, but that does not change the total amount of ink that the pen has left behind.

Are you saying a pen leaves behind the same amount of ink regardless of the type of paper?  (Just checking.)

[arcfide]

8 hours ago, LizEF said:

Are you saying a pen leaves behind the same amount of ink regardless of the type of paper? 

 

Definitely not true, even if that is the claim. Paper surface definitely affects the spread and therefore the pull of the ink from the nib. I think paper is included in both components, but just differently. 

[dipper]

20 hours ago, LizEF said:

Are you saying a pen leaves behind the same amount of ink regardless of the type of paper?  (Just checking.)

I hope I didn't say that 🤔🤔🤔.

 

I am trying to extend the scope and concepts of the language that we use when talking about wetness. So checking is good. Communication difficulties are to be expected initially.

 

I separated two components of wetness but did not invent any words for naming them. I just called them "1" and "2".

One point that may have caused a misunderstanding was a statement that I have reworded below. Italics show the part that may have been unclear previously.......

 

As the pen moves over the paper it leaves behind some total amount of ink. That total amount must be the sum of "1" and "2".

 

We need to separate "1" from "2" to help us talk about, and understand, what is going on in the brief moment that the pen nib is passing over a point on the paper surface.

 

After the nib has moved on, leaving some total amount of ink behind, the ink on top (2) will slowly soak down into the paper, mingling with the ink already in the paper (1). But that later soaking-in process does not  change the total amount of ink at that part of the ink line. The total stays the same, regardless of what proportion of "2" stays on top drying by evaporation, and what proportion eventually joins "1" down inside the paper.

 

[dipper]

12 hours ago, arcfide said:

I think paper is included in both components, but just differently. 

 

I agree 100%.

 

And I am delighted that we are sharing ideas with clarity and precision.

[LizEF]

49 minutes ago, dipper said:

But that later soaking-in process does not  change the total amount of ink at that part of the ink line. The total stays the same, regardless of what proportion of "2" stays on top drying by evaporation, and what proportion eventually joins "1" down inside the paper.

OK, I'm with you now!  I was pretty sure I was misunderstanding, but wasn't sure what else the text I quoted was saying. Now I'm sure.   Thanks!

[InesF]

On 2/6/2022 at 5:57 AM, LizEF said:

Warning!  I have 68 pictures of 18 feeds.

Yes @LizEF, please let us start a new thread about fountain pen feeds!

This can be huge (even if not possible to capture them all - haha, what am I thinking?)

[InesF]

On 2/7/2022 at 6:26 PM, dipper said:

After the nib has moved on, leaving behind ink in the paper = 1) above, and ink on the paper = 2) above, the ink "on top" can continue to soak into the paper, but that does not change the total amount of ink that the pen has left behind.

 

Now components 1) and 2) cannot be separated in any experiments or ink reviews. They both happen together, and we can see only the total end result.

Thank you @dipper!

For what?

For being able to find words for all those magic things happening while we are writing with a fountain pen and while we are busy thinking about the next letter, the next word or the next sentence!

 

Number 1 is way more paper than ink dependent, while number 2 is more related to ink properties (dominantly surface tension and a bit viscosity) and to the nib geometry.

 

On 2/7/2022 at 6:58 PM, Karmachanic said:

Flowgiston, surely.

Haha!  Yes, yes, yes!

 

17 hours ago, dipper said:

On 2/7/2022 at 7:05 PM, LizEF said:

Are you saying a pen leaves behind the same amount of ink regardless of the type of paper?  (Just checking.)

I hope I didn't say that 🤔🤔🤔.

I would say: the feed/nib/ink system is willing to provide the same amount of ink at its tip. If the paper takes it (sucking it up) or not is not part of the whole magic staff you hold in the writing hand.

 

17 hours ago, dipper said:

But that later soaking-in process does not  change the total amount of ink at that part of the ink line.

That's it, in another wording.

 

17 hours ago, dipper said:

And I am delighted that we are sharing ideas with clarity and precision.

That's the power of a community and people willing to discuss open-minded.

 

And that's exactly what makes any research job and any creative process so attractive!

[LizEF]

6 hours ago, InesF said:

Yes @LizEF, please let us start a new thread about fountain pen feeds!

This can be huge (even if not possible to capture them all - haha, what am I thinking?)

Actually, on review, they all seem quite boring.  Not sure they're worth posting at all.  (Also, a mini microscope - the USB / WiFi style rather than the real thing like you see in a lab - isn't the best thing for photographing feeds - the lighting is weird.)

[Sholom]

I go offline for a few weeks and all sorts of wisdom appear, especially from folks who remember their physics courses better than I do. This discussion is just amazing.

 

Some random thoughts: The role of paper adsorption balancing everything else that is going on explains why some of my pen/ink combinations seem especially sensitive to writing speed. (cheap paper and wet pens, mostly). In the case of dyes that actually react with the paper (a small minority of dyes), the speed of reaction would generally be slow enough that it would not have any additional effect on ink flow.  Patents pertaining to feeds and capillary design are I expect mostly ancient if they exist at all. The US Patent Office is often (but not always) very strict about what constitutes a "patentable invention" and something that is "obvious" from simple scientific considerations may be rejected on that basis. Small tweaks to nib and feed design are probably not patentable in the US for that and other reasons. Japan is generally much more willing to allow patenting modest modifications of existing systems so maybe somewhere in the Japanese patent literature there might be some insights into the history of feed design, but that literature requires both language fluency (technical language!) and special expertise in searching through the Japan patent system, both of which I lack.

[dipper]

7 hours ago, LizEF said:

Actually, on review, they all seem quite boring.  Not sure they're worth posting at all. 

 

Agreed.... for most feeds.

 

But then there are the weird ones. Those can be interesting.

For instance here is the most ugly, horribly-designed feed I have ever met:

Sailor Fude deMannen feed! Viewed from the underside. Nib would be on the right-hand side of photograph, grip section on the left and enclosing the ugly mess at centre of photograph.

 

I have three, bought at separate times over a period of two years, and they were all the same.

[dipper]

22 minutes ago, Sholom said:

Patents pertaining to feeds and capillary design are I expect mostly ancient if they exist at all.

 

There is actually an ongoing flow of patents related to fountain pen feed designs. It seems inventors just can't resist the urge.

 

How about making the feed out of two parts split vertically down the central axis?....

https://worldwide.espacenet.com/publicationDetails/biblio?DB=worldwide.espacenet.com&II=0&ND=3&adjacent=true&locale=en_EP&FT=D&date=19950809&CC=EP&NR=0665790A1&KC=A1

[Sholom]

Looks like the inventors were unable to generate any interest from pen makers since various country patents have (all?) lapsed. I've seen mushed feeds on cheaper pens (Osmiroid if memory serves) but on a Sailor??

[arcfide]

A mushed feed is one thing if it still delivers good ink flow and works well and a totally different thing if the malformation results in impeded flow. I have a F-C Music nib that was writing really dry and I couldn't get it to work for anything. I was about to give up on it, but I took the nib and feed apart and gave it a detailed once over, finding that there was a tone of excess plastic bits (probably from the cutting and/or molding) messing with the flow of the feed. It was quite a deal getting that feed cleaned up, but fortunately the design was simple enough that I could do it without things going sideways on me. I took a look at my Platinum Music nib feed to see if I could do anything with it to increase air/ink flow, and decided that I might not want to try given the relative complexity in there. 

[InesF]

12 hours ago, dipper said:

But then there are the weird ones. Those can be interesting.

For instance here is the most ugly, horribly-designed feed I have ever met:

Imaginary dialog:

Worker: Why are we here?

Salesman: People didn't like our newly designed fountain pen - it doesn't write well.

Technician, disassembling a pen: Oh, sh**! The air channel is too short. We have to produce new feeds.

Worker: We have already 150.000 in stock ...

Technician, aiming at the worker: Damm! Melt some more mm air channel in each of them with a hot wire.

Worker: OK, sir!

 

 

The nib/feed design and patent situation is foggy terrain. There are so many and only a few of them are relevant for what was or is really used - many others had never been realised. I red about 20 and flipped through about 30 more such patents and learned: next to nothing. However, I learned that no modern fountain pen is flow limited by its feed & nib system.

 

(But, OK, I didn't believe myself before an empirical prove)

[arcfide]

15 hours ago, InesF said:

However, I learned that no modern fountain pen is flow limited by its feed & nib system.

 

Can you define exactly what you mean by that?