An alternative look at ink wetness

[arcfide]

If anyone wants to play directly with what happens when you change the surface tension of an ink, pick up some White Lightning from Vaness and progressively increase the dosage. You can see, especially with inks that write dry and "flat" on the page with broad nibs, that there is a curve where the inks begin to become more and more wet with more ink pooling on the surface, until there's a point at which they just become detergent and bleed into the paper and feather like mad. 

 

Another interesting feature to look at, which is a cheap and easy way to judge relative ink features, is to tip the bottle upside down, then open the cap and see how the ink spreads on the cap seal. 

[LizEF]

33 minutes ago, arcfide said:

Another interesting feature to look at, which is a cheap and easy way to judge relative ink features, is to tip the bottle upside down, then open the cap and see how the ink spreads on the cap seal. 

I'm thinking maybe you should tip the bottle right side up again before opening the cap - especially if it's Baystate Blue...

[Karmachanic]

3 hours ago, arcfide said:

become more and more wet

 

More wetter?

[RJS]

4 hours ago, arcfide said:

If anyone wants to play directly with what happens when you change the surface tension of an ink, pick up some White Lightning from Vaness and progressively increase the dosage. You can see, especially with inks that write dry and "flat" on the page with broad nibs, that there is a curve where the inks begin to become more and more wet with more ink pooling on the surface, until there's a point at which they just become detergent and bleed into the paper and feather like mad. 

 

Another interesting feature to look at, which is a cheap and easy way to judge relative ink features, is to tip the bottle upside down, then open the cap and see how the ink spreads on the cap seal. 

What is interesting to me is that a wet/low surface tension ink isn't always required to take what appears to be a dry writing pen (with fine nib) and make it feel like it's no longer a dry writer. Though a low surface tension ink in a fire hose of a pen does sound like a recipe for disaster.

[LizEF]

5 hours ago, RJS said:

feel

Feel is all about lubrication, not flow, especially in finer nibs.  (Though I will concede that more flow = more of whatever lubricant may be present = better feel.  But the wetness is an indirect contributor, serving only to increase the volume of lubricant. A lubricant-free wet ink is still going to feel icky, especially in your Japanese UEF nib.)

 

IMO, flow (wetness / dryness) is about two things: appearance -being able to visually discern the volume coming out of the pen is more than with other inks, either because of the appearance of wetness or because the ink comes out in a fatter line, or sinks deeper into the paper; and consistency over the long term - being able to write and write and write and write until the cows come home, and the ink never fades or stops flowing (so long as the pen still has ink in it).  I don't believe one can feel this; one has to observe it visually.

[LizEF]

Just now, LizEF said:

I don't believe one can feel this; one has to observe it visually.

I do think it's actually quite hard to learn to distinguish since dry inks are often poorly-lubricated and wet inks are generally well-lubricated, and therefore an awful lot of us talk about flow and lubrication as if they were the same thing.  The indirect relationship makes this understandable.

 

In fact, I would trust my own assessment of lubrication much more than my assessment of flow (really wish I'd started with the ideas I now have about how to measure flow, but hindsight...).

[Karmachanic]

20 minutes ago, LizEF said:

dry inks are often poorly-lubricated

 

Glycerine is my friend.

[LizEF]

24 minutes ago, Karmachanic said:

Glycerine is my friend.

[RJS]

2 hours ago, LizEF said:

Feel is all about lubrication, not flow, especially in finer nibs.  (Though I will concede that more flow = more of whatever lubricant may be present = better feel.  But the wetness is an indirect contributor, serving only to increase the volume of lubricant. A lubricant-free wet ink is still going to feel icky, especially in your Japanese UEF nib.)

 

IMO, flow (wetness / dryness) is about two things: appearance -being able to visually discern the volume coming out of the pen is more than with other inks, either because of the appearance of wetness or because the ink comes out in a fatter line, or sinks deeper into the paper; and consistency over the long term - being able to write and write and write and write until the cows come home, and the ink never fades or stops flowing (so long as the pen still has ink in it).  I don't believe one can feel this; one has to observe it visually.

To add to the wet/dry/lubricated complexity,  you get inks that dry very quickly in the feed, those that tend to skip on smooth/coated paper, and those that hard start and need prompting. All of those make an ink "feel" dry, and there's more going on there than flow or lubrication issues.

[RJS]

I forgot about a TWSBI pen I had filled with Monteverde Horizon Blue, one of my favourite inks. 3-4 months later it still wrote immediately, though clearly it contained less ink than it had. What was weird, when I wrote two pages with it, was how much wetter it wrote than usual- it spread more and soaked through the paper. Normally I expect the opposite, as inks seem to become thicker/drier/more lubricated as they evaporate. What has everyone else found in similar situations?

[LizEF]

44 minutes ago, RJS said:

To add to the wet/dry/lubricated complexity,  you get inks that dry very quickly in the feed, those that tend to skip on smooth/coated paper, and those that hard start and need prompting. All of those make an ink "feel" dry, and there's more going on there than flow or lubrication issues.

Yes, though I think it's more that they make an ink seem dry, based on behavior, and feel unlubricated (which a dry nib is, by definition) because the ink isn't flowing.

 

Though I don't think any ink is responsible for hard starts - I think that is the nib (or perhaps the pen not sealing well so that the ink is already dry when you uncap).  And I'm undecided on the smooth / hard paper problem - I don't think ink alone can account for this, but I'm undecided whether I believe it contributes (I need to ponder this some more).

 

So much to study, so little time. I think those that dry too quickly on the nib are dry, and probably quite viscous.  Usually they're heavily saturated with dye or pigment.  More pondering, but I gots work to do... 😕

[LizEF]

47 minutes ago, RJS said:

I forgot about a TWSBI pen I had filled with Monteverde Horizon Blue, one of my favourite inks. 3-4 months later it still wrote immediately, though clearly it contained less ink than it had. What was weird, when I wrote two pages with it, was how much wetter it wrote than usual- it spread more and soaked through the paper. Normally I expect the opposite, as inks seem to become thicker/drier/more lubricated as they evaporate. What has everyone else found in similar situations?

I think this warrants scientific exploration - assuming you still have the pen, the ink, and an accurate scale / balance for weighing it.

[RJS]

1 hour ago, LizEF said:

Yes, though I think it's more that they make an ink seem dry, based on behavior, and feel unlubricated (which a dry nib is, by definition) because the ink isn't flowing.

 

Though I don't think any ink is responsible for hard starts - I think that is the nib (or perhaps the pen not sealing well so that the ink is already dry when you uncap).  And I'm undecided on the smooth / hard paper problem - I don't think ink alone can account for this, but I'm undecided whether I believe it contributes (I need to ponder this some more).

 

So much to study, so little time. I think those that dry too quickly on the nib are dry, and probably quite viscous.  Usually they're heavily saturated with dye or pigment.  More pondering, but I gots work to do... 😕

You're right, they merely seem dry due to their bad behaviour. Some inks do seem much more prone to drying out quickly in pens that have less effective seals, I think- Platinum Carbon Black did that to me this week.

In terms of skipping on smooth writing paper, that seems to occur in inks with particularly heavy dye loads combined with nibs that have little tooth. As someone who spent about 30 years primarily writing with Pilot BB, which didn't misbehave in my smooth writing Pilot pens, I always had little tolerance for this.

[RJS]

1 hour ago, LizEF said:

I think this warrants scientific exploration - assuming you still have the pen, the ink, and an accurate scale / balance for weighing it.

I have the pen and it still has a smidgen of ink left inside it. No accurate scales, though, just the ordinary kitchen variety. I do own more of the ink, and it's in a few pens- maybe I'll let them evaporate down and see what happens there....

[LizEF]

1 hour ago, RJS said:

I have the pen and it still has a smidgen of ink left inside it. No accurate scales, though, just the ordinary kitchen variety. I do own more of the ink, and it's in a few pens- maybe I'll let them evaporate down and see what happens there....

[dipper]

On 6/8/2021 at 10:59 PM, Sholom said:

surface tension in this context is really a proxy (generally a pretty good one) for interfacial tension, specifically between ink and nib and ink and paper......

 

Sholom has commented a couple of times previously in this thread, as the example quoted above. A wise and timely thought, in the earlier stages of InesF's experiment design and execution.

 

Until now it has been difficult to see how the deeper complexity of surface tensions might apply to this experimental study. However various recent posts prompted me to recall Sholom's notes. Possibly now is the time to dig a bit deeper into what this "tension" thing is?

 

Here is how I see it..... welcoming corrections, disagreement, etc.

 

1.) Surface Tension is commonly seen in action all around us, but is difficult to understand fully, and difficult to talk about without getting too nerdy for most readers.

There are plenty of special Physics terms used. There is also some university-level Mathematics involved. It can all become very scary.

 

Don't Panic.  (Douglas Adams 1978.) In the points written below all nerdyness has been suppressed. Wording may be vague or long-winded as a result.

 

2.) Liquids do weird things. Inks are liquids. One weird thing is that liquids behave as-if there is a skin stretched over the surface of the liquid. Unlike the real skin of a toy baloon the imaginary "skin" at the surface of a liquid pulls with a constant force however far it gets stretched out. Weird eh?

 

3.) The size of the tension force in the skin of a liquid depends on what the liquid is made of. The size of the force varies with temperature. The size of the force also depends on what other material the liquid is in contact with.

 

4.) In general usage when we quote a value for "the surface tension of .... (water, say)", that means the size of the force at a surface with liquid on one side and air + a bit of water vapour on the other side.

A liquid in contact with glass, or metal, or plastic, or ebonite, will have different sizes of tension force in the liquid surface that is laying "on" the solid.

For example, a raindrop on a window pane has one tension acting all over its curved surface that is in contact with air, but some different value of tension in the flat surface touching the glass.

The various tension forces in the surfaces of liquids in contact with a selection of different solids includes this intriguing case: The tension in the surface of plain water in contact with pure silver metal is almost exactly zero! Take your best silver goblet ( 😉 or thimble or inkwell), half-fill it with tap water, observe the curve in the water/air surface where it meets the water/silver surface at the sides of the container. .... There is no curve! The upper water/air surface continues perfectly flat all the way up to the silver. It looks really strange.

 

5.) In the experiments by InesF reported in this thread each ink is given a measured value of "surface tension". That value was determined by measuring the weight of a drop of ink as it falls away from the tip of a narrow glass tube. Those drops were supported, until they grew too heavy and fell off,  by the surface tension in the sides of the drop hanging down in air. Those values are therefore the ink surface tension values at an ink/air interface.

Those values were then used in a mathematical method of analysis to see if there is a link between that specific measured ink property and a separate measurement of "wetness" of each ink.

 

6.) "Wetness" and other measured variables are also rigorously defined in InesF's work. (See pgs 1, 2, etc of this thread, or wait to read an eagerly anticipated blockbuster pdf.)

As far as reasonably possible other factors were held constant. Same two pens used, same two papers, same method of drawing lines, etc, throughout the experiment.

Importantly, all lines were drawn at a speed of pen movement over the paper that was slower than the speed at which the ability of the pen to supply a uniformly wet line was affected.

 

The definitions of "surface tension" or "wetness" used in the study can guide us how to make use of the results of the analysis. They also guide us in judging the limits of how far the experimental results can sensibly be applied.

( Different pens? Different paper types? Inks not included in the experiments? Lines drawn faster?)

 

(This is all good scientific method by the way.)

 

7.) One major result from the experiments and the subsequent analysis of the data collected was as below. (With apologies to InesF, I have expanded the wording for clarity.)

 

The volume of ink laid down per unit length of line, by two sample pens, on two types of paper, under nearly identical experimental conditions, measured for a large number of different inks, was found to be that the largest volumes of ink were laid down for those inks with lowest ink/air surface tension values, and least volumes of ink were laid down for those inks with the highest ink/air surface tension values.

 

Some other measured ink properties also showed a link with quantity of ink laid down. The dominant relationship was the inverse link between wetness and surface tension.

 

There was some randomness seen in the experimental results. The statistical computer software used to analyse the data confirmed that the surface tension effect seen is significant, and is not the result of random chance.

 

8.) Now returning to the subject of different surface tension values at various ink/solid surfaces:

The behaviour of ink when written onto paper by a fountain pen involves the ink being in contact with some number of different solid materials that are parts of the ink chamber, breather system, ink feed, and nib. Finally the ink contacts paper, that is even more complex than the pen parts, having a surface texture and some absorbency.

(All those factors existed in the ink wetness experiments, but were held constant throughout.)

 

At some of the interfaces between ink and solid surfaces there is also a small local ink/air surface (breather vent into the main ink chamber, capillary slot and breather path sharing same space under the nib body, fins at exposed sides if the nib, ink between the tines, and ink at edge of the contact patch between nib and paper.)

 

In all that complexity the ink moves however it wants to move. There are no pumps or injectors. Ink and air are the only moving parts in this wonderful machine (reserving flex nibs and possibly soft vintage rubber ink sacs for another day).

 

The different surface tensions in the ink at all these different solid surfaces may influence how the ink behaves.

 

It is to be expected that all sorts of anomalies will be seen if we examine the wider field of ALL pens, ALL papers, ALL writing speeds, etc, and compare observations with the predicted surface tension - wetness relationship.

 

Also, if we use the word "wetness" to mean anything different from that used in the "An Alternative Look At..." experiments then the predictions from the experiments become less applicable.

 

9.) This is how scientific understanding has always worked, and developed. We now know that Newton's Laws of Motion are "wrong" at speeds near the speed of light. But that theory is still good enough for NASA to use it when navigating to The Moon and Mars.

Similarly, the relationship measured between ink surface tension and wetness is also useful - if we always bear in mind the scope of the experiments and the definitions used.

 

 

 

 

[squirrels]

6 hours ago, RJS said:

I forgot about a TWSBI pen I had filled with Monteverde Horizon Blue, one of my favourite inks. 3-4 months later it still wrote immediately, though clearly it contained less ink than it had. What was weird, when I wrote two pages with it, was how much wetter it wrote than usual- it spread more and soaked through the paper. Normally I expect the opposite, as inks seem to become thicker/drier/more lubricated as they evaporate. What has everyone else found in similar situations?

While it's not exactly the same, I have found that there is at least one ink (probably many) out there that can have its bleed/feather/spread characteristics improved by adding water (Noodler's Heart of Darkness, I used to dilute it 1:1 when I used it). This actually makes sense because water has a pretty high surface tension (I am told) which is usually lowered in inks by adding surfactant. By adding water you are (presumably) diluting the surfactant and increasing the surface tension (you are also diluting the biocide, so be careful).

 

5 hours ago, LizEF said:

Though I don't think any ink is responsible for hard starts - I think that is the nib (or perhaps the pen not sealing well so that the ink is already dry when you uncap).

I think it must be a combination of the nib, ink, and seal. The reason why I say this is that I experience dry out and/or hard starts with some inks and not others in my current main pen, which cannot be explained by the nib alone, and there are certain inks (but not all inks) that will almost immediately dry up when I lift the pen for a moment while writing, which cannot be explained by the cap seal. The nib is also quite dry AFAICT, which is pretty likely to affect this.

[LizEF]

1 hour ago, dipper said:

Ink and air are the only moving parts in this wonderful machine

And yet look at how complex it is.

 

Wonderful post, @dipper!  Thank you so much for the science lesson.    That was well worth the read, and I imagine I'll be re-reading it at some point.

[LizEF]

1 hour ago, squirrels said:

I experience dry out and/or hard starts with some inks and not others in my current main pen

The speed at which ink dries out is definitely an attribute of the ink.  (But it's worth noting that if the pen seals well enough (Platinum 3776 Century or TWSBI Eco, for example), the ink ain't dryin' out in the capped pen.)

 

I don't consider "trying to write with a pen where the ink has dried on the nib / in the feed" to be "hard start".  Though others may well consider them the same thing.  And I concede, that it may seem the same to the user - especially one who hasn't experienced the difference.  I also concede that I may be the only one with such a narrow definition of "hard start".  To me, "hard starts" is a consequence of baby's bottom.  What you're describing is simply the ink drying.

[squirrels]

1 hour ago, LizEF said:

The speed at which ink dries out is definitely an attribute of the ink.  (But it's worth noting that if the pen seals well enough (Platinum 3776 Century or TWSBI Eco, for example), the ink ain't dryin' out in the capped pen.)

 

I don't consider "trying to write with a pen where the ink has dried on the nib / in the feed" to be "hard start".  Though others may well consider them the same thing.  And I concede, that it may seem the same to the user - especially one who hasn't experienced the difference.  I also concede that I may be the only one with such a narrow definition of "hard start".  To me, "hard starts" is a consequence of baby's bottom.  What you're describing is simply the ink drying.

That's a very reasonable distinction to make. I suppose if there's no (or effectively no) ink evaporation it shouldn't matter how fast the ink dries on the nib for the purposes of hard starts.