An alternative look at ink wetness

[InesF]

Thank you @Sholom, I'm pleased by your comment about the paper.

 

On 7/17/2022 at 9:35 PM, Sholom said:

I'm still wondering about what the mechanism of conductivity's effect on ink performance is. That conductivity varied widely between inks is not surprising since many dyes in their "commercial" grade (as opposed to extra high purity inks for inkjet inks or biological and optical applications) are loaded with salts that come from the process of isolating the dyes from the reaction mix that produced them. Around 20 years ago I was involved in a project that wanted to use a dye called Basic Blue 3 and was surprised and mildly horrified to discover that the Basic Blue 3 that one could buy in small quantities from chemical supply houses was only about 30% dye; the rest were the salt(s) that were used to precipitate the dye from its synthesis solution. For multiple reasons this particular dye would not be a great choice for a fountain pen ink, even though it is a gorgeous shade of cyan-blue. For many dyes the salt-free form, if commercially available at all, would be nice to use in inks but costs dearly and would not be economically feasible for use in even a high-end fountain pen ink. I wonder whether conductivity really is a proxy for salt content and dye polarity and hence for the overall polarity (in the broad sense of solvent polarity parameters) of the solution? This also gets me thinking, on a hot humid day without air conditioning, that ambient humidity and its effect on paper should also have effects on ink behavior that will also vary with the properties of different papers (sizing agents, fiber types like cotton vs. wood pulp, etc). I think Ines will understand what I'm asking but please don't feel bad if this is all opaque to my fellow readers: this is geeky chemistry and physics talk and I am just thinking out loud. Thanks again Ines!

 

Indeed, in organic chemical synthesis there are some substance you precipitate by adding salt to a solution, always resulting in salty products. Which manufacturer uses which dye (and in which concentration) is usually not announced. Therefore, we can only guess - and we may guess wrong in many cases. However, the number of suitable dyes is limited, as they have to be used in aqueous solution, typically without any organic "supporting" solvent. Most obvious among them is cyan blue (=turquoise) which is most probably the exact same dye for many manufacturers.

Some dyes change colour with pH and/or with polarity - and their stability may be influenced as well. The requirement of aqueous solution limits the possibilities. If pH is critical, buffering salts may be used and adding more salt(s) than necessary may add intensity or may reveal a fine colour undertone or may, simply, tame a nasty behaving dye on paper.

 

When I chose to measure conductivity, I didn't think about all those aspects at first. It was more of a trial and error attempt as I hoped to catch heavily buffered inks. PCA made the effect of conductivity to line width and to ink delivery amount visible. I still do not have a final explanation about the chemistry behind, but I guess  it may depend on ionic interactions of the ink with either the cellulose fibers or with the paper sizing being in concurrency with ionic or polar interactions of the dye. Diamine Sargasso Sea ink behaves as if its surface tension would be 60 mN/m (instead of 51), for example.

 

Unfortunately I ran out of the absorbent paper type and my attempts to get a good replacement failed so far.

(If I would had known in advance ....  )

 

There are still secrets to discover in the data set. 👩‍🎓

[InesF]

There is another "final" list of ink properties, with 5 new inks added since last time.

 

Biggest surprise is Platinum Citrus Black: it's the fist ink among the 83 measured exceeding waters surface tension!

 

Have a nice summer time!

[recluse]

3 hours ago, InesF said:

There is another "final" list of ink properties, with 5 new inks added since last time.

 

 

I don't know if it's appropriate to ask, and if it's not I apologize. Is it possible to get some kind of text version (CSV or pretty much whatever) of this table? 

[dipper]

6 hours ago, InesF said:

PCA made the effect of conductivity to line width and to ink delivery amount visible.

Remember the adage "Correlation does not imply causation".

[txomsy]

7 hours ago, dipper said:

Remember the adage "Correlation does not imply causation".

That's why @InesF said nothing about conductivity itself but about it being associated with ionic content which may actually be considered relevant to drive ink-paper attraction changing the ink-feed-air balance to a different ink-feed-paper one. And spoke only of "guess", not implying any actual causal relation.

 

Sorry, but while I go agree with you, and many do indeed forget that old adage, in this case, the wording chosen by @InesFhas been delightfully and exquisitely appropriate, something I often miss in so many other authors.

[InesF]

Thank you @txomsy!

Still struggling finding the right words (but becoming better over the years ...)

 

9 hours ago, dipper said:

Remember the adage "Correlation does not imply causation".

Yes, you are right. In this case conductivity cannot be totally independent from other (both, measured and not measured) properties. While I'm aware of that, I still have no final answer.

[amberleadavis]

The work you have put into this is amazing, thank you for sharing.

[InesF]

Here is another "really, really final" table with fountain pen ink properties. Only four new inks arrived since July and there are (currently) no more plans to acquire more.

Sure.

I think.

Maybe,

or so.

 

 

All the best!

Keep on writing!

[InesF]

A short update of the properties list with two new inks added. I was gifted them from Stilo e Stile. Thank you!

 

Robert Oster Tempest Sky surprised with having the lowest surface tension of all inks I tested so far. While I love the colour, the ink doesn't behave that well. It has a high tendency to feather and bleed (no surprise). Adding Gum Arabic to increase viscosity above 1.2 mPa*s may tame it a bit.

Stilo e Stile Roman Centurion Red is also a lovely colour and suitable for daily use with wet writing pens.

 

And here the table:

[Lithium466]

Thank you for that update. While I have nothing else to contribute (unless I have some inks you might want to try, like some Sailor or Pilot maybe? I can send you samples), I am just thankful for the content you provide. 😊

[InesF]

Thank you @Lithium466, you are welcome.

Some month ago, I decided to not add more inks to my collection and to stop updates of the table. The measurements for two inks cost me an afternoon of work (OK, four inks is not much more, also an afternoon...). Rarely, if ever, more updates will follow.

 

Sites like Mountain of ink list almost 2000 ink reviews: so much work to review and post, impossible work to measure all the parameters. The list will always be incomplete, be it 75, 750 or 2000 inks.

[Lithium466]

Haha, I do understand you. In a previous life I used to do online reviews (unrelated to fp) and totally get the feeling of ever uncompleteness and overwhelming market offer.

 

But my offer was more "just like that" without review request, as for once we can see a list of (most?) of your inks 😂

In any case feel free if that can be of interest for you. I recently went to the Pelikan hub and had the opportunity to try and trade so many inks, some I ordered a bottle, and some I was very interested in buying but will certainly not after having testing them!

[LoveBigPensAndCannotLie]

This is really cool, thank you for doing this!

 

I wonder if anything psychological goes into how "wet" an ink feels besides the tangible physical properties. I was surprised to see Waterman Serenity Blue towards the dry end of the spectrum, since I've never really had any flow issues with that ink, I always thought it was above average in wetness based on my experience with various pens and papers.

 

Rohrer & Klingner Alt-Goldgrun, on the other hand... I love the color and shading of that ink but I've found that it is so dry that it does not perform well in many of my pens. But according to your findings, it has a decently lower surface tension compared to Waterman Serenity Blue, which is interesting. Maybe I perceive it as drier because it is a lighter color. 

[amberleadavis]

19 hours ago, LoveBigPensAndCannotLie said:

This is really cool, thank you for doing this!

 

I wonder if anything psychological goes into how "wet" an ink feels besides the tangible physical properties. I was surprised to see Waterman Serenity Blue towards the dry end of the spectrum, since I've never really had any flow issues with that ink, I always thought it was above average in wetness based on my experience with various pens and papers.

 

Rohrer & Klingner Alt-Goldgrun, on the other hand... I love the color and shading of that ink but I've found that it is so dry that it does not perform well in many of my pens. But according to your findings, it has a decently lower surface tension compared to Waterman Serenity Blue, which is interesting. Maybe I perceive it as drier because it is a lighter color. 

 

 

I found Alt-Goldgrun to be dry before, but then I received a newer bottle and it was a wetter ink.  I wonder if the formula changed?

[LoveBigPensAndCannotLie]

5 hours ago, amberleadavis said:

 

 

I found Alt-Goldgrun to be dry before, but then I received a newer bottle and it was a wetter ink.  I wonder if the formula changed?

 

When did you get the newer bottle? I have only one bottle but it is from 2020, so not that long ago. But perhaps it changed very recently. Maybe I should get another bottle if anyone can confirm. I really love this color but the dryness of the bottle I have puts me off from using it in most of my pens.

[amberleadavis]

Oops, I mistyped, I got a new sample.  I don't know the year of the sample, but I received it in the last few months.

[Sholom]

My now older (2018??) bottle of Alt-Goldgrun seems quite wet (and on some papers is a bit spread-prone) in a (generally wet) Parker 45 gold F, but it is prone to drying in the nib with too infrequent use. In any case, I find it sufficiently unproblematic that it is always in at least one pen.

[bidn]

On 5/23/2021 at 8:23 AM, InesF said:

You have already experienced that some inks are wet while others are dry and, furthermore, you know about the existence of wet and dry nibs. If you write or draw a line with your fountain pen, you see either a wet trail left behind – or not. So far the facts.

At this point I asked myself: why is it so?

My two friends, Google and DuckDuckGo, both helped me to find hypothesis, theories and explanations in blogs, videos and any form of review – some more, some less convincing. But, to my surprise, no hard facts and no evidence given. The outcome of my recherché didn‘t satisfy me.

During the last three month I tried to figure out how I can measure ink wetness. After some initial fails, I found a way! Heureka! And now I like to present an alternative view at ink wetness.

 

The setup

I measured surface tension, dynamic viscosity and ink consumption of a couple of inks from my collection. Some of them are widely considered to be wet inks, others are classified as dry inks and for some no general opinion can be found.

When submitting this text to the forum I have measured surface tension of 18 inks, viscosity of 13 inks and had made the ink consumption measurement with 2 inks with 3 different fountain pens and one ink with 2 pens, each on three different papers (which is 24 measurements total). This data set will grow over time. As some of the measurements are extremely time consuming (see below in the methods section), the data set will grow slowly. Sorry for that.

The inks were mainly from Pelikan, Waterman, deAtramentis, Rohrer & Klingner, plus one Iroshizuko and one from Diamine. Some of my inks were used as they were delivered, others were already modified long before the start of my test series by addition of Gum Arabic (in the range of 0.3 to 1.5%) to reduce their feathering, spreading and bleeding when used in ’wet‘ fountain pens. I did this empirically, based on my experience with calligraphy inks and with watercolour in dip pens, I didn‘t have any evidence about which ink properties will change with Gum Arabic.

 

The data

This is the collective data table of all measurements so far (more to come):

 

This is how a typical ink consumption measurement looks:

 

Currently, I can‘t measure line width with sufficient precision. Only a more general, nevertheless, consistent classification can be done over all currently tested inks and all pens: ink friendly paper resulted in the narrowest lines that appeared to be wet during drawing, the low quality paper resulted in wider lines that appeared dry but fuzzy and the glossy photo paper resulted in the sharpest and broadest lines with intense colour but did not provide the feeling of being wet.

 

The Interpretation

All of the tested inks belong to one of two groups of typical surface tension: either 60-70 mN/m (water is 73 mN/m) or 40-50 mN/m with the deAtramentis series the Iroshizuko and the Diamine being the inks with the lowest and Waterman, Pelikan and Rohrer & Klingner being among those with the highest surface tension. The iron gall ink Scabiosa is the only exception with low surface tension (and with alcohol smell).

The dynamic viscosities of all inks were highly similar, all in the range of 1.02 to 1.08 mPa*s (water is 1.00 mPa*s) with no clear pattern per brand or per colour type (not all colours measured yet - black, green and brown inks are missing!). Inks with added Gum Arabic showed viscosities of 1.1 or 1.2 mPa*s with one exception: R&K Magenta with 0.5% Gum Arabic and a viscosity in the ’normal‘ range of 1.045 mPa*s. Gum Arabic increases viscosity and, when writing on ink friendly paper, it increases the subjective impression of wetness. When writing on low quality absorbent paper, G.A. does reduce or inhibit feathering, spreading and bleeding but does not change the wet (or dry) appearance when writing.

Remark to Gum Arabic: while a small addition can significantly improve the behaviour of an ink on low quality paper and can improve wetness and shading on ink friendly paper a bit, adding too much can result in ink starvation! Be careful, start slow, test a lot!

The deepest insights and the biggest surprises came from the ink consumption results. The pens were able to deliver around 14 g ink per km line on photo paper while only 4-5 g of the same ink was delivered on high quality ink friendly paper. As a consequence – and most important fact – no pen was in ink starvation (limited ink delivery) when writing on high quality or low quality paper. The lines on the good paper appeared generally wet (with 4 g/km), the lines on the photo paper (14 g/km) and on the absorbent paper (5-7 g/km) appeared more dry!

The setup of the ink spreading test was not optimal. There was next to no difference in the diameter of the spreading circles (or ellipses) – the difference was more in the time needed until the spreading stopped. Some of the inks reached their final diameter within an hour, others moved over night. The time was not measured and I don‘t know how to measure it without watching the spots for hours. However, the so called ’friendly‘ inks showed more smooth while the ’runny‘ inks showed more rough edges at the diffusion fronts. Only the Rohrer & Klingner SketchInk (water prove) and the iron gall ink showed significantly smaller spreading circles and the most highly Gum Arabic modified R&K Alt-Goldgrün showed a bit reduced spreading.

 

The ad hoc conclusions are:

• Different nibs of similar point size lay down similar amounts of the same ink on the same paper.
• The width of an ink line is inversely proportional to its surface tension (drawn with the same nib).
• Feathering and ink spreading seems to be mildly dependent on surface tension for those inks within the ’normal‘ range of viscosity. Higher viscosity reduces this influence on low quality paper and results in ’sharper‘ lines – maybe because the spreading speed is slower
• The surface tension of an ink has bigger influence on wetness than the viscosity – although, the correlation is not strict.
• Wetness is not a consequence of limited nor of un-limited ink flow!
• The paper type has bigger influence on ink flow than any of the ink properties!

So far the hard facts.

 

Outlook & open points

This first set of results is a start. In about 6-8 month I will have collected enough data to start a principal component analysis (multivariate statistics) to find the exact dependencies of ink delivery and ink properties. Please be patient and stay with me while I do more measurements.

Furthermore, I‘m looking for your help:

• I have drawn some model sketches of ink surface and flow patterns – maybe someone can help me with refined drawings based on computer simulations? I had to correct my drawings, sorry, I will post them later!
• I have currently no possibility to measure the line width with a precision better than 0.1 mm. A resolution of ca. 0.01 mm (or better) would be needed to calculate ink consumption per surface area! Do you have any idea?
• Viscosity plays next to no role for the wet appearance of an ink, but counters feathering and spreading of low surface tension inks. Looking back to historic ink making, Gum Arabic, Glycerol and Glycol, sometimes Sugar or Ethyl Alcohol (wine) were the traditional ingredients of choice to customize an ink. As far as I know, none of these shows direct chemical interaction that can explain non-linear behaviour of ink on paper that is not reflected in surface tension and viscosity. What is your idea, what is missing here?

 

Thank you so much for your excellent scientific work,

and even more so, with big congratulations, for your excellent paper :

 

"Identification of fountain pen ink properties which determine the amount put on paper during handwriting", J Materials & Design, 219 (2022) 110739

 

https://www.sciencedirect.com/science/article/pii/S0264127522003616

 

I think that your thead should be made sticky as the #1 thread in this section.

 

 

BTW, here another very interesting paper:

 

Nikolov, "How the capillarity and ink-air flow govern the performance of a fountain pen", J Colloid Interface 578 (2020) 660-667

 

https://www.sciencedirect.com/science/article/abs/pii/S0021979720305877

 

Servus,

bidn

[InesF]

Thank you, @bidn! You are welcome!

Indeed, I cited the paper from Nikolov et al, it is a good and useful work.

[InesF]

Four more inks added to the list, two of them from small volume samples that didn't allow for viscosity measurement.

 

Here the new full list:

 

The new were:

F. Schimpf Morgenröte and Gewitterwolke, both from samples

Lamy Crystal Rhodonite

and Miller Fuchsia, which looks like a re-labeled deAtramentis Fuchsia