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How to reduce feathering?


ferrogallic

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Are there any additive that could be added to an existing ink to make it feather less, beyond the usual thickeners, such as gum arabic? Has anyone measured their effects? Are any preferred for low pH, high pH inks?

 

[According to the article referenced here, it was found that ink actually performs better without gum arabic, but only after it had been accidentally left out from the official government recipe.]

 

@InesFposted an extremely detailed analysis of ink spreading and a theory on ink wetting. Some of the results are:

 

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- Higher viscosity does NOT reduce ink flow of a fully functional fountain pen

- Higher viscosity sharpens the edges of the ink line and let it appear more crisp and more saturated

- Both, higher viscosity and higher conductivity do reduce the ink line width a little bit

- Lower surface tension supports spreading and feathering of inks on absorbent paper

 

 

Unfortunately the surface tension can't be increased easily (some salts increase surface tension marginally, but only in very high concentrations).

 

I found one interesting patent that uses a different approach:

 

To reduce the flow (wetness?), they increase the wetting angle of the ink/nib interface. This is done by adding a flotation agent, which also happens to reduce the surface tension.

 

Feathering is then independently controlled by adding a colloid.

 

https://patents.google.com/patent/US1932248A/en

 

This is a highly alkaline ink, maybe the vintage Superchrome ink used similar ideas.

 

The ink is made alkaline to quickly sink into the paper, but this leads to undesirable effects:

 

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ink to sink rapidly into the paper. However, such ink is unsatisfactory for commercial use because fountain pens when they are held in a horizontal position or with the pen pointed downward as in writing, or in fountain pen desk sets, and also because the flow of such ink is much too free from In addition such inks are undesirable because of that fact.

 

They say that surface tension doesn't matter, but what matters is the wetting angle on the nib.

 

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When the viscosity and surface tension of these inks are measured in comparison with those of ordinary market inks,
no differences are found which adequately explain their undesirable characteristics of bleeding and excessively free flow. We have discovered that these characteristics are controlled in a large part by the ability of such inks to wet surfaces such as the gold of the pen ni-bs. The angle of wetting formed by a drop of with a gold pen is approximately water in contact 30. When alkali in quantity sufficient to produce a quick-drying ink is added to water or to water solutions of dye such as can be used to produce such inks, the angle of wetting between the ink and the gold pen nib words no drop is formed of ink is placed on a alloy stead the ink spreads o of the composition used in the pen,
becomes zero, or in other when a small portion surface consisting of gold but inut in an extremely thin film over the goldsurface. It is this property of perfect wetting which causes the ink to exhibit the characteristics referred to earlier of bleeding and excessive free flow, when used in fountain pens.

 

 

To keep the ink from wetting the nib, they add amyl xanthate. Xanthates do lower the surface tension, see also Fig. 2 of https://pubs.acs.org/doi/pdf/10.1021/ja01308a003#, but increase the wetting angle on the nib:

 

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adding to it chemical compounds capable of increasing the angle of wetting between the ink and the gold pen. The compounds which we have found most effective for this purpose are those-which are used for flotation of minerals and of these we have found the xanthates highly satisfactory for our purpose. As little as .02% of amyl xanthate will increase the angle of wetting of a typical quick-drying, alkalidye ink from 0 to 34 and will wholly prevent the undesirable bleeding.

 

They name a couple of alternative substances to increase the wetting angle:

 

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amyl xanthate is. a member usually but not necessarily characterized by having either carbon double bond sulphur or triple bond nitrogen groups such as for example thiocarbanilid, azobenzene, diazoamino-benzene, p-thiocresol, phenyl-thiourea, phenyl isothiocyanate, butyl xanthate, and sodium xanthate will also substantially improve the 5 flow properties of the ink

 

The ink will still feather, which is fixed by adding starch

 

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The ink will, however, tend to feather and a further phase of our invention involves the addition of a colloidal body such as corn starch which even when as little as .5% is present will overcome the feathering on practically all types of paper. Other colloidal substances such as gums, casein and the like may be used to prevent feathering but starch is particularly desirable because of the type of colloidal solution which it forms in the presence of alkali such as sodium or potasslum hydroxide.

 

Finally, they add bentonite clay to improve the flow. I have no idea why this works.

 

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The flow of the ink may be fur= ther improved by the addition of colloidal clays such as the bentonites. We prefer for our inks to use a special highly colloidal bentonite known to the trade as Wilkinite. This clay when used in amounts as small as .2 of 1% seems to have some favorable effect on the flow of the ink from certain types of fountain pens.

 

 

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Well, gum arabic is a BAD idea for fountain pens.  

You might try diluting the ink with distilled water.  That worked for me with my bottle of Noodler's Bay State Blue -- I now use it in a Noodler's Charlie eyedropper and top off a fill with about 20% distilled water.  

Ruth Morrisson aka inkstainedruth

"It's very nice, but frankly, when I signed that list for a P-51, what I had in mind was a fountain pen."

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Corn starch is what they say worked best for them, at even a very low concentration. That's interesting, I wonder what the best procedure to add it to an ink would be, and whether it would work the same irrespective of pH...

If you are to be ephemeral, leave a good scent.

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Hi @ferrogallic.

Thanks for citing my article! And thanks for extending the basics with other publications, with a patent and with your own thoughts.

 

Non-derivated xanthan is a very common thickener for food and cosmetics. As a polysaccharid it is, in its behavior, not so much different from Gum Arabic. However, the authors of the 2018 article (doi:10.3390/min8040166) used xanthan derivates which did increase viscosity (not reported!) and did reduce surface tension (= reducing the wetting angle) a little bit (from around 70 to 65 units). There are two effects at the same time which are contradicting each other in the behavior of fountain pen ink.

 

The 1933 ink patent is an interesting read for historic reasons, but I recommend to not experiment with such highly alkaline inks. Finally, also in this patent xanthan derivates were used which have influence on the same two ink properties.

 

In contrast to @inkstainedruth and even understanding her concerns, I do not fear using Gum Arabic in fountain pens. With up to a maximum of ca. 1.5% G.A. (but preferably around 1%) in ink, any fully functional fountain pen still works well and doesn't suffer from ink starvation. What happens above that concentration I do not know. And even if you use a fountain pen that tends to dry out (btw., that's not a good pen), G.A. is fully water soluble. If you forgot a pen, you may regenerate it without any problem by sucking it in water (maybe for a full week, or as long as necessary). You may not regenerate a pen with dried waterproof (permanent) ink!

 

Finally, increasing surface tension is next to impossible while keeping the ink fountain pen friendly. Acrylic emulsion and shellac emulsion (the painting media) may increase surface tension, but I strictly recommend NOT to use any of those in a fountain pen. Even dip pens are hard to clean after half an hour line drawing.

 

Commercial fountain pen inks range from roughly 40 up to above 70 mN*m-1, which makes them quite different in their behavior. My motivation to do all the measurements was the prospect of finding a way to predict which ink can fit to which pen. While my intended goal was not fully achieved, I learned to select compatible pairings of ink and pen and to accept incompatibilities. Finally: you can find a fitting colour in any surface tension range!  (And you may tame the low surface tension inks a bit with thickening additives)

 

Good luck on you further fountain pen journey!

One life!

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On 10/28/2023 at 1:53 PM, txomsy said:

Corn starch is what they say worked best for them, at even a very low concentration. That's interesting, I wonder what the best procedure to add it to an ink would be, and whether it would work the same irrespective of pH...

@txomsy That is a good question, I didn't realize the problem. Now that I think about it, I am not even sure that it is possible to make a colloid with normal starch. After all, when grating potatoes, the starch settles nicely at the bottom.. Some plants have much finer starch granules, not sure about corn, but I'd be very surprised if they formed stable colloids.

 

Maybe some type of modified starch? The powder that is used to glue on wallpapers? For baking, starch is roasted and then dissolved in water, dextrin. Both will be stable at neutral pH.

Wikipedia says there is also alkaline (and acid) modified starch, maybe the highly alkaline solution makes the starch stable.

 

Not sure if they gelatinized the starch. Do you think it would be better to have a colloid with nano-sized starch particles, or dissolved gelatinized starch?

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Actually, I don't know. My understanding of these processes is rooted on my understanding of Physics and Chemistry, tuned by a long experience in Biomedicine.

 

As a sugar polymer, starch is highly soluble, but I do not know at which particle sizes it is usually present after industrial processing, would have to look it up. Maybe tomorrow, it's time for dinner now.

If you are to be ephemeral, leave a good scent.

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I re-read the patent, it looks like they use regular starch, and the starch is stable in the alkaline solution:

 

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I Parts Direct pure blue 63 Ex. Con. (Color Index #518, Schultz #424) 1. 6 Flake caustic soda 1. 8 Ammonium meta-vanadate 0.35 Amyl xanthate 0.02 Corn starch 0.05 Bentonite (Wilkinite) 0. 20 Water 100.0

 

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The ink will, however, tend to feather and a further phase of our invention involves the addition of a colloidal body such as corn starch which even when as little as .5% is present will overcome the feathering on practically all types of paper. Other colloidal substances such as gums, casein and the like may be used to prevent feathering but starch is particularly desirable because of the type of colloidal solution which it forms in the presence of alkali such as sodium or potasslum hydroxide.

 

I don't know if the alkaline modified starch would still form a stable colloid at a different pH.

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