A beginner's question about ink chromatography

[Paul-in-SF]

I have been reading some of the threads about chromatography, but they are fairly technical, and also I'm not sure I understand why some people are doing it. For me, sometimes I'm just curious about what color components have gone into an ink. 

 

So yesterday I looked up a brief tutorial on Youtube about how to do it, and I tried it with the material I had on hand, which was a paper towel strip, and the solvent that I had on hand, tap water. The ink I was interested in is by Monteverde, called Innova (I only have it because I bought the pen, and neither has brought me much joy). It is an indeterminate dark color in its native state.

 

Today I found some coffee filters and cut a strip off of one, and repeated the experiment with the same ink. The results were kind of disappointing. There is a photo below of the two strips. In short, the paper towel strip in this case produced much longer travel of the colors, which seemed to reveal the greenish cast of the area just above the original stripe much better than the coffee filter, which just shows it as a sort of muddy grey. I tried the same comparison on a couple of other, simpler inks, and there wasn't much difference between the two materials, except that very light colors like yellow tended to stretch out so much they were harder to see on the paper towel strips than on the coffee filter paper. 

 

So my beginner's question is, if I decide to use paper towel strips as my primitive material of choice, for my own information only, should I worry that the color separations I am seeing are inaccurate? 

 

[inkstainedruth]

I suspect that part of the reason that people do it is because they're trying to see if ink X is a close enough color (based on the underlying dyes) to ink Y (either because ink X is less expensive or -- more likely -- because ink Y is more or less unobtanium...).

I'll admit that when I'm testing inks for myself, I don't do that (I tend not to want to waste the ink, especially in smaller volume samples).

I also don't do ink swabs -- for that, it's the case that I don't feel that a swab gives an accurate depiction of what the color will look like coming out of a pen.

Ruth Morrisson aka inkstainedruth

[lapis]

To answer your question, no you shouldn't worry that the color separations you're seeing are inaccurate.

But what you can do to improve things is as follows (assuming you hadn't already done so )....

1. For the solvent, don't use just water but any water-mixture including an alcohol such as n- or iso- propanol etc.. I always use a 50:50 mix of distilled water and isopropanol.
2. Use a long, slim strip (e.g. 4 inch x ½ inch) of a "better" piece of paper like a cut out of blotter paper (of which there are of course also various types).
3. Don't dip the starting end -- or any other part -- of the paper strip into the ink, but rather use only 1-5 µl (with a pipette or a hypodermic needle or even a dot off a toothpick) and place that in the middle of the paper width, say only ¼ to ½ of an inch from one end.
4. Now stick that end into a glass with only so much solvent in it that it doesn't yet quite meet the ink.

Standing up for a few minutes (up to one hour, depending on everything) the migration of solvent upwards will separate everything nicely. Hang on until the separation of colors goes up as far as possible.

 

Whew!

[Paul-in-SF]

Thanks, lapis. #3 and #4 I think I have covered OK. I drew a line across the paper some distance from the bottom. I then held the strip in the water about halfway between the bottom and the line for about 15 seconds (as recommended in the video I watched). 

 

For #2, by "blotter paper" do you mean the thick stuff that I use in my journal when ink takes too long to dry? That is both expensive and so thick I can't imagine how it would work well for this application (mine is about 0.5 mm thick). So if you mean something else, can you give me an example of what it is?

 

For the solvent, can you elaborate a bit? How does it improve the end result to use that mixture vs. plain water? Does it make the separations easier to see, does it make the colors pop better so that they are easier to distinguish, or something like that? Could using your solvent formula make up for using a less-than-perfect paper strip? 

 

I appreciate your willingness to educate me on this process. 

[lapis]

Right, I meant the thick, absorbent paper used for a blotter, like that sold by J. Herbin. I don't know if that is a "perfect" paper for chromatography, but it works easily and dependably. You can get such blotter paper anywhere. E.g. Gouletpens, Jet Pens, Amazon all sell a pack of 10 Herbin White Blotter Sheets -- around 5 x 7 inches -- for under $10.00. I think that paper is only 0.06 mm thick. These are also available in pink which is just as good (although IMO for a chromatography somewhat "silly"). That is enough paper for >100 chromatography strips. You can also use that paper for a blotter itself, for which the paper was originally intended (I do that all the time and can highly recommend that blotter by Herbin).

 

Using a mix of water and alcohol actually separates the different dyes used in an ink better than any single solvent, even an alcohol alone without water. In one and the same ink, the various dyes (each having its own chemical structure) usually have solubilities which differ enough from each another, so that different solvents will each migrate the dyes at different intensities and/or speeds. That is what separates the ink's dyes on the paper strips and makes their individual compositions easier to see.

 

Another three points. 

1. First, get the individual colors separated as far as possible from each other. That's why I always use paper strips which are at least 4 inches long. Again, depending on the paper and solvents used, that can take at least 20 minutes.
2. You can also use even three or more solvents. Include water for sure, with 1-2 different alcohols, or water plus an alcohol plus acetone. Just make sure that all parts are infinitely water-soluble because if they aren't, they won't dissolve the dyes in the first place to allow any migration. Also, if they aren't all water-soluble, they won't even mix (in form of a solution) with each other.
3. Finally, the whole idea of carrying out and/or presenting any such chromatography is best suited for a comparison of any 2-3-4⁺ inks often considered to be the same or at least very similar. In that case, it's important to examine all inks simultaneously on the same type of paper in the same solvent for the same period of time. Good examples would include a look at the older versions of Waterman's and Parker's blue-blacks. Or an attempt to answer the question, "Which is the blackest black?" (scroll down to the last image).

[SamCapote]

Lapis covered it very well, but when I started doing it, I just used cut up coffee filters.  You can just use water, or add alcohol.  I never used more expensive blotter paper because it was an idle curiosity for me. 
 

The most important thing is to just use a small drop that will be above the water/alcohol level that way you are not coloring the water before it climbs up and separates the dot colors upwards. 
 

Some of us just did this to appreciate the combinations of dyes that went into a formulation.  
 

 

[A Smug Dill]

  On 2/19/2021 at 7:26 AM, Paul-in-SF said:

… I'm not sure I understand why some people are doing it. For me, sometimes I'm just curious about what color components have gone into an ink. 

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I usually do it when I want to test whether two inks are likely and/or largely “the same”, in one of two (types of) scenarios:

1. I have an unidentified ink in the reservoir of a fountain pen, and can find no entry in my inking log book and pen-ink pairing spreadsheet to tell me what it may be. Alternatively, I may have an unlabelled sample vial of ink I don't remember filling, usually as a result of wanting to urgently change inks in a piston-filler or eyedropper-filled pen that was still mostly full of ink; I'd extract the remaining ink from the pen's reservoir in a hurry and dump it into a sample vial, but sometimes I forget to label the vial afterwards.
   
   My vague recollection and/or eyeballs tell me it's likely to be ink X, and in order to confirm that, I'd compare freshly produced chromatograms of the unidentified ink and my bottle of X. Once, when I really had no idea, I went as far as to produce chromatograms of eight inks I know to be in that general colour family and range.
   
   That would be the first step, anyway; if the chromatograms look significantly different, then they can't be the same ink, but even if they look sufficiently similar, I still can't be sure they're the same ink (see below), without performing other tests. Of course, the easier thing to do would be just to discard the unidentified ink, without ever knowing what it is/was, or trying to satisfy my curiosity.
    
2. I have two known inks that look awfully alike on the page (example: Pelikan 4001 Blue/Black and Lamy Benitoite), and I want to know whether they are likely to be the same ink rebadged, and so I perform chromatography on them and compare the chromatograms.
   
   Aside: The chromatograms from Pelikan 4001 Blue/Black and Lamy Benitoite (both ‘fresh’ from my already opened retail bottles, which arguably could already be compromised) using plain water as solvent look remarkably similar, and in fact I couldn't really tell them apart. Soaking a sheet of paper with writing samples of both inks in water for 24 hours didn't reveal much of a difference, either. Finally, it was their respective reactions to bleach that confirmed they are in fact dissimilar chemically.

  On 2/19/2021 at 7:26 AM, Paul-in-SF said:

Today I found some coffee filters and cut a strip off of one,

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  On 2/19/2021 at 6:26 PM, Paul-in-SF said:

For #2, by "blotter paper" do you mean the thick stuff that I use in my journal when ink takes too long to dry? That is both expensive and so thick I can't imagine how it would work well for this application (mine is about 0.5 mm thick).

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I use lab filter paper (which comes in different types, speeds, etc.) but only the relatively cheaper Chinese-made stuff I can buy off AliExpress or eBay, and not from ‘proper’ suppliers to industry, professionals and educational institutions.

 

  On 2/19/2021 at 7:26 AM, Paul-in-SF said:

for my own information only, should I worry that the color separations I am seeing are inaccurate? 

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Only you can decide whether the chromatograms thus produced satisfy your requirements, and then worry (only) when they don't. If you're comparing two or more different inks, for purposes of identification or differentiation, by producing fresh chromatograms for them in a single session, then it shouldn't matter, as long as the solvent and the substrate used are consistent for every ink.

 

  On 2/19/2021 at 11:34 PM, lapis said:

Finally, the whole idea of carrying out and/or presenting any such chromatography is best suited for a comparison of any 2-3-4⁺ inks often considered to be the same or at least very similar.

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Ideally I'd like to produce and put on file chromatograms for most of my >300 inks, in a methodically consistent manner, so that for quick-and-loose identification or differentiation of an unidentified (or newly acquired) ink I won't need to dig up my actual bottles of ink and do fresh chromatograms with them in every single instance.

[white_lotus]

When I was doing ink reviews, I'd include an image of paper towel chromatography. I'd take a half sheet of paper towel, fold that in half to have a square, roughly. Then I'd wet it under the tap, squeeze it out. I'd then just drop one drop from the filled pen (eg turning the converter knob the "wrong way"). Then set that aside in a safe place to dry. Often with something underneath to protect a table surface if the ink spread to the other side, which often happened.

 

I was interested in the color dyes used in making up the ink. Not the specific chemical dyes, but just the color. That was all. Manufacturers also add other chemicals to the ink, but I was never interested in those. Ink is almost all water with some dye and other stuff to make it flow properly, protect it from contamination, and these days make it "sheen" or "sparkle". But water is the main component, so I never bothered to test the solubility of the dyes in anything other than water.

 

 I didn't add a label to the dried sheet. That might have been useful. 😀

The ink on the left is  a muted blue, appeared to be a single dye.

The middle ink used two blue dyes, one a brighter turquoise, the other a darker navy.

The ink on the right was a dark brown, or maybe a black, but I think the former. It used a blue, orange, green, and yellow components in addition to its brown base.

 

Maybe this isn't very scientific, but it made useful comparisons for me.

[lapis]

  On 2/20/2021 at 1:56 PM, white_lotus said:

Maybe this isn't very scientific, but it made useful comparisons for me.

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Good! These things don't always have to be very scientific. The main reason for such "experiments" -- as already coughed out by many of us -- is to compare two (or more) inks with each other. To check out if Ink A is the same as Ink B etc..That's the best and fastest and least expensive way for the majority of us.

[Paul-in-SF]

This is all great stuff, thanks for being willing to participate in an elementary-level discussion. Very interesting. 

[lapis]

I once heard that this stuff was termed Ink 101.

 

[Sailor Kenshin]

I do something similar to White Lotus because I like seeing colors separate.  If an ink has a complex chroma, I like it more.

[grayautumnday]

  On 2/19/2021 at 11:34 PM, lapis said:

Right, I meant the thick, absorbent paper used for a blotter, like that sold by J. Herbin. I don't know if that is a "perfect" paper for chromatography, but it works easily and dependably. You can get such blotter paper anywhere. E.g. Gouletpens, Jet Pens, Amazon all sell a pack of 10 Herbin White Blotter Sheets -- around 5 x 7 inches -- for under $10.00. I think that paper is only 0.06 mm thick. These are also available in pink which is just as good (although IMO for a chromatography somewhat "silly"). That is enough paper for >100 chromatography strips. You can also use that paper for a blotter itself, for which the paper was originally intended (I do that all the time and can highly recommend that blotter by Herbin).

 

Using a mix of water and alcohol actually separates the different dyes used in an ink better than any single solvent, even an alcohol alone without water. In one and the same ink, the various dyes (each having its own chemical structure) usually have solubilities which differ enough from each another, so that different solvents will each migrate the dyes at different intensities and/or speeds. That is what separates the ink's dyes on the paper strips and makes their individual compositions easier to see.

 

Another three points. 

1. First, get the individual colors separated as far as possible from each other. That's why I always use paper strips which are at least 4 inches long. Again, depending on the paper and solvents used, that can take at least 20 minutes.
2. You can also use even three or more solvents. Include water for sure, with 1-2 different alcohols, or water plus an alcohol plus acetone. Just make sure that all parts are infinitely water-soluble because if they aren't, they won't dissolve the dyes in the first place to allow any migration. Also, if they aren't all water-soluble, they won't even mix (in form of a solution) with each other.
3. Finally, the whole idea of carrying out and/or presenting any such chromatography is best suited for a comparison of any 2-3-4⁺ inks often considered to be the same or at least very similar. In that case, it's important to examine all inks simultaneously on the same type of paper in the same solvent for the same period of time. Good examples would include a look at the older versions of Waterman's and Parker's blue-blacks. Or an attempt to answer the question, "Which is the blackest black?" (scroll down to the last image).

Expand  

It's my suspicion that blotter paper is simply high quality watercolor paper. Any good quality watercolor paper should do, though I'd recommend going for the thinner versions, as very thick watercolor paper would hold a lot of the traveling colors under the surface of the paper and too much would become invisible.

 

I use watercolor paper for a ton of different uses - I have an excess of it after I stopped enlarging my own film photo prints and decided not to buy & store developing chemicals & set aside space for storing darkroom stuff - even a collapsible darkroom tent takes up a huge amount of space, and I already have way too many hazardous chemicals in my garage from my dyeing, raw paper/textile fiber processing, cleaning/sanitizing chemical blending, soapmaking, and skin/hair care formulating hobbies... 

 

I do vastly prefer the cheapie precut chromotography strips to blotter paper, watercolor paper, paper towel, coffee filter paper. It's less expensive than my favorite - artist's "teabag" paper. With the ultra thin paper, it's easier and faster to see a greater spread in separation of colors...

 

I use 3:1 distilled water to either 99%+ isopropyl alcohol or 99+% SDA-40B (aka "perfumer's alcohol" - skin-contact-safe denatured ethanol - there's a DIY biodiesel supply company on Amazon called Duda Energy that sells it for a very good price). 
 

I do chromotography to give me a better idea of which specific pure dye ingredients have been mixed to create the color, to better guess at  what other specific solutes or particulates may be present (kaolin, bentonite, mica, nanoglitter, methylcellulose, carbomers, non-water solvents/humectants)

 

... using far more water than ethanol,

dipping the bottom of strips into the same volume of solution at the same depth,

stopping and blow-drying the strip after 20 minutes has passed (I use only enough solution to be fully absorbed into the strip within 20 minutes)

.... gives me a better hints at of how low water resistance is, whether the ink has more or less surfactant present than usual, sometimes whether there are resins present, other interesting attributes.

 

I only include alcohol because I know a lot of "boutique inks" (as Richard Binder calls them) do contain ingredients that are not water-soluble, and I want them to travel up the filter paper as well so that I have a good chance of noticing them, and because alcohol enhances the separation of the pure dye colors within the dye mixes used.

[Bo Bo Olson]

Thanks everyone. I'd seen it done often enough; flying over my head.

But that's more complicated, and not something I need to do for my enjoyment.