Ink / Paper absorbtion rates - what's happening?

[Mark Lindquist]

So we all know that once a substrate is printed, that the print needs to "dry down" as the ink becomes absorbed by the paper, particularly matte paper.  During this 24-48 hour waiting period, remarkable changes take place.  I surmise that the ink is cominglling with the fibres of the print and the water has to evaporate.  Then there is off-gassing.

So what's up with this?  Are the ink molecules and paper fibre molecules rearranging, then finally settling down, or is it just as simple as water evaporating?

Different rates of absorbtion for different papers.  What's really going on here?  This phenomenon is easy to observe, but not so easy to fully understand.

Mark

Spelling syntax edits

[Mark D Segal]

As far as I understand the process, the substrate is the base, and the ink is absorbed onto and in the coating. The main change that occurs is the off-gassing, during which there is some evaporation of the gasses released from the ink once it is sprayed onto the coating. Whether more profound chemical changes occur that also cause a visible difference of print appearance a day later I do not know. With today's high quality papers and inks, drying is very rapid, but the printed surface isn't fully hardened till 12 hours or so after printing.

[datro]

So we all know that once a substrate is printed, that the print needs to "dry down" as the ink becomes absorbed by the paper...

Unlike what happens in the wet darkroom, my understanding is that inkjet prints actually "dry up" very slightly rather than "dry down."  In other words, the print will be very slightly darker when it first comes off the printer compared to later after it has dried.  I've never actually measured this, but I think I've seen it visually, especially in the darker areas of the print.  I'm sure this probably varies (maybe a lot) depending on the ink and paper being used.

Dave

[shadowblade]

So we all know that once a substrate is printed, that the print needs to "dry down" as the ink becomes absorbed by the paper, particularly matte paper.  During this 24-48 hour waiting period, remarkable changes take place.  I surmise that the ink is cominglling with the fibres of the print and the water has to evaporate.  Then there is off-gassing.

So what's up with this?  Are the ink molecules and paper fibre molecules rearranging, then finally settling down, or is it just as simple as water evaporating?

Different rates of absorbtion for different papers.  What's really going on here?  This phenomenon is easy to observe, but not so easy to fully understand.

Mark

Spelling syntax edits

In most papers, the ink doesn't actually reach the fibres. If you look at the cross-section of printed inkjet paper under a microscope, all the pigment is in the upper layers of the microporous layer (which is behind a glossy polymer layer for gloss papers, or on the very surface for matte papers). The carrier fluid reaches the paper base, unless there's a RC layer in the way (not sure if it can soak through baryta layers) but doesn't enter the paper fibres themselves, since they are both internally and externally sized. It just sits in the pores between the fibres, held there by surface tension, until it can evaporate; if it did actually soak into the fibres, it would cause dimensional change, which clearly doesn't happen.

Different rates of absorption is pretty easy to explain - different microporous layers have different affinities for the different carrier fluids and encapsulation resins, while paper bases have different levels of porosity and use a number of different external sizing compounds (gelatin, PVA, etc.) which each have different affinities for water molecules.

[Mark Lindquist]

I should have said "with fine art Matte Papers", where this effect is most pronounced.

I found this graphic regarding  Fine Art Inkjet Paper from Rochester Institute of Technology, and it appears that the ink could go into the paper somewhat, in the absence of an RC layer.  It would make sense that the ink could migrate and "Key" into the uppermost paper fibers without warping the paper. 

In my experience, and I print a great deal, this phenomenon is clearly visible.  The print comes out, it is relatively dull and lifeless, but by 24 hours it is fully in a finished state, looking most like the image on the monitor.

I believe this happens mostly on Matte papers as instant dry papers and RC coatings pretty much give instant results.

No doubt this is entirely dependent upon which paper is being used, but I was hoping to learn of a name for the phenomenon and get additional information about it, not necessarily anecdotal.

Thanks for your replies - much appreciated.

Mark

[shadowblade]

I should have said "with fine art Matte Papers", where this effect is most pronounced.

I found this graphic regarding  Fine Art Inkjet Paper from Rochester Institute of Technology, and it appears that the ink could go into the paper somewhat, in the absence of an RC layer.  It would make sense that the ink could migrate and "Key" into the uppermost paper fibers without warping the paper. 

In my experience, and I print a great deal, this phenomenon is clearly visible.  The print comes out, it is relatively dull and lifeless, but by 24 hours it is fully in a finished state, looking most like the image on the monitor.

I believe this happens mostly on Matte papers as instant dry papers and RC coatings pretty much give instant results.

No doubt this is entirely dependent upon which paper is being used, but I was hoping to learn of a name for the phenomenon and get additional information about it, not necessarily anecdotal.

Thanks for your replies - much appreciated.

Mark

It takes a fair bit of ink for the pigment to reach the base layer. The microporous layer has a huge surface area for the adsorption of pigment particles. If it does, it's probably over-inked - don't forget, if it reaches the base layer, it will start to run along the fibres and you'll get increased dot gain and feathering (unless it's a rare paper where the paper sizing itself is designed to be inkjet-receptive, or if you're mitigating it with a platen heater to accelerate evaporation).

I suspect the change in appearance has little to do with changes in the pigment or ink itself and a lot to do with changes in the base layer. After all, the encapsulated pigments are designed to change as little as possible and be as unreactive as possible - anything else would be bad for longevity.

Consider how colour as visualised is generated by a print. You have incoming white light. A good ink is translucent - it needs to strongly absorb all visible-light wavelengths except the colour you want the ink to be (i.e. for a blue ink, you'd want the pigment to be transparent to blue light, but strongly absorb all other wavelengths) and the particles need to be small enough to minimise reflection, which will scatter the light and reduce saturation and contrast (the exception is black ink, which should be as opaque as possible and whose particles should absorb as much visible-spectrum light as possible, and white inks designed to be able to print a base layer, which should also be as opaque as possible). The light passes through the ink layer, with the wavelengths corresponding to the ink colour passing through and other wavelengths being filtered out. It is then reflected off the opaque layer behind the ink - a baryta layer, RC layer or the paper base - passes through the ink layer again (i.e. being filtered a second time, further increasing the proportion of remaining light of the desired wavelength and, thus, increasing the saturation) before reaching the eye and being interpreted as colour.

Seems simple enough - and it is. But consider what happens to the paper base as you print. Aqueous ink is mostly water, together with some other solvents. When it passes through the microporous layer, it is absorbed by the paper base - the very layer you're relying on to reflect light. What does saturated paper look like? Just dunk a piece in the basin and see for yourself. It reflects less light than dry paper, appearing greyish rather than white. The specularity of its reflections also changes. Effectively, a fresh print is ink in front of grey paper, not white. That's why colours look dull and muddy. As the paper base dries, it becomes white again and the colours appear vibrant. The ink hasn't changed, but the backdrop has. This also explains why RC papers and baryta papers don't exhibit the same degree of change as the print dries - the background, off which light passing through the ink layer is reflected, doesn't change as much when wet, if it changes at all.

[Mark Lindquist]

Now that's an excellent interpretation and explanation.  Appreciate it Doc!

Mark

[John Nollendorfs]

It is my understanding that in coating most papers for inkjet printing, a barrier coating is put down on the raw paper base first, followed by the microporous inkjet receiver layer. The printed ink should mostly get absorbed by the microporous layer. If you are "over inking", some of the ink will lay on top and dry. This could lead to loss of d-max. In "double printing" tests many years ago, we observed that laying down 2 applications of black in an effort to increase d-max had the opposite effect. We developed an target for printing, to maximize d-max results.

John Nollendorfs

[shadowblade]

It is my understanding that in coating most papers for inkjet printing, a barrier coating is put down on the raw paper base first, followed by the microporous inkjet receiver layer. The printed ink should mostly get absorbed by the microporous layer. If you are "over inking", some of the ink will lay on top and dry. This could lead to loss of d-max. In "double printing" tests many years ago, we observed that laying down 2 applications of black in an effort to increase d-max had the opposite effect. We developed an target for printing, to maximize d-max results.

John Nollendorfs

Baryta layers and RC papers have this barrier layer. That's why they take longer to outgas. Most matte papers do not - the carrier fluid goes straight through into the paper base, air can do the same (so they take less time to outgas) and it also becomes possible to apply laminates that soak right through into the paper base.

[Ernst Dinkla]

Baryta layers and RC papers have this barrier layer. That's why they take longer to outgas. Most matte papers do not - the carrier fluid goes straight through into the paper base, air can do the same (so they take less time to outgas) and it also becomes possible to apply laminates that soak right through into the paper base.

I doubt that. Hahnemühle has 3 coating layers applied by Sihl on their best matte art papers. The trick is to pull out the ink fluids fast after a droplet lands on the surface and have the pigment fixed at the surface front, not going deeper or sideways. After that evaporation of the ink fluids should start. So a build up on the paper base of a barrier, fast absorber, top coating is likely. A barrier on the paper base acts more like a membrane then, think Goretex, it blocks fluids but does not block gasses, steam etc.

It could even be a difference in the particle size of the inkjet coating minerals that changes the pore sizes going deepr into the coating layer. Mitsubishi usually gives more details:
https://www.mpm.co.jp/eng/rd/field/inkjet.html


Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2016 update, 700+ inkjet media white spectral plots

[shadowblade]

I doubt that. Hahnemühle has 3 coating layers applied by Sihl on their best matte art papers. The trick is to pull out the ink fluids fast after a droplet lands on the surface and have the pigment fixed at the surface front, not going deeper or sideways. After that evaporation of the ink fluids should start. So a build up on the paper base of a barrier, fast absorber, top coating is likely. A barrier on the paper base acts more like a membrane then, think Goretex, it blocks fluids but does not block gasses, steam etc.

It could even be a difference in the particle size of the inkjet coating minerals that changes the pore sizes going deepr into the coating layer. Mitsubishi usually gives more details:
https://www.mpm.co.jp/eng/rd/field/inkjet.html


Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2016 update, 700+ inkjet media white spectral plots

Multiple layers, certainly. But not necessarily a barrier layer. What the coating needs to do is separate the pigment from the carrier fluid as quickly as possible (keeping the pigment particles on or near the surface, or immediately behind a transparent top coat), and the quickest way out for the fluid is into the paper. Put a liquid-impervious barrier there and the ink on the surface takes longer to dry.

Matte papers do not appear to have a top coat in front of the pigment. I suspect any kind of effective top coating would change the surface appearance of the paper, generally making it glossy, and have pores too small to allow matte black pigments to pass through (instead, you can apply a top coating to matte paper with a protective spray afterwards). Glossy papers almost universally have such a layer.

Obviously, the main job of separating the pigment from the carrier fluid is done by the microporous layer. This has a large surface area to allow for the adsorption of pigment particles, as well as high porosity to allow fluids and gases to pass through quickly. The layer holding the pigment also needs to be transparent to light.

Yes, some matte papers will have multiple coatings. But I do not believe a barrier layer is one of them. It seems more likely that the extra layers would be several different microporous layers - the topmost layer being a transparent microporous layer to separate out the pigment, and deeper layers designed either to hasten the passage of fluid into the paper base (allowing a greater ink load), increase whiteness (and hide some of the paper texture) by using a pigmented microporous layer or help separate out the other, non-water components of the carrier fluid (glycerine, etc.) so that they remain closer to the surface and outgas faster than if they penetrated all the way into the paper base.

You can demonstrate the lack of a barrier layer in many papers using a method I've been using for a number of years to protect and change the surface characteristics of matte paper. Dilute some Timeless with water (4 parts Timeless to 1 part water; you can also add a drop of Photo-Flo to aid wetting). Spray it on the paper and allow it to soak in. Once it's dry, cut through a cross-section of the sprayed paper. You will find that the Timeless has penetrated deep into the paper base, binding the ink receptive layer and the paper fibres into a single, solid mass of ink, Timeless and paper that can't flake or delaminate. If there were a barrier layer preventing fluid penetration, this would not be possible - and it doesn't work on most glossy or baryta papers.

[Mark Lindquist]

I doubt that the best paper companies freely share their formulas and processes.

At the very least, the layering of barriers and or bases is combinatorial and involves semi-permeable membranes.  I still contend that anchoring to paper fibres in matte papers is a requisite condition that contributes to the greater depth that the best of these papers exhibit.  Otherwise, why then would there be the distinctions between papers based soley on their coatings?

Back to my main topic which is the drying time of the ink and carrier fluids.  In a particular case, with the HP Z3200ps printer using Epson Ultra Smooth Fine Art Paper, and using a custom made profile based on the paper preset:  Fine Art Paper More Ink, which employs Quad Inks, (PK,MK,G, and LT G) and indicates the total amouny of ink emplyed to maximize gamut without causing image quality problems. In general, the higher the ink limit, the higher the gamut.  In general, the ink limit setting for Quad inks is 60 and is applied unidirectionally only. 

So, a greater amount of ink is laid down along with a significantly greater carrier.  In my view it follows that the receptor coatings on matte papers must be predominently semi permeable filtering membranes to enable water, glycerin, (combinatorials) to flow through the ink receptors, barriers, etc., into the paper fibers at uppermost levels in particular to prevent puddling.  Evidence of this is when a print is made on a thinner yet sturdy fine art paper such as Canon Premier Matte Pro, that the paper is weighty in the hand and somewhat limp as in water-logged.  It follows that the excess or bound water must evaporate either from the front or from the back.  I contend that as the carriers and chemicals dry, the ink sets, having a bond with the paper (this not unlike shadowblade's excellent example), and cures, albeit slowly to a harder surface.  In so doing, the result is lighter and clearer, whith greater depth.  I've observed that a gloss print will also exhibit these tendencies although at an excelerated speed.  One thing discussed is the fact that any target which is measured within minutes of printing will be innacurate.  Apparently not so much so, however, that the resulting measurements are not at least in the ball park.

Knowing what I do about staining and finishing wood, I have an intuition that the combinatorial elements of the fibers, membranes, filters and surface receptors all play a majpr part in this phenomenonolical aspect of ink drying which can not be merely serendipitous.  The color scientists and teams that work in concert to present their paper offerings are too extraordinarily brilliant for that to happen.



EDIT:  Syntax, spelling

[John Nollendorfs]

Regarding my post about a "barrier layer", it's being taken too literally as a total  moisture barrier. When ink jet papers are being coated, you need a base layer, commonly known as a "barrier" layer put down first to prepare the paper surface for subsequent coatings. Most inkjet papers have a number of coatings applied. There are several different ink jet receptor coatings also. Most common, today is the microporous receptor layer. In the early days of inkjet, attempts were made to print on all kinds of art papers. The most successful ones were "tub sized" papers using gelatin, most notably, Arches. (remember all traditional photo papers were coated with gelatin?) From this, modern ink jet paper coatings evolved. In any event, it is not desirable for the ink to penetrate into the base paper at all. As has been noted, the spectral qualities of ink jet ink come from the very top of the microporous layer. As ink drys, of course the image is subject to changes, just as a "wet pet rock" looks much different when it is viewed dry. (pardon the pet rock analogy)
The coatings are designed to prevent the "spread" of the ink droplet, preserving the small droplet size, and purity of the color.

Modern OEM pigmented ink has incorporated dispersants which function to keep the pigments from clumping and settling. They also have a "coating" agent like a polymer, that keeps the pigments strands separated, and also tends to create a contrasty look to the pigments (wet rock look), that enhances the d-max.

The water portion of the ink evaporates rather quickly, as has been noted. What takes longest, are the glycols, which can form a negative image film on a close-by glass surface. Most of the "dry down" is within 24 hours depending on ambient conditions. The glycols of course take much longer.


John Nollendorfs

[Mark Lindquist]

Here is an earlier 2012 thread where Ernst Dinkla explains about inks and coatings:

Inkjet Coatings

Everyone is saying that the ink does NOT penetrate in to the paper fibres at all but I disagree.

There is too much literature and information out there that supports my "key" theory.

Even Epson's own literature illustrates not just the difference between dye and pigment inks but clearly shows that some pigment particles do penetrate near the surface of the paper.  I have seen this in a lot of literature.  It only makes sense.  Some of the ink must go into the topmost layer of the fibers in order to anchor and provide a more stable reflective base.  Again, I ask, why would there even be different  types of papers if all they did was to provide support for coatings.
I contend that the paper fibers, particularly at their upper most level are involved in this complex equation.

If all the paper did was provide a support for the coatings, then we should have one universal base that is the most stable and simply carries the coatings and served as a universal substrate.

Look at Epson's own graphic illustration attached - doesn't it indicate it and explain it?

In the case of instant dry papers, gloss, semi-gloss, satin, barytes, etc., then yes, I agree the ink does stay confined within the surface layers.

I have a suspicion that for Matte papers, not so. 
Until a scientist who actually works on these issues can prove to me definitively that I'm wrong, then I will stick to my opinion.

Mark

[Mark D Segal]

This paper may be of interest to the topic:

Printability and Ink Coating Interactions

[Mark Lindquist]

This paper may be of interest to the topic:

Printability and Ink Coating Interactions

That's an amazing paper Mark, thank you for providing that link.

A few interesting aspects:

4.5 Summary
Figure 28. Line width on PVOH-silica coatings with additives.
PVOH-coated samples all presented an excellent colour gamut, which is likely as a result of good film-forming capabilities. The sharpness was also good; however, the coatings suffered from high gloss variation and slow ink drying. With the addition of pigment, a new structure is formed with large pores in and between the pigments, and a macro-roughness generated by the large particles. The inkjet droplets can quickly penetrate into the large pores, and the time for surface wicking is reduced, which is beneficial for the blurriness. However, the macro-roughness promotes bulk spreading in the coarse surface structure; this tends to increase the line width. Finally, the ink ends up within the coating and the colourant is partly shielded by the particles; this reduces the gamut area to some extent. Additives such as cationic polymers and PVP can further improve the print quality. The addition of a cationic additive showed an overall positive effect of gamut area. However, it did not always prevent lateral ink spreading. It is suggested that blurriness is a surface wicking that is greatly determined by the micro-structure of the substrate [82], while line width is a bulk spreading that is promoted by a hydrophilic substrate and perhaps also by a slow absorption by the underlying substrate and/or ink.

Additionally, the paper is dealing most specifically on coatings presumably applying to papers such as gloss, semi-gloss, etc., where even still they are subject to micro-cracks whereby ink can escape through.

Also,

"...The purpose of this work has been to gain an increased knowledge of the mechanisms that con- trol the absorption and the fixation of inkjet droplets on coated papers. The focus has been on printability aspects of high quality (although not photographic quality) laboratory coated inkjet papers for printers using aqueous-based inks. Coating colours, made from a wide range of com- mercial, as well as non-commercial coating chemicals, have been evaluated mainly in terms of inkjet printability and runnability. Print quality aspects, such as line expansion, blurriness, and colour gamut were analysed and correlated to structural features of the coating layer, as well as to ink composition. It was determined that coatings with pure polymer binders gave an excellent colour gamut and that, with an addition of mesoporous pigments, the print sharpness improved. Moreover, it was also determined that the printability and the binder demand were affected by the pore size, as well as pore size distribution of the pigments...."

The fine art matte papers I'm referring to have unique properties not covered in this study.  Yet the principles are there.  It appears that chemical composition of the coatings in conjunction with the chemical composition of the inks create the interactions which affect color gamut and all other print quality aspects.

Unfortunately, the study did not delve into the properties and qualities of base components of specific papers.

But definitely an eye-opener for sure.  Now if you could find a study on the reactivity of paper substrates to high quality aqueous ink jet coatings, inks and drying times, I would be thrilled.

Thanks again.

Mark

[Mark D Segal]

That's an amazing paper Mark, thank you for providing that link.

................ Now if you could find a study on the reactivity of paper substrates to high quality aqueous ink jet coatings, inks and drying times, I would be thrilled.

Thanks again.

Mark

Google is your friend.

But so far I have not found exactly what you are looking for. The one attached may provide some further insight. The subject matter quickly gets very technical and presumes specialist knowledge of the various chemical components entering into the coatings, barriers and the substrates. I think this is a rather deep subject. :-)

[Mark Lindquist]

Google is your friend.

But so far I have not found exactly what you are looking for. The one attached may provide some further insight. The subject matter quickly gets very technical and presumes specialist knowledge of the various chemical components entering into the coatings, barriers and the substrates. I think this is a rather deep subject. :-)

Yes I use "The Google" a lot, Mark.  Thank you for taking the time to find this article.  It is a bit deep, but it's certainly not out of the realm of comprehension or even basic understanding.

An interesting quote found from the paper:

"...It has been speculated that the ink penetrates further into the paper due to the hydrophilic nature of the filler [14]..."

Apparently, depending on the lesser or greater use of ColorLok®, the degree to which ink absorbrption by the paper is tunable and controllable.

Also..."...The main purpose of the work was to improve the physical paper-properties such as cockle and waviness without reducing the print quality. This introduction study deals with the effects of paper properties on print quality...."

This article does shed some light, and it is the closest to come near the question of whether the ink does in fact bind with the paper fibre.

To a degree it apparently does, but is prevented more for purposes of controlling flatness - buckling/warping, etc.

Thanks again, I appreciate your unbiased response to the question at hand.

Mark

[shadowblade]

Yes I use "The Google" a lot, Mark.  Thank you for taking the time to find this article.  It is a bit deep, but it's certainly not out of the realm of comprehension or even basic understanding.

An interesting quote found from the paper:

"...It has been speculated that the ink penetrates further into the paper due to the hydrophilic nature of the filler [14]..."

Apparently, depending on the lesser or greater use of ColorLok®, the degree to which ink absorbrption by the paper is tunable and controllable.

Also..."...The main purpose of the work was to improve the physical paper-properties such as cockle and waviness without reducing the print quality. This introduction study deals with the effects of paper properties on print quality...."

This article does shed some light, and it is the closest to come near the question of whether the ink does in fact bind with the paper fibre.

To a degree it apparently does, but is prevented more for purposes of controlling flatness - buckling/warping, etc.

Thanks again, I appreciate your unbiased response to the question at hand.

Mark

'Ink' means more than one thing here. It can refer to the whole thing - pigment, carrier fluid and all - but it can also refer to the carrier fluid alone, which is part of the ink and, undoubtedly, reaches the paper base.

As to whether the pigment reaches the paper base, that really depends how much ink you're putting onto the paper.

Look at a cross-section through an ink dot on a piece of printed paper. The dot is widest at the very surface, becoming narrower and narrower deeper into the layer, essentially forming a hemi-lenticular shape. That is, the more ink is placed on a particular point on the surface at the same time, the deeper the pigment goes. If you put enough ink on the same spot, some of it will reach he substrate. If that happens, that part of the coating has been over-inked - once it reaches the base, it spreads along paper fibres just as on uncoated papers.

So, yes, pigment can reach the substrate, if you dump enough ink on it. But, if the paper is profiled correctly, it shouldn't. And you wouldn't want it to - if it reaches the substrate, it's free to spread in the same manner as on uncoated paper, increasing dot grain and decreasing resolution.

HP's Color-Lok technology is unrelated - it improves the performance of uncoated papers, not coated ones. Effectively, it's a different form of external sizing for the paper, giving the sizing some of the properties of an inkjet-receptive layer to prevent pigment migration along the fibres.

[Mark Lindquist]

'Ink' means more than one thing here. It can refer to the whole thing - pigment, carrier fluid and all - but it can also refer to the carrier fluid alone, which is part of the ink and, undoubtedly, reaches the paper base.

As to whether the pigment reaches the paper base, that really depends how much ink you're putting onto the paper.

Look at a cross-section through an ink dot on a piece of printed paper. The dot is widest at the very surface, becoming narrower and narrower deeper into the layer, essentially forming a hemi-lenticular shape. That is, the more ink is placed on a particular point on the surface at the same time, the deeper the pigment goes. If you put enough ink on the same spot, some of it will reach he substrate. If that happens, that part of the coating has been over-inked - once it reaches the base, it spreads along paper fibres just as on uncoated papers.

So, yes, pigment can reach the substrate, if you dump enough ink on it. But, if the paper is profiled correctly, it shouldn't. And you wouldn't want it to - if it reaches the substrate, it's free to spread in the same manner as on uncoated paper, increasing dot grain and decreasing resolution.

HP's Color-Lok technology is unrelated - it improves the performance of uncoated papers, not coated ones. Effectively, it's a different form of external sizing for the paper, giving the sizing some of the properties of an inkjet-receptive layer to prevent pigment migration along the fibres.

Shadowblade, you know I respect your opinions and your background, etc.  May I point out that the evidence had from prior electron microscopic  sampling of side views of cut paper has been rendered obsolete, since it has been recognized that side view sections cut with the best of blades alter the samples through squashing of the materials, no matter how careful.  New techniques render historical and traditional views inadequate.  A company called Sappi, cuts paper with an argon beam instead of a blade to aide in more accurate investigations.

As I say, without the equipment, expertise and background to back it up, I have a hunch that the ink does combine and lock into the fibers, and I will stick to my opinion, while at the same time thinking about what you are saying.  I am not talking about an exaggerated sloppy combinations, just a level of "key" which enables a combinatorial intermingling of paper fibers with all the elements making up the interaction of ink and coating.  I don't think the paper fiber can be left out of the equation, or why bother having matte papers at all?  The interaction of the ink with the paper and the coating is significant in a combinatorial sense.

As for loading ink, I only am discussing what is found specifically in HP's bulletin regarding Quad inks:

"Fine Art Paper More Ink, which employs Quad Inks, (PK,MK,G, and LT G) and indicates the total amount of ink employed to maximize gamut without causing image quality problems. In general, the higher the ink limit, the higher the gamut.  In general, the ink limit setting for Quad inks is 60 and is applied unidirectionally only."

I appreciate your position and respect your views.  I accept a lot of what you say, however I also have my own understanding and experience having printed so much for so long.

Mark