Simple question about sheetfed printing process
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Alois Senefelder
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Where does the water go ........
A sheet of water about 0.4 microns thick is continuously being supplied to the plate, remember that
water evaporation takes place from the plate surface and water take up by the inking roller train, then by
transfer to the paper.
Regards, Alois
A sheet of water about 0.4 microns thick is continuously being supplied to the plate, remember that
water evaporation takes place from the plate surface and water take up by the inking roller train, then by
transfer to the paper.
Regards, Alois
i've read in few books quite the same statement:
"since part of the dampening solution is printed via ink, plate, and blanket..." (kipphan)
"in the second, third etc. the ink is not transferred to dry paper but at least to a dampened paper surface" (bernd th. grande)
And i was sure that there is not only ink splitting process, but "dampening splitting" also.
A couple of weeks ago i've been told by my employers that blankets stays dry and no dampening transfers to blanket, or to paper.
That was right at the moment when i tried to convince them that going away from using ipa can bring more trouble than saved money from ipa refusal.
My point was that with ipa the dampening solution will evaporates more rapid than without (so less dampening on paper).
So no i'm quite embarassed – maybe i've lacked of logic or just don't understand the printing processes?
"since part of the dampening solution is printed via ink, plate, and blanket..." (kipphan)
"in the second, third etc. the ink is not transferred to dry paper but at least to a dampened paper surface" (bernd th. grande)
And i was sure that there is not only ink splitting process, but "dampening splitting" also.
A couple of weeks ago i've been told by my employers that blankets stays dry and no dampening transfers to blanket, or to paper.
That was right at the moment when i tried to convince them that going away from using ipa can bring more trouble than saved money from ipa refusal.
My point was that with ipa the dampening solution will evaporates more rapid than without (so less dampening on paper).
So no i'm quite embarassed – maybe i've lacked of logic or just don't understand the printing processes?
'Where does the water go?' was a big topic of debate back in the early nineteen-ninties with a lot of competing research done by such luminaries as McPhee and Fadner. Much of the theory presented at the time seemed contradictory, at odds with things I had observed in the pressroom. These theories have been mostly resolved now, though whenever researchers get together there is rarely agreement about anything, as any reader of this forum can appreciate.
Almost all of the water reaching the paper (with the exception of presses equipped with brush, spray, or centrifugal dampeners that expose the substrate to a lot of mist) is contained in the ink making up the image area. The image area will be anywhere from three to fifteen percent water (depending on what expert you believe) but the amount of water reaching the non-printed area of the paper is negligible. The transfer of water through the press can best be described as one wet surface presenting water to another surface, one that will accept or reject water based on the receiving surfaces 'surface energy'. The blanket is not a particularly water receptive surface, so the water presented to it on the background area of the plate is just left there by the blanket.
As for the running of IPA, almost any printer in the US could run as much alcohol as they like (in some states this might involve giving up solvents for cleaning the press) and in this hyper competitive market if there was any advantage to running IPA, everyone would be forced to use it in order to compete. This, of course, has not happened. I listened to one pressman complain to me about alcohol replacement fountain solution until his quality guy walked up and refuted every claim the poor guy had made. It seemed that by every measurable parameter, quality and productivity were better without IPA than with.
Almost all of the water reaching the paper (with the exception of presses equipped with brush, spray, or centrifugal dampeners that expose the substrate to a lot of mist) is contained in the ink making up the image area. The image area will be anywhere from three to fifteen percent water (depending on what expert you believe) but the amount of water reaching the non-printed area of the paper is negligible. The transfer of water through the press can best be described as one wet surface presenting water to another surface, one that will accept or reject water based on the receiving surfaces 'surface energy'. The blanket is not a particularly water receptive surface, so the water presented to it on the background area of the plate is just left there by the blanket.
As for the running of IPA, almost any printer in the US could run as much alcohol as they like (in some states this might involve giving up solvents for cleaning the press) and in this hyper competitive market if there was any advantage to running IPA, everyone would be forced to use it in order to compete. This, of course, has not happened. I listened to one pressman complain to me about alcohol replacement fountain solution until his quality guy walked up and refuted every claim the poor guy had made. It seemed that by every measurable parameter, quality and productivity were better without IPA than with.
Thank you for your answer. One question: suppose you're running 4 color job KCMY order, large format (960x1300).
And your black plate has little image areas, like this:
Will the water transfer be the same, so no water in non-image area as you're describing?
That is quite debatable. First is quality guy – did he ever worked as a pressman? Theoretical advantages can be like a holy grail especially if you're good at talkin'.
I, personnaly, don't know any techspec who can argue that ipa:
1. increase solution's viscosity which improves transfer over the bareback fount rollers
2. reduces surface tension, so a thin but stable and uniform film forms on plate
3. cooling effect from constant evaporation on rollers and plate, which stabilizing ink rheology and uptake of the fount
4. improves runoff from the plate, gives rapid adjustment on in/water balance
Also in europe most presses have integrated fount units, so without ipa the danger of overmulsification is much greater than on us-most presses with direct fount units
Alois Senefelder
Well-known member
The Golden Rule of Lithography -
1) Minimum of Ink 2 Mininmum of Damp 3) Minimum of Pressure
Regardless of the Size of Image Area - a thin film of F.S is required just to keep the Plate from "Catching-up"
In the EU Alcohol enriched Fountain Solutions are being banned, next most Printing Presses in the World are - German or Japanese Manufactured
Regards, Alois
1) Minimum of Ink 2 Mininmum of Damp 3) Minimum of Pressure
Regardless of the Size of Image Area - a thin film of F.S is required just to keep the Plate from "Catching-up"
In the EU Alcohol enriched Fountain Solutions are being banned, next most Printing Presses in the World are - German or Japanese Manufactured
Regards, Alois
D
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IMO the real issue is having the "right" amount of ink for the job. Ink on the paper is what you see and what you sell. The control of the amount of water is important for quality but it is not required to be any specific amount and anyways it evaporates.
It is the same with any printing process. It is the control of the placement and amount of ink that is important. Ideally it should be consistent and predictable.
In modern offset, there is still not positive control of the ink but that is the way printers want the process to work.
It is the same with any printing process. It is the control of the placement and amount of ink that is important. Ideally it should be consistent and predictable.
In modern offset, there is still not positive control of the ink but that is the way printers want the process to work.
Any theoretical discussion of litho technology (especially fountain solution and alcohol) always causes people on this forum to start expressing their opinions and observations and I think this is the best thing that happens here. I have been formulating and selling alcohol replacement fountain solutions for a long time and have done many thousands of hours of experimentation (almost all of it done on press, in pressrooms, running commercial work), but still do not present my ideas as undisputed facts as my fellow forum goers are sometimes fond of doing.
The assertions
"1. increase solution's viscosity which improves transfer over the bareback fount rollers
2. reduces surface tension, so a thin but stable and uniform film forms on plate
3. cooling effect from constant evaporation on rollers and plate, which stabilizing ink rheology and uptake of the fount
4. improves runoff from the plate, gives rapid adjustment on in/water balance"
are all true, except the second half of the third one and the fourth one in its entirety. As for #1, the increased viscosity causes a press with continuous dampening to consume much more fountain solution to print a specific volume of printed work than would be used running IPA replacement products. This has advantages and disadvantages. #2, most unsuccessful alcohol replacement fountain solutions (and there were a lot of these back in the day) reduce the surface tension to levels well below those of IPA, but still didn't work (many didn't work at all). #3, there is some cooling yes, but presses running the same form side by side with and without IPA showed no evidence of this being of any value. These tests were run over and over with consistent results. A lot of this testing was done at the time we were trying to figure out 'where the water went' and a high speed commercial web makes water disappear at a pretty rapid rate.
To suggest somehow presses in Europe have a greater need for alcohol than the exact same presses installed in another hemisphere is hardly supportable.
The assertions
"1. increase solution's viscosity which improves transfer over the bareback fount rollers
2. reduces surface tension, so a thin but stable and uniform film forms on plate
3. cooling effect from constant evaporation on rollers and plate, which stabilizing ink rheology and uptake of the fount
4. improves runoff from the plate, gives rapid adjustment on in/water balance"
are all true, except the second half of the third one and the fourth one in its entirety. As for #1, the increased viscosity causes a press with continuous dampening to consume much more fountain solution to print a specific volume of printed work than would be used running IPA replacement products. This has advantages and disadvantages. #2, most unsuccessful alcohol replacement fountain solutions (and there were a lot of these back in the day) reduce the surface tension to levels well below those of IPA, but still didn't work (many didn't work at all). #3, there is some cooling yes, but presses running the same form side by side with and without IPA showed no evidence of this being of any value. These tests were run over and over with consistent results. A lot of this testing was done at the time we were trying to figure out 'where the water went' and a high speed commercial web makes water disappear at a pretty rapid rate.
To suggest somehow presses in Europe have a greater need for alcohol than the exact same presses installed in another hemisphere is hardly supportable.
That's mean that you're right the person i was looking to talk to 'cause i've got one question still without answer (maybe because i don't have proper chemical edicution)
foreword: in our company quite everything worked great, except spontanious carboning problems. One day our supplier told us that he knows easy way to reduce it almost to zero by using specific pair of ink and fountain additive (for ipa consumption by 1-5%). That information he got from head company in europe (hostmann-steinberg). So they bring us this pair (reflecta+substifix hd). We've made couple of tests (actually a lot of tests with 3 different inks and 2 fountain additive) in e.g. stressfull conditions with lots of ink on the paper (350+%) and clean opposite side at folding. Strange, but we've found out that the use of recommended pair shows clearly less carboning problems. So everybody got happy we've switched to this pair and go on workin'.
But with less carboning we've faced another problems: strong chemical ghosting which we didn't see for a long time and strange exothermic reaction in a printed pile (and folded pile, and sewed pile)
Didn't knew what to do and went back to the previous fount (you can read about it here) – and magically problem with heated piles and chemghosting have gone (but returned another problem with ink unstableness in middle-long runs).
And now the big question – what can go wrong if one adds more ipa than recommended 1-5% into the mix with fount that contains ipa replacements?
Alois Senefelder
Well-known member
mmm A surfeit of IPA
1) Drunkenness, Bankrupt or Asphyxiation
Regards, Alois
PS what is "Carboning"
1) Drunkenness, Bankrupt or Asphyxiation
Regards, Alois
PS what is "Carboning"
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"Carboning refers to micro-scale rubbing of ink, under high pressure and with minimal movement, against the white sheet facing it, such as occurs on a trimmer. In particular, carboning occurs after cutting bled-off illustrations if the print is lying against white paper."
It sounds to me like what is referred to as 'carboning' is what we used to call 'chaulking' defined as when ink behaves as if dry for the pressman (jobs do not block in the delivery and can be backed-up) but mark or smear in the bindery. This was caused by pigment migrating to the surface of the ink with the wax while the ink dried underneath this layer. As for the generation of heat in the pile, it seems the ink in question was loaded up with oxididzers and ingredients to stimulate oxidation in order to achieve a harder dry surface. Oxidation produces heat. The solution for chalking was usually to add vehicle (varnish) to the ink to reduce the overall pigment load, leading to a thinker film that would dry without chalking.
"And now the big question – what can go wrong if one adds more ipa than recommended 1-5% into the mix with fount that contains ipa replacements?" I have not observed problems when running more IPA than recommended along with fountain solution products designed to run without it, but I must qualify this by saying I have not often seen this set of circumstances. In the early days of IPA replacement, customers were presented mostly with two part products (an inexpensive fountain solution and an expensive alcohol replacement) and when things did not work to the customers satisfaction (which was almost every time until about 1990) the pressmen would dump the replacement and go back to IPA, not use both together. Chemically speaking, there really isn't much in the form of incompatibility between IPA and the general mix of solvents and surfactants used in modern IPA replacement products, I would think the biggest problem of using both would be the increase in cost.
Back in the nineteen seventies I worked for a while in a sheetfed shop that used ethanol (rather than isopropyl alcohol) and we would have been reluctant indeed to give that practice up (if anyone had suggested it at the time, which no one did) because we used it as much to augment our beverages as we did to add to our fountain solution.
"And now the big question – what can go wrong if one adds more ipa than recommended 1-5% into the mix with fount that contains ipa replacements?" I have not observed problems when running more IPA than recommended along with fountain solution products designed to run without it, but I must qualify this by saying I have not often seen this set of circumstances. In the early days of IPA replacement, customers were presented mostly with two part products (an inexpensive fountain solution and an expensive alcohol replacement) and when things did not work to the customers satisfaction (which was almost every time until about 1990) the pressmen would dump the replacement and go back to IPA, not use both together. Chemically speaking, there really isn't much in the form of incompatibility between IPA and the general mix of solvents and surfactants used in modern IPA replacement products, I would think the biggest problem of using both would be the increase in cost.
Back in the nineteen seventies I worked for a while in a sheetfed shop that used ethanol (rather than isopropyl alcohol) and we would have been reluctant indeed to give that practice up (if anyone had suggested it at the time, which no one did) because we used it as much to augment our beverages as we did to add to our fountain solution.
CPT, I'm amazed someone had an internet based pdf that Alois had not already offered up!
Yesterday a techspec from poland come to our place to explain some of my questions about ink/fountain situation and behavior.
In the middle of our chat he said that from practice he knows that ink can absorb about up to 40% of water and even more. He was speaking about ink/water behavior on press.
I've mentioned that such percents cannot be found in pressroom, only in the lab tests, 'cause i remember that American Ink Maker made such tests and found water content about 5-15% and fogra made such tests too – and that was a long time ago when everibody realised that water pick-up in lab is much higher and do not generally correlates one to another.
After that he showed me a PRESENTATION with one screenshot from taga proceedings 1976 which he believes to approve his position. After that he said that fogra is just a bunch of managers and there are no real researchers.
So i just don't know what the heck am i supposed to do with all that stuff.
By the way, do anyone have a taga proceedings papers from 1976?
Thank you Dan, i've got a little clearer vision printing processes now.
Alois Senefelder
Well-known member
Nomenclature !
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