| |
| | |

Printer Forum   

 Forgot password?
View: 2409|Reply: 19

The Perfect Lithographic Ink - Not Yet Born - Year 2012

[Copy link]

Post time: 2013-2-22 15:17:17 |Show all posts
I touched upon this in another thread, but would enjoy a little feedback to the concept as we are approaching much more complex galaxies, such as the NanoSphere!
Help me out Gordo, Erik, Al. Anyone please comment.
See gentlemen, litho can be dramatically improved, by changing of the ink formula based on given coverage or take off for a given print form. This coverage factor is an everchanging variable.
The rigors that are put on an ink in very light to very heavy coverage are dramatically different. The idea would be to keep the same replenishment rate for each ink, regardless of coverage. More study would have to be done to find the ideal ink film thickness, say for each process color.Then, based on total percent covearge for that ink, that print form, the strength of that ink would be adjusted to accomodate the coverage. This would be ideal. If the inks and extender portion are formulated properly, you force constant replenishment based on take off. This would allow your ink to run at a constant state of proper micro emulsification, without adjustment to the dampeners. Ink stability in the train, ink setting and drying would be improved and much more predictable.
The design needed on press to achieve this is reachable. If you have 4 Full Strength process inks dispensed from pumps, that would be the ink used for a full coverage, 100% solid sheet. With the inks, you would have a let down extender also designed to be pumped and mixed for each changing print form. Knowing the exact total coverage for each color, the ink would be pumped and mixed with the proper amount of let down extender to maintain constant ink film thickness and constant replenishment. This is an ideal situation to take litho closer to science, although it shall always remain an art.
COVERAGE, is the most important factor and the one thing that presently cannot be controlled. The example of an ink system as just described, would control a major variable not yet properly explored or developed.
Your thoughts are encouraged. Thank you.  D

Post time: 2013-2-23 20:41:00 |Show all posts
John MacPhee is an engineer and his work tended to be a little different than many of the other researchers.  He had a practical view to his work.  There were also a lot of interesting papers by Goss (Rockwell Int.) that looked at some press dynamic issues of inking and water application.  Unfortunately that did not prevent them from making a complete mess out of a press concept called a "Positive Feed Keyless" system in around 1995.  They sold about four of these press concepts but I understand they had to convert all of them back to conventional ink fountains.   At that time, it took me about 30 minutes of analysis to see that that concept was unworkable.  
I like looking at these technical papers but I am also critical about the technical papers presented in this industry.  The technical papers in this industry are filled with experimental results and with dubious mathematical modelling.  Many theories presented are no more than observations.  Observations are not theories.  There has been little effort to develop theories that actually explain what is happening.  
There is always the stated interest to gain more knowledge but very little to solve problems.  Many of the technical paper generating groups are not in the problem solving business but in the technical paper generating business.  
I like looking at the observations, comments and conclusions in these papers because they provide some data or phenomena descriptions that help me in my efforts.  Often after reading their works I understand the  issues better than they do.  The reason for this is that my work has been to develop a theoretical structure to explain the process and their observations help to support or help to refine my theoretical views.  Their comments and conclusions also tell me what state of "cluelessness" they are still in.
My ultimate goal is to obtain practical solutions but as an engineer, educated in a theoretical based institution, I know that to obtain predictable results requires valid theory.  So I have had to generate that theory on my own because it does not exist in this industry.  There are tons and tons of experimental results and lots of myths but not much valid theory to correctly explain why things happen.  
Offset printing is a difficult process.  Not because the problems are difficult but because there are so many relatively simple problems that have not been addressed at a fundamental level and these problems interact with each other.  Most efforts to improve the process try to target and address symptoms of faults in the process and the technical solutions tend to be band aid solutions plastered over existing faults.  This results in expensive technology that helps but does not fully satisfy.  
To look at improving the offset process, one not only needs to focus on specific problems but at the whole process with its pre and post considerations.  Look at the whole and find what is important and what is noise.  What has to be fixed first before one can repair the whole process?  Well my view has been and still is that ink feed is THE critical problem to correct.  
I like the potential of offset lithography.  Offset is an existing process.  Runs every day all over the world.  I am not attempting to make a new process but just putting the pieces of the puzzle in place so it can work better.  Offset works today, on the other hand, even with all its potential, Landa's process does not work.  I wish the press manufacturers would have some faith in their own process and try something new with offset.

Post time: 2013-2-23 18:55:30 |Show all posts
Bob Peterson, thank you for that additional educational reply also. The paper stock certainly has an effect on your color. If the proofs and the ink printings were on the same substrate, the problem would not be eliminated, but it would be minimized. Thank you again Bob, wonderful contribution.  D

Post time: 2013-2-23 17:38:14 |Show all posts
I would not necessarily put the onus on the ink manufacturers. The colorants used by Epson are in all likelihood not the same pigments that ink formulators can use in their inks. The ink guys are limited.
Black is carbon black and alkali blue normally. This is the least likely to cause a problem.
Cyan is Phthalo Blue, Pigment Index no. 15:3.
Magenta is Lithol Rubine, Pigment Index no. 57:1
Yellow is normally AAA Benzidine, Pigment index no. 12:1
These are the available pigments that the ink maker has to work with to make your ink. Many times, when trying to match a proof, the proofs are made from dyes, rather than pigments. When this occurs, you have a condition known as METAMERISM. This is the problem you face.
It would be easier for Epson to create their proofs from ink pigments than it would be for an ink maker to make inks from the Epson colorants.
If we used the Epson colorants, they would be soluble in water, have no lightfastness and would not have nearly enough strength in order for you to run a reasonable lithographic ink film. They are more problems, but the solution may be for a progressive ink company and a company like Epson to form a joint venture to overcome the problems you and others face on a normal basis.
It takes work and commitment by both fields of the industry to overcome your issues. It should be done, because you sir, are the customer.

Post time: 2013-2-23 15:47:51 |Show all posts
Providing the proof and press are calibrated to gray balance, the pigments/dyes being used by the proof and the press are the same, the problems with matching under multiple light sources lies in the substrates optical brightener content. The paper used for the proof, in most cases, contains zero optical brightener or an amount that remains constant. Whereas, the press is printing on various substrates, with varying amounts of OB.
Sometime, get yourself a black light and view various production papers versus your proofing paper. All of the papers will fluoresce differently. What you are seeing is the amount of optical brightener. This is what causes, in most cases, the difference between the proof and the press under different light sources, other then the 5000K that the gray balance was calibrated in.

Post time: 2013-2-23 14:08:24 |Show all posts
Ink set = CMYK
Constant complaint, "this blue, gray, etc. doesn't look anything like the Epson proof?" Question, "are you viewing and comparing in a D50 environment?" Answer, "uh, what?"
We can't be the only printer that experiences this frustrating issue. Epson has done a great job of formulating inks that reduce/eliminate the effect of different light sources when viewing an Epson proof outside of D50 lighting. My hope is that someday offset ink manufacturers will be able to do the same.
I have answered this complaint 5 times in the last 3 weeks alone.

Post time: 2013-2-23 12:25:27 |Show all posts
Ink needs to be able to form that much sought after micro emulsion. It needs to have the capability to continually accept fountain solution(water) in the presence of everchanging COVERAGES.
Much stride has been made by the ink formulators in studying this in a controlled lab environment. The Duke emulsification tester was the one of the initial pieces of equipment used in the studies. The Surland curve has been a well utilized test method in conjuction with the Duke.
Advancements in technology have lead to equipment like the Kershaw emuldsification tester. It not only tells you about the way a particular ink emulsifies solution, but also shows the effect on an inks rheology as more solution is forced into the ink median. Great progress has been made in ink formulations using the Kershaw, particularly web heat set, coated publication, where press speeds are hitting 3000 fpm. Very interesting R&D for the lucky techs who still have the opportunity to work on it.  D

Post time: 2013-2-23 10:28:07 |Show all posts
Yes, Mr. MacPhee is who I couldn't remember.  He was always a good source for mathematic models for just about anything.  
One of the main purposes of the project I was referring to was to determine where fountain solution 'went' during the printing process (these observations were made in the late 1980's) and the film thickness observations were just one of the many supplemental inquiries based on the same set of observations. The theory of the ink system acting as a self-regulating reservoir for fountain solution while printing and the idea of considering the plate cylinder to be an active part of the dampening system were the primary conclusions we drew.

Post time: 2013-2-23 09:07:39 |Show all posts
Todd define "ink set".
Also from a practical sense, why is this so importantly needed?
Are color comparisons being made? Just trying to best understand. Thanks. D

Post time: 2013-2-23 08:03:18 |Show all posts
Ink set.   All black inks.  Wish granted.
Maybe not.  The colour of the paper will change.  :-)

Post time: 2013-2-23 06:48:40 |Show all posts
How about an ink set that remains color constant outside D50 lighting? That's my wish.

Post time: 2013-2-23 05:21:17 |Show all posts
Gents, All very good interactive discussions. I'll thank you as continue to ponder 'perfect lithographing'. I know there is still room to improve it.

Post time: 2013-2-23 04:13:38 |Show all posts
John Macphee   at Baldwin??  I don't think he was a Dr.
Yes, you bring up a good point.  What you see can seem to differ from the calculations.  The calculations usually assume just ink in the roller train.  With water being mixed with the ink, the overall ink film will be different from the calculation but the ink component in those films should basically follow the calculation.  
You would have to superimpose the water going into the system over the ink going into the system.  Water is going up the roller train while the ink is going down, although both are going up and down at the same time.  This is one reason I like the idea of adding water higher up in the roller train because then there are less conflicting paths for water and ink and that should make the mixed ink film at the form rollers more consistent.
With ink, there is basically just one way out and that is via the print.  With water there are multiple paths, out via the non image area, out via the water mixed with the ink and out via evaporation on the roller train.
If one wants to be picky, yes it is very complicated and calculations will not show exactly what is really happening.  These kind of calculations are very helpful to aid thinking but are not at all good enough to describe what is happening with any accuracy.
This does not worry me too much because what is most important is that "on average, the amount of ink that is printed, must always equal the amount of ink that goes into the press, irrespective of variations in ink film on rollers".  
Systems with inconsistent ink feed will result in inconsistent printed outfeed on average.  
Systems with consistent ink feed will result in consistent printed outfeed on average.

Post time: 2013-2-23 02:39:48 |Show all posts
I have done some research on this subject in the past and have never been able to reproduce the relative ink thicknesses predicted by this method.  Bob Bassimer from Sun and Dr. 'whats his name?' from Baldwin would provide me with calculated ink film thicknesses based on what we were calling 'splitting theory' at the time (their algorithms for this changed frequently) but the film thickness in the upper ink train never seemed to contain anywhere near the predicted weight of ink compared to the form rollers.  Almost all of this work was done on webs running at what we used to call high speed (around 1800 fpm) and the observations made did not differ much from experiment to experiment.  Unfortunately, all of the documentation of this work was seized by a former employer and there was far too much data to attempt to remember.
We did observe the relative volume of fountain solution compared to ink in the ink unit differed based on the coverage being printed; higher when coverage was light and lower when coverage was heavy. I have always advised customers having trouble with light coverage forms to add ink vehicle to the ink and this is usually beneficial to at least some extent.

Post time: 2013-2-23 01:01:32 |Show all posts
I like what you are presenting, but I do think that there are certain variables that just can't be eliminated with the current way the process functions. I would assume that mixing the ink differently would change tack, visocity, splitting properties, and of course, dot gain as was already mentioned. It would seem that if you wanted to adress the problem of having to always change ink settings based off of coverage you might have to look at a different part of the process that affects it. (Just thoughts from a printer though)

Post time: 2013-2-22 23:10:43 |Show all posts

Could the problem be in one of your assumptions?
Are you assuming that high coverage has thicker ink films on the roller train than lower coverage at the same density?  If this is one of your assumptions I can see where this would lead you to thinking of having a more consistent ink film on the roller train.
It is true that higher coverage will result in thicker ink films on the roller train than lower coverage but the thicker ink films are only near the ink fountain.  For high coverage, where more ink is being transported down the roller train, the ink film is getting thinner and thinner due to the affect of splitting.  By the time one gets to the form rollers, the ink film should be close to the same for high coverage as it is for low coverage.  (Mathematically they are not the same but they are close. This depends upon the number of form rollers.)
So in the existing offset press, the ink films are almost constant at the form rollers which in a way was what I think your goal was.

Post time: 2013-2-22 21:11:58 |Show all posts
Erik, you are correct. The only way it could possibly be feasible is in take offs of great differences, like 10% versus 100%. I see where the constant ink feed and varying strength would interefere with print and dot quality. I'll ponder this some more to try to offer better litho improvement. Thanks, D

Post time: 2013-2-22 19:56:21 |Show all posts
If I understand your approach correctly, I see some problems.  
You want to obtain a constant density that is independent of take off.  Well this is done now basically by printing high or low coverage with the same ink film thickness.  What this requires is an uneven ink feed down the roller train.  You seem to want to get to this state of constant density with a constant ink flow rate across the press independent of coverage, using your dilution idea with the extender.
If you use a more diluted ink with extender for the low coverage that ink film will be thicker than the less diluted ink film for the high coverage to try to get to the same density.  Density is more related to the pigment amount in the film and not the thickness of the film.
What if the high and low coverage are screens?  With inks of different strengths, there will more likely be differences in dot gain, which would make prepress very difficult.
If you have a form on the press which has very high coverage on say the gear side and very low coverage on the operators side, what ink do you use.  
Maybe I am missing something but right now there are too many issues that are problematic.

Post time: 2013-2-22 17:58:48 |Show all posts
Erik, it is not a problem. It is the notion of reaching the perfect lithographic state via the ink median.
Example: If you have a maximum possible 1000 sq. inch image area on each plate and the image for a particular form was 100% Solid, you would use the properly formulated Full Strength process ink for that scenario. Let's say that image is changed to 10 sq. total inches for the next form. The ink would then have a let down or extender added to the full strength ink to accomodate the change in COVERAGE. The ink would be reduced in strength by at least 1/2 the pigment amount. This would be done so that you are carrying the same amount of ink through your roller train, to the plate, blanket and finally paper. The idea is to keep your density the same, no matter what the take off. Again, the idea is to keep the ink usage constant regardless of the coverage and form. Constant replenishment!
As far as different "formualtions for each form", the most critical ink formulation would be for the let down extender. It would have to have the same, similar rheological properties as the 4/C inks. A neutral median would have to be reached, so the use of only 1 extender would be needed. This can be done, actually quite easily, by someone with the expertise of proper litho ink formulation.
Taking it one step further, the engineers would need to devise a pumping station for 5 ink entities. Black, Cyan, Magenta, Yelow and Extender. In the engineering, they would have to develop a blending device, that would deliver the proper strength ink, based on the print form.
I hope this doesn't sound too far fetched, but it truly is a concept that can approach perfect, easy running lithography, from a runnability and printabily standpoint.
Lastly, if you can keep the balance of your consumables consistent as well as your temperatures, lithography can be as easy as running a Landa Nanographic press. One exception, with Litho you will have a minimum of 2X the QUALITY of print.  D

Post time: 2013-2-22 16:25:28 |Show all posts
I have been reluctant to comment because even after reading it a few times, I don't think I understand what you are trying to say.  I don't understand the specific problem you are trying to address and I don't understand the specific method you are suggesting to correct it.
When you say "coverage" do you mean the total coverage of the image on the plate or coverage in areas of the plate?
Are you suggesting to modify the ink formula for the whole ink fountain per plate image or are you suggesting to pump different modified ink formulations in 4 zones across the press?
Have you thought about how different ink formulations will affect dot gain?
I am sure this is more clear in your mind but it is still too difficult for me to picture the concept and therefore it is difficult to comment one way or the other.   Hopefully you can provide some more clarification.
You have to log in before you can reply Login | register

Advertise on OASQ.COM| Contact us| Archive| OASQ

2021-11-29 07:26 GMT-8

Powered by Discuz! 7.2

Release 20121101, © 2001-2021 OASQ.

To Top