Positive Ink Feed Simulation Test

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I suppose that in the interest of a fair test we need to further define overdampening. The operating window for correct dampening at times can be pretty large. Ive seen this operating window open and tighten up as many variables change. For instance some inks are more water repellant than others. Ive seen the operating window close with pressroom climate. ive seen it change dependant of the substrate being printed on. Ive also seen it change based up the mechanical condition of the press. Some fountain solutions will operate in a wider or narrower window. The addition of alcohol in the fountain solution will open that window up dramatically.
Eric are we to understand that in your test we should not be able to overdamp the image under any of these variables? For the purpose of this test are we to overdamp as we see fit?
To me there is slightly overdamped and then there is overdampened where the plate is so wet that its casting a glare in the pressroom and blinding people as they pass. Dont laugh ive seen pressman run their plates THAT wet. My understanding of your technology is to make things a bit more user friendly for the press crew. Would your technology allow for a pressman that always runs his plate soaking wet?
 
Alois Senefelder said:
Regards, Alois, see PDFs


" Where would we be without a little frivolity "

**** Had a problem uploading 1 more PDF - a Important one !!!!!!!
Click to expand...

Hi Alois,

I can partly agree with the statement in the PDF. I agree totally that one does not want to have an ink in water emulsion. That would be very bad.

But the implication in the PDF is that by just adding more water that is going to happen. This I would argue against and for the following reason.

If one has a positive ink feed, the extra water will mix with the ink and get printed out. Water also goes out of the system in the non image area. What one will see in the print on the paper is a similar amount of ink that has a lot more water. Water evaporates and what is left is basically the same amount of ink one would have if there was less water.

With the existing ink feed system, when the extra water is applied to the roller train, ink and water mixture can go back to the ink fountain via the ductor and this starves the roller train of ink. As more water is applied to the roller train it is very clear that the ink in water emulsion can develop much faster because there is less and less ink on the rollers.

The question becomes, how much water can the ink take before it gets to that ink in water emulsion? I have read somewhere that it was reported that the water content in the ink during printing can be as high as 600%. Yes this is an unstable emulsion. That sounds high but if true, it implies that there is a much bigger window than what one has normally thought.

My view is that the problem is not of too much water in the ink but the loss of ink going back to the ink fountain or at least being stopped from going into the roller train at the high coverage range.

The test should help with this issue.
 
turbotom1052 said:
I suppose that in the interest of a fair test we need to further define overdampening. The operating window for correct dampening at times can be pretty large.
Eric are we to understand that in your test we should not be able to overdamp the image under any of these variables? For the purpose of this test are we to overdamp as we see fit?
To me there is slightly overdamped and then there is overdampened where the plate is so wet that its casting a glare in the pressroom and blinding people as they pass. Dont laugh ive seen pressman run their plates THAT wet. My understanding of your technology is to make things a bit more user friendly for the press crew. Would your technology allow for a pressman that always runs his plate soaking wet?
Click to expand...

Yes, it should be independent of those variables.

In my previous testing. Yes the plate was soaking wet and would reflect a glare. On one test the press operator set the dampening to full and was shocked that it did not washout.

I would not mean that operators would run at such high levels. It is just to demonstrate the independence and the range. As far as dot gain goes, on one of these tests the measured dot gain was surprisingly little affected. Not sure why but I suspect the measured values and the actual quality of the print might not be exactly related. Something to look at.

When I say overdampening I am suggesting maximum value that the dampening system will be able to adjust to. I have poured water directly into the roller train on one test and that was too much but it was probably hundreds of times the amount of water normally used.

Use your judgment and push the water way past what you think is high and then lets see what happens.

As you commented about some printers getting to a point where the plate is too wet. From what I understand this can be due to their inexperience and they are afraid to reduce the dampening because the density will increase and the plate may scum. This is a benefit of positive ink feed. The water can be lowered to the correct levels for quality printing without the worry of the density shooting up and potentially scumming the plate.
 
Alois,
I have studied the the Duke water Pick up (the old) emulsification curve in the lab. to see if there is a correlation between that and a printing press. The way an ink is emulsified on press is totally different than the way a Duke Water Pick Up (the old) tester does. I have tested an ink that picked up 100% water on the (old) Duke and ran the ink on press with no problem. There are new lab. equipments out there, including the new Duke that test the viscoelastic properties and rheology of ink (visosity and yield value) as it emulsifies. The ink is emulsified by spraying a mist of fount into it and mixing it under constant shear. This will give the ink formulator an idea how different resins can hold up to different founts. The old Duke test, perhaps, can be used as a QC tool to see if one batch of ink picked up 50% water one day and the next batck picked up 100%water the next time. This is only my finding and hope it doesn't offend anyone.

George John
 
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Alois Senefelder said:
Gentlemen,


The emulsification curve of the Ink/Dampening solution can be used to predict press performance.



Regards, Alois
Click to expand...

Forgive me but I don't understand the graph in this pdf. At the risk of exposing my washed out brains, shouldn't the vertical axis measure grams ink/grams dampening solution? Looks like the less water the more washed out the image by this curve . . . but it's a while since I did maths at school . . .

Roy
 
I don't understand this graph either.

First of all, what is the meaning of the horizontal axis? Is it elapsed time while the press stands still? If not while standing still, then at what speed was it running when the data was recorded?

It seems to me that something like number of impressions or press cycles would be more meaningful, so that it could then be said that at one level of water content in the ink, it takes a certain number of press cycles for a certain effect to be noticed on the plate, or on the printed sheets, or by whatever means.

Also, there are 5 plotted curves clearly labeled A-E, but there are 7 descriptive text labels interspersed among the curves. Which goes with which curve?

Thanks Roy, for refocusing our attention on this "important" graph.

Al Ferrari
 
Al Ferrari said:
I don't understand this graph either.
Click to expand...

Al, Roy and George,

In 1997 I was listening to a presentation at the TAGA conference and the speaker was talking about lab testing. He made a surprising comment. He said that none of the lab tests correlated with press performance but they just kept doing them anyhow because they had nothing better. Their testing would show if there was a change in the materials though.

I have tried to identify who this was but so far I haven't been able to. His comments stuck in my head and I still think that lab tests have little value related to press performance predictability.

I am hoping that the test results from the simulation test will be more revealing. Hope to see some results soon.
 
re Emulsification Curve

re Emulsification Curve

Gentlemen,


For more information please read --- Aage Surland's article " Factors determining the efficiency of lithographic inks" TAGA Proceedings 1983



Regards, Alois
 
Not so fast Alois,

Thank you for the reference source for that chart. But having been the one who posted the chart on this forum and characterized it as "important" for us to consider it in this discussion, you should in some way respond to our questions about it.

What does the X-axis mean, and how do we associate the 7 text labels with the 5 curves plotted on the chart? And what of Roy's question about the Y-axis?

Otherwise, it would appear to be just a quaint reference, and that you had not given it much thought yourself.

Al Ferrari
 
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Roy and Al,
This is a lab. test where you take 50 gms of ink and place it in the Duke Water Pick up tester. Then you add 50 MLs. of press ready fountain solution or distilled water and start the machine. There are two paddles that turn 90 revolutions per minute. You decant the solution every minute upto 10 minutes and measure how many MLs of the fountain solution is absorbed by the ink. That is the % you see on the vertical axis of this graph. The horizontal axis is time in minutes. The theory was that an ideal ink will pick up about 30-40% water early on and will level off at 5 minutes of this test.
Hope this helps to understand the test procedure.
 
Thank you George,

That does help a great deal to make sense out of the lab test. This explanation should have been provided by Alois.

Now the X-axis begins to take on some meaning. But how do we apply this time concept to press conditions?

Al Ferrari

EDIT: I just saw George's earlier comment to Alois regarding the relevance of the lab test to press conditions:

"Alois,
I have studied the the Duke water Pick up (the old) emulsification curve in the lab. to see if there is a correlation between that and a printing press. The way an ink is emulsified on press is totally different than the way a Duke Water Pick Up (the old) tester does. I have tested an ink that picked up 100% water on the (old) Duke and ran the ink on press with no problem. There are new lab. equipments out there, including the new Duke that test the viscoelastic properties and rheology of ink (visosity and yield value) as it emulsifies. The ink is emulsified by spraying a mist of fount into it and mixing it under constant shear. This will give the ink formulator an idea how different resins can hold up to different founts. The old Duke test, perhaps, can be used as a QC tool to see if one batch of ink picked up 50% water one day and the next batck picked up 100%water the next time. This is only my finding and hope it doesn't offend anyone.

George John"
 
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Now the X-axis begins to take on some meaning. But how do we apply this time concept to press conditions?

Al Ferrari.

Al, Unfortunately this test has no correltaion to press performance or pess conditions or ink water balance on press, . The Water Pick Up % is not consistent even in the laboratory because one can squeeze more water out of the ink when you decant every time, if you want to. This is why we deveopled a test called 'Ltiho-Dyna-test to predict ink/fount perfromance of press. This is nothing but a Ryobi press and we can run variuos inks and fountain solutions to check out the scum point and wash out point of inks. If the plate is clean quickly, you have less make-ready waste. For the test the ink feed is kept at 2 Notches or to achieve SWOP density and the water setting will be changed from 2-10. some ink will scumm at lower setting and other might wash out at higher settings. The ink that cleans up at lower water settings and will not wash ou at higher settings will impart wider lattitude and easy control in the pressroom on wider, faster presses. This was proven again and again on web offset and Sf presses. This is a good test for new resin, flush and raw materal manufacturers. One can argue that this is not as good as testing on a 40 inch commercial press but is an economical way for ink formulators to test new products in the lab. knowing that the result will correlate with the filed.
George John
 
George John

We have tested ink and fountain combinations the same way for years. We use a Komori for our testing. George everything you have said is absolutely 100% the ways it works.
 
George John said:
This is why we deveopled a test called 'Ltiho-Dyna-test to predict ink/fount perfromance of press. This is nothing but a Ryobi press and we can run variuos inks and fountain solutions to check out the scum point and wash out point of inks.

The ink that cleans up at lower water settings and will not wash ou at higher settings will impart wider lattitude and easy control in the pressroom on wider, faster presses.
George John
Click to expand...

George,

Interesting test on the Ryobi and as you say it is much better than the lab test.

I would think that it is possible to do the Positive Ink Feed Simulation Test on that Ryobi. I would expect that one will not get to the washout point with this test method. Since you do these tests often, I am guessing that you will see the difference in performance right away.

Something to think about.

Erik
 
The Graph !

The Graph !

Hello fellow Lithographers and Mr. Al Ferrari


The answer you seek lie within ............................................. PDF


Regards, Alois
 

Attachments

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I hope that next week there will be some results from the simulation testing. A few people have said they will try the test and it should be interesting to see how they view the results. I hope they are able to follow through.

There are strong opinions on both sides of this issue and only test results will help to provide an objective view.

On the traditional side, a failure of the simulation test might make many very happy because it would support their view but it also would lead to the same old status quo situation without much hope of any great improvement in the offset process. No great opportunity to challenge the continued advance of digital presses.

On the positive ink feed side, a successful test result opens a whole new world of opportunities to move the offset process forward and gives the potential for press operators to continue their craft with a process that is more consistent and predictable. A real challenge to other printing processes.

I hope everyone has a good weekend and I hope some are planning to do the test.

Erik
 
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