Ink quality

[Alois Senefelder]

The How ---

The How ---

Hello fellow Lithographers and "J"

The answer is Densitometry

" Another important consequence, especially for the reflection densitometer, is that the density value of an ink sample is approximately proportional to the physical thickness of the ink or, in other words, the Ink Film Thickness."

I enclose some PDFs for you, which I hope you find interesting.

Regards, Alois

 

[Deleted member 16349]

Hello fellow Lithographers and "J"

The answer is Densitometry

" Another important consequence, especially for the reflection densitometer, is that the density value of an ink sample is approximately proportional to the physical thickness of the ink or, in other words, the Ink Film Thickness."

I enclose some PDFs for you, which I hope you find interesting.

Regards, Alois

The density value is not an absolute value related to ink film thickness. It is a relative value with respect to a particular combination of ink and paper.

The same ink film of a particular ink can have a lot higher density when printed on a coated paper than when printed on an uncoated paper.

The PDFs are of interest but one has to be careful in understanding that they are for a specific combination of ink and paper.

 

[Cold]

Not sure what was meant by the values in Mills.

A value in mills, can be derived by using a wet film thickness gauge, such as an old Peto gauge. This, however, would only give you the ink film thickness on a particular ink roll in the ink train, and does not correlate directly to the ink film thickness on the printed piece.

 

[Deleted member 16349]

A value in mills, can be derived by using a wet film thickness gauge, such as an old Peto gauge. This, however, would only give you the ink film thickness on a particular ink roll in the ink train, and does not correlate directly to the ink film thickness on the printed piece.

That makes sense.

Of course that ink film value would be with water included in the emulsified ink.

 

[Cold]

That makes sense.

Of course that ink film value would be with water included in the emulsified ink.

Also, as it is a reading off a roll int the roller train, it does not account for ink transfer, substrate, blanket transfer, founatain solution as you indicated and pressure settings, etc. It simply tells you how thick the ink is on that particular roll, which is typically measured in mills.


Cold

 

[Lab Rat 1]

When supplying customers printed proofs, we print on a IGT C1 proofer at a film weight of 1.4gm2. This works fine for most plastic, coated paper and board substrates. When printing on uncoated paper or board stocks, We sometimes have to push the film weight to 1.5gm2 to a max of 1.75gm2. Just more fuel for the fire.

 

[D Ink Man]

Keep it up! I love infernos, especially when it's burning the stink.

 

[otherthoughts]

In case anyone's interested?

In case anyone's interested?

I suspect that this item is comparable to what "@Cold" referred to as "an old peto gauge"?

I've seen such gauges, and heard how they were typically used.

Back in the old days, before presses had guards enclosing their ink trains. You could place the gauge on the hard plastic oscillating roller that was contacting the last two ink form rollers. You would do this as the press was running, letting the gauge rotate briefly between your thumb and index finger as it was brought into contact with the oscillating roller. Then you would remove the gauge from the roller and read the ink mark on the gauge.

Wasn't that a dangerous thing to do, you might ask? Sure it was! But so were a great many things that we did back then and thought nothing of it.

I never owned or used one of these gauges during my pressman days and the only thing I really wanted one for, was to try to monitor/measure the thickness of overprint varnishes being applied to the sheet. A reflection-densitometer was of no use in measuring the thickness of the film of varnish being applied. And the normal methods of judging ink film thickness, weren't as reliable when it came to judging varnish film thickness. I suspect that I would have had a tough time reading the marks that varnishes would have left on the gauge, if I'd had one anyways.

Wet Film Thickness gauge link
http://www.uvprocess.com/Data%20Sheets/wet_film_thickness_gauge/DSO-THICKNESSB.pdf

Best Regards
OtherThoughts

 

[gordo]

You could place the gauge on the hard plastic oscillating roller that was contacting the last two ink form rollers. You would do this as the press was running, letting the gauge rotate briefly between your thumb and index finger as it was brought into contact with the oscillating roller. Then you would remove the gauge from the roller and read the ink mark on the gauge.

Wasn't that a dangerous thing to do, you might ask? Sure it was! But so were a great many things that we did back then and thought nothing of it.

This activity is sometimes referred to technically by press operators as "degloving" - a term you should not Google if you are of a sensitive disposition.

best, gordon p

 

[D Ink Man]

"THE" Ink Film Thickness Gauge

"THE" Ink Film Thickness Gauge

It is an equivalent to what a medical doctor would use on you when having a checkup or physical. That medical device is a stethascope. Without it' a doctor could not a quick determination of your heart and pulse rate. The ink film thickness guage is the equivalent to that, only for lithographers. I still have 8 fingers and 2 thumbs and use it every opportunity that presents itself. Whem you know printing, ink formulation; strength and transfer you can make mutiple conclusions on the thickness redings you collect. A 1 mil guage is best, but a 2 mil gauge will work. Handle it like a newborn baby, one drop on a concrete floor can damage it that can render it next to useless. Rip those protective guards off the units' or obtain a jimy device that allows them to be open while on the run. Let's get back to learning and knowledge by their usage. Priceless! Truly, D.

 

[janezl]

I never tested it so far, but here is another proposal:
Needed:
- information of sheet ink coverage - you can get it from any decent CIP3 programme. Using some (additional) calculation will produce, how many sq mm/inch of sheet is covered with ink.
- relatively precise scale to weigh paper

1. On a scale, you weigh (let us say) 50 sheets of paper. Result = mass1
2. Print sheets, out of stack, you take out 50 printed sheets and measure their mass = mass2
3. Calculation mass2-mass1 will produce how much ink+fount emulsion arrived to sheet
4. You calculate ink film thickness out of known data: coverage, weight, specific weight of ink

Janez

 

[D Ink Man]

janezl, Sir

janezl, Sir

janezl, In all due respect; I read and comprehended your reply and my opinion it has some merit and considerstion. But truthfully, it would be equivalent to killing a house fly with a sledge hammer. I know your intentions were good and probably the fact that the safety guards on the newer presses make a practical I.F.T. guage next to impossible to use, that is why you offered. I go back to those 'jimy' devices that allow a person to open the guard while running. If you check with the press manufacturers' and talk to the right person, I'm sure they can help you and I. You may have to sign a waiver in case one of your digits ends up flying out the back of the unit. However with proper training and know how it is a SAFE procedure. One last mention, all ink film thickness is, is the thickness of the ink in your roller trains, in relation to the ink density being put down on the printed sheet. Both elements need to be known. D

 

[The Heidelberg Guy]

This activity is sometimes referred to technically by press operators as "degloving" - a term you should not Google if you are of a sensitive disposition.

best, gordon p

Seen it happen....... Not pretty...........

 

[jlind]

Ink Quality and Ink Film Thickness

Ink Quality and Ink Film Thickness

From the first day I started work at GATF, this was a subject of interest. In the end, ink film thickness was measured, if you believe in the Heisenberg Uncertainty Principle.
1. Weighing paper with ink on it, forget it.
2. Weighing aluminum foil with clear coating on it, after going through a press, useful.
3. Weighing a printing disc from a Prufbau or IGT, before and after printing a solid, repeatable, and the source of standards numbers/recommendations, like ISO 12647 etc. ISO 2846 etc.
4. On a big press, wearing coveralls, with good scraping techniques, weighing the amount of ink used after running 1000 sheets of paper, or more the merrier, interesting precision. (See TAGA paper by John MacPhee)
5. On a really big press, like a MAN Roland web equipped with LinkTech ink meters, and knowing the ink coverage on the plate from Agfa Apogee or CIP4/3? data, again, interesting data and real time ink consumption information, and by extension, ink film thickness in grams per square meter. (GATFPress Research Technology Report, 2004)
6. Further review of past TAGA papers will show many efforts to measure water film thickness on the press, usually with InfraRed sensors aimed at the plate and blanket. I don't think it was every commercialized.
I think the LinkTech system is currently the best answer, but it's aimed at web presses.

John Lind
Cranberry Township PA
724-776-4718

 

[D Ink Man]

Now this really interests me!

Now this really interests me!

Quoted by jlind: 6. Further review of past TAGA papers will show many efforts to measure water film thickness on the press, usually with InfraRed sensors aimed at the plate and blanket. I don't think it was every commercialized.
I think the LinkTech system is currently the best answer, but it's aimed at web presses.


Thanks, hopefully more elaborations on this. D

 

[otherthoughts]

Bad Brains?

Bad Brains?

Gordo/The Heidelberg Guy, thanks for pointing out my earlier lapse in judgement.

I never intended to suggest that anyone place themselves at risk.

Safety features are added to presses for a reason. They're intended to prevent people from being needlessly injured. Press manufacturers aren't adding these safety features randomly, far from it, they are adding these safety features precisely because too many people have been seriously injured and hurt.

Today, I wouldn't even entertain the thought of exposing myself to the kind of risks that "I thought nothing of" so long ago.

If I wanted to measure and monitor the IFT using such a gauge today. I would leave the safety guards in place and develop a mechanical apparatus that would work within the confines of the existing safety guard configuration and intention, never placing my personal safety at risk. A physically mounted and mechanically triggered IFT gauge would likely be more accurate and reliable than a hand-held version would be capable of achieving, I would think.

D Ink Man, I respectfully disagree with you about removing or defeating the safety measures engineered into one's equipment intended to prevent injury. However, I do agree with you that knowing the readings produced by an IFT gauge is far superior than not knowing them, and for a whole host of reasons. Don't you think that it would be fairly simple to implement such a mechanical IFT gauge apparatus? My speculation as to the reason why such a feature isn't offered is due to the fact that the information provided by an IFT gauge is more of an ink technician's tool than it is a pressman's. What do you think?

Best Regards
OtherThoughts

 

[turbotom1052]

as a pressman ive used in the past an ift guage to "learn" what the correct ink film thickness should look like. After many years of running a press i can now just look at the last form roller and tell visually with pretty good accuracy when im carrying the correct ink film on the rollers. One of the best ways to learn the visual cues that tell of correct ink film thickness is to just open up the roller guard as the press idles and quickly look at the "nap" of the freshly split ink film.

 

[D Ink Man]

There is only one person that can formulate a spot color that requires an extraordinary thick ink film. Try making a pMS 539 blue that is suitable for aqueous or UV coating.
It has been achieved on a booklet for the US Senate. pMS 539 is one of the US Senate's standard colors.
This ink formula was achieved and printed with one impression with the finest reversed out vignettes you have ever seen. And it was aqueous coated in line, no alkali blue. Only one mortal man has achieved this. D Ink Man