Consiistent-excessive dot gain/TVI on all units.

[Alois Senefelder]

Hello CC


My answer in a PDF - one I typed earlier !!!!!



Regards, Alois I find it hard to believe that a precision made press such a Mitsubishi would out of tolerance on every unit.pdf

 

[cementary]

Cementary,


The answer is different inks from different manufacturers have different..... Water Pick-up Rates.


Regards, Alois

So maybe mr. CCLyde should test more inks?

 

[Alois Senefelder]

Hello cementary,



Don't we all wish it could be that simple ! There are at least 100+ Input parameters and variables just printing a single colour sheet.


Regards, Alois

 

[CClyde]

Sorry for the delay, I've been out of town and out of the office for a few days.

alibryan: we have two other presses but have not run any consistent tests on them until last week.
It appears to be the ink, or ink/water balance.
Our two colour Heidelberg runs mostly spot colour and solids (forms, business cards etc.)
A test run with our process black and a pantone showed the pantone was great, the black was the same problem 30+% gain.

cementary: it appears we have a similar problem. We tested two different ink manufacturers, three different tacks and two different sets. All were process inks, I didn't think of test a spot.
We now see spot colours printing fine, process printing with the gain.
I'll have a chat with our ink guy today. Thanks

Alois: Your link is not working for me.

If it is a change in water take up, it has to be because of a new chemical makeup in the inks we've used for years. It makes sense that it is an ink/water balance/chemistry potency, because according to the people I've spoken to, many companies are using these inks without any known problems.

 

[cementary]

If it is a change in water take up, it has to be because of a new chemical makeup in the inks we've used for years. It makes sense that it is an ink/water balance/chemistry potency, because according to the people I've spoken to, many companies are using these inks without any known problems.

I think it could be a new resin in formulation. Or maybe any other "eco-nail" for printing industry coffin.
From my experience many companies don't care much because of high dot gain and especially because of deformed dot on printed sheet. The answer for them is "compensation curve"
All print shops with whom me or my colleagues talked to do not see any problem in their high dot gain and they do not have microscope to see their deformed dot.
One reason is because same supplier do not see problem too. They intend only to sell ink and don't care how it work. Technical support is very poor. Actually most of the support is lots of talking to convince us that problem is not in the ink or ink/fount pair.
Other reason is that printers are still able to sell their printed sheets to the customer – position is "why bother" consistency?

Just today we've finished another set of tests with manroland servicemen who cheked again all rollers/cylinders/pressures/bearers etc.
And we've test different inks – with one of the ink we've obtain acceptable result.
Test method was simple as we've tired printing charts: we've output a linear testfrom with 70% all over the plate (200 lpi, round dot, 0 degrees).

With our "bad" ink there were a lot of big horisontal lines over the sheet from head to tail – like form rollers gone made and trying to beat the plate to death. Dots were distorted with ragged edges. That's when we're undestand that fount cannot clean the spaces well enough (tested with lots of water levels)

With our "acceptable" ink there were no lines or distorted dots on the sheet at all. I've finally saw a sheet 70x100 full of clearly printed 70% dots right out of our press. And they all were round, not perfectly, but good enough for wet offset.

 

[CClyde]

I think it could be a new resin in formulation. Or maybe any other "eco-nail" for printing industry coffin.
From my experience many companies don't care much because of high dot gain and especially because of deformed dot on printed sheet. The answer for them is "compensation curve"
All print shops with whom me or my colleagues talked to do not see any problem in their high dot gain and they do not have microscope to see their deformed dot.
One reason is because same supplier do not see problem too. They intend only to sell ink and don't care how it work. Technical support is very poor. Actually most of the support is lots of talking to convince us that problem is not in the ink or ink/fount pair.
Other reason is that printers are still able to sell their printed sheets to the customer – position is "why bother" consistency?

Just today we've finished another set of tests with manroland servicemen who cheked again all rollers/cylinders/pressures/bearers etc.
And we've test different inks – with one of the ink we've obtain acceptable result.
Test method was simple as we've tired printing charts: we've output a linear testfrom with 70% all over the plate (200 lpi, round dot, 0 degrees).

With our "bad" ink there were a lot of big horisontal lines over the sheet from head to tail – like form rollers gone made and trying to beat the plate to death. Dots were distorted with ragged edges. That's when we're undestand that fount cannot clean the spaces well enough (tested with lots of water levels)

With our "acceptable" ink there were no lines or distorted dots on the sheet at all. I've finally saw a sheet 70x100 full of clearly printed 70% dots right out of our press. And they all were round, not perfectly, but good enough for wet offset.

That sounds like the problem we're having.
Our ink guy says nothing has changed and as they are a very large supplier, he would have heard something from other printers if there was a problem.
We are going to try some ink variations and see if there is any change.

 

[Alois Senefelder]

Hello cementary,

I'm finding hard to believe that you are having so many problems !


Take me step by step through your SOPs

(!) What Plates are you using ? (2) Are the plate correctly Imaged ? (3) Post a pic of thes "Horizontal Lines ?

Next this is important - can you obtain a set of "Presensitized Plates - NOT CtP


Regards, Alois

 

[Alois Senefelder]

Hello CClyde and cementary,


I'm a great believer in K.I.S.S.


Do you know the......... How and the Why of gummming the plate is a critical step in Litho Plate Making?

If so, do you pratice this step.......if not why don't you?


Regards, Alois

 

[CClyde]

Hello CClyde and cementary,


I'm a great believer in K.I.S.S.


Do you know the......... How and the Why of gummming the plate is a critical step in Litho Plate Making?

If so, do you pratice this step.......if not why don't you?


Regards, Alois

Not sure what you mean by K.I.S.S.
We are using Kodak SonoraXL plates that don't have/need gum, they have their own coating that clears on press with water. You can gum them after printing for a safety measure, but they don't need gumming.

 

[cementary]

Hello cementary,

I'm finding hard to believe that you are having so many problems !


Take me step by step through your SOPs

(!) What Plates are you using ? (2) Are the plate correctly Imaged ? (3) Post a pic of thes "Horizontal Lines ?

Next this is important - can you obtain a set of "Presensitized Plates - NOT CtP


Regards, Alois

Plates are kodak capricorn gt on one ctp and kodak sonora for second ctp. Plates are all imaged correctly as we've saw problems with chemistry in the past but long ago eliminate them by standartising platemaking process.
It is not far from switchin' to sonora completely, but anyway we see this problems on both plates – process and processless.
Actually we do not have many problems – for this moment all of them are eliminated but one – ink/fount.
I'll try not to forget to take a picture of "lines" tomorrow but here a description: imagine standard horizontal lines from too hardly form rollers setting. Then imagin that all of them have different width and there are a lot of them over the sheet.
And by the way – serviceman from manroland as former pressman is great believer in k.i.s.s. too as most of our best pressmen. He is also great believer in, what he called "long ductor" printing

 

[CClyde]

This problems seems a little more widespread than people want to talk about.
We recently sent a job out to a local trade printer because we didn't think we should risk it with the gain problems we're having.
Press sheets came back with the same problem we're having.
They matched the proof close enough for the client, but they had to run Magenta down to 1.0-1.1, Cyan to 1.2-1.25 Yellow was good, Black was OK, (not critical to the sign-off colour).
Trap solids were Orange and bright purple.
There's something going on that printers are either afraid to deal with, or don't know how.

 

[Alois Senefelder]

Hello CClyde,


Can you give us an inkling of what the common attribute might be be?



Regards, Alois

 

[CClyde]

Hello CClyde,


Can you give us an inkling of what the common attribute might be be?



Regards, Alois

The common attribute appears to be printing way below SID to keep tone values due to excessive gain.
This results in either printing solids/RGB at proper density at the cost of screens, or printing screens at very low density at the cost of solids.

 

[Alois Senefelder]

The Saga...


Hello CClyde,

Having re-read your introduction to the problem, you made a comment I quote (The dots looks a little soft on the edges but not slurred )

that needs investigating.

We need to see good pictures of the following (A) High fidelity pictures of a 40% and 60% halftone image area of the plate

(B) also pictures of the same images printed and include images of printed text - 10/12pt type


Regards, Alois

 

[curiosity]

Been reading this interesting post the past few days. I believe CClyde is correct (This problems seems a little more widespread than people want to talk about.). I've proffered that to my colleagues on more than one occasion. We too have been experiencing this for the past several months. We've "worked" it to the point that only our black unit suffers from excessive TVI.

Don't recall who described their dots (soft but not slurring), but same here. Know what he's talking about. Also know that describing said dots and/or capturing images of same dots isn't as good as seeing for yourself. Of course, experience at scoping dots helps a lot!

We're scheduling soon to clean out the black unit and put cyan in. I will post results when I know. Alois is correct too. Ink and water! Chemistry sure is fun, ain't it?! Just wish there was an easy way to predict effect when something upstream is altered.

 

[gordo]

USB microscopes capable of taking excellence diagnostic images (200x) of halftone dots are less than $75 on eBay. There is no excuse why any print shop would be without one.

Here's an example:

Reference M printer:

vs current M printer:

And as Alois stated - ink, water, squeeze, doubling, slur, etc will also show up - sometimes more clearly - in text.

 

[cementary]

USB microscopes capable of taking excellence diagnostic images (200x) of halftone dots are less than $75 on eBay. There is no excuse why any print shop would be without one.


And as Alois stated - ink, water, squeeze, doubling, slur, etc will also show up - sometimes more clearly - in text.

Gordo, could you please-please-please post some more high resolution picture pairs of reference / bad dots. We're going to have another talk tomorrow with our suppliers. I think your authority is just what we need as it appears to be that we have never been able to print anything close to your reference magenta dot.

 

[gordo]

Gordo, could you please-please-please post some more high resolution picture pairs of reference / bad dots. We're going to have another talk tomorrow with our suppliers. I think your authority is just what we need as it appears to be that we have never been able to print anything close to your reference magenta dot.

Only if you promise to buy a microscope! LOL
I don't know how much this will help but here goes my long-winded (but needed) explanation ...

When you're analyzing a press sheet examining the halftone dots (and solids) under high magnification can help reveal press issues.

You always start with the image on plate. The paradigm is that the plate is represents your desired image. The image on the plate gets inked and and is transferred without distortion or alteration to the substrate (perhaps with a blanket as intermediary).

Here's the image on the plate:

Note that the image area (the dots) is solid and is fairly even in density and that the edges of the dots are clearly defined (sharp).

On an offset press the dots are inked in the presence of a solvent - fount solution - that is trying to prevent the ink adhering to the non-image area. The ink is also partially emulsified with the fount solution. This emulsification with a solvent will to some degree distort the integrity of the ink film on the plate. Then the ink is transferred to a blanket - which will again distort integrity of the ink film. Finally the ink is transferred from blanket to substrate under pressure - both of which will distort the dot some more (mostly, but not only, dot gain).

What you're trying to do is minimize the level of distortion through the process so that the halftone dots align as well as possible with the source image on plate.

Here are some samples:

Acceptable Cyan dots

Acceptable (barely) Black dots

Acceptable Yellow dots

to be continued in the next post

 

[gordo]

the continuation of the previous post

Here's acceptable Orange dots from an extended gamut press run where the ink vendor knew how the spot color ink was going to be used

Here's unacceptable Orange dots from an extended gamut press run where the ink vendor didn't know how the spot color ink was going to be used

Here's the Black printer dots on the left side of the press vs the right side on the same press sheet

​I hope this is helpful.

 

[CClyde]

Hi Gordo
I would very much like to get a scope, but after years dealing with all the bull in digital camera marketing, I can't find a microscope that doesn't confuse magnification with zoom, digital with optical magnification, focal area with distance etc.
Can you recommend one that will do the job right?

Thanks for any help.