Consiistent-excessive dot gain/TVI on all units.

CClyde

Well-known member
I am baffled as are the three experts we've brought in to help figure out what is going on.
We have a 30+% gain (23% TVI@ density) at 50 that appeared on all four units recently.
The dot looks a little soft on edges, but is not slurred, not doubling, not emulsified, not picking/snowflakes.

Checked: chemistry/water, pressures, ink, blankets, dampening rollers.
We imaged same test file on different CTP to isolate laser/imaging (SonoraXL plates), imaged same test on Sword plate to isolate plate type.
Changed fountain chemistry to two diferent manufacturers.
8 hours of test runs with one expert after conditioning ink rollers, new blanket and dampening roller. water PH, conductivity, total PH, new chemistry (with buffer), new and different inks,
three different paper stock.
Run to our previous SID K-1.6, C-1.3, M-1.4, Y-1.0
No change in total gain/TVI with any of our tests. Cleaning and replacing rolers and chemistry cleaned the dot slightly, but no change in gain/TVI.
The only test that had positive results was dropping chemistry below minimum recommended.
A two step at 2 ounce/Gal each. Recommended minimus is 3 (typo edit)
The test was clean, 18% midtone gain and consistent accross 23"X38" sheet on each unit.
The problem of course is this mix required minimal water and caused massive picture framing and will not be stable beyond a 500-1000 sheets.
Mitsubishi 3F 6
Kodak SonoraXL plates imaged at 175lpi
Hossman Inkredible (Ultima and Rapida) inks
Flo Gloss and Dull 60pt paper

Any ideas greatly appreciated.
 
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Slammer

Well-known member
maybe something similar to a recent problem, customer had a euclidian dot causing heavy TVI in the midtones, changed to round and the TVI went back to normal-ish values.
 

CClyde

Well-known member
maybe something similar to a recent problem, customer had a euclidian dot causing heavy TVI in the midtones, changed to round and the TVI went back to normal-ish values.
Thank you Slammer

The euclidian we've used the last 15 years is Creo's/Kodak's euclidian which is a round--square euclidian. There is no exclusively round option in our workflow (Prinergy).
I'm not against trying anything, but something has changed and if it's the dot, it would have to be from laser or plates, which we've checked, since the same dots have been working for years.
 

Alois Senefelder

Well-known member
Dot Gain,

Hello CC,


Questions: 1) Is this problem only on 1 Press ? 2) have you the time/date when this problem started ?

3) How many sheets before you achieve - Ink/Water Balance and a Good Sheet ? 4) Search through the waste and see if any evidence of the problem shows.

5) Check FS Inflow/Outflow temperature..... also Roller Trains and Blankets ?


Regards, Alois
 

Cornishpastythighs

Well-known member
Did you ever have good dot gain numbers, if so what in your process has changed. Is your press mechanically in good condition, As Alois says when did the problem start.
 

CClyde

Well-known member
Dot Gain,

Hello CC,


Questions: 1) Is this problem only on 1 Press ? 2) have you the time/date when this problem started ?

3) How many sheets before you achieve - Ink/Water Balance and a Good Sheet ? 4) Search through the waste and see if any evidence of the problem shows.

5) Check FS Inflow/Outflow temperature..... also Roller Trains and Blankets ?


Regards, Alois
Thank you Alois

1) It is only on one press.

2) It began on black unit (2) in March 2015. We corrected it with a plate curve. That was not a solution, but it was our only option and kept the press running.
It began to creep slowly into all units about 4 months ago. We saw the magenta unit (4) moving first and when we saw cyan (3) starting we shut it down and started maintenance and trouble shooting. That's when we found it was on all four units and equally peaked out at 30% gain. (this maximum threshold had me baffled. All four units hit it, but do not exceed it)

3) 200 sheets average on cold start of our testing (23in X 35"in sheet)

4) Do you mean see if there is evidence in the make ready? Not sure what I would look for.

5) The chiller temperature is 50F on all four units and recirculates. I don't know if the pressmen have checked outflow, I'll ask them to do that.
 

gordo

Well-known member
Thank you Slammer

The euclidian we've used the last 15 years is Creo's/Kodak's euclidian which is a round--square euclidian. There is no exclusively round option in our workflow (Prinergy).
I'm not against trying anything, but something has changed and if it's the dot, it would have to be from laser or plates, which we've checked, since the same dots have been working for years.
Unless there's been a massive change Prinergy has always had a round dot - non-Euclidean - halftone dot. It is the preferred AM dot for offset printing.
 

cementary

Well-known member
Thank you Slammer
The euclidian we've used the last 15 years is Creo's/Kodak's euclidian which is a round--square euclidian. There is no exclusively round option in our workflow (Prinergy).
I'm not against trying anything, but something has changed and if it's the dot, it would have to be from laser or plates, which we've checked, since the same dots have been working for years.
Unless there's been a massive change Prinergy has always had a round dot - non-Euclidean - halftone dot. It is the preferred AM dot for offset printing.
true, see screens
real round.png roundsquare.png.jpg round and roundsquare.png.jpg
 

CClyde

Well-known member
Unless there's been a massive change Prinergy has always had a round dot - non-Euclidean - halftone dot. It is the preferred AM dot for offset printing.
Thanks gordo.
My mistake, I thought they dropped the round.
Just checked and their "Maxtone" does include round.
I'll try it, but it seems a long shot since we've used euclidian without a problem for years.
Although, ….
it is possible the combination of euclidian and SonoraXL (using SquareSpot, a steep, sharp shoulder spot) could cause be the cause. I'll have to think about that and test it.
 

CClyde

Well-known member
Did you ever have good dot gain numbers, if so what in your process has changed. Is your press mechanically in good condition, As Alois says when did the problem start.
Thanks Cornishpastythighs (nice handle)

We've had good numbers. The pressmen tell me it's a recent problem, roughly 4 months. But I'm not sure how they define "problem" because they've not put any serious (long range 1/4 and 3/4 tone work) colour critical work on for some time. It is amazing how they can hit good tone values with such high gain. But they are compromising trap/solids and good RGB to get quads and vise-versa.
Nobody here can find anything that has changed. Something must have, but we cannot figure out what.
 

cementary

Well-known member
Checked: chemistry/water, pressures, ink, blankets, dampening rollers.

Flo Gloss and Dull 60pt paper

Any ideas greatly appreciated.
What about different paper manufacturer? Did you try different stock?
Maybe your ink supplier change the formulation? How many founts did you try?

Check circullation system and tubes – they may be contaminated.
 

CClyde

Well-known member
What about different paper manufacturer? Did you try different stock?
Maybe your ink supplier change the formulation? How many founts did you try?

Check circullation system and tubes – they may be contaminated.
Thanks cementary
We've tried a number of different stocks and the live jobs that were originally showing the problem included a few more.
We have tested on Flo Gloss, Flo Dull and similar Anthem stock in our tests.
When no change was seen we stuck to Flo Dull to keep our tests consistent and it's less expensive.
We've tested Hossman (three different tacks), Sun and another that escapes me right now.
Unigraph and Prisco.
Complete flush and cleaning of fountains and chillers.
 

cementary

Well-known member
Complete flush and cleaning of fountains and chillers
You know we're right now facing quite same problems for about year. We've tried quite all the same what you did.
Our main ink supplier Huber (guess it's your hossman – hostmann-steinberg).
For now we've stuck with interesting point – our main ink Reflecta rl 250 gives us 34-35 percent on 50% patch for linear plates 200 lines real round dot (kodak capricorn) in all units on two manRoland (705&708)
We've tried also Resista rs and Quickfast 260 and Alpha Intense 363 (new inkredible as they told me) – all the same.
But we've found several cans of Quickfast 250 and this ink dropped dot gain by 10% – to 24-25 on each unit. Supplier insists that only difference between 250 and 260 quickfast series is the amount of siccatives but refuses to explain such big dot gain difference between the two.
For mechanical part we're think (for now) to call for maintence for our form/blanket cylinder pair because of two points:
1. the problem dot we see already on the plate with ink in the unit (try it with you microscope)
2. we've found one section (in two presses) where we see good dot and measure good dot gain (20 on 50).

I've got a feeling that there is a problem with bearer rings but i'm not educated enough to investigate further
 
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wyagow

Well-known member
I'm not educated either and this is a long shot but did you guys by chance change the kind of plates you are using? I recently conversed with a pressman that was having a similiar issue only to find out they had changed to a diff plate manufacturer and the plates increased in thickness over what they had been using. This caused an increase in squeeze between plate cylinder and blanket. Once they realized that and adjusted blanket packing accordingly their problem disappeared.
 

gordo

Well-known member
One has to avoid a scattered approach to solving a problem and hoping that something might accidentally be the solution.
Isolate and investigate prepress and press room separately.
You need to check the dots on plate - is are the tones on the plate correct? I.e. the right plate curve, correct exposure/development, brand, age, etc.
Do the halftone dots have integrity? You need your USB microscope to take some pics to compare with your golden reference standard and/or to post here. All shops should have a golden reference file with associated presswork that they can check current work against.
 

Prepper

Well-known member
Just out of curiosity, are you measuring with the same instrument all the time, or different ones at different consoles? Did you check your instrument?
 

CClyde

Well-known member
One has to avoid a scattered approach to solving a problem and hoping that something might accidentally be the solution.
Isolate and investigate prepress and press room separately.
You need to check the dots on plate - is are the tones on the plate correct? I.e. the right plate curve, correct exposure/development, brand, age, etc.
Do the halftone dots have integrity? You need your USB microscope to take some pics to compare with your golden reference standard and/or to post here. All shops should have a golden reference file with associated presswork that they can check current work against.
You're right, I was getting side tracked in my last post.
Since this problem began we have eliminated the plates by imaging on different CTP devices, imaging different plates (processed plates and processor-less plates) on same and different CTP devices. The processed plates can be directly measured, the processor-less plates cannot)
We've eliminated stock by changing to different weights and finishes and manufacturers.
We've eliminated ink by changing brands, tack, and manufacturers.
We've eliminated fountain by testing PH, conductivity, alkalinity and temperature of water, changing to bottled water with good PH, ppm/Conductivity. Changing fountain solution manufacturers and three different mixes (ounces/gal).
So it appears to be an on-press problem.
We've replaced blankets, form rollers, dampening roller.
We've run in three different dampening modes with water ranging from 40% to 70%.
I think it is pressures but I won't have a good scope to analyze the dot until next week.
The pressmen assure me the pressures are to spec, but I think we have to start with one unit and check/reset every roller, cylinder and gap to be certain.
 

danremaley

Well-known member
I am baffled as are the three experts we've brought in to help figure out what is going on.
We have a 30+% gain (23% TVI@ density) at 50 that appeared on all four units recently.
The dot looks a little soft on edges, but is not slurred, not doubling, not emulsified, not picking/snowflakes.

Checked: chemistry/water, pressures, ink, blankets, dampening rollers.
We imaged same test file on different CTP to isolate laser/imaging (SonoraXL plates), imaged same test on Sword plate to isolate plate type.
Changed fountain chemistry to two diferent manufacturers.
8 hours of test runs with one expert after conditioning ink rollers, new blanket and dampening roller. water PH, conductivity, total PH, new chemistry (with buffer), new and different inks,
three different paper stock.
Run to our previous SID K-1.6, C-1.3, M-1.4, Y-1.0
No change in total gain/TVI with any of our tests. Cleaning and replacing rolers and chemistry cleaned the dot slightly, but no change in gain/TVI.
The only test that had positive results was dropping chemistry below minimum recommended.
A two step at 2 ounce/Gal each. Recommended minimus is 3 (typo edit)
The test was clean, 18% midtone gain and consistent accross 23"X38" sheet on each unit.
The problem of course is this mix required minimal water and caused massive picture framing and will not be stable beyond a 500-1000 sheets.
Mitsubishi 3F 6
Kodak SonoraXL plates imaged at 175lpi
Hossman Inkredible (Ultima and Rapida) inks
Flo Gloss and Dull 60pt paper

Any ideas greatly appreciated.
>>>>>I have a couple - check water temperature at pan and roller temperature - cooler may help. I would try another ink set, maybe Wikoff (they have a heavy pigment load). The most expensive item in ink in the pigment. When consulting I asked the ink companies "why" they don't list the pigment load on the can - maybe you would know what your paying for (vehicle & varnish)! For doubling issues I place a patch in the color bar of 3%YMCK - it's very easy to spot doubling with more 'white space' than any other size dot! Dan Remaley
Phone with any questions 412.889.7643
 

cementary

Well-known member
The pressmen assure me the pressures are to spec, but I think we have to start with one unit and check/reset every roller, cylinder and gap to be certain
A month ago we've checked this with manRoland serviceman – pressures were ok. That's what he write in the official conclusion paper. He is also wrote that the press is in exellent condition (brand new rollers, regular maintance and so on). He insisted that our problem relates purely on ink or ink/fount compatibility. To prove that he made the following: in the yellow unit he put pantone reflex blue. Dot gain on yellow was 35-38% on 50% patch (yepp, 85%, i'm not kidding). With pantone the same unit in absolutely same condition showed 23% (with switched off tempering contour, as we've found out later).
Today our "brand new" expert from europe ink company said that our high dot gain is ok. And our distorted dot is ok (you can see pictures of the dot in one of my threads). We just should compensate a little bit more.
But he could't explain why another ink (from epple, premium print series) showed lower dot gain (10% lower – we've made a test yesterday)
 
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