Super Hot Cyan

[Paultheprinter]

Re: Super Hot Cyan

Hi,

Maby your not missing the point at all. The press should be an easy variable to check thats why we have colour bars. If the press is the issue then you will see a difference in ink weights to match the proofs or a difference in dot gain on the two sheets. In your last senario you state the printer ran the cyan up to get a bit more impact in a small area, ok thats fine but realy he or she should hit standard weight and if colour is not acceptable adjust artwork or proofing, by adding more ink and probable more water the printer could be causing and over emulsification of the ink, when the second side is printed the ink is over wet, screens look darker because there filling in and printer reduced ink weight to achieve visuall match. Get a press sheet and check ink weight and dot gain, if there is less ink there should be less dot gain, on my press we run 40 and 80% tints at 1.4 on the cyan we get aprox 15% on a 40 and 11% on an 80 but at 1.2 it down to 11 on a 40 and 8 on an 80. If the ink has emulsified than expect to see more gain than this and maby a reduction on the split between the two figures, i was taught a 40% will always spread more than an 80% if theres more dot gain on a 80 than a 40 theres a transfer issue somewhere,if this is the case then its impossible to proof for a moving target, nail the press operator its his job to asses the output of his press. I doubt it could be anything but the press as you have checked the actuall values on the plate, that prity much rules out your involvement.

Paul

 

[heatset]

Re: Super Hot Cyan

If the press is printing with too high a density the plates have nothing to do with it. It's a press problem, not a pre-press problem.

Several possible explanations have been offered. Density is strictly a function of ink film thickness, it has nothing to do with pre-press, I don't care what you've done to the plates.

Just set the density on the color bar to your standard and go. If you don't match the proof running standard density then you can look at dot gain on the press, gray balance and such before determining if it is a press or pre-press issue.

 

[Prepper]

Re: Super Hot Cyan

Exactly why I read my proofs, films and plates regularly, films on most every job, that way if there's a problem I know it didn't come from prepress. Main point is, if there is a problem, I fix it and it doesn't get to press and I don't have to try and diagnose the problem and I don't have to first prove that its not the plates before someone will begin to check out the press.

Just what we have to do. Has saved me some headaches and more importantly makes sure that the plates are right when they hit the press the first time, every time.

This situation in our shop has turned out to be roller settings most of the time, once was oscillation, once was fountain solution...just way too many variables on a press!

Terry

 

[Username]

Re: Super Hot Cyan

Sounds like you've got your ducks in a row. We are in the same boat. We keep our monitors in line, proofers clean and calibrated, plates are read regularly (and don't drift), curves are all good, etc. etc. The only variables we really ever see is on press. But, according to the man, the press and it's operators are always right.....period. The press only prints what's on the plates and there isn't a darn thing they can do about it. I'd go in there and ask him about fountain solution and rollers, etc., but he's busy watching Nascar.

My sarcasm is starting to gain momentum....I think this should be moved to the Rant forum.

 

[mrheidelberg]

Re: Super Hot Cyan

That is very true.................. the press operator IS always correct ...........lol

 

[Paultheprinter]

Re: Super Hot Cyan

Hello,

I believe the press operator is always right!.............backtrack begins now. As a press operator i would be lying if i said i could produce a sheet exactly the same day in day out, I earn my money by constanly monitering values and changing variables to keep withing standards, this ensures i get a acceptable result the majority of the times. Pre press is so advanced now with ctp that we never see plate values change enough to cause issues with colour, most of the time it blankets hardening causing poor transfer, water logged ink causing dot gain or us cutting corners to get jobs printed.
But theres one thing which we cant argue and thats what the colour bars and control strips tell us , its hangs us operators 99 times out of 100. Then the operators say things like i couldnt get the weight up on that section because........ its all boll***s, we can but we chose not to because we think for that job it would be ok, or because we have chemistry or press issues which we havent sorted which makes doing that more trouble than its worth. Standardise production, give tollernaces and find out why your falling out of tollerance and fix it, if the press operator is any good he or she will let the sheet do the talking.

Paul

 

[Sierpe]

Re: Super Hot Cyan or 'runaway Cyan'

Re: Super Hot Cyan or 'runaway Cyan'

Username;
Lot ideas coming your way regarding ‘runaway Cyan’. Yet, is not clear to me if the problem happens at the beginning of the production run or when the press is running several minutes later. If this happens at the beginning of the run likely the density profile wasn’t there to begin with. If the problem happens long after the start up, well into the production run, then is a different problem altogether.
Reading the thread, I think *Paul Green* ideas about 'ink stability' and *Dwane Hollands* (2 cents) about 'reproduction curves' might have something to do with this problem. Sometimes the uncompensated shallow mid-tones make press operators run higher densities to compensate and achieve the desire color rendering bringing about 'ink stability issues' such as runaway densities during the run.
In the other hand, *John Lind* is right about that 'ink fountain sweep' and ducting can be out of control. Best results can be achieved when sweeps are set higher that 50 percent, the higher the sweeps the better control and stability operators have during the run. If ink fountain sweeps are any lower, the response is slow and sometimes with low coverage jobs ink might build up in the rollers causing 'ink stability issues'.
Please report back your discoveries. We are interested in this topic.
Regards,

Jan

 

[An Inky]

Re: Super Hot Cyan

Username,
A couple of questions; you state that things are running along well and the suddenly you hit a job with a problem, does the problem go away on the next job or does the problem persist? When the problem occurs have you tried moving the cyan to a different unit? If so does the problem follow the ink?

 

[ar17]

Re: Super Hot Cyan

"Calcium Carbonate leeching out of paper. "
any idea how to monitor or measure the calcium carbonate content? thnx

 

[jlind]

Re: Super Hot Cyan

ar-king:
There isn't an easy way. If you have a pH meter, you can buy a pricey calcium ion selective electrode, but it would be fouled by ink and fountain solution scum pretty quick. The indirect and easy way is to watch the conductivity drift of the fountain solution, but that could be materials coming from the ink and the paper, and the wash up solutions. Very tough question.
John Lind
Cranberry Township, PA
724-776-4718

 

[Username]

Re: Super Hot Cyan

Good question about the problem going away on the next job. Mysteriously, after the problem job, the plate disappeared and the press was washed up, etc. for the next job. Once again, I checked the job files, profiles, curves, etc. and the problem photos that I measured have between 20 and 40% cyan in them, not 80.