Need some help ink/water in balance or something

[viclpp]

We are running a job that has like different shades of pink. From dark to light screen. We see the ink breaking down and color looks really spotty.

This is on a 100lb silk text sheet. When we put on a 100lb gloss text, everything looks really smooth and good print.

We had to cut the sheet down and run it short grain on the 100lb silk text. Will it have any effect running it short grain? registration looks fine.

I will upload some pictures later

 

[BeauchampT]

Does the breakdown happen while print is wet or as it starts to dry?

If it is after drying, I would suspect it is the paper absorption (not uniform throughout sheet), though hard to say without seeing a sheet.

 

[viclpp]

This is a fresh sheet pulled off of the press. We are thinking it is the sheet also because we then tried to run 80lb silk text and it is a lot smoother.

 

[gordo]

We are running a job that has like different shades of pink. From dark to light screen.

Is this a spot color or a process color job?

gordo

 

[viclpp]

it is a 4 color process.

We just got back with the paper distributor and they said it is the paper. the coat on the paper is unevenly spread. I guess that's what happens when you buy cheap paper. lol

 

[DotBox]

it's probably the grain; here's a test

it's probably the grain; here's a test

Not having a sample in front of me, my gut feeling is that it's NOT the coating on the sheet, even though the sales rep is telling you it may be (they all talk a good game, but most rarely know what they are talking about technically, in my experience). If you are running "wrong" grain stock on a multi-color press, screens can look blotchy because of sheet instabilities. The grains break a little bit more while being squeezed by each successive unit of the press, causing the sheet to not "snap back" to the proper position, which in turn causes slur on later units. The image on each sheet will vary based on how much grain breakage occurs at what unit. When that happens, even consecutive finished sheets may not look identical, and may give the same appearance as a sheet with bad coating or some other flaw.

Short grain paper ALWAYS causes problems on the press. It's just a matter of whether you can get away with it with a particular image. My guess is, you can't get away with it on this particular job. If you want to test this theory out, try test-printing the image on that same 100lb gloss text you used before, but WITH THE GRAIN WRONG, just like the job stock (which I assume you didn't do before). It will probably appear somewhat different than the job stock does, but will still show signs of the same basic problem. If not, then it probably isn't the grain after all, and the job stock might indeed have issues.

It's worth a try, in my opinion. Good luck.

 

[viclpp]

I will definitely give that a try.

Thanks,
Victor

 

[dleather]

I think it IS the coating, because you said when you run on another sheet it's okay. You can usually tell if it's the coating by looking at the sheet under a black light. It will be easier to tell if it's been printed on, but look at a clean sheet and a printed sheet. If you see spider-webbing, or crackling/flaking, it's due to bad coating and you should go get a credit from the paper mill.

 

[DotBox]

(Sorry for the double post - most of the following is repeated in a different post below. My bad, thought I was editing, not posting a second reply)

If you suspect a possible grain problem and use another sheet to confirm it, you had better make sure both grains are running the same way. Sticking regular stock in the press and then saying "See? The problem went away!" doesn't prove ANYTHING unless the other stock had the grain running wrong too.

I've been printing for 25 years and I've seen bad coating like twice, total. Odds are, that ain't it. It can't be completely ruled out yet, but if you already KNOW you've got wrong grain stock...well, if you hear hoofbeats, it's probably a horse, not a zebra. Cheers.

 

[dleather]

...but if you already KNOW you've got wrong grain stock...well, if you hear hoofbeats, it's probably a horse, not a zebra. Cheers.

This is true...

 

[DotBox]

dleather, if both a coating problem and a grain problem are possible, then a test stock run through the press should have wrong grain as well, otherwise you haven't proven anything. If a test sheet with normal grain prints just fine, what fixed the problem? Was it better coating or correct grain? You need to keep something constant, otherwise you're just guessing.

I've been printing for 25 years and I've seen truly bad coating like twice, total. Odds are, that ain't it. It can't be completely ruled out yet, true, but if you already KNOW you've got wrong grain stock...well, if you hear hoofbeats behind you, it's probably a horse, not a zebra. Cheers.

 

[dleather]

dleather, if both a coating problem and a grain problem are possible, then a test stock run through the press should have wrong grain as well, otherwise you haven't proven anything. If a sheet with normal grain prints just fine, what fixed the problem? Was it better coating or correct grain? You need to keep something constant, otherwise you're just guessing.

I totally agree - I'm just saying it takes about 15 seconds to flash a black light on a sheet in a dark room and see that there's a coating problem. It takes a lot more time and generates a lot more waste to run any press tests, especially given that the mill is willing to concede it is their fault, which doesn't happen often. I'd pick the low apples first and start with the coating issue.

Good luck, viclpp

 

[Alois Senefelder]

Rubbish !

Rubbish !

Dot Box

Sir, You are talking - RUBBISH !

I suggest you learn about the "Fundamentals of Paper Making"


" From knowledge to competence is a great step -- from ignorance to competence
an even greater one"

Regards, Alois

 

[DotBox]

I'm sorry you feel that way Alois. But that doesn't change the fact that I presented a likely cause, explained it, and further gave a way to test it. Without seeing the sheet in front of me, I would STILL bet a day's pay it's wrong grain paper causing the problem, regardless of what your reference may or may not say about this particular issue. I've seen grain issues causes all sorts of strange and unusual problems over the years, none of which were ever addressed in print, as far as I could ever tell. Cheers.

 

[Kaoticor]

I would be inclined to look away from grain direction as a problem (not to downplay anyone's advice or say "never", just presenting reasoning). Dimensionsal stability would affect register, but shouldn't give you the problems you are describing. In fact, running different grain directions can be a requirement depending on where you work.

Many finishing lines require grain direction changes based off of folding requirements. Printing different grain directions can be a necessity depending on the product and your employer. I do agree, that you must be consistent as part of troubleshooting principles are concerned.

In any case, you mentioned that the paper company has taken upon themselves to say bad coating, so yes, 100% go with that! But maybe keep this in the back of your mind if you ever have this problem again and the "coating" is fine.

 

[DotBox]

kaoticor, the problem with what you suggest is that if it ISN'T the coating, then they will receive new paper from the mill and could easily end up with the exact same problem, again. They need to first check what effect grain is having on this job, IMO, for all the reasons previously given. OF COURSE some jobs HAVE to be run with the grain short, for myriad reasons. That doesn't mean every cross-grain job will come out looking perfect. We run "wrong" grain stock all the time, usually for efficient use of the parent sheet or for bindery purposes, but we have lowered expectations when doing so. We don't try to run super high-end work on wrong grain stock. The grain of the stock should always run across the press for superior quality work off the press. Usually it doesn't make all that much of a difference, but sometimes it does, and this might be one of those times. They have (or at least had) the ability to find out if grain is a factor here or not, and that is the correct approach right now, if the job is still on-press. "IMHO."

For what it's worth, I'm now done with this topic. Just trying to help a fellow printer find an easy answer before going through with a paper claim that may accomplish nothing for him. Checking for grain problems is pretty easy, ya know...

 

[Lennyr]

Lenny R.

Lenny R.

This type of stuff is happening more and more due to the state of the paper industry. Sometimes it's because the surface fibers of the sheet are so loose that they pick of on to your blankest, or the ink absorbs so fast and so deep into the sheet that the dots get screwed. What I've been doing with these issues is sizing the sheet myself. It gives the sheet a better printing surface. This method (very old school) has saved me more then once.
I do have to warn though; sizing varnish means longer dry time.
The other problem is designers that design jobs with screen values that run from 100% and down. The question always comes down to "do I hold the solids and plug the screens or vice a versa. If this was a spot job I'd suggest splitting the screens out and running them on different units.
Lenny R.

 

[BeauchampT]

One other question for our original poster...has this problem always occured with this paper stock, or is it relatively recent? If it is new, than perhaps it does prove a coating problem. If this is the first time you've run that paper, perhaps it indicates another weakness in your press.

For example, how old are your blankets?? An old blanket that is not giving enough pressure will create very odd 'mottling' patterns (I've got no better description, but I've heard it called uneven impression) that can look similar to coating problems.

 

[viclpp]

We just did the test. Cut the paper long grain with the 100lb silk text we were having trouble with, and it came out spotty also. Ran the 100lb gloss text short grain and the image came out fine.



Thanks,
Vic

 

[viclpp]

One other question for our original poster...has this problem always occured with this paper stock, or is it relatively recent? If it is new, than perhaps it does prove a coating problem. If this is the first time you've run that paper, perhaps it indicates another weakness in your press.

For example, how old are your blankets?? An old blanket that is not giving enough pressure will create very odd 'mottling' patterns (I've got no better description, but I've heard it called uneven impression) that can look similar to coating problems.

We tried replacing all blankets and packing. Measuring to spec. No luck.

Then we tried replacing the water form and meter roller. Outcome was the same.

Thanks for the help everyone.