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]

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...