Hi everyone,

Here's this week's head-scratcher...

At my place of work, we print business cards 4up on sheets of 5.5" x 8.5" stock (no, that's not the head-scratcher ), and an odd problem has been brought to my attention.

One of our customer's business cards has a light blue (PMS 299) gradient running across the width of the card from the bottom edge to about two-thirds of the way up the card.

The artwork is created in Adobe Illustrator, then placed in InDesign where I step and repeat it to be four-up.  From there, I create an uncompressed PDF file with crop marks / registration marks / etc., which I then place in another InDesign file which I send to our RIP for color separated platemaking.  (As far as I know, the RIP turns the artwork into TIF-based output, but my understanding of the process is hazy at best.)

The gradients on the bottom two cards invariably print just a bit lighter than the gradients on the two cards above them. (Although from the pressman's perspective, the lighter gradients are the ones that the ink rollers print first, if you get what I'm trying to convey here.)  And I'm trying to figure out why this is... 

It's the exact same artwork file, just stepped and repeated.

I've thought about using the "Place" command four times (instead of once and then using "Step & Repeat" three times), but we haven't had any orders from this customer recently and I don't want to waste any plates doing this.

Anybody have any thoughts?

Cheers, John the Fontaholic

are the values the same on the ripped file?

On a small press - think about the form roller circumference. Ink load is strongest at the head and weakest at the tail I think it goes. Are you feeding the sheet 8.5 into the gripper or the 5.5? We fed the 8.5 into a Printmaster when we had one.

Try turning the grads so they are head to foot - ie the grads are next to each other rather than a 4" step apart. Putting a large ink take out bar at the bottom of the form may help, forcing the press to require more ink on the rollers rather than less, for a light colour.

Another idea is the blanket may be tired and there may be a depression ("smash") area - that would yield more and less pressure over the area of the sheet.

Quote from: Tracy on January 10, 2014, 08:53:34 AMare the values the same on the ripped file?

They're supposed to be, but something is causing the bottom two gradients to print lighter than the top two.

I suppose the only way to find out is to take a densitometer reading of the plate after it's been processed?

Cheers, John the Fontaholic

Quote from: Chilbear on January 10, 2014, 08:54:05 AMOn a small press - think about the form roller circumference. Ink load is strongest at the head and weakest at the tail I think it goes. Are you feeding the sheet 8.5 into the gripper or the 5.5? We fed the 8.5 into a Printmaster when we had one.

Try turning the grads so they are head to foot - ie the grads are next to each other rather than a 4" step apart. Putting a large ink take out bar at the bottom of the form may help, forcing the press to require more ink on the rollers rather than less, for a light colour.

Another idea is the blanket may be tired and there may be a depression ("smash") area - that would yield more and less pressure over the area of the sheet.

The sheets are fed into the gripper on the 8.5" side, so that (from my perspective) the bottom two gradients are the first to hit the ink load (I suppose this means that what I perceive as the lower half of the press sheet is actually the "head" from the pressman's perspective).

I'll suggest the idea of running them head-to-foot to the pressman and see what he says. (And he's one of those people who always has something to say...  :angry:)

Tired blankets are certainly a possibility -- I can ask him about this as well. (Oh, goody...  :lipsrsealed:)

Cheers, John the Fontaholic

Try rotating the file 90 degrees. if the lightness problem persists on the same part of the image, then it is something in the RIP process. If it follows that the lightness is in the same position on the press, then blanket issue may be to blame.

Quote from: Grimace on January 10, 2014, 11:00:45 AMTry rotating the file 90 degrees. if the lightness problem persists on the same part of the image, then it is something in the RIP process. If it follows that the lightness is in the same position on the press, then blanket issue may be to blame.

I'll bring this up to the pressman as well.  Thanks!

Cheers, John the Fontaholic

Gradients can and do trick the eyes. It could be an Optical illusion.

Quote from: jimking on January 10, 2014, 12:50:22 PMGradients can and do trick the eyes. It could be an Optical illusion.

Good point, maybe cut the press sheet and compare to see how obvious any color change is.