I'm just about to send a CD-booklet 134mmX122mm (34pp)for print in a Guangzhou printshop – and the language barrier makes it a bit difficult to get all points across; I'm wondering about what I need to explain about the overprinting. Every page of the book is slightly yellow-toned (A-master yellow-toned) with white background, greyscale illustrations on every page.

When overprint preview is on, greyscale illustrations blend with the yellow pages like they're supposed to, removing the white background of the illustrations.

How can I make sure that overprinting behaves in this way when they print the booklet? The obvious solution, I guess, would be to print on yellow toned stock paper, but since there are full-color images on some pages – that won't be possible. How can I make sure that the printers overprint the white correctly? Does anyone have any experience with this?

  • Will a screenshot of the separations preview not sufficiently serve that purpose? – 13ruce Aug 17 '15 at 18:11
  • I have added screenshot for clarification – just wondering if there was something else I can do. – Fryxell Aug 17 '15 at 18:20
  • hiring a translator for the language barrier seems like a good idea too. – Ryan Aug 17 '15 at 19:32
  • @Ryan Sometimes it's easier to simply modify the files, and doesn't add to the budget besides the time you spent doing it! Not always easy to find someone who speaks mandarin and (in my experience) you can't always talk to the printer directly; there's an agent who's like a salesman... and that salesman usually just nod to what you say with an empty stare as if you were explaining him the String Theory! Maybe I've met too many unmotivated agents or salesmen ;) – go-junta Aug 17 '15 at 19:57

The way you'll make sure overprinting is applied is simply by adding your background color to the color recipe of your gray illustration.

Background CMYK + Gray CMYK = Fake Overprint of the gray.

If the gray is a rich gray, you don't need to literally add the ink; as long the gray contains the same value or more of yellow/cyan/magenta than your background, you'll be fine.

And then also add the overprint setting but at this point it won't be necessary!

You're right to do something more "forceful" than trying to explain yourself. It's very hard to deal with printers in China and you need to provide your files as easy to print as possible. They also have old RIP and your overprint settings could be ignored or simply removed.

Example of a "fake" or "forced" overprint in CMYK with a normal gray (50% black):

Example of forced overprint gray rich on light background printed in China

Result in CMYK

In Adobe Acrobat Preview, you can verify your results or any software that shows you the CMYK separation

CMYK overprint

Result without the black separation showing.

That's how it should look like. It will give you the same result as the gray overprint since the background and the gray add up together.

black overprint preview

Example with a rich gray

Rich gray overprint

Result with the black separation removed

There's no white "knockout" on the yellow, that's like overprint: Every separation of cyan, magenta and yellow contains the same amount of ink as the yellow background.

Rich gray without black separation

Example without overprint or rich gray (or if your overprint setting is ignored by RIP/Printer)

That's what you don't want. That's what could happen if you don't enrich your gray and only use an overprint trapping on your gray separation.

The method above will guarantee you the other separations won't get knockout or trapped without overprint like this!

What you don't want

If you're using that overprint effect to create 2 shades of black when the illustration overlaps the yellow background, you'll need to do some Pathfinder work on that illustration to split it, and then apply the 2 types of gray where you want them (eg. the rich gray with yellow on the background part, the gray without yellow on the white part, etc.)

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