Illustrator How-To: White Overprint Gotchas
While working at my father-in-law’s print shop last year, I wrestled with one file that gave us much trouble when we tried to separate it. It was a white logo that knocked out of a solid spot color background. The file looked right on screen, and the proof print that we made looked fine. But on the plate, the logo disappeared. The culprit? The logo, which was filled white, was set to overprint. I remember thinking at the time, “Who in their right mind would ever set white to overprint?”
A few days ago, I was designing a piece for a client where I wanted to place the company logo and knock it out of a colored background. So I opened the original black logo in Illustrator and changed all black-filled objects to white. Then I saved the file with a new name and placed it into InDesign. However, upon placing the logo in InDesign, the logo itself was invisible. And then it all made sense:
1. I had Overprint Preview turned on in InDesign. (I wanted to see a better interpretation of the Metallic Pantone color I had been using for the background.)
2. My logo had initially been colored black and was set to overprint when it was originally created.
3. When I changed the fill color to white, the overprint command was still applied to the object.
The fact that I had Overprint Preview turned on in InDesign saved me. Otherwise I would have had no idea, and the job would have gone to press that way. And because this was one of those crazy deadline jobs, I would have requested some quick proof print to sign off on — and the composite proof would have shown the logo — and then of course, I can just imagine the phone call I would have gotten from the client when the job was delivered.
Illustrator CS2 does have a feature that allows it to detect when you’ve specified an overprint for an object that is painted white (Figure 1), but this happens only when you’re applying the overprint — not as in the case above where the object already had the overprint, but the color was changed from black to white. I would assume that in the real world, this is the real cause for the problem we’re dealing with. I think people are smart enough to know that white shouldn’t be set to overprint.
Figure 1. Illustrator’s white overprint warning.
So I was really happy to learn that there is something out there that offers some kind of help. It’s called WOP2KO, and it’s a $25 plug-in for Illustrator CS2 from Doug Habben, also known as Worker72a. The non-abbreviated name of the plug-in is White Overprint to Knockout.
Here’s a description that I pulled from the Worker72a Web site:
A fast, efficient method for preventing problems on press caused by white art and text objects incorrectly set to overprint. It takes only a few seconds and pays for itself with the first problem it catches.
How does it work?
- Open a Document.
- You will find the “Set White OP -> KO” command under the Object menu.
- The active open document will be scanned for text and path objects specified as 0% CMYK or 0% tint spot or global color fills or strokes that have been set to overprint. This includes locked or hidden art and art on locked or hidden layers. All overprint whites will be set to knockout.
- Please Note: Spot or Global swatches that have been defined as 0% CMYK will not be set to knock-out except in cases where an object also has a 0% tint value. To include 0% CMYK defined swatches, temporarily redefine them as non-global process color swatches before running WOP2KO.
The plug-in is Mac OS-only at this point.
If you’ve ever been bitten by the white overprint issue, I think you’ll find that 25 bucks is a small price to pay for a good night’s sleep the night before you go on press.
Doug’s site also has a free plug-in that alerts you to when white overprints exist in a file at open time. White Overprint Detector is an Illustrator CS2 plug-in for Mac that automatically scans CMYK documents when opened and alerts you if white overprint text or paths are found. It doesn’t remove the overprints — that’s a job for WOP2KO.
By the way, I should mention that I really think this is something that Adobe needs to address directly within the application. While the plug-in is a good workaround, I’d much rather see some intelligence or feature built in that will help avoid these kinds of issues in the future.