Anyone have any experience with VOID bars?

[determined]

We have a weird thing going on here...a customer used this "void" screen bar on every odd page in a book. Using the same image (bitmap tif file)...it's placed on pages with pretty much the same artwork on each page (with some different images, nothing that would really matter...). Anyway, some of the pages printed the way they were supposed to (you couldn't really see the word "void") and some did not (the word was very obvious). There was no real rhyme or reason to the rotation of the pages, or anything like that. It had to be run at 150 LPI to work(?) which it didn't on some pages(?) Anyone? Anyone?   

[determined]

Oh and one other thing...you can't see the difference between the pages that work and the ones that don't in Acrobat, only on a plate

[David]

yeah, we have done these before and they are a PITA.
They can't be rotated, and must be output at the line screen and res that they were imaged at.
We actually had to do a press test for these. Some company made a set of these (at various settings), we imaged a plate and then was able to pick the one that worked for OUR presses.

These guys are super sensitive to press variables, any thing like printing long or short will make them readable (not a good thing).
I would tend to think they you may have a press issue, since some worked and some didn't.
Are you running these like a 8pp layout, one up or what?

[mwc]

There was no real rhyme or reason to the rotation of the pages, or anything like that. It had to be run at 150 LPI to work(?) which it didn't on some pages(?) Anyone? Anyone?   

You say the screening changed on pages?...I'd say that's the crux of the problem...
When doing this kind of work, the pre-screened tif of the VOID text is trying to blend in with a the background value of the box....and any wayward press gain in that area...or screen frequency change will absoulutely affect your outcome.  (your output curves or the tint values in the boxes needs tweaking)

[determined]

it was like a 32 page layout, it worked on some of the pages and not on others...same artwork, PDF out of INDD CS4, all the pages 150 LPI. Presently running all kinds of tests....