Custom Printing: Bleeds and Multi-Signature Printing

Two of my print brokering clients came to me with similar questions/problems this week. Both are producing print books, but the issues in question would be equally relevant whether they were producing catalogs, magazines, or any other multi-signature custom printing jobs.

First of All, What Is a Press Signature?

A press signature is a collection of pages that the printer imposes (positions in a computer file so all pages will be imaged onto a large custom printing plate and then printed onto a large press sheet). For offset printing, the press sheet sizes might be close to 25” x 38” or even 28” x 40” or larger depending on the printing press. All of these pages are then printed at the same time (often with four book or magazine pages lined up above four other book or magazine pages on one side of the press sheet, and with the same configuration on the opposite side of the press sheet). (Many presses will only allow for printing one side of the sheet. Then, after the ink is dry, the opposite side can be printed.)

When the pressman has printed both sides of the sheet, he can fold the sheet multiple times at right angles to come up with a booklet of folded and attached pages that can be perfect bound or saddle stitched into (potentially) a much larger print book, magazine, or catalog. These folded signatures are either nested into one another (and then stapled) for saddle stitching or stacked (and then glued into the spine of the cover) for perfect binding.

Since this is a very visual process, I would encourage you to research press imposition and press signatures online, and look at the photos on Google Image. You can do the same thing by folding an 8.5” x 11” sheet of paper in half, then in half again (at a right angle), then in half again (at a right angle). This will show you how a flat press sheet can be folded (by the folding equipment in your printer’s post-press, or finishing, department), and it will also show you why you need to prepare bleeds according to your printer’s requirements.

What Are Bleeds?

Images or text on your two-page “reader spread” (any facing pages you see when the print book is open in front of you) can extend off the page on the top, sides, or bottom. Or they can bleed across the gutter (the vertical line between the two facing pages in the page spread). If they extend off the top, bottom, or sides of the paper, these “bleeds” must also be extended (usually 1/8”) off the page in the InDesign art file, so they can print beyond the trim lines and be trimmed off after printing without any white edges showing.

This is because trimming equipment is not always precise. If you have a photo that just comes to the edge of the press sheet and is trimmed inaccurately, there will be a visible white line at the edge of the paper. “Bleeding” an image or solid color off the edge of the paper and then trimming the sheet on your printer’s trimming equipment avoids this error.

All of this would be easy to grasp if not for the fact that a “printer spread” (two pages side by side on a press sheet) is not the same as a “reader spread” (two pages side by side in a printed book). If you look at press impositions online, you will see that book pages next to one another on a press sheet are in fact not usually consecutive or even near one another. To turn a flat press sheet with non-consecutively positioned pages into a folded and trimmed 8-page or 16-page press signature, your printer’s imposition software (usually) places individual PDFs of each page in a specific location such that once the 16-page printed press signature has been folded and trimmed, only then will all pages be consecutive.

Because of this, setting up bleeds in an art file for a multi-page (or multi-signature) printed product can be a challenge.

This was the problem my clients were having. Both were producing print books with bleeds.

Bleed Issues with My Client’s Books

One of my clients is a “fashionista.” I have written about her color swatch print books before. They are small books that help women choose colors for fabric and make-up based on their complexions. The color books themselves are like the PMS color swatch books used for graphic design and custom printing. In my client’s books, each page has a color on the front and text on the back. All pages are drilled and then attached with a screw-and-post assembly.

My client was comfortable preparing bleeds for this print book in InDesign because all pages were separate and could therefore bleed on all four sides. There was no “gutter” between pages. But now she is producing a 116-page perfect-bound book with bleeds and crossovers (the technical term for bleeds that start on the left-hand page and extend onto the right-hand page). So she’s not sure how to proceed.

The other client just received an online proof of her client’s 8.5” x 11” perfect-bound book, which has bleeds around the top, bottom, left, and right trim margins as well as crossovers. The first online virtual proof she saw had problems with parts of bleed elements appearing on other pages or otherwise appearing to not bleed correctly.

So both clients were frustrated.

How We Addressed the Issues

The first client’s problem was easier to manage than the second’s. I simply told her that for any pages bleeding on the outside trim margins, she should extend the photo boxes in InDesign 1/8” off the page. For anything that didn’t cross over the gutter margin between facing pages she should stay in the “live matter” image area (i.e., within the visible columns on the InDesign page). And for anything that needed to cross over between pages, she should start the photo on the left-hand page within the image area, and end on the right-hand page within the image area. For an image that would bleed into the gutter and then stop, she should just end the photo box at the gutter margin. (Why? So a sliver of the image would not show up on the facing page or—based on the description of press signatures I presented earlier—on a page elsewhere in the book. This could be a disaster.)

The second client’s problem was harder to diagnose. Keep in mind that both clients (depending on what the particular printer needed) would most probably export a press-ready PDF from the InDesign file in which they had created their respective books. And even though they were creating the books with “facing pages” to better see how their double-page spreads would look upon completion, their printer most likely would have asked them to export the book as a PDF with single pages (not two-page spreads). These single pages would then be imposed into the press signatures of their respective books (for instance, each of the 16 pages in one press form would be individually imposed as single PDFs onto a computerized version of the press form, which would yield four printing plates to produce the 4-color press sheets).

When my second client saw her virtual proof with parts of photos extending onto other pages and what appeared to be missing sections of other bleeds, she panicked and called me. After my encouraging her to call the prepress technician at the printer directly, we discovered that the PDF proof had no trim marks. Therefore, extraneous images (and parts of images) that would have been trimmed away on the post-press trimming machine all showed up on the proof. That is, all of what appeared to be errors would have been removed, and the final print job would have been perfect. However, without the printer’s trim marks on the proof, there was no way to know this.

What We Can Learn from My Clients’ Jobs

1. 1. Most importantly, ask your book printer how he wants the InDesign files prepared and whether he wants to receive the final job as “native” InDesign files or as a press-ready PDF file. If it’s the latter, ask for his specifications. Not all printers have the same imposition software or the same workflow, so not all printers want their files set up in the same way.

1. 1. Particularly ask about how to address bleeds that extend only to the gutter. You don’t want part of the image on a two-page reader spread early in the signature to show up on a page later in the signature. (A good printer would catch an error like this, but you want to to make things as easy as possible for your printer.)

1. 1. Keep all text, images, or color solids either within the live matter image area or bleed them 1/8” off the page (top, bottom, right, and/or left).

1. 1. When distilling a PDF file of your InDesign artwork, make sure you set the export function to include the bleeds, or they will disappear at the trim marks and not extend off the page.

1. When you have questions about any of these items, which are complex and often addressed differently by different book-, catalog-, or magazine-printers, ask for the head of the printer’s prepress department and voice your concerns. Your printer will appreciate this proactive stance, which will avoid later problems.

This entry was posted on Tuesday, July 10th, 2018 at 1:53 pm and is filed under Printing. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.