A: What you're describing is called "creep." It's the result of push-out when outer signatures are laid over top of inner signatures on the saddle. Here's how to visualize the effect of creep-and how we at Bindagraphics help our customers plan for it:
Make a dummy of your saddle-stitched project, using the same stock and the same number of pages that will be used to print the job. Use a razor to cut about 1/4" into the dummy, as shown:
Now remove the razor and open the dummy. You'll see that the cuts in the pages on outer signatures are closer to the outer (trim) edge than the cuts in inner signatures. Obviously, if the book is trimmed to make the outside margins "right" on the outer signatures, the outside margins will be narrower on inner signatures. To compensate, the job needs to be stripped so that outside margins on the inner signatures are wider; the cuts in your dummy will show up much wider.
Q: I know Solutions is mainly for printers, but as an apprentice designer I find your publication helps me learn how to design more intelligently for my customers' benefit. I realize that lots of different size sheets are used in offset printing, but there must be some standards. Can you list the standard sheet sizes, so I can figure out what trim sizes will be most efficient for printing pamphlets and books? Thanks for your help.
A: Yes, there are several standard sheet sizes, and for that reason there are standard trim sizes which can be efficiently printed, multi-up, on those sheets.
You should find the table at the top of the next column useful.
More often than not, as a designer you'll be doing your customer a favor-by saving him money-if you design to one of the standard trim sizes.
But if a particular design really demands a non-standard trim size, you should still consider press sheet size to try to use the sheet efficiently. For an example of what can happen when you don't, see Oop$! (overleaf).
Designing for Imposition
Q: I'm making a living as a designer but, frankly, I got into the business via my interest in Macintosh computers and I don't have any background in printing. Twice lately I've found myself involved in discussions with clients and printers about imposition. I now know what the word means-barely. But I have no understanding of how to design printed materials with imposition in mind. Can Solutions help?
A: Both this question and the preceding one address the increasingly- important area of graphic arts design by professionals who do not have a background in the graphic arts.
We call this an "increasingly-important" area because the "desktop-publishing" revolution has multiplied many times over the number of people who are doing the work of design without, in some cases, ever having seen the inside of a print shop or bindery. We appreciate that this phenomenon is problematical for many of our commercial- printer customers. Some have been driven to distraction by "ready-for-camera" jobs that aren't close to being ready. Others have developed their own electronic pre-press departments and inevitably get directly involved in design issues. We don't know how all these developments will ultimately shake out, but in the meantime, we welcome all corners to the field and to the Solutions family of readers. Here are some basics that may be helpful to you as a newcomer to the field of graphic arts design.
First, a definition-
Imposition is the positioning of the pages on the press sheet so that when the sheet is folded and trimmed the pages fall in the correct order, in the correct orientation (i.e. right side up), and with the correct margins.
Let's do a simple exercise to get a feel for the issues involved in imposition.
In the following illustration of a press sheet, the page numbering may at first appear to make no sense:
But as the sheet folds-each fold at right angles to the previous one-the page numbers fall into proper sequence and position, producing a "signature."
There are numerous impositions-for example, there are more than 30 correct ways to fold a 16-page form, and a nearly infinite number of incorrect ways-so if you're new to this trade and uncertain of the pitfalls or possibilities, get the bindery involved early. Remember, 76% of printing mistakes happen in planning, so spend your money there. Call me at Bindergraphics if you need help with a job that will come to us for finishing.
Meanwhile, here are a few more critical definitions:
Signature: A sheet of paper which when printed and folded will make up all or part of a publication. (A signature is sometimes referred to as a "section," especially in perfect-binding or case-binding.)
Form: A series of pages laid down on a plate so that when printed they will make up one side of a signature. The outer form contains the lowest folio, which will always be on the outside of the signature. The inner form always contains the second-lowest folio, which will always be on the inside of the signature.
Folio: Page number.
This only scratches the surface of the subject of imposition. Stay tuned to Solutions for more.