What the heck are they, and do they matter?
Book signatures, also called sigs, are large sheets of paper (parent sheets) with multiple book pages printed on them. These sheets are folded and then trimmed to create consecutively numbered bundles of pages that can either be glued or sewn into the book’s binding. The use of book signatures is a clever way to make book printing less labor-intensive, more materials efficient, and reduce paper waste. Check out my short stop-motion video that helps to explain what I am discussing here visually.
The process of arranging pages on a parent sheet to create signatures is called page imposition. The printer will organize the pages so that when printed, folded, and trimmed, all of the book’s pages make smaller 4, 8, 16, 32, or 64-page booklet bundles, or the less common 12, 20, 24, and 36-page booklet bundles. These booklets are then bound together to create the complete book.
You will notice all the numbers are in multiples of 4. Because even with the smallest 2-page booklet, there will always be the backside of the paper. When counting your book’s pages, include both sides and blank pages too.
Your printer will determine the size and number of signatures by considering the book’s dimensions, page count, binding method, press size, and parent sheet paper size.
On-demand book printing does not use book signatures.
If you are printing your book on-demand, you can stop reading now. But don’t! Book signatures are a super-cool and elegant solution to the ancient art of book printing. And understanding signatures may answer some questions you may have had about books in your collection. Such as “Why are there so many blank pages at the end of this book?” Or “Why is all the color grouped?” Or “Why does this paperback book not lay flat like this hardcover?”
Why on-demand printing does not use book signatures
Except for rare instances, on-demand printing does not employ signatures for two reasons:
- Digital press paper size is too small—usually no larger than 13” x 18”. There is just not enough paper to carry multiple pages.
- Digital books are typically perfect bound, using a glue binding. Perfect binding does not require a booklet fold to sew the pages to the spine. You may notice how perfect bound books rarely lay open flat. That is because the pages are notched and glued to the spine, while sewn bindings use the centerspread of the gathered booklets to sew to the spine. The stitched booklets make a book where the pages move more easily, open more naturally, and don’t fall out.
When does a printer use book signatures?
Book signatures are typically only used in larger run offset printing where the press can handle larger sheets of paper, sometimes as large as 23”x35”. There are two significant benefits of printing on larger sheets:
- When printing multiple pages on larger sheets, the printer does not have to replate and clean the press as often.
- By imposing the pages in book signatures, the printer does not have to collate the pages manually. If done correctly, after printing, folding, and trimming the large sheet, the printer ends up with perfect, consecutive ordered, multi-page booklets. The printer will gather these smaller booklets together to create the complete book. Again this will all make sense if you watch my short (2-minute) stop-motion video.
The imposition of pages on a book signature can look a bit screwy and make little sense flat, but it all comes together beautifully when folded and trimmed.
If the printer manages signatures, why is this important to me?
- It matters if you are not keen on having blank pages at the end of your book. If you know, you may be able to design your book to the exact signature page count.
- You may save money if you know your signature sizes. Let’s say your book is 162 pages, and your printer can productively print 16-page signatures. By reducing your page count by two pages, you may save money and not have blank pages at the end of your book. This example is hypothetical, but you get the point. More factors determine the signature-size that your printer considers, so you don’t want to assume. Just ask them.
- You want full-color but can’t afford color throughout your book. If you are ok with having your color pages grouped in a section of your book, inserting, a color signature may be an option to have full-color without paying for an entirely full-color book. You see this done more often in older books where color plates are all within a section. To do this, you will need to work closely with your printer and have some flexibility to make this work.
How do I use book signature information?
First, you will need a page size and close page count to give your printer. If you can be flexible, ask your printer what the closest most productive page count will work for them to keep costs down. If reducing the page count by just a few pages can save, it may be an easy thing for you to do. It is also nice to know if there will be extra pages at the end of your book. Instead of having them blank, you can add an author bio, an epilogue, credit contributors, or add a teaser for your next book. Why waste the pages if you have them? If you want to insert a color signature section, you will need to work closely with your printer to arrange that, but it may be a way to have color when you did not think it possible.
And finally, not all signatures have to be the same size, and only your printer will know what works best on their press. But understanding the process can sometimes help you get more bang for your buck.