The Role of Signatures in Offset Printing for Books
In offset printing, the pages of books are commonly printed on large sheets of paper, with multiple pages printed on each side of these sheets. Known as signatures, these large sheets will be folded down and trimmed after they are printed.
The use of signatures allows multiple pages to print per press impression, which reduces the number of printing plates needed and minimizes paper waste. It also streamlines the printing process and binding operation.
What is Imposition?
Imposition refers to the process of arranging a book's pages so that once the printed signature sheets are folded and trimmed, the pages will appear in the correct order.
Your printer will likely use special imposition software to arrange the book's pages into the optimal layout. The objective is to fill the master sheet as fully as possible. Imposition is performed during the pre-press phase of production, just prior to creating the printing plates.
The illustration shows an example of how the pages of an 8-page booklet might be imposed. Notice that the pages appear out of order, with some upside-down. However, this configuration will produce pages with the proper orientation, and in the correct sequence, once the signature is printed, folded, and trimmed.
In this example, four pages will print on the front of the signature sheet and four pages will print on the back. After printing, the two-sided signature will be folded in half horizontally (so that page 3 contacts page 2, and page 6 contacts page 7). Then the sheet is folded again vertically (so that page 4 meets page 5). The booklet will be bound along the fold that forms its spine. All remaining folds are trimmed off to allow the pages to open freely.
If you have any questions about book printing or have an upcoming book project, give Formax a call at 866-367-6221. We specialize in book printing and will be happy to discuss your project with you. If you already know your specs and would like a quote, submit our easy quote request form. We look forward to assisting with your next book project!
Take care! Rick
