Creating a book spine is a critical aspect of the book design process. Whether hardcover or softcover, all perfect bound books require a book spine. But all too often spine measurements are overlooked during the design phase, and you end up with problems. Too thick of a spine, and your book closes with a tent-like gap. Too thin, and your book won’t close at all.
When you’re building your files, the width of the spine must be calculated and that measurement must be built into your cover art. Yes, there is some math involved, but it’s not difficult and after a few tries, you’ll get the hang of it. Of course, with all math problems, there is an equation:
In short, take the number of text pages and divide by the PPI.
What’s PPI? It stands for Pounds Per Inch. All papers have a PPI; you can ask your printer for the PPI for your paper stock. The chart below lists some PPI’s for papers on our floor.
Here’s an example: Say you have a 500 page book and you choose a 70# Natural uncoated paper for the text pages. Using the chart above, the PPI is 385. Your equation is: 500 divided by 385 equals 1.29870.” Rounded up, your spine width is 1.30.” Simple, right?
There are some tools and templates on the PG website Resources page to help you calculate spines: http://www.pubgraphics.com/resource-center.htm
Lastly, keep in mind these important considerations:
- for hardbound books, add an additional 0.14 to the width (to accommodate the boards)
- The minimum width of a hardcover spine is .0375
- Max spine width is 21/4″ or 1200 pages
- Avoid imagery/copy in the gutter– keep it 2mm away– as glue won’t adhere to the spine