Hint from a Book Artist:
Board Sizes and Unsupported Stitches
By Christine Cox
“Coptic” and other link stitches are easy to sew, flexible, beautiful, strong, historic and the fact that you can incorporate the board attachment into the sewing makes them a logical choice for a lot of projects. Because these stitches are not sewn over tapes or cords they are called “unsupported,” meaning that the spine will naturally move fairly freely over time.
Because the stitch is so beautiful, book artists often choose to leave it exposed at the spine, which reinforces this weakness from the unsupported sewing.
When a book that hasn’t been rounded and backed sits on a shelf for years, it sags. The weight of the paper pulls the book block down, making the thread stretch. Sooner or later, the book block will sit down on the shelf and the formerly straight line of sewing will curve down in the middle (see photo). In addition to being unsightly, the stretched out thread loosens up the book even more.
Gravity at work makes unsupported stitches an iffy choice for books you’ll want to keep for a long time, but sometimes artists make compromises in the name of art, and not all books are meant to last forever.
Keeping in mind that unsupported link stitches were abandoned historically for a reason, the secret to preventing the sag is to make the boards and the book block almost flush at the tail (bottom) of the book. In other words, the boards are the same height as the book block, plus the normal square (the measurement from the edge of the book block to the edge of the board) at the head, plus a smidge extra (maybe about 1/16″, depending on the size of the book) at the tail. Don’t make the boards and block completely flush because any misalignment in folding the paper or sewing the sections will stick out beyond the board edge.
The squares at the head and fore-edge will still match, so nothing will look odd.
To recap, the fore-edge and head will have squares. The tail will be almost, but not quite flush with the boards.
This tiny, 1/16″ adjustment in the relationship between the sizes of your boards and paper will make your book weather the years looking better and staying a little tighter.