The book board used in book case construction consists of many layers of board. If the book cloth is damaged or torn open at a corner, the different layers of board are often visible. When damaged corners are repaired with plastic tape, the book board is not repaired, it is only covered up. To truly repair the book corner, the various layers of book board must be glued to one another and the book cloth repaired or replaced.
In some cases the corners are damaged while the book cloth is still intact. Other times the book cloth will be torn or missing. In either case, cut through the book cloth on the top and fore edge of the board. Cut well past the damaged board into sound board and cloth.
Separate the layers of board and use a microspatula or knife to apply PVA glue to several of the book board layers. The PVA will seep through the thin layers of board so every layer does not need to have glue applied. The number of glued layers depends on the condition of the book board.
If the original book cloth covers the corner, paint a small amount of glue on the wrong side of the book cloth and smooth it over the corner. (If the book cloth needs to be replaced, follow the instructions for Attaching New Corner Book Cloth in a separate post.)
With fingers or a folder, press the book cloth onto the board, moving from the base of the repair up toward the comer edge. Wipe away any excess glue with a cloth or paper towel.
Note how much excess glue came out of the corner and use that as a gauge to decrease or increase the amount of glue used. A small amount seeping out is good because it means that the glue has reached all the layers of cardboard. Too much adhesive seeping out is wasteful and makes a mess to clean up.
For sharp flat corners, cover each side of the corner with wax paper or non-stick material and clamp between two pieces of book board using bulldog clips. Use dense mat board or book board, not corrugated cardboard that will compress under the pressure of the clips.
Another way to achieve flat corners is to lay the repaired comer flat against the work table and weight it down with a paper covered brick.
Corners do not have to be sharp or flat to protect the book. Some older books may look more “natural” with rounded corners, especially when only one or two corners are repaired. If rounded comers would look better, mold the corners into position while the glue is wet and let the repair dry without weight or pressure.