Using simple materials you can perform basic book mending in your library.
Recently I mended a large book at my church. The spine of the Sacramentary was split and hanging loose. Since it was a copy that we would keep and use for years I performed what is called "casing-in." Casing-in a book refers to a process in which the book block is attached to its cover by gluing the end sheets and spine cloth to the inside surfaces of that cover.
If the end sheets and/or spine cloth wear out or split at the gutter of the book, the book block comes loose from its cover. The book can be repaired by replacing the end sheets and spine cloth and "recasing" it in the cover. (The terms "hanging" and "rehanging" a book are also used by some librarians.)
If the end sheets are not completely detached, cut through them to separate the book block from the covers. Next, prepare the book and the cover. If the original end sheets are brittle or not glued down firmly, they can often be peeled or lifted off easily. Removing the old paper around the edges of the cover is necessary in order to prevent them from showing under the new end sheets.
Remove the old cloth and paper from the book's spine if it is loose or bulky. If it doesn't lift off easily, wet with water until soft enough to scrape off. Next, measure the book block and cover and then gather the materials needed: new end sheets; spine cloth and paper. An end sheet is a single piece of paper of sufficient weight or strength to support the book. It is folded in half along the grain of the paper to match the dimensions of the book block.
Apply a 3/8 inch strip of glue along the folded edges of the new end sheets and affix them to the front and back of the book block, pressing them down with a bone folder. Once both end sheets are firmly attached you can prepare the spine of the book.
The most important element in securing the book to its cover is the spine cloth. The cloth tape is a very dense, but flexible. Cut a strip the length of the book block and at least two to four inches wider than the spine of the book. Placing the book block in a vise (i.e., between the knees), pull the cloth tape down over the spine tightly.
It is now time to case-in the book. First, put the book block inside the cover, aligning it exactly as it should fit when completed. Then, after opening the top cover, place a piece of scrap paper between the two halves of the end sheet. This prevents the glue from running down onto the pages of the book. Coat the top surface of the end sheet with glue. Then put the super cloth down over the end sheet and cover it with glue, as well. You can pull the scrap paper out at this time.
Continue to hold the book block in alignment on the bottom side of the cover, and close the top cover over the glued surface of the end sheet. Next, immediately open this cover and check to make sure the end sheet is properly positioned.
If the newly glued end sheet needs adjusting, there are a few seconds in which to push or slide it a few millimeters in any direction. Ideally, the end sheet should be about 1/8 inch back from each edge of the cover. Then firm the end sheet down with a bone folder, squeezing out any excess glue. This process is repeated on the other side of the book and cover. Once both end sheets are glued to the cover, place waxed paper between the covers and end sheets and press the book in a book press. (Glue won't stick to the wax paper.)
Once the new end sheets are entirely dry glue the original end sheets over them, if they were illustrated. Then, the book must again be placed in a book press overnight or until the paper is dry. You may use large books for this if you cover the mended book with wax paper.
In another situation with a book that had a cracked spine I approached the mending with a different attitude. We had ordered an updated version and this book would be disposed of. I utilized red duct tape to repair the book and keep it in a usable state until the replacement arrived. The spine of the book was the same shade of red as the tape. The repairs were not noticed by anyone. It was not necessary to go through the casing-in procedure for this particular book.