The best book glue is one that is designed for use on porous surfaces, creates a permanent bond, and will not damage the surface of books over time through erosion or discoloring. This type of adhesive can be used to reattach pages inside a book, as well as the cover, back panel, and binding agents along the spine. It is typically available for purchase at local craft stores and through Internet ordering.
A common choice among libraries for book glue is the polyvinyl acetate variety, more commonly referred to as PVA glues. This type of adhesive is designed for use with porous materials, making it ideal for use with paper and book bindings, and is available in a book specific variety. It requires a longer drying time than most other types of glue, and also needs pressure to permanently secure the material. When using this adhesive to repair books, users can clamp pages together, as well as bindings and book covers, using pressure clamps purchased at a local hardware store. This type of glue may need 24 hours or more to permanently set.
Contact cement may also be used to bind pages and covers together in books. This type of adhesive tends to expand over time as it sets, and can often causing bubbling along the spines and pages of books where they have been exposed to the material. The bond it creates, however, is permanent, and it will not damage the pages over time.
Both contact cement and PVA glues do not require additional chemicals to activate the adhesion process, and can be brushed onto the surface of books using craft brushes. This allows for an even application of the adhesive and covers the full surface area where damage may have occurred. Hot glues are not recommended for use as a book glue. These glues tend to dry quickly and leave lumps at the application site, which are visible on the exterior of the book. They also cannot be brushed into place, and frequently leave gaps along damaged areas where pages remain unattached.
The selected book glue should be labeled as acid free. If the package labeling does not specify that it has been made without this ingredient, it is likely that it contains this corrosive element. Acid containing glues may be used on a wide variety of arts and crafts projects. When exposed long term to paper and book bindings, however, the acid begins to eat away at the paper pulp. The result is often a higher level of decay at the weakest points of the book than had the pages and binding never been repaired at all.