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Preserving Your Books

A guide to handling and storing books in order to prolong their life and prevent damage.


This guide is an introduction to basic techniques for handling and storing small collections of books. Many people have books they value due to their importance as heirlooms, or due to their monetary value, and which they wish to preserve for the future. The most effective and economical preservation measures are preventive: proper storage, environment, and handling. If books are damaged, however, there are options to treat that damage and prolong the life of a book.

The preservation guidelines described here have been used by the Library of Congress in the care of its collections and are considered suitable by the Library as described; however, the Library will not be responsible for damage to your collection should any result from the use of these procedures.

Please note that the Library does not offer digitization, preservation, or conservation services to the public.

If you are interested in donating books to the library, please follow the instructions on this page.

Key Preservation Terms

The following terms are frequently used throughout this guide.

Acid-free: Acid-free materials have a pH of 7 or higher. Almost all newly manufactured paper and cardboard materials are acid-free but will create acids in the future through their degradation unless they are buffered (see below).

"Archival" only as it relates to materials used to store and house collections items): Archival is not a legally defined term. Products advertised as "archival" should be acid-free, lignin-free, and buffered. "Conservation grade" also doesn't have a legal definition; it should also meet those standards.

Buffered: Materials that are buffered are treated with an alkaline substance, typically calcium carbonate, with a high pH value in order to lower the pH to below 7. This neutralizes any acids present in the materials, and "buffers" against any future acids that may be created through the natural aging process or through interactions with the surrounding environment.

Image of a before and after of a conservation treatment at the Library of Congress
Before and after image of a conservation treatment performed at the Library of Congress

Conservation: is concerned with the preservation of the physical artifact itself, as opposed to solely the information contained within it. This involves corrective action to treat damage as well as working to prevent it.

Lignin-free: Lignin is a component of wood, which is usually present in paper made from wood. As lignin ages, it produces a high level of acid. Paper or cardboard made from wood pulp that will be in contact with important books for the long term should have had the lignin removed for that reason.

Preservation: a holistic set of activities which preserves the information and physical condition of books and other cultural artifacts by minimizing and mitigating chemical and physical deterioration.

These books show red rot.
Several of these books show red rot.

Red rot: Present on many 19th- and early 20th-century leather-bound books due to the method by which the leather was manufactured, red rot is the powdery deterioration of leather, especially at the hinges of the book where the leather flexes. It is not reversible but may be stabilized in some cases.

Relative humidity: Relative humidity (abbreviated rH) is the percentage of the maximum amount of water that can be in the air at a given temperature. Most books are best stored at a stable, non-fluctuating relative humidity of no higher than 55%. Relative humidity levels above 60% risk causing warping as well as mold growth on books, and relative humidity below approximately 30% can also cause warping due to contraction. Rapidly changing humidity is also a cause for concern.

Restoration: refers to treatment of a book or other artifact to bring it back to its presumed "original" condition, which can involve the addition of non-original material. In other countries and languages, however, “restorer” is sometimes synonymous with “conservator”.

“Preservation,” “conservation,” and “restoration” are three terms which are sometimes used interchangeably. However, they refer to three interrelated but distinct approaches to handling and treating these materials.

“Conservator” and “conservationist” are not synonymous. A “conservationist” is concerned with the preservation of nature.

Parts of a Book