Acid in Books — Preserving the Law Collection

If you have visited our Reading Room you may have noticed some of the books have a white dot on the spine.  This does not mean the books were bought on clearance or as factory seconds.  The white dots indicate the books have gone through a process of deacidification or have been printed on acid free paper.

Acid in paper can lead to brittle pages.  Left unchecked, these brittle pages continue to deteriorate until the books are unusable, literally crumbling in ones hands.  The acid can come from the ground wood pulp used in fiber stock or additives such as bleach.  Once books become brittle, there is no process to restore them to full strength.  Deacidification attempts to remove or neutralize these harmful acids in books before extensive damage to the paper can occur.

The Library of Congress’s (LC) Preservation Directorate administers the Mass Deacidification Program which is performed under contract by Preservation Technologies.  Books are put into a chemical bath which pushes alkaline into the paper, creating a buffer to any harmful acids.  The bath does not damage the bindings, pages, or inks.  Some readers have remarked the books “feel funny” after deacidification, however, the process does not leave any residue on the books or fingers.

Recently, several staff members from the Law Library paid a visit to the Preservation Technologies facility in Pennsylvania where they were able to see the process from start to finish.

Books from LC awaiting inventory and inspection.

Library materials are sent to Preservation Technologies in tubs.  Upon arrival the containers are opened, all contents are inventoried and inspected.  This process is conducted in the same manner regardless of subject.  Law books are co-mingled with those from other areas of the Library of Congress.

Applying white dots by hand.

All materials undergoing deacidification receive a white dot, usually on the spine below the call number.  Additionally, a label is placed on the inside back cover of each book indicating the item has been treated by Preservation Technologies.

Books waiting to be "dipped."

Books are then mounted on racks which allow the pages to fan open during the process.

Books “in suspension.”

Books are lowered into the alkaline bath.  The treatment lasts approximately 30 minutes.

Emerging from the milky bath.

Following removal, books are placed in another container to collect any raw materials from the process which can be used again.

As the name implies, this process is used for mass deacidification.  For rare and special materials that cannot travel, the Library is able to process these items onsite.  Contrary to the name mass deacidification, Law Library staff members were impressed by the “hands on” process.  Some had envisioned an assembly line of machines.  There is very little automation besides the “washers.”  Preservation Technologies staff members were involved in every step of the process.

Deacidification slows the aging process, retards embrittlement of pages, and extends the life of paper-based materials.  This preservation process eliminates the need for future, expensive reformatting processes. The Library deacidifies approximately 1 million manuscript sheets and 250,000 books annually.  Visit the Reading Room and look for the little white dots.