the following article is copyright Northeast Documentation Center
TECHNICAL LEAFLET emergency Management
DRYING WET BOOKS AND RECORDS*
There are currently five ways to dry wet books and records. All have undergone at least minimal testing under emergency conditions; several have been used extensively. These are described to assist you in making the best choice given your circumstances: cause of damage, level of damage, number of items involved, rarity/scarcity, personnel available, budget available, drying service available. Advice from a conservator or preservation administrator experienced in disaster recovery can be helpful before making the final selection(s). Successful recovery operations have proven that it is less expensive to dry
original collections than to replace them, even if they are replaceable.
It is important to understand that no drying method restores materials. They will never be in better condition than they were when drying began. If time must be taken to make critical decisions, books and records should be frozen to reduce physical distortion and biological contamination.
Air drying is the oldest and most common method of dealing with wet books and records. It can be employed for one item or many, but is most suitable for small numbers of damp or slightly wet books and documents. Because it requires no special equipment, it is often believed to be an inexpensive method of drying. But it is extremely labor intensive, it can occupy a great deal of space, and it can result in badly distorted bindings and textblocks. It is seldom successful for drying bound, coated paper. Book and paper conservators should always be consulted for the drying of rare or unique materials. They may choose
to air dry items or may suggest one of the other alternatives.
This is the newest method to gain credibility in the library and archival world, although it has been used for many years to dry out buildings and the holds of ships. Large commercial dehumidifiers are brought into the facility with all collections, equipment, and furnishings left in place. Temperature and humidity can be carefully controlled to specifications. Additional testing is being undertaken, but the technique is certainly successful for damp or moderately wet books, even those with coated paper, as long as the process is initiated before swelling and adhesion have taken place. The number of items that can be treated with dehumidification is limited only by the amount of equipment available and the expertise of the equipment operators. This method has the advantage of leaving the materials in place on the shelves and in storage boxes, eliminating the costly step of removal to a freezer or vacuum chamber.
Books and records that are only damp or moderately wet may be dried successfully in a self-defrosting blast freezer if left there long enough. Materials should be placed in the freezer as soon as possible after becoming wet. Books will dry best if their bindings are supported firmly to inhibit initial swelling. The equipment should have the capacity to freeze very quickly,and temperatures must be below -10°F to reduce distortion and to facilitate drying. Documents may be placed in the freezer in stacks or may be spread out for faster drying. Expect this method to take from several weeks to several months, depending upon the temperature of the freezer and the extent of the water damage. However, caution is advised: with this method leaves of coated paper may adhere to one another.
VACUUM THERMAL DRYING
Books and records may be dried in a vacuum thermal drying chamber into which they are placed either wet or frozen. The vacuum is drawn, heat is introduced, and the materials are dried above 32°F. This means that the materials stay wet while they dry. It is an acceptable manner of drying wet records, but often produces extreme distortion in books, and almost always causes blocking (adhesion) of coated paper. For large quantities of materials it is easier than air drying, and almost always more cost-effective. However, extensive rebinding or recasing of books should be expected. This method is a solution for
materials that have suffered extensive water damage.
VACUUM FREEZE DRYING
This process calls for very sophisticated equipment and is especially suitable for large numbers of very wet books and records as well as for coated paper. Books and records are placed in a vacuum chamber frozen. The vacuum is pulled, a source of heat introduced, and the collections, dried at temperatures below 32°F, remain frozen. The physical process known as sublimation takes place - i.e., ice crystals vaporize without melting. This means that there is no additional swelling or distortion beyond that incurred before the materials were placed in the chamber. Many coated papers can be difficult to dry without sticking together once they are wet. Because it is nearly impossible to
determine which papers will block, all coated papers should be treated the same way for the purpose of vacuum freeze drying: before any drying takes place, and ideally within six hours of becoming wet, materials should be frozen at -10°F or
lower. They may then be vacuum freeze dried with a high potential for success. Rare and unique materials can be dried successfully by vacuum freeze drying, but leathers and vellums may not survive. Photographs should not be dried this way
unless no other possibility exists. Consult a photograph conservator. Although this method may initially appear to be more expensive because of the equipment required, the results are often so satisfactory that additional funds for rebinding are not necessary, and mud, dirt, and/or soot is lifted to the surface, making cleaning less time consuming. If only a few books are
dried, vacuum freeze drying can indeed be expensive. However, companies that offer this service are often willing to dry one client's small group of books with another client's larger group, thus reducing the per-book cost and making the process
HOW TO AIR DRY WET RECORDS
Wet records may be air dried if care is taken to follow guidelines suggested by preservation experts. The technique is most suitable for small numbers of records that are damp or water damaged only around the edges. If there are hundreds of single pages, or if the water damage is severe, other methods of drying will be more satisfactory and cost effective. Stacks of documents on coated, or shiny, paper must be separated immediately to prevent adhesion, or they must be frozen to await a later drying decision. Care must be taken with water-soluble inks as well. Records with running or blurred inks should be
frozen immediately to preserve the written record. After the items are dry, conservators can be contacted for advice and assistance.
If records must be air dried, the following steps will help achieve satisfactory results. Wet paper is extremely fragile and easily torn or damaged, so care must be exercised. Once wet, records will never look the same, and at least some cockling or distortion should be expected.
1.Secure a clean, dry environment where the temperature and humidity are as low as possible. The temperature must be below 70°F and the humidity below 50%, or mold will probably develop and distortion will be extreme.
2.Keep the air moving at all times using fans in the drying area. This will accelerate the drying process and discourage the growth of mold. If materials are dried outside, remember that prolonged exposure to direct sunlight may fade inks and accelerate the aging of paper. Be aware that breezes can blow away single records. Train fans into the air and away from the drying records.
3.Single leaves can be laid out on tables, floors, and other flat surfaces protected if necessary by paper towels or clean, unprinted newsprint. Or clotheslines may be strung close together and records laid across them for drying.
4.If records are printed on coated paper, they must be separated from one another to prevent them from sticking together. This is a tedious process, which requires skill and patience. Practice ahead of time will prove useful. Place a
piece of polyester film on the stack of records. Rub it gently down on the top document. Then slowly lift the film while at the same time peeling off the top sheet. Hang the polyester film up to dry on the clothesline using clothespins. As the document dries, it will separate from the surface of the film. Before it falls, remove it and allow it to finish drying on a flat surface.
5.Once dry, records may be rehoused in clean folders and boxes. Or they may be photocopied or reformatted on microfilm or fiche. Dried records will always occupy more space than ones that have not been water damaged.
HOW TO AIR DRY BOOKS
Air drying is most appropriate for books that are only damp or wet in places, such as along the edges. Books that are soaking wet should be vacuum freeze dried to minimize cockling of leaves and distortion of bindings. Books containing coated paper should be frozen while still wet and vacuum freeze dried. Books with running or blurred inks should be frozen immediately
and also vacuum freeze dried.
1.Refer to steps 1 and 2 of the previous section.
2.Interleave every few pages, starting from the back of the book, turning pages carefully. For interleaving, use paper towels or clean, unprinted newsprint. Be careful not to interleave too much or the spine will become concave and the volume distorted. Complete the interleaving by placing clean blotter paper inside the front and back covers. Close the book and place it on several sheets of absorbent paper. Change the interleaving frequently. Turn the book over each time it is interleaved.
3.When books are dry but still cool to the touch they should be closed and laid flat on a table or other horizontal surface, gently formed into the normal shape, with convex spine and concave front edge (if that was their original
shape) and held in place with a light weight. Do not stack drying books on top of each other. In no case should books be returned to shelves until thoroughly dry; otherwise mold may develop, particularly along the inner margins.
4.Dampness will persist for some time in the inner margins, along the spine, and between boards and flyleaves. This is particularly true of volumes sewn on oversewing machines. Check often for mold growth while books are drying.
5.If the edges are only slightly wet, a book may be stood on end and fanned open slightly in the path of a flow of air as from a fan). To minimize distortion of the edges, lay volumes flat under light pressure (e.g., paper-covered bricks)just before drying is complete.
6.If you can establish an air-conditioned room capable of maintaining a constant relative humidity of 25 to 35% and temperatures between 50 and 65°F, books with only wet edges can be dried successfully in approximately 2 weeks
without interleaving. Do not try to dry books printed on coated paper by this method. In most cases, the only chance of saving such books is to freeze them while wet and dry them by vacuum freeze drying.
Sally Buchanan: 6/94
* The author acknowledges expertise from many people who have contributed to the understanding of disaster recovery methods. These include Willman Spawn, Peter Waters, Olivia Primanis, and the staff at NEDCC.