The successful recovery of water-damaged library and archival materials depends on timely response to a disaster. Rapid response maximizes recovery of collections materials and expedites the restoration of services. To extend decision-making time regarding salvage and replacement, freezing is the most viable option for most institutions. Because it inhibits mold growth, freezing allows the time to determine if value, use, and format of the original are important, or to de-accession or purchase replacement materials or materials in a different format. Freezing also provides a respite to review insurance policies and vendor contracts. Finally, freezing will allow time to find space for air drying, determine if there is adequate staff and time to air dry, and to handle large incidents in a smaller, more controlled atmosphere.
This leaflet will walk you through the process of freezing books and records, and it will explain how to dry them once retention and funding decisions have been made. For a more general introduction to recovery, see NEDCC Leaflet 3.6 “Emergency Salvage of Wet Books and Records.”
Before beginning any recovery efforts, the water source must be considered. Rarely is the water clean and free of debris. What is contaminating the water? Is the contamination corrosion from a pipe, dirt and debris from a flood, salt water, or is there sewage involved? If the water is sewage-contaminated, call in a professional recovery service immediately; do not deal with the salvage in-house. If the water is only contaminated by rust, dirt, or salt water, rinsing wet books and records before freezing helps by removing debris that could be difficult to clean off after drying. If sufficient trained labor and time are available for this step, set up three or four bins of clean water. Holding books closed tightly, dip them gently in the water moving each book from bin to bin. This process will expose them to successively cleaner water and remove much of the surface debris. Over time, make the last two bins the first two, replace the dirty water in the first two bins, and move the clean water bins to the final rinse stage. If records are mud-covered, rinse by supporting the records on a piece of plexiglass or other rigid, inert support, and rinse with a gentle stream of water from a hose or pitcher. Do not rinse if the inks are soluble; instead, freeze them immediately, mud and all.
Begin by working with priority items first, if you know what they are. Realize that these materials are going to be fragile, especially if wet, and that they will be larger and heavier than normal. Sort materials by degrees of wetness as you remove them from the shelves. Taking time to do this will make drying much more efficient. Degrees of wetness can be considered with these main categories in mind:
Damp: Cool to the touch, having been exposed to high humidity; can be identified after the event by mold formation.
Slightly wet: Noticeably wet with staining to the textblock, binding, folder, or pages, no more than ½” in from the edges. These areas will have been in immediate contact with water.
Wet: Noticeably wet with staining more than ½” in from the edges up to saturation; can be based on the length of time exposed to water.
When packing materials for freezing, work with sturdy, uniform packing containers. Label each container as to content and the degree of wetness. Loosely wrap books with wax or freezer paper and pack one layer deep, spine down. Pack books of similar size in a box to prevent distortion.
When packing records, leave documents in their boxes and folders if possible. If boxes are damaged, pack folders into containers laid on their sides for ease of filling. Interleave with wax or freezer paper every couple of folders.
Pack oversize materials of similar size and wetness between flattened cardboard boxes and wrap with tape. There is no need to interleave with wax or freezer paper unless the items are printed on coated paper or have colors that could bleed. Move packed items to a freezer immediately.
Ideally, your disaster plan identifies local freezer space that is available in the event of an emergency. If there are no such spaces in your area, it is possible to rent a freezer truck or portable walk-in freezer. Make sure whatever you rent is of sufficient size and can maintain temperatures at or below 0° F to prevent the thawing and re-freezing that exacerbates distortion in paper-based materials. When filling the truck, do not over-pack. Spreading materials out as much as possible will speed the freezing process.
Because freeze drying will cause more harm than water for some commonly held non-book materials, the following materials should NOT be frozen:
Materials can remain in the freezer indefinitely and will eventually dry there. If drying in the freezer, expect items to be inaccessible for several weeks to many months, depending upon the temperature of the freezer and the degree of wetness. However, the goal should be to return these materials to circulation as quickly as possible to maintain service continuity. There are two primary options for drying frozen materials: air drying and vacuum freeze drying.
Vacuum freeze drying is best suited for large numbers of wet books and records as well as for materials with water-sensitive inks and coated paper. Frozen books and records are placed in a vacuum chamber. A vacuum is pulled and a source of heat introduced while the overall temperature remains below 32° F. The materials are dried by a process called sublimation: the water in the solid phase (ice) is removed from the materials in the gaseous phase without passing through the liquid phase. Thus there is no additional wetting to cause distortion beyond that incurred before the materials were frozen. If materials have been stabilized quickly after becoming wet, very little extra shelf or storage space will be required when they are dry.
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. In addition, mud, dirt, and/or soot are lifted to the surface, making cleaning less time-consuming. If only a few books are dried, vacuum freeze drying can 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, reducing the per-book cost and making the process affordable. When dealing with commercial vendors for drying, communicate clearly from the beginning about costs, handling, and expectations.
Air drying is the most common in-house method of dealing with water-damaged books and records. Because it requires no special equipment, it is often believed to be an inexpensive method of drying. However, air drying is labor intensive, diverts many hours of staff time to regularly monitor the process, and often results in a distorted finished product. It is not an option for books with coated paper. The rehabilitation costs after air drying tend to be greater than other methods because most bound materials require some form of treatment from pressing to full rebinding; documents often need flattening and rehousing.
Due to the time required for air drying, it is not unusual for mold to develop during large-scale operations.
In addition to mold growth and coated papers blocking, another consequence of air drying is the extra amount of shelf space required for collections. Depending upon how long materials spend in the freezer and the length of time spent air-drying, the amount of additional shelf space required after drying can be 20% or more.
Air drying is most suitable for small numbers of records, so work with small batches from the freezer at a time. Records with water-sensitive media should be left in the freezer as long as possible or vacuum freeze dried.
Note: Books containing coated paper should be vacuum freeze dried and not air dried after freezing.