Effective Salvage and Recovery Procedures for Library Materials

Water is the most common and most destructive threat a library collection faces during a disaster. A burst pipe, a monsoon flood, or even the water used to put out a fire can soak thousands of volumes within minutes. What happens in the hours that follow decides whether a collection survives or is lost forever. Salvage and recovery procedures are the systematic, time-tested steps that conservators use to stabilise wet materials, stop further deterioration, and bring damaged items back into usable condition. Understanding these procedures is essential for anyone responsible for protecting books, photographs, and digital media.

Why water is the biggest enemy of collections 🔗

Paper is made from cellulose fibres that absorb water rapidly. When a book gets wet, the fibres swell, the pages cockle, and the binding distorts. The real danger, however, begins after the water settles. Wet paper is the perfect breeding ground for mould, and in warm, humid conditions, mould can begin to grow within 48 hours. This is a serious concern in much of the country, where high temperatures and humidity accelerate the problem far faster than in cooler climates.

The Florence flood of 1966 remains the most famous example of large-scale water damage. When the Arno River overflowed, it left thousands of books at the Biblioteca Nazionale Centrale damaged by water, mud, and oil. The recovery effort that followed shaped almost every modern salvage manual we use today, including the foundational guide written by conservator Peter Waters.

The immediate threats to different materials 🔗

Not all materials react to water in the same way. Paper-based collections swell, weaken, and risk ink bleeding. Coated or glossy paper, common in art books and magazines, is especially dangerous because the pages stick together permanently if they are allowed to dry while pressed against each other. Microforms such as microfilm and microfiche can often survive immersion but must be kept wet and sent to a processor for rewashing. Photographic materials are the most fragile of all, because water can cause the emulsion to soften, separate, and stick to neighbouring surfaces.

Acting fast and assessing the damage 🔗

Speed matters, but reckless speed causes more harm than good. The first step is always to establish the nature and extent of the damage before touching anything. The National Archives guidance, drawing on Waters’ work, warns that overcautious or inadequate appraisals of damage can lead to the loss of valuable materials as well as confusion during the recovery operation.

Weather is often the deciding factor. When conditions are hot and humid, salvage must begin almost immediately to prevent mould. When it is cold, there is more time to plan carefully and test procedures. Before any wet material is moved, the area should be prepared with good lighting, fans, dehumidifiers, and work surfaces covered in plastic sheeting.

Building a recovery team 🔗

A successful recovery depends on organised teamwork, not enthusiastic individuals acting alone. An effective team is led by someone with practical experience and is supported by custodians who know the collection, conservators who can train workers, and technical staff such as electricians, plumbers, and building engineers. The National Archives stresses that a well-briefed and dedicated team works far better than untrained volunteers who may unintentionally cause damage. Salvage crews should take short, regular breaks, because exhausted workers make costly mistakes.

Salvage of paper and books 🔗

The two main techniques for recovering wet books are air drying and freezing. The choice depends on how wet the materials are, how many there are, and how valuable they are.

Air drying 🔗

Air drying is best for small numbers of books that are only damp or slightly wet. A wet book should never be opened forcefully or closed tightly, because wet paper tears easily and will not slide. The National Archives advises handling swollen volumes gently and passing them undisturbed to a dry area, where they can be packed flat in boxes and separated with freezer paper and polystyrene sheets between each open book.

To air dry a damp book, stand it upright, fan the pages open slightly, and place absorbent paper between sections near the spine. The drying area should have good air circulation, low humidity, and a stable cool temperature. Books printed on coated paper should never be air dried after they have begun to dry, because the pages will block together permanently.

Freezing as a stabilisation step 🔗

When there are too many wet books to dry quickly, freezing is the most important emergency measure. Freezing does not dry the books; it simply stops the clock. By lowering the temperature below freezing, mould growth halts, ink bleeding stops, and further swelling is prevented. This buys valuable time to plan the next steps. Materials should be packed and shipped to freezing facilities within a few hours, since the NEDCC notes that saturated books should be frozen and then vacuum freeze-dried to minimise cockling and distortion. Books with running inks or coated paper must be frozen immediately while still wet.

Restoring photographic and electronic materials 🔗

Photographs, optical discs, and magnetic tapes each demand their own approach. Treating them like paper will destroy them.

Photographs 🔗

Photographs are extremely sensitive to water and should be among the first items recovered. Wet photographs can be rinsed in clean water and then air dried face up on a clean surface, or frozen if they cannot be dried in time. The general order of recovery, according to the NEDCC, is that colour materials are recovered before black-and-white prints, which come before plastic-based films. Some early processes, such as albumen and platinum prints, can survive immersion for 48 hours or more, while certain historic items like wet collodion negatives must be treated without delay.

Optical discs and magnetic tapes 🔗

For CDs and DVDs, recovery is usually straightforward. They should be air dried in a single layer and rinsed first if the water was dirty or salty, taking care not to scratch the data surface. Magnetic tapes require very different handling. Crucially, the National Archives warns that magnetic tapes must never be frozen or freeze-dried, because freezing can stretch the tape and cause lubricants to migrate. Wet tapes should never be played, as this causes irreversible damage. Instead, they are kept wet or air dried and then sent to a professional recovery service. For electronic records, checking for an undamaged backup copy is almost always more practical than salvaging the damaged media itself.

Freeze drying and vacuum freeze drying 🔗

When a disaster affects an entire collection, large-scale drying technology becomes essential. Two related processes are used: freezer drying and vacuum freeze drying. Both rely on a scientific principle called sublimation, where frozen water turns directly into vapour without passing through the liquid stage. Because the water never becomes liquid again, the paper avoids the swelling and damage that liquid water causes.

Vacuum freeze drying is widely regarded as the best method for large quantities of wet books and for delicate materials. The frozen items are placed in a sealed chamber, the pressure is lowered, and a small amount of heat is introduced so the ice sublimates away. Research has shown that freeze drying does not have a detrimental effect on the strength of paper, even in books over a century old. The NEDCC confirms that vacuum freeze drying is best suited for large numbers of wet books as well as for materials with water-sensitive inks and coated paper, which cannot be safely air dried.

The main advantages are clear. The process handles huge volumes at once, preserves coated paper that would otherwise be lost, and minimises the cockling and warping seen in air-dried books. Its main limitations are cost and the need for specialist vendors, since the equipment cannot be improvised in an ordinary library.

Prioritising salvage efforts 🔗

In a real disaster, it is rarely possible to save everything at once. This is why every library needs a clear set of priorities decided in advance, ideally written into a disaster plan before any emergency occurs.

Value, uniqueness, and replaceability 🔗

Priorities are generally based on two questions: how valuable is the item, and how easily can it be replaced? Rare books, unique manuscripts, archival records, and the catalogue itself rank highest, because they cannot be replaced if lost. The catalogue and shelf records deserve special attention, since they are the key to reassembling the entire collection afterwards. By contrast, common books that are still in print and easily purchased again may be a lower priority, and in some cases replacement is cheaper than recovery.

The physical condition of an item also affects its place in the queue. Materials that deteriorate fastest in water, such as photographs and coated paper, must be handled before more robust items, even if those items are individually less valuable. The guiding principle from the NEDCC is that the choice of method should always be governed by the nature, value, and condition of the damaged material.

Documenting and tracking the collection 🔗

Throughout the operation, careful record-keeping prevents chaos. Crates should be numbered, their contents recorded, and items packed in shelf order wherever possible. When a label is lost, identifying information can be pencilled on a slip of paper and inserted with the item, since wet paper itself should never be marked. This documentation ensures that once materials return from drying, the collection can be reassembled accurately.

What do you think? If your library faced a sudden flood tomorrow, which three categories of material would you rescue first, and why? And given the cost of vacuum freeze drying, how should a small institution balance the expense of recovery against simply replacing items that are still in print?

References

1. https://en.wikipedia.org/wiki/Peter_Waters
2. https://cool.culturalheritage.org/bytopic/disasters/primer/waters.html
3. https://www.archives.gov/preservation/conservation/library-materials-04.html
4. https://www.archives.gov/preservation/conservation/library-materials-06.html
5. https://www.nedcc.org/free-resources/preservation-leaflets/3.-emergency-management/3.6-emergency-salvage-of-wet-books-and-records
6. https://www.nedcc.org/free-resources/preservation-leaflets/3.-emergency-management/3.7-emergency-salvage-of-wet-photographs
7. https://www.archives.gov/files/preservation/records-emergency/pdf/audio-video-tapes.pdf
8. https://core.ac.uk/works/76456499
9. https://www.nedcc.org/free-resources/preservation-leaflets/3.-emergency-management/3.12-freezing-and-drying-wet-books-and-records