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13. Low cost freezing and drying in an emergency

13.1 General considerations

The process that follows has as its key feature the use of a normal freezer for the stabilization of wet documents and books, followed by conventional air-drying. It is suitable in those situations where quantity of wetted materials is not great, and where help and time are available. The materials to be frozen and later air-dried should be selected by priority based on whether they are just damp or soaked, slightly or very damaged, and whether valuable and irreplaceable.

The freezing of a bundle or stack of documents should not be a problem. However, during the thawing and drying operation there may be a risk that soluble inks and colors will feather or run. As to books, the technique works well when limited to relatively modern editions. With older, larger, and heavier books the drying treatment becomes somewhat complicated; the weight of water can seriously damage their structure. For material printed on coated paper, the best and, perhaps, only method for salvage is to freeze while wet and freeze-dry.

13.2 Materials required

If clearing is required: plastic pails, sponges, a handy source of water, drainage; paper towels are always handy for this wet operation.

Preparation for freezing: work table, plastic sheeting for work surfaces (the plastic is useful for many things), freezer paper (Kraft or similar if none available), tape, sturdy boxes or plastic milk crates if transporting is required.

Freezing: domestic chest freezer or other.

Air Drying: electric fans, hand-held driers.

Mold Prevention: thymol crystals (a fungicide) and a suitable solvent (ethanol, denatured alcohol) to make interleaving sheets; for this purpose unprinted newspaper stock or strong tissue.

13 3 Recovery of water-damaged materials

13.3.1 Handling wet materials

The materials selected for freezing are taken to the area where cleaning, if required, will take place, or to the work tables for wrapping. Extreme care must be taken in handling the wet materials in order to reduce the risk of damage with its consequent high cost of repairs and restoration.

No attempt should be made to separate one or more documents from a soaked pile. If for some urgent reason a document has to be removed, cut a sheet of plastic a bit larger than the document to be removed. Place the plastic over the soaked document and with a fine tool (spatula, knife) lift one corner so that it adheres to the plastic sheet. Lift gently; the surface tension of the water will cause the document to stay with the plastic. To release, place both on an absorbent paper with face of document down; with tool hold corner of document down and lift the plastic sheet with care.

If an archival box is soaked replace it in situ with a fresh one if safe to do so. This will prevent the contents from spilling out.

Soaked books should not be opened or closed. To do so will cause severe strain on the structure of the book and damage to such elements as hinges and spines. A soaked book should be taken to the work area as is. Soaked covers should not be removed; they help support the text block and lessen the risk of damage.

13.3.2 Cleaning and washing

Before freezing, it would be helpful to remove soilage from the water-damaged materials. Many times this is not possible because facilities are not available, or because of the urgency of the situation. In any event, if soiled books are kept firmly shut they can be dipped in running water (flowing slowly) and the soil gently sponged away. A pile of documents with soiled surfaces cannot undergo the same method of treatment. One way to remove soilage is to play a gentle stream of water over the pile through a soft rubber or plastic tube than can be pinched for control of flow.

13.3.3. Wrapping and packing

Wrapping supports wet materials; it keeps a bundle of documents or books from freezing one to the other. Wrap books singly; documents in stacks as thick as a book. I! the freezer is nearby, place items there as each is ready. If at a distance, use cardboard boxes or milk crates for transport. Do not wait for large pile. The sooner stability takes place, the less risk of mold. (Note: Some conservators feel that with large quantities of soaked materials, complete wrapping is unnecessary; separation of items with freezer paper works well).

13.4. Freezing

These are freezing sources: Upright fee cream freezers, commercial frozen food lockers, domestic chest freezer, the freezing compartment of a domestic refrigerator. The literature recommends a freezing temperature of -20 F (-29 C). The first three units have this capability; the last, with higher temperatures, does not.

13.5. Air drying

13.5.1. Picking a work area

The work area should be such that air-drying will be encouraged and mold infection discouraged. Much depends on the weather; summer or winter, humid and hot, cold and dry. Bower and Brandt (37) describe an operation where prevailing variables were used to produce a very satisfactory environment for air-drying a number of soaked files. These, still in their cabinets, were moved into the basement of a heated building. The winter weather outside ranged between 7 and -28 C (19.4 and -18 F). The heat in the building's basement wee lowered as much as possible; the relative humidity reached 30 percent.

In summer, particularly it hot and humid, the task may be more difficult. Ii the work area bale air that can has a temperature of about 18 C (64.4 F) and a relative humidity of 50 to 60 percent, mold growth can be held in check. Ii air conditioning is not available, open windows and dove to encourage circulation and get rid of stagnant air; use electric fans to assist. It the humidity remains at high level, the use of dehumidifier- may be in order. These are available at appliance outlets and, in some cases, can be leased. When dehumidifiers are used, close doors and windows; use electric fans for circulation. (Note: An inexpensive hand-held instrument, the sling psychrometer, will give sufficiently accurate readings of temperature and relative humidity to eliminate guesswork).

The working area will need several tables for the operation; working surfaces should have protective plastic sheeting Have sufficient electrical outlets for fans, air driers, dehumidifiers, and other equipment. Use heavy duty, well-insulate-d cable extension cords.

13.5.2 Drying documents

Frozen documents can be dried with relative ease. If blotting paper (newsprint stock or paper towels will do) is available place on the work table. Unwrap each bundle and place on the absorbent. Electric fans blowing over the documents will circulate the air and help thawing and evaporation. Hand-held driers will hasten drying. As the topmost document dry sufficiently to be handled safely, lift off and place on another surface for further drying. By removing the top document, the next one is better exposed to the air for evaporation. When it becomes safe to divide the pile into smaller ones, drying will also be speeded up.

With a bit of ingenuity, any number of methods can be found as drying surfaces for documents as they are lifted from a pile: tiers of plastic screens secured to wooden uprights, nylon cords over which the documents are draped, the lawn outdoors if conditions permit.

Soaked absorbent paper and other wet scrap materials should be removed from the work area in order to keep the humidity level down.

13.5.3 Drying books

Book thawing followed by the evaporation of its moisture is a slow process. It takes time to dry from the outside in. Place the book on its side on blotting paper or other suitable absorbent. Use electric fans to assist thawing. Do not use heated driers since the drying rates of the components that make up the book vary; unnecessary strain and tension should be avoided. When the book is thawed stand upright (on its head to compensate for shelf sag), open covers slightly for support; do not fan out. As the book dries it can be opened a bit more for additional area exposure to air. Change absorbent often; remove soaked papers from room.

13.6 Pressing

Normally, a book contains about seven percent moisture. It is never totally dry even when reposing on a shelf for a long period. Documents comport themselves in the same way. However, neither would respond to pressing with so little moisture. On the other hand, when thawed books and documents are air-dried to the point where they feel "dry" to the touch, they usually have more than the amount of moisture required for response to pressing.

Documents with wrinkles, cockling, or creases can be flattered by pressing between boards with a light weight on top. Press several at a time; separate each with silicone paper (wax paper will do). As to books, place each on its side on a flat surface; with thumbs on the front edge press inward gently to form a rounded back. Place book between pressing boards with light weight on top. Do not stack books for pressing.

13.7 Prevention of mold infection

Should it appear that conditions are favorable for mold infection of books, a practical method of applying an inhibitor is by interleaving with fungicidal sheets. The method is particularly useful when the amount of materials to treat is not great.

In this technique sheets of paper (newsprint stock, strong tissue) are cut a bit larger than the item to be treated. The sheets are dipped in a thymol solution. For this purpose, a 10 to 15 percent solution of thymol crystals in ethanol, acetone, industrial denatured alcohol, or trichlorethane (one pound of thymol crystals in one gallon of solvent, or 450 grams of the crystals in about four liters of solvent) is recommended (5). The sheets are placed on a surface protected with plastic sheeting for drying (which is rapid). To store, put sheets in a sealed container or wrap in plastic since thymol is very volatile.

Interleave books in their upright position when dry enough to open slightly without the risk of damage. Place the thymol sheets in the text block at intervals of about 25 millimeters (one inch). Change frequently. Do not interleave too much lest the spine of the book suffer damage. Because of their construction, books are easier to interleave. However, there is no reason why the same technique cannot be used on documents.

Care must be exercised in preparing the thymol solution because of the toxicity of the products. Rubber gloves should be used along with a painter's respirator, and goggles. If the fungicidal sheets can be prepared outdoors, so much the better.


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