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Freeze drying is a process now used by the restoration industry when saturated books, papers, documents, photos, and textiles need to be saved from the destructiveness of water. Lyophilization, as it is also called, is familiar to most people for its use in processing many foods and medicines. Safe enough to be used in items consumed on a daily basis, this process is recommended by the Library of Congress, particularly when coated paper items are at risk of becoming damaged and unusable.
Lyophilization is perfect for document restoration use, and this process has been used successfully on many different types of media. Film, photos, papers, including those with specialty finishes, can all be rescued from the landfill. Books and magazines are also candidates for this method. Swelling of these items when exposed to water and then allowed to air dry is well-known. Lyophilization prevents this warping, keeping swelling to a minimum.
Paper absorbs water easily because paper is porous. As water is absorbed, the fibers in the paper swell, and as they dry, they become distorted. The freezing of water-saturated books and other items keeps the water from spreading throughout the item. The below-zero temperatures prevent the development and growth of mold, as well. Ink on frozen documents is unable to bleed and run, which other methods have been unable to match.
Rare books, including those that are leather-bound, can be preserved when treated by the lyophilization method. Because moisture is converted to vapor without ever becoming a liquid and then wicked away from the items, they slowly but steadily dry. Warping is greatly minimized of all materials, and leather never shrinks in size, eliminating the chances that leather items might split as they dry.
Film and photos can also benefit from lyophilization. Like ink on paper, freezing also prevents the running of photographic inks, saving one-of-a-kind photos. Curling of some types of media is unavoidable, but further work with a conservator can remedy this reaction.
Document restoration using lyophilization is not something that can be done at home or in the office. It can begin there, in the freezer (if it is set on the lowest temperature setting) and then continue with a professional company that has the proper equipment to complete the process. It would take months to accomplish at home what a professional restoration company can do in only a week or two (and often less) with commercial-grade equipment.
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