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Foreword

Freeze-drying is a familiar term thanks to the propaganda given certain consumer foods and beverages available on the market. These vary from dehydrated strawberries to brownish Crystals in a Jar that with hot water are converted to a cup of coffee. Some people may know that such products are made in a vacuum chamber, the same type as those used as simulators for training astronauts, or testing satellites and moon vehicles before launching them off into space. But, mention a vacuum chamber or simulator as an effective tool for drying a ton of documents soaked by a broker water main, or stacks of books soaked by the fire hoses used in fighting a blaze, and the number of those up-to-date diminishes.

Among archivists and librarians are many who remember "reading something about it" in professional periodicals, but retain a fleeting idea of what the process is, how it works, how it applies to them. Hence, the purpose of this study: to fill the information gap. To this end, the study summarizes a broad spectrum of data that includes, among other relevant facts, the behavior of paper when wet, its vulnerabilities in this condition, stabilization by freezing, vacuum chambers and how they dry, and selected case histories where such chambers were used successfully to salvage water-damaged documents and books.

The study cites two methods in current use for drying water-damaged archival and library materials: vacuum freeze-drying by sublimation and vacuum-drying by evaporation. The emphasis is on freeze-drying. Here, the wet materials must first be frozen. This produces a condition of total stabilization which, in turn, provides un unlimited span of time to think, plan, and decide what course of action to take. These advantages, however, do not indicate that vacuum-drying is automatically downgraded. As the study reveals, it is a very effective method of drying. But, since the materials normally are not prefrozen, certain exigencies could arise. For example, depending on conditions, wet materials might have to be placed in a chamber as quickly as possible to prevent attack by mold.

Many people-conservators, conservator-scientists, and manufactures-kindly furnished information on freeze-drying in response to letters written to them by the author. They warrant profuse thanks and gratitude for the time they took from their busy schedules to provide a reply.


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