Freeze drying frozen books

Subsequent to freeze stabilization, wet books can be thawed and air dried with or without interleaving or they can be vacuum dried in heated chambers (5). The moisture in frozen books can be sublimed by freeze drying (10) or removed by a vacuum/thaw/outgassing process (8), with microwave energy (6, 14), with dielectric energy (6), or by solvent extraction with or without vacuum assistance (5). 

Freeze-Thaw, Vacuum Drying (1A, IB). The frozen books were laid with the spine vertical on metal shelves inside a large chamber. A controlled amount of heat was applied to the shelves to thaw the ice and to allow the water to evaporate. A vacuum was established to remove the water from the books. Progress in removing water from the books was checked by noting the return of the book s weight to its original value. 

Freeze-Thaw, Vacuum Drying (2). The frozen books were arranged separately in a horizontal position on the shelves of a small freezer dryer. The temperature of the shelf was set above freezing and held constant to supply energy for thawing the ice and evaporating the water. A vacuum to remove the water vapor was applied until the book became dry. 

Freeze-thaw vacuum, inter leave-air, and solvent extraction processes offer the greatest potential in drying these types of coated- and uncoated-paper books after they have been wetted and frozen. The drained-air, vacuum-air cycle, vacuum, microwave, and dielectric drying processes work well on uncoated paper, but they fail to dry books containing this type of coated paper. Small and large units for freeze-thaw, vacuum drying have been used successfully to remove water from these frozen coated and uncoated books. 

In the field of frozen food, the book by Tressler and Evers, The Freezing Preservation of Foods, and for dehydrated foods, Von Loesecke s Drying and Dehydration of Foods are valuable references. 

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