VACUUM FREEZE DRYING
WHAT IS VACUUM FREEZE DRYING? Freeze drying is a technique by which material is frozen, then, dehydrated by sublimation with complete retention of form. Sublimation is the process by which the contained water passes directly from a frozen to a gaseous avoiding a liquid state completely. In the first step before vacuum freeze drying, the water-damaged articles are quickly frozen. This minimizes the formation of ice which can damage the paper in water-damaged books, documents. Frozen material is placed into a vacuum chamber where the freeze-drying process takes place. The time needed to completely dry materials varies according to the thickness of the material, type of paper and degree of saturation. Vacuum freeze-drying does not distort, is noninvasive and produces no chemical damage.