|Vacuum Freeze-Drying, a Method Used to Salvage Water-Damaged Archival and Library Materials: A RAMP Study with Guidelines (UNESCO, 1987)|
Freeze-drying is a salvage process; salvage in the sense that its purpose is to save water-damaged archival and library materials from destruction. This is done by freezing to stabilize, then sublimate to dry. It will not return to pristine condition any books or documents which were in a damaged state at the moment they were frozen for subsequent drying. Freeze-drying will not press out cockled or wrinkled sheets and pages, nor straighten out warped covers. These will be locked in that position on drying. It will not release the pages of a book printed on coated shock if blocking has set in before freezing.
It will not remove discoloration, tide marks, or stains that were there at the start. Freeze-drying will not press out vellum or leather. And as pointed out, it will not destroy mold spores.
In short, apart from the end purpose of the process, frozen materials come out of the vacuum chamber in just about the same condition as they entered. At the end of the drying cycle some will look surprisingly good; others will be scheduled for minor repairs. Some may have to bear the high cost of restoration; some may have to be discarded or replaced. In any case, the fault is not in the freeze-dry process. It is still the most effective method known for the physical, chemical and biological stabilization of water-damaged archival and library materials, especially when large quantities are involved and time is of the essence.