In such catastrophic events where hundreds, thousands of documents have been damaged by water, freeze-drying documents has become the most reliable and effective technique for restoring damaged items.
The process consists of freezing as quickly as possible all the affected documents or books, in order to reduce their physical alteration and biological contamination, as well as to stop the loss of pigments or original inks. It is also important to act before the cellulose of the book or file becomes a block.
Once the freezing process is complete, a special high-pressure vacuum chamber will be used, in which, when the time comes, with the right levels of temperature and pressure, the moisture will be sublimated (the water will pass directly from solid to gaseous state). At the end of the process, the freeze-drying technique will have removed the moisture from the documents, stopping the proliferation of mould and avoiding complications such as adhesions, stains and deformations.
However, the quality of the restoration will depend on the material being freeze-dried. There are some pieces made of different materials with different absorption properties that could be deformed due to the different rates of drying and expansion.
These are some of the typologies that can be freeze-dried with good results: