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Re[2]: Freeze Drying

     There is also good information on Disaster Preparedness. See UC San
     Diego's info at:  http://orpheus.ucsd.edu/preservation/idisas.html

     Good luck!

______________________________ Reply Separator _________________________________
Subject: Re: Freeze Drying
Author:  "Book_Arts-L: READ THE FAQ at http://www.dreamscape.com/pdverhey";
         <BOOK_ARTS-L@xxxxxxxxxxxxxxxx>  at {ucsdhub}
Date:    12/3/98 2:00 PM

This is being forwarded for for Ton Cremers due to technical reasons.


> Wew just recieved some books that have been freeze dried because of
> water dammage.  My question is what becomes of the water in the
> books when the books are brought back to normal temps?  I assume it
> doesn't just melt, there would be water on the books again.  How is
> it they get rid of the water exactly?

The following text was made by Sally Buchanan at http://www.nedcc.org/
The  Northeast Documentation Center (specialized in the conservation
of paper-based materials)
Ton Cremers


There are currently five ways to dry wet books and records. All have
undergone at least minimal testing under emergency conditions; several
have been used extensively. These are described to assist you in
making the best choice given your circumstances: cause of damage,
level of damage, number of items involved, rarity/scarcity, personnel
available, budget available, drying service available. Advice from a
conservator or preservation administrator experienced in disaster
recovery can be helpful before making the final selection(s).
Successful recovery operations have proven that it is less expensive
to dry original collections than to replace them, even if they are
It is important to understand that no drying method restores
materials. They will never be in better condition than they were when
drying began. If time must be taken to make critical decisions, books
and records should be frozen to reduce physical distortion and
biological contamination.

Air drying is the oldest and most common method of dealing with wet
books and records. It can be employed for one item or many, but is most
suitable for small numbers of damp or slightly wet books and documents.
Because it requires no special equipment, it is often believed to be an
inexpensive method of drying. But it is extremely labor intensive, it
can occupy a great deal of space, and it can result in badly distorted
bindings and textblocks. It is seldom successful for drying bound,
coated paper. Book and paper conservators should always be consulted
for the drying of rare or unique materials. They may choose to air dry
items or may suggest one of the other alternatives.

This is the newest method to gain credibility in the library and
archival world, although it has been used for many years to dry out
buildings and the holds of ships. Large commercial dehumidifiers are
brought into the facility with all collections, equipment, and
furnishings left in place. Temperature and humidity can be carefully
controlled to specifications. Additional testing is being undertaken,
but the technique is certainly successful for damp or moderately wet
books, even those with coated paper, as long as the process is
initiated before swelling and adhesion have taken place. The number of
items that can be treated with dehumidification is limited only by the
amount of equipment available and the expertise of the equipment
operators. This method has the advantage of leaving the materials in
place on the shelves and in storage boxes, eliminating the costly step
of removal to a freezer or vacuum chamber.

Books and records that are only damp or moderately wet may be dried
successfully in a self-defrosting blast freezer if left there long
enough. Materials should be placed in the freezer as soon as possible
after becoming wet. Books will dry best if their bindings are
supported firmly to inhibit initial swelling. The equipment should
have the capacity to freeze very quickly,and temperatures must be
below -10=B0F to reduce distortion and to facilitate drying. Documents
may be placed in the freezer in stacks or may be spread out for faster
drying. Expect this method to take from several weeks to several
months, depending upon the temperature of the freezer and the extent
of the water damage. However, caution is advised: with this method
leaves of coated paper may adhere to one another.

Books and records may be dried in a vacuum thermal drying chamber
into which they are placed either wet or frozen. The vacuum is drawn,
heat is introduced, and the materials are dried above 32=B0F. This
means that the materials stay wet while they dry. It is an acceptable
manner of drying wet records, but often produces extreme distortion
in books, and almost always causes blocking (adhesion) of coated
paper. For large quantities of materials it is easier than air
drying, and almost always more cost-effective. However, extensive
rebinding or recasing of books should be expected. This method is a
solution for materials that have suffered extensive water damage.

This process calls for very sophisticated equipment and is especially
suitable for large numbers of very wet books and records as well as
for coated paper. Books and records are placed in a vacuum chamber
frozen. The vacuum is pulled, a source of heat introduced, and the
collections, dried at temperatures below 32=B0F, remain frozen. The
physical process known as sublimation takes place - i.e., ice crystals
vaporize without melting. This means that there is no additional
swelling or distortion beyond that incurred before the materials were
placed in the chamber. Many coated papers can be difficult to dry
without sticking together once they are wet. Because it is nearly
impossible to determine which papers will block, all coated papers
should be treated the same way for the purpose of vacuum freeze
drying: before any drying takes place, and ideally within six hours
of becoming wet, materials should be frozen at -10=B0F or lower. They
may then be vacuum freeze dried with a high potential for success.
Rare and unique materials can be dried successfully by vacuum freeze
drying, but leathers and vellums may not survive. Photographs should
not be dried this way unless no other possibility exists. Consult a
photograph conservator. Although this method may initially appear to
be more expensive because of the equipment required, the results are
often so satisfactory that additional funds for rebinding are not
necessary, and mud, dirt, and/or soot is lifted to the surface,
making cleaning less time consuming. If only a few books are dried,
vacuum freeze drying can indeed be expensive. However, companies that
offer this service are often willing to dry one client's small group
of books with another client's larger group, thus reducing the
per-book cost and making the process affordable.

Wet records may be air dried if care is taken to follow guidelines
suggested by preservation experts. The technique is most suitable for
small numbers of records that are damp or water damaged only around
the edges. If there are hundreds of single pages, or if the water
damage is severe, other methods of drying will be more satisfactory
and cost effective. Stacks of documents on coated, or shiny, paper
must be separated immediately to prevent adhesion, or they must be
frozen to await a later drying decision. Care must be taken with
water-soluble inks as well. Records with running or blurred inks
should be frozen immediately to preserve the written record. After
the items are dry, conservators can be contacted for advice and
If records must be air dried, the following steps will help achieve
satisfactory results. Wet paper is extremely fragile and easily torn
or damaged, so care must be exercised. Once wet, records will never
look the same, and at least some cockling or distortion should be

1.Secure a clean, dry environment where the temperature and humidity
are as low as possible. The temperature must be below 70=B0F and the
humidity below 50%, or mold will probably develop and distortion will
be extreme.

2.Keep the air moving at all times using fans in the drying area. This
will accelerate the drying process and discourage the growth of mold.
If materials are dried outside, remember that prolonged exposure to
direct sunlight may fade inks and accelerate the aging of paper. Be
aware that breezes can blow away single records. Train fans into the
air and away from the drying records.

3.Single leaves can be laid out on tables, floors, and other flat
surfaces protected if necessary by paper towels or clean, unprinted
newsprint. Or clotheslines may be strung close together and records
laid across them for drying.

4.If records are printed on coated paper, they must be separated from
one another to prevent them from sticking together. This is a tedious
process, which requires skill and patience. Practice ahead of time
will prove useful. Place a piece of polyester film on the stack of
records. Rub it gently down on the top document. Then slowly lift the
film while at the same time peeling off the top sheet. Hang the
polyester film up to dry on the clothesline using clothespins. As the
document dries, it will separate from the surface of the film. Before
it falls, remove it and allow it to finish drying on a flat surface.

5.Once dry, records may be rehoused in clean folders and boxes. Or
they may be photocopied or reformatted on microfilm or fiche. Dried
records will always occupy more space than ones that have not been
water damaged.

Air drying is most appropriate for books that are only damp or wet in
places, such as along the edges. Books that are soaking wet should be
vacuum freeze dried to minimize cockling of leaves and distortion of
bindings. Books containing coated paper should be frozen while still
wet and vacuum freeze dried. Books with running or blurred inks should
be frozen immediately and also vacuum freeze dried.

1.Refer to steps 1 and 2 of the previous section.

2.Interleave every few pages, starting from the back of the book,
turning pages carefully. For interleaving, use paper towels or clean,
unprinted newsprint. Be careful not to interleave too much or the
spine will become concave and the volume distorted. Complete the
interleaving by placing clean blotter paper inside the front and back
covers. Close the book and place it on several sheets of absorbent
paper. Change the interleaving frequently. Turn the book over each
time it is interleaved.

3.When books are dry but still cool to the touch they should be closed
and laid flat on a table or other horizontal surface, gently formed
into the normal shape, with convex spine and concave front edge (if
that was their original shape) and held in place with a light weight.
Do not stack drying books on top of each other. In no case should
books be returned to shelves until thoroughly dry; otherwise mold may
develop, particularly along the inner margins.

4.Dampness will persist for some time in the inner margins, along the
spine, and between boards and flyleaves. This is particularly true of
volumes sewn on oversewing machines. Check often for mold growth while
books are drying.

5.If the edges are only slightly wet, a book may be stood on end and
fanned open slightly in the path of a flow of air as from a fan). To
minimize distortion of the edges, lay volumes flat under light
pressure (e.g., paper-covered bricks)just before drying is complete.

6.If you can establish an air-conditioned room capable of maintaining
a constant relative humidity of 25 to 35% and temperatures between 50
and 65=B0F, books with only wet edges can be dried successfully in
approximately 2 weeks without interleaving. Do not try to dry books
printed on coated paper by this method. In most cases, the only
chance of saving such books is to freeze them while wet and dry them
by vacuum freeze drying.


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