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Subject: Vacuum drying books

Vacuum drying books

From: Dale Peters <petersd>
Date: Thursday, September 15, 1994
In response to Michael Rhode's request for suggestions, I would like to
share a experience in vacuum freeze drying, being struck at the time by
the general recommendation of this method of conserving water-damaged
material, and the dearth of technical information in support thereof.

The unit operated by the South African Medical Research Council was
large enough to accommodate a single volume, and while already frozen to
-18 degrees Celcius by refrigeration, the solid block was immersed in
liquid nitrogen, with a temperature of -196 degrees Celcius, to ensure a
solid state and direct sublimation to the vapour state, to avoid the
surface distortion effects of liquid water. The weight of the volume was
used as a control to determine the duration of the cycle, and after 72
hours at -70 degrees Celcius and 100 millitor vacuum pressure, the
decreasing weight was noted to level off.

My personal estimation is that at that point the paper had become
desiccated, a slight cockling was noted and the glued spine was also
slightly concave, compensated by a short period of equilibration in our
ambient subtropical climate. Three years later the volume is still in
circulation, so the operation must be rated a success, but any specific
recommendations on this procedure would be useful.

Dale Peters
Paper Conservator
Campbell Collections of the University of Natal
220 Marriott Road, Durban, 4001
South Africa

                  Conservation DistList Instance 8:20
               Distributed: Wednesday, September 21, 1994
                        Message Id: cdl-8-20-003
Received on Thursday, 15 September, 1994

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