Preparing materials for freeze-drying

Reni Teygeler <rene.teygeler [at] wxs__nl> writes

> ... Does anyone have any experience in packaging before
>deep-freezing for preservation purposes, or does anyone have any
>suggestions?

It has been our experience that if the objects are only being frozen
in preparation for freeze-drying as opposed to storage in a freezer
(being frozen for a day or two as opposed to a longer period)
packaging is not overly important. If, however, the objects are
going to be stored in a frozen state for any length of time, you
need to find a reasonably air-tight packaging technique. The purpose
of this is to prevent ice condensation on the surface of the
specimen which can introduce unnecessary ice and, in the case of
thawing, extra water. We have traditionally wrapped items a
"form-fitting" medium like SaranWrap or aluminum foil, then placed
them in either Ziploc bags or high quality Tupperware containers.
One of the key things to keep in mind is what, if any, temperature
fluctuations your freezer unit is subject to (be it intentional
defrosting cycles to prevent condenser freeze-up or accidental power
loss). These brief thaws increase the potential for cryoclastic
damage to artifacts and, thus, increase the need for air-tight
packaging. If you have any additional questions, please feel free to
contact me.

Jeff. S. Illingworth
Supervisor, R. L. Andrews Center for Perishables Analysis
Director, Curation and Conservation
Mercyhurst Archaeological Institute
501 East 38th Street
Erie, Pennsylvania  16546
814-824-2581
Fax: 814-824-2594


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                  Conservation DistList Instance 16:11
                  Distributed: Friday, August 2, 2002
                       Message Id: cdl-16-11-005
                                  ***