Distorted cellophane

Laura Wahl <lwahl [at] hagley__org> writes

>I am currently evaluating a collection of printed plastic packaging
>films, dating from approximately 1940-1970. The materials are a mix
>of cellophane, polyethylene, acetate, and possibly polyvinyl
>chloride. Many of the items are folded and cannot be safely opened
>without creating tears. ...

Presuming that humidification will help, I suspect that some
experimentation will be needed to determine the optimum humidity
levels for manipulating the cellophane. This will demand accurate
control over the microclimates used for humidification.
Humidification can be done in high tech chambers or simple plastic
tents. There are a number of common methods of controlling the
humidity:

Microclimate control units units can be very accurate, and humidity
levels can be precisely varied. These devices were originally
designed to maintain constant humidity in museum display cases, but
have also been used in conservation labs to provide "stepped"  or
"ramped" increases in humidity when treating artefacts.
Unfortunately, purchasing a microclimate control unit for a single
treatment may not be cost effective.

Another option would be to humidify and introduce compressed air
into a tent, bubble or chamber. (Humidification of the air would be
accomplished by using the standard tubes, valves, and bottles often
used for nitrogen anoxia.) Be aware that some compressed air sources
may introduce oil and other contaminants.

A stepped humidification could also be accomplished (with more
labour) by using a series of pre-humidified passive buffers and a
circulating fan (a very, very small one).

You will need a good, recently calibrated instrumentation for all
these methods. I would also be cautious about doing this at
temperatures above room ambient (control, condensation and other
problems immediately come to mind). Hopefully, the treatment can be
done without tears,

Jerry Shiner
Keepsafe Microclimate Systems
416-703-4696 ext 701


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                  Conservation DistList Instance 22:33
                Distributed: Saturday, December 6, 2008
                       Message Id: cdl-22-33-004
                                  ***