Vacuum packing

Tony Owen <tony.owen [at] aucklandcity__govt__nz> writes

>I am interested in hearing about other people's experiences with the
>use of Vacuum Packing as a means to preserve documents. Has anyone
>experienced any problems with this system or has any concerns that
>one may encounter when considering to use this method?

In the 1990's, vacuum packaging of documents was promoted by a Dutch
firm. They were trying to create another market for their
specialized plastic bags. The system is very straight-forward: A
stack of documents is inserted into a plastic bag, and the unsealed
bag is placed in the chamber of a vacuum packaging machine (these
commonly available units are usually used for food packaging, eg, by
a butcher for packing meats). The chamber is sealed by lowering the
top cover, and a vacuum pump then withdraws most of the air from the
chamber. When the chamber reaches an appropriate "vacuum", a sealing
bar with electric heaters is energized, and the bag is heat-sealed.
Air is then allowed back into the chamber, and the normal
atmospheric pressure squeezes the "vacuum packed" papers in the bag,
reducing the stack to about 60% of original depth.

I experimented with this system for a commercial application--it is
waterproof, reduces storage shelving needs by almost half, and slows
down the degradation of paper from atmospheric pollutants. When
combined with a small oxygen-absorber sachet, it may also
substantially slow degradation processes that involve oxygen (and
most do), and substantially prolong the life of the documents.

However, I don't believe this system has ever been examined by a
professional conservation lab, and I would like to know more about
the effects of off-gassing that might be trapped in the envelope.
I'm curious whether the sealing out of pollutants and moisture
reduces the off-gassing? Would the effects of an oxygen scavenger be
as dramatic as I suspect? During my own work with the system, I also
noted some off-setting of poorly fused photocopy printing under
pressure in the vacuum sealed packages.

Should you decide to do this, I would strongly recommend that you
use a good quality barrier film to make your bags--some plastics can
be quite permeable, and this is for long-term storage. (More
information on barrier film and oxygen absorbers is on our website
<URL:http://www.microclimate.ca/>.

In addition, I suggest you first package a phone book or thick pile
of newspapers--the transformation from floppy paper to
hard-as-a-brick mass is astounding.

js


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                  Conservation DistList Instance 21:19
                 Distributed: Wednesday, August 8, 2007
                       Message Id: cdl-21-19-003
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