Historic food collections

Fiona Cahill <f.cahill [at] scott__aq> writes

>We are a team of conservators working at Scott Base in the Antarctic
>on artifacts (predominately food) from Shackleton's Nimrod
>expedition hut (1908). We have recently started to conserve a number
>of sealed glass bottles containing both vegetables (e.g. onions and
>midget gherkins) and fruit such as cherries and redcurrants. The
>majority of the bottles are in very good condition with no visible
>mould growth. We want to keep the visual integrity of the contents
>as they have retained their original form and colour. The bottles
>are sealed with a layer of thin leather, a cork stopper and a wax
>seal covered with lead sheet.
>
>... our main
>area of interest is the evaporation of fluid over time from the
>jars.  We would prefer to keep the contents in the jars rather than
>disposing of them. We understand that topping up and rehydration of
>specimens occurs in spirit collections, but has this ever been
>applied to food? ...

The food industry regularly uses oxygen-free storage to dramatically
increase shelf life of products. I've seen some dramatic examples.

Escal transparent barrier film (extremely effective for preventing
both moisture and gas permeation), as well as a variety of oxygen
scavenging products (eg Ageless and RP System) are readily
available.

Setting up a system for long term oxygen-free microclimate around
individual, or small groups of jars is straight forward. I suspect
that as any fluid that escaped the jar would be trapped (as gas) in
the surrounding envelope, the increase in vapour pressure in the
envelope might slow the escape of more fluid from the jar seals.
High humidity levels will not adversely affect the film or oxygen
absorbers.

Storage of the jars in a cold environment might help as well. As the
jars will have substantial heat mass, a cooling system allowing some
small variation in temperature levels (read less expensive), might
be adequate. Oxygen absorbers will continue to work in a cold
environment, or a general oxygen-free microclimate using a nitrogen
purge could be set up fairly easily (read relatively inexpensively),
as the refrigerator case would already be well sealed.

More information is available at <URL:http://www.keepsafe.ca> and I
would be pleased to advise more specifically about these solutions
on or off line.

Jerry Shiner
Keepsafe Systems
Microclimate Technologies International


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                  Conservation DistList Instance 21:4
                   Distributed: Friday, May 11, 2007
                        Message Id: cdl-21-4-007
                                  ***