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.
>
>The literature on the conservation of food collections appears to be
>pretty sparse. Our research tools are restricted to the Internet
>(due to our location). Any information would be useful, but 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? ...

Preserving biological material in fluids:

Try to find a copy of the book Care and Conservation of Natural
History Collections Eds. Carter and Walker, 1999, Publ. Butterworth
and Heinemann and copies should (hopefully) be available via
secondhand book websites. This will give you a large amount of
information about jar seals--especially the lead foil seal and
additional information about the use of pig bladder seals for such
jars going back in time to the early 18th century as well as
preservatives in current and past use.

As to topping up: you will need to draw off and analyse some fluid
using a fine-needle syringe through the cork and ensure that the
needle has a piece of fine wire running through it when piercing the
cork or the needle will be clogged with cork!  The fluid may just be
a mild saline--especially if there are instructions on the label
advising washing before consumption.  Cherries may be preserved in
water and glycerol if the fluid is quite dense and I wouldn't rule
out the possibility of waterglass (sodium silicate) although this
was primarily used to prevent eggs from sulphidation.

I am always rather cautious about adding fluids to items that are
well-preserved: the problems of osmotic pressure and colour leaching
are foremost.  The OP problem can be overcome by Schleren optic
testing to ensure that the fluids are of similar, even, exactly
equal specific gravity or by using a specific gravity meter
(available from Anton Paar).

There are techniques and formulae in the above reference for
preserving certain vegetable dyes in situ but the present author has
not been able to test whether these are actual preservatives of the
natural dyes or colour replacements.

If you have any specific questions, feel free to get back to me.

Simon Moore, MIScT, FLS, ACR
Senior Conservator of Natural Sciences
Hampshire County Council
Recreation and Heritage Department
Museums and Archives Service
Chilcomb House, Chilcomb Lane
Winchester SO23 8RD, UK
+44 1962 826737


                                  ***
                  Conservation DistList Instance 21:4
                   Distributed: Friday, May 11, 2007
                        Message Id: cdl-21-4-006
                                  ***