There is some discussion about this problem in an article by Barbara
Keyser entitled: "Time and Mrs. Tiber and Food Technology" in, J.IIC-CG
(Journal of the International Institute for
Conservation-Canadian Group) v. 7, Nos. 1&2, Spring, 1982. Pp. 47-52; and
in an abstract from the IIC-CG 13th Annual Conference (Victoria, B.C.,
1987) entitled "Has Time and Mrs. Tiber Had its Time?" by Richard Gagnier
and Marion Barclay.
 
This relates to an art exhibit consisting, in part, of jars of preserves
discovered on an abandoned farm.  This work belongs to the National
Gallery of Canada.  You may be able to contact Richard Gagnier in Ottawa
at (613) 990-1946.
 
The Canadian Conservation Institute at, 1030 Innes, Ottawa, Canada  K1A
0C8 (613) 998-3721) should be able to route you to someone in their
Conservation Research Services branch who can give you some advice about
the cans.  My recollection is that they preserved some canned goods
recovered from an artic expedition by making a hole in the bottoms of
cans and freeze drying the contents.
 
A serious danger in handling artifacts in the condition you describe is
botulism poisoning.
 
Jack C. Thompson
Thompson Conservation Lab.
Portland, OR
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