Gasket materials

I am replicating some cast iron barometer cisterns. I need to find a
material to serve as a gasket between the cover and the body. The
criteria that I would like is:

    1.  non reactive to mercury
    2.  non reactive to iron
    3.  slightly compressible
    4.  lifetime of 200 years +/-  a couple
    5.  will not decompose into chemicals that will react with
        either the iron or the Hg
    6.  not hygroscopic

Piece of cake, right? Any ideas would be most welcome.

Jim Moss


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                  Conservation DistList Instance 17:24
                 Distributed: Tuesday, August 26, 2003
                       Message Id: cdl-17-24-010
                                  ***