Hi Everyone,

This is especially directed to the sulfur isotope people.  I am designing
borehole stoppering equipment for our deep, hot boreholes in South Africa
and need to be sure that there are not any materials concerns here. In the
past, we found that nothing beats a simple rubber stopper for sealing off a
hole longer-term from mine air.  We will almost certainly be facing this
again.  I would like to enter the field with an assortment of stoppers that
will plug pretty much any borehole we encounter.  There are several
material options,
however.

        Natural rubber          Cheap and effective

        Silicone rubber         Pricey and effective

        Neoprene                Cheap and effective

Sulfate reduction is a major, major process in many of these boreholes,
nevertheless we don't want to obfuscate our results when sulfur species
concentrations become low.  I assume that natural rubber exudes sulfur
cpds.  Any idea if this is a big deal?  Any other worries about rubber
formulations I should known about?

Thanks,
Duane P. Moser, Ph.D.

Department of Geosciences
Princeton University
Princeton, NJ 08544

Phone   Office: (609) 258-1383
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