[Nhcoll-l] More on jars

[Callomon,Paul]

Folks,

So here's a jar question that perhaps someone has answered:
In "glass disease" the non-silicate components of, say, soda glass gradually leach out of the silicate matrix and onto the surface as hydrated compounds. This happens more where humidity is high, as water is involved in the latter stages of the reaction. In vials found in dry collections, the resulting compounds can be seen as droplets of moisture on the surface of the glass. They will be on both the inside and outside if the vial is only stoppered with cotton, allowing its internal humidity to be close to ambient.
Where the jar or vial is full of fluid, however, the values representing the difference in pressure between the internal structure of the glass and the external environment will differ between the interior and exterior. So the question is: will the rate of migration of the non-silicate compounds differ accordingly - that is, will they tend head for the outside of the jar, where the pressure differential is higher? The answer, if there is one, may have a bearing on the extent to which glass deterioration will contaminate the fluid in the jar.

Paul Callomon
Collection Manager, Malacology, Invertebrate Paleontology and General Invertebrates
________________________________
Academy of Natural Sciences of Drexel University, Philadelphia
1900 Benjamin Franklin Parkway, Philadelphia PA 19103-1195, USA
callomon at ansp.org<mailto:callomon at ansp.org> Tel 215-405-5096 - Fax 215-299-1170

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