[Nhcoll-l] More on jars

[Dirk Neumann]

Hi Paul,

glass is a amorphous melt which allows small molecules to diffuse 
through the glass (compare e.g. stick honey glass jars); same happens 
with water, but at the same time water diffuses through the glass, it 
carries dissolved ions, too.

Depending on the surrounding humidity, water evaporates from the micro 
water layer of the container surface. If humidity inside the storage 
room fluctuates, the evaporations fluctuates, too. If you have highly 
polar solvents such as MEK as denaturant in your alcohol, leaching 
rather increases and puts the glass under high physical stress which 
results in micor-fizzures which will open into small visible cracks.

Can show some pictures on this at SPNHC in Berlin if this would be of 
interest.

All the best
Dirk


Am 29.10.2015 um 18:10 schrieb 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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-- 
Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
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Staatliche Naturwissenschaftliche Sammlungen Bayerns
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email: Dirk.Neumann(a)zsm.mwn.de

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