[meteorite-list] Recommended humidity for public display

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From: mark ford <markf_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:53 2004
Message-ID: <6CE3EEEFE92F4B4085B0E086B2941B31D928_at_s-southern01.s-southern.com>

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=20
Howard,
=20
I too thought that 0% would be the ideal too, but then I read up on
humidity in 'terrestrial' mineral collections, and it turns out that too
low a humidity can be just as bad as too high (effectively causing
stress cracking in crystals and initiation of crumbling of specimens as
well as catalyzing rusting etc)
=20
And the temperature also has a big effect on corrosion rate, Obviously
their natural environment is pretty dry (although don't forget some
contain water!) but once you introduce water, pollution (SO2) and oxygen
etc into the equation you have a whole new ball game!
=20
The biggest surprise I hadn't considered was the [rate of change] in
humidity and temperature, if you expose rocks to continuous small
fluctuations in RH & Temperature, this causes stress micro-cracking in
crystaline structures and this allows microscopic water molecules to
enter deeper inside, causing corrosion from within!
=20
So I guess it's not so clear cut as 0% _at_ -273..
=20
Mark F.
=20
=20

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<o:p> </o:p>

Howard,<o:p></o:p>=

<o:p> </o:p>

I too thought that 0% would be the =
ideal
too, but then I read up on humidity in ‘terrestrial’ mineral
collections, and it turns out that too low a humidity can be just as bad =
as too
high (effectively causing stress cracking in crystals and initiation of
crumbling of specimens as well as catalyzing rusting =
etc)<o:p></o:p>

<o:p> </o:p>

And the temperature also has a big =
effect
on corrosion rate,  =
Obviously their
natural environment is pretty dry (although don’t forget some =
contain
water!) but once you introduce water, pollution (SO2) and oxygen etc =
into the
equation you have a whole new ball game!<o:p></o:p>

<o:p> </o:p>

The biggest surprise I hadn’t
considered was the [rate of change] in humidity and temperature, if you =
expose
rocks to continuous small fluctuations in RH & Temperature, this =
causes
stress micro-cracking in crystaline structures and this allows =
microscopic
water molecules to enter deeper inside, causing corrosion from =
within!<o:p></o:p>

<o:p> </o:p>

So I guess it’s not so clear =
cut as
0%  _at_ =
-273..<o:p></o:p>

<o:p> </o:p>

Mark =
F.<o:p></o:p>

<o:p> </o:p>

<o:p> </o:p>

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=00
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Received on Wed 10 Sep 2003 04:35:31 AM PDT

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