[meteorite-list] Recommended humidity for public display

From: Howard Wu <freewu2000_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:53 2004
Message-ID: <20030911002644.41055.qmail_at_web9306.mail.yahoo.com>

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Interesting! However, many earth rocks are hydrates and of course would suffer from a dry enviroment. I recall some gypsum crystal in the Lemman caves with a +99% RH that were being damaged by human entrance to there lair. Howvever most meteorites have spend 4.5G in the vacuum of space (RH=0%). Perhaps those hydrated CI, CM2 or mars rocks may need humidity. Still I would vacuum pack or Argonize my collection if I could. Other than than that, yes, T' and H' stabiltiy like they do in libraries and musuems would be desirable.
 
Howard Wu


mark ford <markf_at_ssl.gb.com> wrote:


 

Howard,

 

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)

 

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!

 

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!

 

So I guess it’s not so clear cut as 0% _at_ -273..

 

Mark F.

 

 



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<DIV>Interesting! However, many earth rocks are hydrates and of course would suffer from a dry enviroment. I recall some gypsum crystal in the Lemman caves with a +99% RH that were being damaged by human entrance to there lair. Howvever most meteorites have spend 4.5G in the vacuum of space (RH=0%). Perhaps those hydrated CI, CM2&nbsp;or mars rocks may need humidity.&nbsp;Still I would vacuum pack or Argonize my collection if I could. Other than than that, yes, T' and H' stabiltiy like they do in libraries and musuems would be desirable.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Howard Wu</DIV>
<DIV><BR><BR><B><I>mark ford &lt;markf_at_ssl.gb.com&gt;</I></B> wrote:</DIV>
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<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt"><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Howard,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">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></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">And the temperature also has a big effect on corrosion rate,<SPAN style="mso-spacerun: yes">&nbsp; </SPAN>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></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">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 &amp; 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></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">So I guess it’s not so clear cut as 0%<SPAN style="mso-spacerun: yes">&nbsp; </SPAN>_at_ -273..<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Mark F.<o:p></o:p></SPAN></FONT></P>
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Received on Wed 10 Sep 2003 08:26:44 PM PDT


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