[meteorite-list] Why is aluminum foil better for protection?

[karmaka]

Hello Jim,
 
Maybe this is an answer:

"C2  carbonaceous  chondrite  falls  with 
 phyllosilicates  in  their  matrices  adsorbed  volatile 
 organic-carbon  compounds  from  laboratory  sample-
 storage  materials  within  one  day,  between  sample 
 preparation  and  analysis"

from: 
TERRESTRIAL  WEATHERING  OF  CHONDRITES  IN  NATURE  AND  CONTINUING  DURING 
 LABORATORY  STORAGE  AND  PROCESSING:  REVIEW  AND  IMPLICATIONS  FOR  SAMPLE 
 INTEGRITY.  Michael A. Velbel

 http://www.lpi.usra.edu/meetings/lifedetection2012/pdf/6019.pdf

Best regards,

Martin
 
Von: "Jim Wooddell" <nf114ec at npgcable.com>
 An: "Meteorite-List" <meteorite-list at meteoritecentral.com>
 Betreff: [meteorite-list] Why is aluminum foil better for protection?
 Datum: Sun, 29 Apr 2012 17:50:32 +0200
 
Hi all!
 
 Being one that has always doubled plastic bagged finds, I would like to ask 
 why aluminum foil is considered to be better at protecting from 
 contamination?
 
 In fact, I witnessed two times where different techniques, aluminum foil and 
 membrane boxes were replaced with plastic bags because there were issues 
 with those techniques and stress to the specimens.  And in those cases we 
 did not have to be PhD's to see the stress placed on the specimens.
 
 I think this is a very important topic in handling meteorites.
 
 1.  At the Sutter Mill fall, I watched NASA employee's handing out small 
 squares of aluminum foil.
 This foil had been cut in squares about 5 or 6 inches square.  It was 
 removed out of a PLASTIC bag and then handed to those that needed it without 
 the use of gloves and then some were folded up and placed in a pocket.
 So, technically, no one could tell you what was on that foil when a specimen 
 was placed in it.
 2.  The specimen had already been on the ground in an area that is moist 
 from morning dew, etc. Additionally, it rained!
 3.  Because people really wanted to see the specimens, the foil was 
 constantly opened and close around the specimen.  In one sample I looked at, 
 crumbs were seen in the foil!  Note that these appeared very delicate and 
 once these samples were seen by us we all immediately made efforts at 
 protecting them at best we could and gave good instruction on handling.
 
 To me, it was clear foil was a bad idea.  And I know I can be totally wrong 
 about such things.   Most of us there immediately protected the specimens 
 once seen.  In fact, we were filmed using good technique in handing a very 
 nice sample, using plastic bags and doubling them.
 
 1.  Most people do not handle the inside of a plastic bag.  So any 
 contamination from the bag likely remains constant and can probably be 
 predicted if it is that critical.
 2.  The bags protected the sample by allowing people to view the sample 
 without removing it from the bag as opposed to the aluminum foil constantly 
 being opened and closed.
 3.  The plastic surface was much more friendly to the surface of the 
 specimens.
 
 4.  Moisture in the bags could be better controlled if necessary by use of 
 absorbent.
 
 So, how is aluminum foil better??? What do we protect the sample from better 
 by using aluminum foil?  Cosmic rays?  I am missing something here and I 
 would appreciate a good qualified answer because right now, from what I 
 witnessed, it's a myth that does more harm than good!
 
 Anyways, I scored enough fragments and I am happy I did not skunk and I am 
 glad Mike did not get bit by that rattle snake!  I talked to a few of the 
 locals and rangers in the area and they all said they do have a lot of 
 rattle snakes in the area and now is when they come out.  So those that are 
 still there, be safe!
 
 Back home in AZ....now, what to do with those fragments!  What awesome 
 CAI's!!!
 
 Jim
 
 
 
 
 
 
 Jim Wooddell
 http://k7wfr.us
 
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