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

From: Jim Wooddell <nf114ec_at_meteoritecentral.com>
Date: Sun, 29 Apr 2012 10:42:34 -0700
Message-ID: <C68792BB767D4678926DEA497B2610C8_at_Grande>

Hi Martin!

It rained...and the dew was enough to completely soak your boots in less
than 15 minutes of walking though the grass. After the second day, it was
noted the white appearing inclusions (CAI's) were disappearing on the
surface of some specimens and was noted by most of the group. Mine still
have them and currently sit in a desiccator. I do not have a way to contain
them in evacuated nitrogen chamber!

Volatile is a great word to use. I was using fragile. These are very much
both, I think!

Jim




----- Original Message -----
From: "karmaka" <karmaka-meteorites at t-online.de>
To: "Jim Wooddell" <nf114ec at npgcable.com>;
<Meteorite-list at meteoritecentral.com>
Sent: Sunday, April 29, 2012 9:24 AM
Subject: Re: [meteorite-list] Why is aluminum foil better for protection?


> 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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Received on Sun 29 Apr 2012 01:42:34 PM PDT