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

From: Jim Wooddell <nf114ec_at_meteoritecentral.com>
Date: Sun, 29 Apr 2012 08:50:32 -0700
Message-ID: <5C586A6432F7427F90D2A5578C04699C_at_Grande>

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
Received on Sun 29 Apr 2012 11:50:32 AM PDT