[meteorite-list] Cleaning a 13kg "Bessey Spec"! :-)

[ensoramanda]

Hi Dean, all...

Many thanks to all those who replied to me with tips on cleaning caliche 
from meteorites and to you, Dean, for my 13kg "spec" which has become 
the subject of several hours of careful cleaning.

The monster before cleaning, below...showed great potential even though 
quite weathered....but most was hidden under 2/3rds caliche. The exposed 
area had some fusion crust but most had been scoured away and polished 
by the sand and wind. Lovely thumbprints though.

http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/DSCN0009.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/DSCN0008.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/DSCN0007.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/2080_1.jpg

Looking closely when it arrived I could see tantalizing glimpses of what 
appeared to be flow lines, lips and bubbly fusion crust in some thinner 
areas of caliche. So I decided to brave it and set to work cleaning. 
Because of the delicate features I wanted to preserve I did almost no 
mechanical scraping or wire brushing but used brick cleaner (dilute HCl 
acid) and small stiff paint brushes to gradually dissolve the caliche 
and I was surprised how well it worked.

I regularly washed the acid away with deionised water and bicarbonate of 
soda to try and stop too much acid penetrating too deep. After a while 
some of the well preserved fusion crust was revealed. Some areas almost 
look fresh with bubbling and very thick accumulation. Remnants of flow 
lines and roll over lips too....

I did try some rust removers on some of the rust spots too....but they 
seem very difficult to remove...nothing really worked ...infact I had to 
reuse the brick cleaner to remove residues that were left.

Once I was satisfied I could reveal no more without damaging the 
meteorite I decided to make sure I had removed all the acid and 
chlorides left which might cause future problems and used the galvanic 
method described here...

http://www.alaska.net/~meteor/Galvanic.pdf

I used the less agressive washing soda method in a large bucket with 
plenty of  perforated aluminium foil wrapped around the meteorite to 
allow circulation and electrolosys to work overnight.  I did this twice 
until the bubbling reaction stopped.

Finally I rinsed well again with plenty of dionised water and left the 
meteorite to dry thoroughly in the oven on a low heat for a couple of 
nights. It remains to see how stable this meteorite is over time...we 
will see.

I know many collectors like to leave pieces as found without tampering 
with their looks....but in this case I felt that the exercise was worth 
it.  There was so much hidden away under all that caliche.

Take a look here and see what you think of the cleaned up result!

http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4198b.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4170b.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4177b.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4189b.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4195b.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4194a.jpg
http://i117.photobucket.com/albums/o43/LaburnumStudio/13kgNWA/IMG_4199b.jpg


Please be aware that these methods are probably risky and who knows what 
the long term effects may be...so I would advise caution to anyone 
trying this with acids etc.(The troilite and probably other surface 
minerals in the meteorite will obviously be changed to some degree, as 
evidenced by some sulphurous smells during cleaning) Different 
meteorites may react in different ways and some deposits may not 
dissolve away.  So please don't try this on something you may regret 
ruining. I would not like to be held responsible for that. I was more 
interested in the aesthetic external qualities in this case...so was 
willing to take the risk....although I may polish a window in an 
uncrusted area next...just out of curiosity! :-)

Regards

Graham Ensor.