Charlie,

I would leave the shell casings alone if they have a fairly stable
patina. If you polish them bright then the tarnish will show very
prominently and you'll be polishing these things continually and
wearing down the surfaces. The rule for almost all arms conservation
these days is that if they have a stable oxidized surface then leave
it alone (other than dusting) - and if they are bright when you get
them then you can either maintain the bright metal appearance or to
let them sit and gradually form a patina.

And if you feel you must polish brass or copper alloys please, please
do NOT use Brasso! I have spent so many untold hours reversing the
damage from Brasso on historic metals - it contains high level of
amonia that can cause stress corrosion cracking, in some instances I
have see dealloying effects, and then there are those residues that
will get trapped in the crevices and will go white and then green as
they corrode the alloy too. USe the absolute gentlest polishes
possible and also the ones that are easy to to clear from all parts of
the surface. And please keep bare fingers off metal surfaces as your
fingerprints will etch deeply into them.

If you live in a high salt or pollution environment (The Mac Arthur
Memorial is in Norfolk, Virignia and close enough to the ocean) then
you might consider lacquering polished metals to protect them from
rapid tarnishing and corrosion.

Cheers!
Dave

David Harvey
Conservator, Los Angeles California

On 8/13/07, Charlie Knight <[log in to unmask]> wrote:
> I was recently asked what the "proper" thing to do with a spent shell casing
> (brass) is, regarding its display. Specifically, should it be cleaned up and
> polished, or should it be left "as is"? (This particular casing in question has no
> special engraving, etc., but is just a regular spent large-caliber artillery shell
> casing.)
>
> I am of the opinion that regular, plain shell casings (i.e. those with no special
> engraving denoting any special significance) should be left as is just like they
> came out of the cannon breech, while any which have been made into trench
> art or display pieces should be polished. I'm curious as to what any others
> think or do with similar such critters.
>
> Charlie Knight
> Curator, MacArthur Memorial
>
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