The trouble with brasso and other commercial polishes is that that can
either be acidic, caustic, have abrasives, and contain amonia. These
help the polish to work very rapidly and provide instant gratification
to the household user. However, these same qualtities are extremely bad
for historic and artistic metals that are in collections. I have seen
stress corrosion cracking form amonia, pitting and erosion of original
surfaces and finishes by acids, and actual holes worn into 18th century
candlesticks from daily polishing. Often the less than thorough
application of polishes leaves accretions behind (white or green
powerry material packed into crevices) and these accretions can cause
further problems.
We have long since passed the time when every piece of historic metal
has to be poilsihed bright. It has long been recognized now that a
genuine and stable oxidation is a sign of age and autheticity and so
the metals found in militaria, clocks, and decorative arts collections,
with the qualified exception of silver, is just not routinely polished
anymore. Your volunteers are simply polishing away the value of your
collection.
You also need to be well aware of the original surface finish of the
piece - if a metal has a very high polish you will need to use the
least abrasive cleaning method possible. If it is coarse and rough then
perhaps it never was polished bright to begin with.
Conservators will mix up their own polishes or use the highly
specialized polished used in metallography. The safest one is to use is
precipitated chalk, mix that wih distilled water into a paste, add a
drop of a non-ionic surfactant, and clear that completely with a soapy
rinse of distilled water and the same non-ionic surfactant. Then rise
with distilled water.
But again, I would offer a huge caveat. If you do not understand what
you are doing and how to properly clean and polish an historic or
artistic metal object, don't do it.
Cheers!
Dave
Conservator
Los Angeles, California, USA
-----Original Message-----
From: Marielle Fortier <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, 1 Jun 2005 08:41:38 -0400
Subject: Brasso Alternatives
Good morning,
In the dry ice thread a few of you mentioned brasso. Items in our
collections like cannons, belt buckles and insignias have in the past
been routinely cleaned with Brasso. I have been looking for an
alternative to help my "cleaners" change their ways. What does this
listserve use? Thank you for your advice.
Marielle
**********************
Marielle Fortier
Registrar
NUM
Vermont
**********************
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