Removing graffiti from bronze

Donovan Michael Gray <dgray [at] ga__wa__gov> writes

>We have a cupola structure that appears to be bronze.  It might be
>brass but most likely bronze based on other installations in the
>building.  Some people have recently signed their names and dates on
>it with what appear to be Sharpie pens.  Everything I've
>investigated so far as a cleaning technique will likely remove the
>patina, which would suggest we have to clean the entire structure,
>rather than just where the graffiti is.

I oversee the conservation and maintenance of the monuments and
memorials of bronze, stone, and other materials on the Minnesota
State Capitol Mall here in St. Paul.  I've used acetone to remove
marker graffiti from our Korean War Memorial bronze twice over the
past few years.  It successfully removed the marks without
disturbing the patina.  By patina, I'm referring to a uniform,
smooth artificially applied chemical coloration layer. Marker on
powdery natural corrosion layers such as copper sulfate or carbonate
might penetrate and stain it, making it more difficult to remove. In
the latter case, you might want to consider cleaning and
repatination overall and applying a protective coating.  Having a
protective coating such as wax or an acrylic on the surface will
make graffiti removal much easier.  You might want to have a
conservator take a look at the structure and propose a treatment.

As for dealing with the signers, making them undo their damage or
pay for the clean-up might be a suitable punishment if that is
possible.  Cleaning up the graffiti as quickly as possible is
important to discourage further vandalism.  If you're interested, I
can send you a copy of our emergency response plan for the mall
monuments.

Paul S. Storch
Senior Objects Conservator
Daniels Objects Conservation Laboratory (DOCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd. West
St. Paul, MN  55102-1906
651-297-5774
Fax: 651-297-2967


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                  Conservation DistList Instance 19:26
                Distributed: Saturday, November 19, 2005
                       Message Id: cdl-19-26-004
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