Polyurethane varnish on oil based mural painting

I am currently working on a conservation concept for a mural
painting, which is basically oil paint on plaster (gypsum). There is
a varnish on top and after a few analyses and investigations the
varnish turned out to be some sort of polyurethane lacquer, which was
applied in the mid 1980's. It might be necessary to remove that
varnish, but at the moment I have no idea how to achive a removal in
a sensitive way, without damaging the actual painting. I've read
that polyurethane lacquer is quiet resistant to solvents and
stripper, so I wonder if anyone has some experience or ideas on how
this could be done. Maybe it's impossible and not even worthwhile to
look for a solution.

Marco Buerger
Student of conservation science at CICS University of Applied Sience
    Cologne


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                  Conservation DistList Instance 23:40
                  Distributed: Friday, April 16, 2010
                       Message Id: cdl-23-40-033
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