Polyurethane varnish on oil based mural painting

Marco Buerger <buerger.marco [at] web__de> writes

>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.

I have often encountered similar problems and my advice is this. You
must find out, ideally through a cross-section and consequent
chemical analysis, whether a layer of dirt, organic or other
extraneous matter exists between the original paint layer and the
lacquer. If extraneous material does exist, then focus in finding a
solvent that will swell that layer, in that way, when the dirt under
the lacquer swells, theoretically, the lacquer should come off
easily. A good supporting agent for this operation is P. Cremonesi's
solvent-gels.

Alternatively, laser treatment might also be an option.

Daniela Murphy Corella, wall painting specialist
Associazione Bastioni
Florence. Italy


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                  Conservation DistList Instance 23:41
                 Distributed: Saturday, April 24, 2010
                       Message Id: cdl-23-41-001
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