Polyurethane stained Carrera marble

Two new Carrera mantels were carved in Italy and shipped over to my
client, and were installed by myself and a mason I always work with.
They were pristine and beautiful. The house is under renovation, so
they were carefully covered using Polyethylene tape and 2 mil poly
sheeting.

After the floor sanders were done I went in to check on the mantel
status, and lo and behold the poly had been torn off, a major brown
stain was evident in the middle of the mantel top, and tide
lines/marks of light orange on the surface and brown below the
surface had appeared. The poly tape had somewhat melted, and the
glue had separated and stuck to the stone.

You can see where cans of polyurethane were put down on the shelf
and then hurriedly wiped up, probably with mineral spirits, which is
a commonly used thinner for oil based urethanes, or varnishes. All
this did was wash the material deeper into the pristine white mantel
shelf.

I have tried a poultice of laponite and lacquer thinner covered with
polyethylene for increasing periods of time. This took off some of
the surface tide lines, and a little material below the surface, but
nothing else.  I've tried mineral spirits, and also acetone
saturated cloths covered with cling wrap in areas. Nothing.

I have recreated the situation on small scrap pieces of Carrera I
have from another job, and am trying further experiments to remove
the deep stains in my studio.

Any suggestions, or previous experiences with this situation would
be greatly appreciated.

Louise Freedman
L.H. Freedman Studios
Architectural and Sculpture Conservation
(A division of Boston Creative Inc.)
35 Congress St. Suite 302A
Salem, MA 01970
Cell: 617-320-7798


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                  Conservation DistList Instance 21:29
                 Distributed: Sunday, November 4, 2007
                       Message Id: cdl-21-29-016
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