one of
the largest museums in the United States, is currently
undergoing a massive renovation project expected to cost
approximately $31 million. Part of this renovation project
involves the Museum’s exterior stone façade and terra cotta tile
roof, which is under going gentle cleaning, repair and
re-pointing in order to prevent water infiltration.
The museum reported roof leaks, and water had
been coming in; though fortunately there were no reports of
damage to art work. While the renovation project is about
stopping water infiltration through the exterior envelope of the
building, it is
also
about restoring the vibrancy of the building’s exterior back to
life.
The Museum has more than four acres of cobalt
and sea-green roof tiles that need to be removed and cleaned.
The roof tiles were made in the 1920s, and there had been no
measures taken to clean them since they were created and
installed.
The reported roofing leaks were the impetus for
the Museum to also look into a facelift. The tiles need to be
taken down and cleaned of roofing tar and weatherproofing
adhesive. A cleaning process needed to be identified that would
not damage the tiles in any way. Preservation architects worked
with art conservators from the museum’s own staff to make many
of the decisions and oversee the cleaning project.
Dry Ice Blasting was chosen as the optimal
solution to remove the tar and weatherproofing adhesive from
these tiles.
The process damaged neither the ceramic finish
nor the overlay on the tiles. The cleaning process also gave an
even appearance when the tar was removed from the tiles.
Each tile required only a
couple of minutes of dry ice cleaning to thoroughly remove the
tar and
roofing adhesive. Over a period of five days, about 200 of these
roof tiles were removed from their original location, cleaned
with dry ice and placed back on the roof of the museum.
The restoration work to clean these terra cotta
roof tiles will continue throughout the summer. The goal of
stopping the water infiltration into the building is being
reached while at the same time restoring a pristine and vibrant
appearance to the terra cotta tiles.
The dry ice cleaning process enabled the
Philadelphia Museum of Art to effectively clean 90-year-old
historical terra cotta tiles that had not been touched since
they were originally installed. The terra cotta tiles were
chosen for their lightweight material, ease of production and
low maintenance requirements.
Each tile was handcrafted and is estimated to
have a replacement cost today in excess of $10,000 per tile;
extreme care in the handling and cleaning of these tiles is
critical. This cleaning process is unlike other traditional
cleaning processes in that it is environmentally safe,
non-abrasive, and produces a pure, clean surface.
Dry Ice Blast cleaning provides restoration
contractors with a cleaning method that creates added value for
their business. It has been used in several other notable
historical cleaning projects with monumental results:
• Lead Paint Abatement on the Utah State
Capitol;
• Cleaning Marble monuments outside the Chicago
Federal Building;
• Cleaning limestone statues in Spain;
• Removing mold and calcium deposits on the
Charles Bridge in Prague;
• Historic church restoration;
• Erasing fire damage to turn-of-the century
homes;
• Restoring log cabins.
Most restoration work requires a cleaning method
that is non-abrasive and chemical-free. Dry ice blasting meets
both criteria, in addition to being a dry process and not
creating any secondary waste streams. The goal is to restore a
structure to its original state and to uncover the underlying
surfaces of the structure without causing any damage to these
surfaces. Dry ice blast cleaning allows the restoration
contractor to achieve the desired cleaning results by removing
the contaminant, without damaging the substrate.
