Stained Glass Restored at Princeton
The university presented these firms with a particular challenge. To minimize disruptions to users, the entire restoration had to be completed in two years, and the chapel had to remain open during the project. Begun in July 1999 and completed in December 2001, the project recently won a 2002 New Jersey Historic Preservation Award.
A Careful Facelift
Most of the stained glass windows had been installed in the 1920s and 1930s. "Stained glass windows have a first life of 60 to 100 years, based on the exposure, the alloy in the lead, and the size of the individual panels," says Arthur Femenella, president of Femenella & Associates.
While the glass will last forever, Femenella adds, the lead is known to weaken over time, so the windows are installed so they can be removed and the lead replaced. In the Princeton University Chapel, enough bowing and bulging, lead fatigue, and broken glass existed to warrant a full restoration of the windows in concert with the masonry overhaul.
The chapel windows were set into grooves in the stone — a time-tested method that required extremely careful removal of the panels. As each panel was removed from its limestone grooves, it was documented in photographs, crated, and shipped to one of the stained glass studios. Femenella's team eventually produced 23,000 slides of the window panels, a treasure trove for future restorers and scholars.
The team then backed up the photographic documentation with full-size rubbings of the windows on vellum, which were annotated. Each panel was then disassembled and cleaned. Broken pieces were repaired or, when the original glass could not be salvaged, replaced. Many pieces had to be repainted. The panels were then releaded, waterproofed with linseed oil putty, and shipped back to the chapel for reinstallation. The project also included the restoration of more than 50 leaded clear windows.
"After it's all cleaned and the replacement pieces are painted, the windows are reassembled into new leads," Femenella explains. "The original leads were pure virgin lead, and it's not the best thing to make stained glass windows out of. We replaced those leads with a much stronger alloy."
Although the lead in a stained glass window poses no threat to the environment or to visitor health, many safeguards were implemented to protect workers during the project. The scaffolding at each window was covered with double layers of plastic, which was sealed to the stone with tape, and the enclosure was checked every day for leaks.
A negative air machine with appropriate filters was employed to draw air to the exterior. Furthermore, all employees wore Tyvek suits and custom-fitted facemasks. Lead levels within working spaces were periodically tested, and employees took occasional blood tests to monitor lead levels as well.
To prepare for the reinstallation, a traditional support system of saddle bars and copper tie wires were soldered onto each window panel. Then the windows were carefully refitted into their original openings. At the time the windows were originally removed, templates of the stone openings had been made to ensure that the reassembled windows would fit back in. The reinstalled windows were sealed with a polyurethane caulk that was tooled to resemble the original putty.
One of the biggest challenges with the reinstallation, Femenella says, was ensuring the consistency of the work produced by the various stained glass studios. "While all the studios were very good, everyone has their own way of doing things," he says. "We did a lot of touching up on site, to give it an even look."
Set in Stone
The other key aspect of the restoration involved repointing the exterior masonry, in the facades of limestone, sandstone, and granite. Work included disassembly of limestone pinnacles, resetting existing pinnacles with stainless steel anchors, replacing severely degraded sections with new fabricated units, and miscellaneous other repairs.
Stone masons carved some new stone pieces by hand. Masonry Preservation Group also installed a new accessible ramp made of compatible stone.
Partially funded by the New Jersey Historic Trust, the cost of the chapel restoration topped out at $10 million. Of this, $4 million was devoted to the stained glass, $4 million to the masonry, and the rest to the complicated scaffolding that covered parts of the chapel throughout the project.
The scaffolding contractor, Safway Steel Products, also built containments in the chapel interior, protecting users from dust and debris. The scaffolding earned an Excellence Award from the Philadelphia Chapter of the General Building Contractors Association.
To further minimize disruption to the community, the team worked on only two elevations at a time. This allowed wedding parties and other users to experience relatively unencumbered views of the historic chapel.
One of these users knew first-hand how much effort went into preserving the chapel's beauty. Six months after the restoration, as light filtered through the stained glass, Arthur Femenella walked his daughter down the Princeton University Chapel aisle.
Kim A. O'Connell is a freelance writer who specializes in environmental and preservation journalism.