The burglars who broke into the Church of the Covenant last month did not get away with much. But the damage had already been done.
The thieves entered the Back Bay church by breaking a Tiffany stained-glass window with a fire extinguisher, smashing its intricate, graceful design. Graced with the image of the disciple Dorcas, the window is one of more than 40 that circle the sanctuary, part of what the church calls the largest Tiffany church interior in the country, perhaps the world.
“This is a hurt,’’ said Charlene James, a member who is leading a campaign to have the church recognized as a national historic landmark.
Restoring the window will cost as much as $60,000, and the church is unsure how much insurance will cover. For a congregation of just 125, the expense will be a burden. But the void left by the window’s destruction has been the true hardship, members say.
“It’s like looking at a dinner table where a family member is missing,’’ said Jennifer Wegter-McNelly, the church’s interim pastor. “It will be such a relief when we have her back.’’
As soon as church officials discovered the break-in, they called Roberto Rosa, a stained-glass conservator in Needham. An admirer of the church’s collection and the craftsmanship of designer Louis Comfort Tiffany, Rosa promptly began the painstaking work of repairing the smashed window.
The bottom third of the window sustained the bulk of the damage, with about 70 percent of the glass shattered. While some original pieces are beyond repair, Rosa said that most of Tiffany’s work can be saved.
“I have no doubt we can salvage it,’’ Rosa said. “We will try to retain as much of the original glass as we can.’’
Rosa, who has restored stained glass for more than two decades, likened the repair work to assembling a jigsaw puzzle, a time-consuming process of matching colors. Piecing together small shards, many picked up from the church floor, took days.
“There’s no rushing, really,’’ he said. “We have to be respectful of the original artists and the glass they used. And every square inch is different.’’
The Tiffany style, which involves layers of colored glass, is rarely practiced today and is challenging to replicate, Rosa said.
“They used the glass as a medium, instead of the paint,’’ he said with a hint of wonder. “The way the windows change with light, it’s incredible. It’s an art form that is not really with us anymore.’’
Built just after the Civil War, the stone church was one of the first public buildings in the newly filled-in Back Bay, and its soaring steeple has been a prominent feature of the skyline ever since.
But it is the collection of stained-glass windows, little known even in Boston, that truly sets the church apart. The windows were part of a sweeping redesign in the 1890s, and have not changed since.
“It’s one of those hidden gems,’’ James said. “It was a revolution in stained glass, and it’s preserved just as it was.’’
The church’s application for historical recognition, which has already cleared several major hurdles, said that while other religious interiors feature stunning Tiffany collections, none match the Church of the Covenant’s in “scope, complexity, integrity, or originality.’’
“The decoration at the church is intact and virtually unchanged from its original form,’’ the application states.
A stained-glass specialist commissioned by Tiffany & Co. in the early 1990s concluded that “there are very few churches in the world that have interiors completely designed by Louis Comfort Tiffany, and none as complete or important as the Church of the Covenant in Boston.’’
There are fewer than 2,500 designated historic landmarks, according to the National Park Service.
Ironically, the intruder was only able to gain access to the window because of work being done on that side of the church, including the installation of new protective barriers. The intruder probably climbed onto the first level of scaffolding to break the window.
James hopes landmark status will make the church eligible for grants to better protect the windows in the future.
“I’m thinking of saving all the windows,’’ she said.Peter Schworm can be reached at email@example.com. Follow him on Twitter @globepete.