An elaborate window-cleaning at Pennsylvania Academy of the Fine Arts

The stained-glass rose window at the Pennsylvania Academy of the Fine Arts is rarely noticed, although it dominates the North Broad Street facade of the historic building.

Of course, most windows accomplish their task best by not being seen.

But not stained glass.

Stained glass usually announces itself, transforming an interior with ethereal light, drawing an eye to conspicuous arrays of color.

But the academy's rose window and its supporting cast of colored, textured, and stenciled panes that fill the central arch on the Frank Furness and George Hewitt-designed front are retiring in their demeanor, camouflaged almost.

This week, the window and its many panels - 511 pieces of glass - are being cleaned and restored; leading has been removed and replaced; and the whole array is being returned to its quiet perch, a process that should be finished by Monday.

Their absence has drawn attention to the windows.

"We've been watching the Convention Center across the street, where they're putting in these huge windows with huge equipment," said Heike Rass, an academy communications officer. "And we're over here working with these small delicate pieces of glass. It's the past and the future right across from each other."

Rick Prigg, a graduate of the academy and general manager at Philadelphia's Willet Hauser Architectural Glass studio, is in charge of the restoration.

"Up in the upper section, most of the glass is in pretty good shape," he said after scrambling down from about 25 feet of scaffolding in front of the windows on the second floor.

Other sections, well, not so good, Prigg said. Some glass had been replaced in the past. Some glass had apparently been broken when a tree fell through the window. (There is no record of such an accident, but that's what Prigg was told.) Some glass had been installed backward, he quickly learned. And a whole set of panels was bowing out, threatening to launch out onto Broad Street.

The building was restored in 1975, but the glass was simply cleaned. Some time before that, however, "the bottom area was taken out," Prigg said Friday. Studying those panels, Prigg realized they had been reinstalled upside down.

"It's one of the things I'm most pleased with discovering," he said. "It was a real surprise."

The major thing that Prigg discovered, though, is that there is not much to discover about the windows. The academy could locate no record of who designed them or when they were installed.

The building opened in 1876, and presumably the windows and their stenciled floral and leaf panels were installed at the same time.

In fact, the stenciling blends neatly on the interior with carved decorative leaf patterns on the walls of the interior stairs. And amid the riot of blue and red and gold decorative elements, the translucent panes with their subtle greens and reds and textures fade into the background. They do not draw attention to themselves.

"The stenciling we did very little with," Prigg said. "Paint on stained glass is very delicate, so when you are working on old pieces, that's one of the things you're most concerned with."

For one thing, to fuse the paint to the glass, the whole has to be fired in a kiln to at least 1,200 degrees Fahrenheit. A lower temperature leaves the paint surface vulnerable to water damage in particular. Best not to mess with it.

Prigg has extensively documented each of the rose ensemble's 511 panes and has noted what, if anything, has been done to it; there will be a record for future conservation efforts.

"In 100 years, I want the guys who go up there to know exactly what I did," Prigg said.