YOU CAN SEE where the stained glass is buckling in its window frame, the pieces almost ready to pop out

"That's because the cement has washed away over the years," says Dale Waters, whose crew is repairing the windows at Church of the Epiphany, 1317 G St. NW. "Stained glass is heavy. It's an inch thick sometimes."

The Tiffany window is so thick its panels have to be limited to 2 feet by 2 feet. There couldn't be a half-dozen of these antiques left on the East Coast, Waters mutters. This one dates from about 1905.

"An artist would work two solid years on one of these things and get paid $1,000. A window that size would cost about $70,000 today. But the Tiffany . . . Well, you couldn't put a price on that."

The gothic-arched window, 12 feet by 4 feet, shows a pensive evening pastoral with cypresses and a moon, not specifically religious but quietly beautiful in the evening sun.

"No one's really seen it for years, with that storm glass they had on it. We're using Lexan plastic to protect it instead. For every $5 put on the collection plate, $2 goes for heat. We'll reduce that to 50 cents." The firm, Shenandoah Studios of Front Royal, Va., fixes church windows all over the East, recementing, bracing with steel, replacing broken panels.

Waters likes to talk about the Tiffany. "Each piece was individually made and the layers were built up so you had what amounted to two windows. A red section would be backed by blue to enrich the color and give a sense of depth. Then after it was all laid out on a table, the lead would be poured between the pieces." Nowadays, H-channeled lead stripping comes ready-made.

The first stained glass windows here go back to 1847, only three years after the historic church itself was built for the parish. In those days G Street was virtually the city's northern border and K Street was a pasture. A prominent parish: Jefferson Davis worshiped here before the unpleasantness. The bell tower has 15 bells instead of the usual 12 so the national anthem can be played.

"When the big window in the sanctuary was unveiled the people saw that one of the angels was naked," remarks the rector, Dr. Edgar Romig. "They were shocked." He points out the angel, quite modest but definitely male.

Over the choir loft, an early Victorian window, very architectural and geometrical in design, admits a sober light. "People didn't like it for a long time, but that kind of design is coming back now," he says.

Stained glass windows, unlike newspapers, do not thrive on topicality. During World War II some medallions depicting the food lift to Europe and Eddie Rickenbacker's rescue from a raft in the Pacific were donated but later were replaced by something more timeless. One successful exception is a portrait of a former rector at his study in Oxford, painted small on another window.

The newest additions are six panels high in the clerestory showing the days of the Creation, done by Rowan LeCompte (who designed Washington Cathedral's dazzling rose window) and donated by several parishioners, and Romig. Stunningly modern, these range from a morning-light window of abstract blue water shapes to a golden evening-light Adam and Eve.

The rector eyes the cables snaking across the worn floor, the dropcloths sagging over pews, the ladder propped against the rose window, damaged recently by rocks. "We don't get many rock-throwers," he says. "Time and pollution are the real enemies."

We stand contemplating this undoubted fact.

Then the organist, who has been tuning up, gives us a shot of Bach through the trompette-en-chamade mounted at the back of the winter-gloomy church, and fills the air with silver sound, and the backs of our necks prickle, and we all smile.