Dieter Goldkuhle, a tall, bearded man with a German acent, is groping for words.

Questions about his own work seem to make him uncomfortable, but when the questions turn to the art of stained glass, Goldkuhle talks freely of the art's medieval origins and its vibrant transformation by modern artisans.

"Stained-glass windows appeared as medieval comic books in an age when only the clergy could read," says Goldkuhle, a mater craftsmen whose work is so respected that some of the foremost stained-glas artists in the country have trusted him to execute their designs. "Now, a lmost everyone can read, and we no longer need these ilustrations to teach the Bible. Instead, the message of the glass itself can come through."

The works at Goldkuhle's home amply illustrate his point. The front door of his modern, split-level house in Reston is surrounded by glass panels by artist Robert Pinart. Each panel combines clear and frosty glass.

"Through the clear glass, you can see the grass and brushes, so the seasons themselves become part of the design," Goldkuhle says with a noticeable German accent. "Also, the window is made to see as you go up and down two flights of steps. So you see, there are many levels of depth to the picture."

Working the environment into a design is one of the modern approaches in stained-glass art, but Goldkuhle believes there is stil much merit in the older, ilustrative designs.

"I have worked on this (older) type of window at the (National) Cathedral," he said. "The Maryland window, for example, which illustrates church history, or the YWCA window, which shows the acheivements of women."

Goldkuhle is the craftsmen of 65 windows at the cathedral. This prodigious work is the landmark of his 22-year career, which started in a small town in West Germany.

There, at his father's insistence, Goldkuhle became a journeyman in stained glass. For many years, he worked at the craft throughout Western Europe, and in his neatly typed resume he described this period as his "Year of Wanderlust."

That wanderlust, he says, was partly what brought him to this country in 1962, but the major reason was an opportunity to work at the National Cathedral.

"I met a man in London who was associated with the Cathedral," Goldkuhle said, "and he wrote a recommendation both to the people here and to a pair of designers, the LeComptes. Then, when I came to the States, I folowed up on the letters."

Although he first worked in New York, he eventually went to work with Rowan LeCompte and other artists at the Cathedral. Six years ago, he was chosen to execute LeCompte's design for the West Rose window.

"It was in intense collaboration; LeComplte and I worked closely together almost every day for two years," Goldkuhle says. "When you work like that on a piece, you can do nothing else. It is sometimes very painful."

The intensity of the work shines through in the glass. Visitors to the Cathedral often are startled by the richness of the colors -- the artisans call it "saturation" -- which is achieved by using thick chunks of glass to refract light. The effect is almost prismatic.

Goldkuhle brings out a small, round "light-catcher employing the same method -- a warm mixture of syrupy reds and blues.

"This method was first used by John LeFarge, a comtemporary of Tiffany," Goldkuhle explains. "He used stained glass like paint, doubling and sometimes quadrupling the thickness of the glass to create this tone."

In Goldkuhle's studio is a huge work by LaFarge, "Peacock's Peonies" (circa 1885), which Goldkuhle is restoring for the Smithsonian.

"The glass was so thick and heavy that it sagged and buckled in places. So I reworked all the leading and added four brass verical braces and the usual horizontal bars to hold the pieces in place."

Bringing 20th century techniques to 19th century works is all in a day's work, to hear Goldkuhle tell it.

But Brenda Belfield, who designed the YWCA window at the Cathedral, says he is too modest.

"He is so meticulous and so infinitely patient," Belfield says. "I've seen him recreate specific chunks of glass, making special molds."

Belfield has worked with Goldkuhle on 24 Cathedral windows, and she expresses great respect for craftsman of his caliber.

"Since medieval days," she said, "there has been a traditional devision of labor between the patient, meticulous craftsmen like Dieter, and the creative designer.

"In California some designers are starting to do their own crafting. But I think this system is more efficient, since I can go on to a new design while Dieter is still putting one together. Also, it calls for two very different skills -- two different kinds of people."

The glassmaker's art inspires enthusiasm that is not easily stilled.

"I must love it because I know how painful it is to create such beatuy," Goldkuhle says. "The Glassblower gives of his own breath, blowing into a semiliquid to make a bubble. This is flattened and goes through a long process -- all done by hand -- before it goes to the warehouse."

His home is a repository of the wonders of modern glass.

"I have quite a collection," he observes cheerfully, looking about a room filled floor to ceiling with glass bins. Each bin is marked according to hue -- medium and dark mulberry, warm white, streaky red, cobalt.

"Our medium is really light," he says. "In the bins, the glass is lifeless, static.

"The light changes the glass every minute, every day, there is something . . ." he stumbles for words and stares at the floor. ". . . Its something almost mystical about the art and I hold it in the greatest reverence."

And his work as a craftsman?

"I am not falsely modest, but I am just a craftsman. I cannot design.

"But working with my hands, that seems to come easily to me. And when I see a work done well, as beautifully as it can be done, then I marvel."