Architect Frank O. Gehry designs his geometry-defying buildings with aerospace software. But for his latest piece of furniture, he got up close and personal. Those signature curves are literally his own.

Gehry's new chair, to be launched by the Knoll company this fall, is a delicate crimp and fold of metal. Seat and back float on slim tubular steel legs. Aluminum surfaces glow. The chair looks light as titanium. But for the high cost of the space-age material, it might have been.

"I love designing furniture," says Gehry from his office in Santa Monica, Calif. "I sketch furniture probably more than anything else that I do."

Gehry is known for startling curvilinear structures like the Guggenheim Museum in Bilbao, Spain. The same aesthetic plays out in his model for an addition to the Corcoran Gallery of Art, unveiled last month. In the case of the chair, what came after the sketch was as bold a statement.

"The original idea was that he would sit on the chair, and we would take his form," recalls Liz Needle, vice president and general manager of KnollStudio. "It would be made of a material that was moldable, and adjust to the shape of the user. It's not really possible to do that."

What's a visionary for if not to challenge convention? After sketching a doodle that would test any known production process, Gehry hand-crafted the first model. Grabbing a chair in his office, he threw a sheet of silvery paper over it. When he sat down, the paper crumpled all around him in pure Gehry curves.

Son of Bilbao.

"We were thinking of something with a similar look," admits Needle, whose company wanted a high-profile competitor in the cafe chair market.

KnollStudio has dubbed the chair "Fog," after the architect's initials. Gehry has experimented with novel furniture forms before. In the 1960s, he made chairs out of cardboard. In the early 1990s, he fashioned a collection for Knoll in strips of bent maple. He has even designed a museum for chairs, the Vitra Design Museum in Weil am Rhein, Germany, a sparkling white forerunner of his metal period.

Fog is not quite a miniature Bilbao, but there is an echo. Like the building, the chair is elegant, sculptural, functional and, at $390 to $450, affordable in its class.

But purists would be right to see Fog as Gehry toned down for popular consumption. The production line made it so. The design went through several incarnations, including a gleaming rumple of stainless steel, before settling into its current sleek form. The single molded sheet that Gehry had envisioned proved too expensive, as did the use of titanium.

In an earlier conversation while the chair was in development, Gehry had explained, "We tried to do a titanium chair. We can't do it to be competitive with other metals."

And in the end, it didn't make sense. Titanium is prized for weightless strength, which is "not very relevant in the chair game." Nor does a cafe chair need the durability of a 747 titanium landing gear.

So, in the tradition of Charles and Ray Eames, who abandoned a single sheet of molded plywood to fashion the "potato chip" chair, Gehry's single surface became two, on straight legs. The back gives when you sit.

"The challenge was to retain the Gehry flavor in the face of mass production," says I.D. Magazine's editor in chief, Chee Pearlman, who put Fog on the cover.

A prototype drew attention at the Neocon trade show last month in Chicago. But in its quest for stardom, the main test is yet to come. Knoll would like Fog to become the power lunch chair of choice at Conde Nast's new cafeteria in New York.

Gehry designed the sky-blue titanium space opening in December. But Conde Nast is holding out for something cushier. For its trend-setting editors, all those Gehry curves may have to be covered up with leather.

Question for Corcoran-watchers: Would that be like adding Corinthian columns to Bilbao, or a cascading Gehry to William W. Corcoran's old mansion?

CAPTION: The "Fog" chair takes its name from the architect's initials. But its form evolved from an impulsive moment in Gehry's California office.