NOW, YOU AND I, if we were set down in 13th-century Venice, would never have a nice day. No one would understand our Italian, and the British ambassador couldn't make head or tal out of our English. What could you do for a living? Be a mountebank, maybe. Play the rebec. Become a saint and have your picture taken in a tapestry.

But look at this William Adair. He would simply drop into the nearest gilder's shop, take off his doublet and get to work. There must have been hundreds of gilders in Venice then. As late as 1830 there were still 150 in New York City. They are all but extinct.

And nothing has changed. Nothing.

They still use rabbit-skin glue to make the 23-karat gold stick to the gesso, or plaster undersurface. (You know when it's tacky enough by twisting your knuckle on it, and if it makes a certain squeak, that's a whistling tack. Don't ask me how they said it in Venice.) In Russia, Adair says, they swear by sturgeon bladder glue: It's stickier and adapts to the weather better. The gold leaf is dusted with the foot of an arctic hare, the hairiest hare there is. They polish the gold with a dog's tooth or, the latest thing, a chunk of agate.

And the gold itself: There are still some people who hammer it by hand. Extruded as thin as a machine can get it, a ribbon of gold is cut into squares which are stacked, alternating with leaves of ox intestine, to make 25-page books, which are then wrapped by 20s in a parchment pack called a cutch -- another peculiar word gilders have to learn, Adair mutters. Those 500 sheets of gold total a quarter of a troy ounce, and when the beaters have hammered them for 12 hours, the gold will be one micron or 1/250,000th of an inch thick and worth something over $1 a sheet. The pounding has to be done on the ground floor, by the way, or the walls will crack.

"You can't pick it up with your hands," says the 31-year-old master gilder, "you use a gilder's tip, a thin fur brush. And you lay it on a leather gilder's cushion with a little windscreen around it. It's all very medieval."

A stamp-sized bit of gold leaf in your hand marries itself for an instant to your fingerprint when you touch it, and then disappears like talcum.

Bill Adair came to the Museum of American Art nine years ago, a sculptor straight from his University of Maryland, with BFA, got a job sweeping floors, learned gilding from resident master Oliver Anderson, toured the gilders' shops of Europe on a grant and now is galloping off in all directions, it seems. He has a book contract. He spends so much time at the White House that he keeps his gesso in the president's refrigerator. He has gilded "30 or 40" Chippendale mirrors for State. His own two-year-old restoration shop already has a staff of five.

"We have 15 years of work ahead of us at the White House alone," he says. Washington is a very gold-leaf town.

Gilding may be maddeningly meticulous work -- six weeks full time to restore, prepare and gild one large frame; 400 hours to do the White House Lansdowne portrait of George Washington -- but a passion goes with it.

"Nobody cares about frames!" Adair flashes. "Even in museums! They paint them with bronze paint, they cover them with Dutch metal, which is brass and copper and tarnishes, they repair them with chewing gum! You can see the teeth marks!"

Changing styles in frames give clues to art scholars, and the Bethesda native has organized a fascinating show on the history of frames, now at the Humphrey Building.

But the passion goes deeper. Adair loves gold. He loves its everlasting brilliance, its soft smoothness, its antiseptic purity. He loves its translucence in the leaf, glowing warmer if placed over a red base, brilliant over blue, deeper over yellow. He dotes on incredible subtleties, the alloys that tint gold orange, green, yellow, white, the delicate burnishing that highlights curves and ridges on an ornate frame.

"Gold was meant to be seen by candlelight in a dark chamber," he murmurs. "In churches, with those narrow windows and soft lights, it can seem magical. A gold picture frame is no mere decoration, it's functional. It makes the light seem to come from the canvas itself. Sometimes it's so bright it overwhelms the picture and you actually have to tone it down . . . "