When tourists come to the ancient Irish town of Waterford, they naturally stop at its oldest building, a stalwart circular tower built by Reginald the Dane in 1003. But Waterford's most popular attraction is far less historic: the Waterford Glass Factory.

Although the factory is modern, the crystal is still made by an age-old process, blown by mouth and cut by hand. Within, craftsmen perform a mysterious alchemy, transmuting by fire the raw materials of silica sand, red lead and potash into the gleaming crystal that decorates palaces, churches, embassies and opulent homes the world over.

Tours (in groups of six or less) begin in the factory showroom, which glints with all the patterns and permutations of Waterford. No hard sell, though; in fact, you cannot buy anything on the premises.

As we walked over to the factory, our guide, Hilda, told us the history of Waterford glass.

In 1783, two brothers, George and William Penrose, put up 10,000 pounds (about $21,000) -- no fortune, even then -- and founded a flint-glass factory in Waterford. Success was swift. Waterford won medals at exhibitions, and was eagerly sought at home and abroad. But during the 18th century, licenses, export duties and high wages became crippling. In 1851 the factory closed.

It remained closed for a hundred years. Then, in 1951, a handful of Irish businessmen, eager to support both Irish industry and Irish tradition, got Waterford going again. They imported glass-blowing masters from Germany and Italy and master cutters and engravers from Czechoslovakia. Today in Waterford you find a lot of un-Irish names among the Murphys and the Kellys.

The venture paid off. Waterford now is the largest producer of high-quality crystal in the world, employing 25,000 people, most of whom are Irish.

There are four stages in the manufacture of crystal: blowing, cutting, polishing, and packing and quality control. The blowing is done in a huge room like an aircraft hangar. Each master blower with a team of three or four helpers works around his own furnace. He used traditional tools: hollow irons and wooden templates. (The furnaces, though, are modern and never are allowed to go out, because it would take weeks to heat them again.)

We watched one team making pitchers. A lump of molten glass at white heat was taken from the furnace and blown into a perfect bulb. Waste glass was cracked off at the top and the lip was fashioned. Then the handle was attached, the artisan all the while swinging the piece to keep its shape. It looked simple. It isn't.

I was struck by how young many of the workers were. They are apprenticed at the age of 16. It takes five years to become a qualified blower or cutter, and another three years to master the trade.

We moved on to watch half a dozen girls marking rough lines in black wax crayon on uncut glasses. These lines serve as guides for the cutters, although they looked far too imprecise to be useful.

In the next room rows of cutters sat at their cutting wheels. Originally the wheels were turned by apprentices, later by steam. Today they are electric, which makes them faster and sharper. With this single cutting edge, and the deftness of his hands, the cutter fashions all the beautiful and intricate Waterford patterns.

Each man works on his own pieces, in his own private world -- cutters are encouraged to wear earplugs or radio headphones to protect them from the whine of the wheels. The first deep cuts are made on a carborundum wheel; they are then polished and smoothed on a sandstone wheel.

Cutters are paid by the piece, so they cannot afford to make mistakes. Each piece is checkd before being stamped "Waterford." "But no piece is perfect," said Hilda. "How could anything made by hand possibly be?"

I also visited the engravers' room, not normally open to visitors because of the exacting concentration the work demands. In this room craft becomes art. The engravers work on various collectors' items -- sporting trophies, commemorative pieces, limited editions. Completely freehand, using a small, electric-powered copper wheel, the engraver creates three-dimensional designs and pictures in the glass, often taking weeks over a single motif.

Wateford comemorates most Irish historical and sporting events. I watched the engravers working on vases depicting scenes from Shakespeare, and Waterford globes. These hollow glass globes are engraved with precise latitude and longitude, and the continents are depicted in heavy diamond cutting. They turn on chrominum rods and are set in cut crystal bases. Each piece takes several months of work.

Some of the most famous pieces of Waterford crystal are the 16 chandeliers in Westminister Abbey, installed in 1965 to mark the abbey's 900th anniversary. Each chandelier is 10 feet high and 3 feet wide, and consists of 500 pieces of mouth-blown, hand-cut crystal. Waterford chandeliers also hang in Independence Hall, Philadelphia, and the Kennedy Center, Washington. And there's a new Waterford tradition: On St. Patrick's Day, the Irish ambassador in Washington presents the president of the United States with a Waterford crystal bowl filled with Irish shamrocks.