The vegetable dye costs $1,000, and, in its powdery state in its 40-pound cardboard drum, it looks orange.

On Saturday morning at about 9 o'clock, three hours before the start of Chicago's St. Patrick's Day Parade, Mike Butler and the other three members of his crew will gather at a city boat slip on the North Branch of the Chicago River.

They will don special garb: white, papery hospital coveralls and two sets of gloves, rubber and cotton. They will put on old shoes. And they will transfer the drum of dye into a small city-owned, wide-bottomed boat, powered by an outboard motor.

Three of the men will get into that boat. The fourth, Butler, will climb aboard a second small craft.

They will motor out to the locks at the entrance of the river to Lake Michigan to gauge the current of the water. And, by 11 a.m. or so, they will begin to dye the Chicago River green.

As hundreds of marchers and parade officials congregate among the floats lining Wacker Drive 30 feet above the river, one of the men will open the drum in the middle of the boat and, using an old coffee can, will scoop out some of the dye powder.

He will pour the powder into a flour sifter, and then sift the dye, slowly and carefully, into the river. As he does so, a second man in the boat will begin the same process.

It's a crude and primitive procedure in an age of push-bottom ease. But, unlike other methods tried in the early years, back in the 1960s, it works.

At first, the orange powder will float in clumps and turn yellow. Then, as Butler, the driver of the second boat, zig-zags up and down the river, the propeller of the motor will operate like a giant Mixmaster and stir up the dye to its intended lime-green color.

On the bridges over the river, well-wishers will cheer. Some will want to throw down cans of beers. But the men in the boats won't take them up on the offer. They'll keep their eyes on their work as they ride up and down, back and forth across the water, in the annual alchemy of St. Patrick's Day in Chicago.

"It's a ritual of the parade," says Mel Loftus. "A lot of people figure it wouldn't even be right if they didn't see the green river."

Loftus, now a consultant with the Plumbing Council of Chicagoland, has worked on the parade since 1958, been its coordinator since 1987 and is this year's grand marshal.

Although it seems such an essential part of Chicago, the downtown St. Patrick's Day parade didn't begin until 1956 when several smaller neighborhood parades were combined and centralized. And the river-dyeing tradition is of even more recent vintage.

It all began with Stephen Bailey, the business manager of the Chicago Plumbers Union and the chairman of the parade from 1958 until his death in 1966.

"Bailey was almost like a professional Irishman," Loftus recalls. "Two weeks before the parade, he'd be wearing a green bow tie and a green bowler."

He was also the boyhood friend of Mayor Richard J. Daley, the father of the city's present chief executive, from the then-Irish enclave of Bridgeport.

The story-which may contain more than its share of blarney-is that Bailey was in his union office when a worker wearing green-stained coveralls came in, explaining that he'd been using dye to trace a leak from a building into the river.

"How does it look when it comes out in the river?" Bailey asked.

"A beautiful green," he was told.

And Bailey smiled, the river-dyeing idea springing full-blown into his head.

But according to another tale that Bailey himself told, the river wasn't the first choice for greening. His friend the mayor thought that a spectacular way of celebrating St. Patrick's Day would be to dye a portion of Lake Michigan green. But he was quickly dissuaded from the idea.

"It was just too big a job," Loftus explains, "and it really wouldn't have been seen by the people in the parade."

(In 1965, Bailey-or was he fronting for Daley?-came up with still another coloring proposal: Why not paint the Wrigley Building green for the day? The owners nixed that plan in the bud.)

The man initially entrusted with turning the river green was William J. Barry, a Chicago port employee who died in 1985. Mike Butler, a city and county official for nearly four decades, took over the task in the early 1970s.

"Bill was from Bridgeport," Butler says. "The mayor trusted him. Bill'd do anything for the mayor. Even though he was a little afraid of water, he went out there. That's how much he loved the mayor."

The chosen

Butler, now 59 and retired since last September, isn't afraid of water, having boated since his childhood.

Although he missed the parade last year because of a shoulder injury, he's back this year and plans on continuing "as long as I can climb down into that damn boat."

Butler's crew includes his son Mark, 28, who runs a car wash outside Milwaukee; Jim Horath, a truck driver for the Chicago Park District; and Tom Rowan Jr., a lieutenant in the Chicago Housing Authority police force.

One year, the crew had green jackets made with the words, "Wizards of the Emerald River," on the back.

"There's pride, just to say you do it," Butler says. "We feel very much like we are the chosen.

"They applaud us. People tip their hats to you. You feel like you're king for a day."

The first year of river-dyeing, the boat crew used an oil-based Air Force dye that kept the river green for nearly a month and caused an outcry from environmentalists. So a vegetable dye was substituted.

The dye is so harmless, Loftus says, that, "if you drank it-except for the pollution in the river water-it wouldn't hurt you. It's just food coloring."

The city doesn't pay for the dye; that comes out of the $50,000 or so that's raised each year through the sale of ads in the parade's ad-book. The plumbers union, now headed by Gerald Sullivan, the parade's general chairman, continues to organize and help underwrite the event. The two boats used this year are being provided by Robert Sempe of the city's transportation department.

Butler and his crew work for free.

"It's not the easiest job in the world," Butler says. "It's messy. It can be dangerous at times. You go back and forth in the water, and you could hit something and that could tip over the boat.

"There're times when there's ice in the river, and that's when you worry. You hit a chunk of ice-hell, the bow of that boat, it wasn't made to be an ice-breaker."

Everything green

By about 12:30 p.m. Saturday, the drum of dye will be empty.