When Kathleen Hennessy first donnned her top hat and tattered tuxedo last summer, she stood in front of a full-length mirror and watched her face turn scarlet.

"I looked just like somthing out of 'Oliver Twist,' the spitting image of the Artful Dodger," she recalled "I wondered what K.C. was getting me into."

What 24-year-old K. C. Hill was getting her into was the curious occupation of sweeping chemneys. Tired of working alone in Washington, Hill, one of the early male graduates of the once all-female Vassar College, persuaded Hennessy, also a Vassar grad, to leave her Kentucky home and join him on the job last summer.

Since then, Hennessy has shed her bashfulness, and she and Hill have become the Artful Dusters, two of about a dozen chimney sweeps in town. Wearing baggy Dickensian garb and scooting around the city in a sooty van, the team has dusted about 100 stacks in Washington and the suburbs.

At $40 a chimney it's good money, according to Hill, especially considering that neither of them could land a steady job after graduating from school.

"K. C. studied ecology in school, and I studied religion.It's nice to have a skill because a liberal arts education doesn't mean very much," Hennessy said.

It also helps to have a list of the 750 Vassar alumni living in the Washington area. The dusters frequently phone alumni and have obtained half their clients from the list.

The other half includes people who happen by while the dusters are on the job and realize they haven't had their flues cleaned in years.

The other day, the dusters were at the Bethesda home of Vassar graduate Latisha Noyes. "Aren't they a delight? You know, when we were in France, it was a law that you had to have your chimneys cleaned," Noyes said. "If you didn't the concierge would be after you."

"It's still a law in France, Scandinavia and England," Hill said. "How old is your home, Mrs Noyes?"

"About twenty years, I believe."

"How many times has your chimney been cleaned?"

"Never."

A common reply, everywhere we go," Hennessy said.

"A leaflet distributed by the dusters explains what can happen:

"When wood is burned in a fireplace, it gives off acetic and pyroligneous acids which combine with moisture in the air to form creosote. This accumulates on the chimney walls and is highly flammable. Should a spark ever ignite the creosote, the ensuing fire could destroy your home."

Hill said he decided to become a chimney sweep several years ago when he came across an old copy of Mother Earth News that contained a how-to-article on the trade.

He sent away for $1,500 worth of dusting equipment, including extendable plexiglass rods, steel brushes, a vacuum cleaner and an array of tools, and tried them out on Vassar chimneys during his senior year.

The highlight of his apprenticeship, he recalls, was the day a rod broke and his brush became lodged in a chimney 50 feet above ground.

As he struggled to retrieve the brush, a roofer gave him some advice Hill said he hasn't forgotten: "He told me not to look down."

Since then, Hill has become a walking almanac on his work. "The profession is only about 200 years old," he said. "It started in London when people began to wonder why whole sections of the town would go up in flames every year."

He attributed the fires to the buildup of the sooty, flammable creosote inside chimney walls and sparks that could trvel up the flues and touch down on shingled roofs.

In those days, children often performed the job of cleaning flues, because they were small enough to squirm down chimneys. They wore old undertakers' clothing to hide the soot.

"We wear old tuxedos because they're the closest thing to undertaker's clothes we can find," Hill said.

At one time, Washington residents were legally required to clean their chimneys every year. The problem isn't as great today because many chimneys contain fireproof lining. Still, 40,000 chimney fires in the United States caused over $23 million in damage in 1977, according to the National Association of Fire Prevention.

"With the energy crisis more people are burning wood in fireplaces without realizing that creosote will build up despite the lining," Hill said. "The job is actually fun. You have your own hours, a real trade, and then there's time left over to pursue your own interests. But I'd be stretching it to say theres a connection between ecology studies and this."

Hennessy said, "Someone even went so far once as to say that chimney sweeping is a natural extension of my studying religion, that I wanted to be closer to heaven."

Actually, most of the dusters' work is done from ground level, depending on the construction of the chimney involved. A friendly dispute goes on between the dusters over who performs the more important function.

Hill's job is to extend the rods with a steel brush attached to one end and scrub the flue. On pleasant days he enjoys ascending to the roof and scrubbing from the top down.

Hennessy, wearing a filter mask and surrounded by sooty throw rags, works with brushes and a vacuum cleaner on the fireplace and smoke chambers, the open area of a chimney just above the damper. She cleans up the cresote, ashes and soot that fall from Hill's labors.

"I'm the one who gets dirty," Hennessy lamented, wiping her brow.

"But your job is more important," Hill insisted. "The smoke chamber is the key part of the structure."

"Right," she answered, unconvinced.

The dusters said they plan to continue working in Washington for another year or so. "It's not like we want to do this forever," said Hill. Eventually we're going to get married, once we find a little more stability in our lives."