Armed with a belching paint machine and handfuls of tiny crushed glass beads, Wayne A. Gentry and his nephew Richard D. Leite venture into the streets of Cambridge every night.

They are nocturnal artists, private contractors who are making the streets safe for motorists by painting all the city's crosswalks, zebra lines and stop bars with white paint and shiny glass beads. But they are also first-hand witnesses to the city's nightly escapades.

Gentry, 24, and Leite, 19, are employed by Expert Lines, a private company commissioned by the Cambridge Traffic Department to paint the city's street markings twice a year.

The four crews, which have been working for approximately three weeks, are finishing the last streets this week. They complete between 60 to 70 crosswalks a night, although Gentry says his personal record is more than 100.

"You definitely need to do it this often," said Gentry. "There's much traffic [in Cambridge]."

Although they paint between 11 p.m. and 5 a.m. to avoid blocking traffic, the noise from their paint machine disturbs people in certain residential areas.

"It woke me up," said M. Samuel Liu '93, who heard the crew working outside his Adams House room. "At first I thought it was the Lampoon, then I looked out and saw this funny-looking machine."

Once, a Cambridge resident even called the police because of the noise from the paint machine, said Gentry.

"They don't understand that the lines avoid accidents," said Gentry. "We're doing something for the community ...we're the ones who have to be here at night."

But both Gentry and Leite, who work Sunday through Thursday, said they don't mind the night hours too much, and they like the work overall.

"Work is work...you take what you can get in Massachusetts," said Gentry who has been working with Expert Lines for a year. "Times are tough but the pay seemed pretty good."

Awake at the darkest and most silent times of the night, the crews are witness to all nocturnal happenings. "It's exciting seeing what goes on in the city at night," said Gentry. "It's interesting."

Gentry and Leite also have to deal with pedestrians and motorists who often knock down and steal the cones they use to block the streets. "Kids knock the cones down and take them away all the time," said Gentry. "We easily have to buy 100 cones in a year."

Gentry said most of their problems with drunks banging into cones occur on Thursday nights. Two weeks ago, an allegedly drunk driver who hit the workers' cones and crashed into four cars later blamed the crew for the accident, according to Gentry.

"There were 2000 other cars avoiding the cones," said Gentry. "With him we had a problem."