Dennis Bergevin has a head full of hair. And it's his. So why, when he spies someone on the street with long, silky hair, does he hold out a business card and say, "If you ever want to sell your hair, call me."

Why does he need 2,000 wigs?

And why does he have shelves of boxes labeled: "goatees," "mustaches," "sideburns," "facial hair" and "short beards"?

These questions don't bother Bergevin, but they bother his mother. According to Bergevin, his mother "is scandalized! That's just not a way for an adult to make a living." He probably hasn't told her about the business cards. But she surely knows that her 34-year-old son, a former portrait painter and a former hairdresser, directs the New York-based company Charles Elsen and Associates: the ones who, for the past decade, have put wigs and makeup on the heads and faces of the Washington Opera's singers. On Feb. 2, when the curtain falls for the opera's 30th season, the trunk lids will close on Bergevin and his associates' annual four-month residency in Washington.

"Given a fashion industry setting," says Bergevin, "I don't think I could do the same kind of work. To march in with 10 beautiful women and put some powder and trendy eye shadow on them and tease their hair -- I couldn't do that."

Instead of worrying about some glamor goddess' hair, Bergevin worries, at least for the run of "Christopher Columbus," about a chef's little French mustache, and a little girl's yellow braids, and Queen Isabella's brunet hair -- spiked and curled at the top to have a recognizable, Joan Collins look.

Part of what challenges Bergevin about opera is "the great transitions that often have to be made in coming to a character." Unlike actors in other dramatic arts, who are often cast because they "look the part," opera singers "don't always fit the role they are playing. In opera, the voice is more important."

But with every voice a face and, usually, some hair must come, and Bergevin's operation -- a nomadic crew of eight associates, technicians and apprentices -- keeps the faces and hair looking good -- or fiendish, or tubercular, or royal. They travel across the country, usually in two-week stints, defining cheekbones, gluing glitter onto lips and receding the hairlines for more than a dozen opera organizations, including ones in Los Angeles, San Antonio, Cincinnati and Pittsburgh.

The business was founded in 1974 by the late Charles Elsen -- a tenor at the New York City Opera with an aptitude for makeup. Bergevin was as good with hair as Elsen was with facial makeup.

The whole thing began in San Diego with a haircut and ended in New York with a partnership. "I was working as a hairdresser in a salon," recalls Bergevin. "I cut Charles' hair, and he invited me to come backstage to watch. I was bowled over. I couldn't believe that there was such a thing as this happening: giants, dwarfs and mermaids! I was astounded. I said, 'May I please come back tomorrow night?' And I watched him turn all these women into exotic monsters, into wiggling creatures . . . it was just amazing!"

Bergevin was hooked. With a grant from the National Opera Institute, Bergevin joined Elsen, relocated to New York and embarked on an odyssey in the world of wigs. "For the first three years I didn't pick up a makeup brush at all. I just concentrated on learning wig building, styling and periods," says Bergevin.

"The first thing Charles and I did in the beginning," recalls Bergevin, "was to make sure that we could handle any of the standard operatic repertoire." That meant purchasing wigs (preferably made of human hair) -- 18th-century white wigs for "Manon" and Egyptian-style wigs for "Aida" and Japanese wigs for "Madame Butterfly." Some of their first wigs came from the Max Factor studios, in Hollywood, which had decided to sell out its wig department. "Fortunately, Charles was in Los Angeles at the time, with the New York City Opera. The wigs were on sale, and he bought a large pile of them all at one time," he says.

"I am always on the lookout for wigs," says Bergevin. He puts in bids for the wigs from Broadway shows that are closing, hunts out old family-operated wig stores, and, of course, buys hair and builds wigs himself.

Opera is nothing if not collaborative, and Bergevin's art is as dependent on a track of stage lights as it is on a bottle of Final Net. Ask him to describe a great professional moment and he answers, "When there is a follow spot, that's the best of all for me. Finally -- light directly on the singer's upper torso and face. I can really see my work."

When it comes to hair, the ultimate technical nightmare would be, says Bergevin, "a wig falling off. On stage." Pausing long enough to knock on the wooden handle of his chair, he continues: "Luckily, in 10 years, it has never happened during the performance that a wig has gone completely off . . . I have been on the side of the stage, seen that a wig is loosened on a singer, that it has slipped back . . . and I've stood there, with my hand on the back of my head, pushing my hair forward, holding a bottle of spirit gum, saying, 'Please don't fall off,' and asking the stage manager, 'When do they make their exit?' "