When Todd Robbins slides a footlong pair of scissors down his throat, you wince.
When he hammers a 4 1/2-inch nail up his nostril, you squirm.
But the real cringing comes when Robbins bites into a light bulb and starts noisily crunching the broken glass in his mouth -- and then swallows it.
Such is the nature of an art that could be lost forever if Robbins, who is also an accomplished fire-eater, weren't so determined to pass the torch.
Robbins is "dean" of the Coney Island Sideshow School, a twice-annual course for the nonsqueamish few who aren't put off by a curriculum that includes "fundamentals of sword swallowing," "broken glass walking" and "hand in animal trap."
A half-dozen hardy souls have signed up -- tuition is $600 -- for the fall session of six four-hour classes beginning today on Coney Island, at the southern tip of Brooklyn. The school is offered by Coney Island USA, a nonprofit organization chaired by Robbins that exists to preserve this arcane slice of American tradition.
On Saturday, between performances of his off-Broadway show "Carnival Knowledge," Robbins explained that Coney Island was home to one of the nation's last remaining "10 in 1" sideshows, so called because they put 10 acts -- snake charmer, bearded lady, magician, contortionist, knife thrower and so forth -- under one tent.
During its heyday in the early 1900s, Coney Island attracted up to 1 million people on summer weekends -- drawn by the sun and surf, of course, but also by elaborate attractions such as Luna Park and Dreamland. The resort, Robbins said, was known as the "Nickel Empire," after the admission price to the rides, games and sideshows.
Robbins, a Long Beach native with a theater arts degree from Cal State Long Beach, came to New York years ago with the idea of acting in conventional drama. But he gravitated toward carnival life, an interest that had captured him at age 12, when he first witnessed a sideshow. His fascination was encouraged by some early lessons from a Long Beach neighbor who was a retired carnival professional.
Until Robbins' school opened two years ago, finding such a veteran to show you the ropes was about the only way to acquire an education in sword swallowing and other sideshow lore.
"There's no place to casually pick this up," Robbins said. "This stuff is incredibly dangerous. It's not something you're going to get at the Learning Annex."
Robbins, only half-joking, said the real danger of eating light bulbs isn't the chewing or even the swallowing. It's what happens in the two or three days that follow. During performances, he chases his "light meal" with a swig from a Windex bottle. The container is a gag, but the fluid -- a mixture of blue-tinted water and alcohol -- serves as an antiseptic.
When he needs medical attention, Robbins visits the house physician for New York's Metropolitan Opera Company. As distinguished a post as that may be, Robbins said, the doctor is tickled to have a patient who occasionally comes down with a scratched esophagus from swallowing a sword the wrong way.
One of the keys to surviving in the business is maintaining a healthy respect for its dangers, Robbins said.
"Siegfried and Roy for 40 years created the illusion that what they do is family entertainment, when in reality it's life and death," Robbins said, adding that Roy Horn's recent mauling by a tiger was a tragic reminder.
Robbins occasionally turns away prospective students, particularly younger ones, who strike him as too cocky or immature to be properly cautious.
Graduates of the Sideshow School include schoolteachers and business people who incorporate some of what they learn into their day jobs. A motivational speaker who wants to "nail home" a point might employ Robbins' "human blockhead" routine, for example.
Although Robbins occasionally uses magic tricks, what he likes about the sideshow arts is the absence of illusion. Those are real light bulbs he's munching -- more than 3,000 in his career to date -- and that's a real lighted cigar he puts out on his tongue each performance.
"Seeing someone do the impossible can inspire you to rethink what's possible in your own life," he said.