NEW YORK (Reuters) - Magician David Blaine climbed atop a wobbling platform above a high-voltage Tesla coil in a tent on a Manhattan pier on Tuesday, dressed in a 20-pound chain-mail suit, and proceeded to shoot purplish arcs of lightning out of his hands and the top of his head.

The event - an unusual sort of press conference at which journalists were asked to stop their ears with foam plugs - was a preview of a stunt he will undertake starting on Friday, when he plans to stand on a 20-foot-high platform for 72 hours without food amid an artificial lightning storm crackling between low-current, million-volt Tesla coils.

"I had wanted to do this for years," he said.

The magician's past endurance stunts include sitting in a box suspended above the River Thames in London for 44 days with only water, and standing unharnessed on a 100-foot-high pillar in New York City for 35 hours.

He described how this latest idea grew out of an image he had of himself at the center of a giant plasma globe. Realizing the idea would require him to exist in an airless vacuum - a feat beyond even Blaine's prowess - he adapted the idea to instead use Tesla coils.

"Being in the middle of a lightning storm, it feels so amazing, being in an environment you shouldn't be in," he said.

Blaine's stainless steel chain-mail suit is a so-called Faraday suit, an adaptation of the principle of the Faraday cage in which an enclosure of highly conductive material shields whatever is within the enclosure from an electric field.

It is a version of the sort of protective suit some linemen wear when working on high-voltage power lines or hobbyists make for themselves when playing with homemade Tesla coils.

72 HOURS OF STANDING

Stuart Weiss, Blaine's doctor, said the main risks of the stunt include exposure to the ozone and nitrous oxides that are a byproduct of ionized air, which humans should not inhale in large quantities.

A ventilation system will ensure Blaine has breathable air and a special visor in his helmet will protect his eyes from the ultraviolet radiation of the arcing electricity.

Because Tesla coils are noisy, he will wear noise-cancelling earphones that will also allow him to hear and communicate with people on the ground, including members of the public. He will suck water through a tube, urinate through a catheter, and has been fasting to avoid the need to defecate.

Intel Corporation is sponsoring the event to promote notebook computers that use its processor technology.

Blaine said he hoped to inspire children to learn about physics - for example, it is not the volts, even a million of them, that can kill, but the amps. The electric current, measured in amps, produced by a typical Tesla coil is low.

William Allen Zajc, chairman of the physics department at Columbia University, applauded the magician for making physics seem exciting. He said the stunt was basically safe, though could prove risky if the suit deteriorated from the exposure.

"To me, the amazing thing is that he plans to stand there for 72 hours, not that there's a million volts or these impressive lightning bolts passing through the Faraday cage that surrounds him," Zajc said.