THERE can't be many 35-year-olds whose employers have included Bjork, Pepsi Cola, MTV, the World Cup, Renault, Citroen, and the Olympic Games. Still fewer whose primary product is fire. Christophe Berthonneau qualifies on all counts, and there are stamps in his passport from Britain, Australia, Spain, Canada, Portugal, Italy, Russia, Belgium, and the United Arab Emirates to prove it.

There isn't a word to sum up what Berthonneau does. You could try pyrotechnician, but that makes him sound like a jumped-up Guy Fawkes. It's no ordinary firework-maker whose company includes architects, composers, acrobats, and actors. He works with engineers as readily as he works with choreographers. You could call him a fire artist, but I suspect he'd just as soon settle on alchemist. Where the alchemists of old sought eternal truths in their transformation of base metals into gold, Berthonneau creates a kind of total theatre in his fusion of fire and music.

The man who lit up the World Cup finale at the Stade de France, and the closing ceremony of the Barcelona Olympic Games, is coming to Edinburgh with his Groupe F company to put that extra spark into the city's Hogmanay celebrations. There are two early evening showings of A Little More Light in Princes Street Gardens on December 30 and January 1, and a presentation of The Birds of Fire in George Street to coincide with the Hogmanay bells. The performances feature original live music that both feeds off and inspires the visual display.

''The work between the musicians and the fire is very important,'' says Berthonneau, taking the chance to light a cigarette, a rare treat for a man who works with explosives. ''Part of the alchemy is the capacity not to have the music simply accompanying the fireworks, or the fireworks simply accompanying the music. Some of the music is the same every time, but within that there is improvisation. The music is at the centre of the show.''

Although Berthonneau is French, the son of an actress who instilled in him a love of theatre, he spent his early career in Spain. This is significant. When it comes to street theatre, the Spanish are louder, brasher, and altogether more alarming than the French, who tend to get tangled up in narrative niceties.

Having developed a passion for explosives while working for the experimental French company

Ilotopie, Berthonneau moved to Barcelona and found a home from home. He was one of the technicians behind Dimonis, the thrilling spectacular presented by Barcelona's Els Comediants in the playground of George Heriot's School in the Edinburgh Festival of 1989. He's also worked with Tramway favourites La Fura dels Baus.

''Spain, Italy, Portugal, China, Japan are all countries with a rich culture of fireworks,'' says this dedicated student of the art. ''In France we have a stricture for cultural events: it's very important to have something cultural inside, or some artistic expression. In Spain, it's more the idea to be generous, to have an event, to have an image, to be in festival, for pleasure. I like this idea of pleasure. My work is very abstract - everybody can take what they want.''

Frequently playing to tens of thousands at a time, Berthonneau cannot afford to be precious about his art. He might talk about the dramatic shape of his work, but audiences don't need to seek deeper meanings. Where the average Hollywood movie will feature two or three special effects, Groupe F's productions are nothing but special effects. The aim is to capture both the thrill and the fear of the flame, and to draw the audience into the centre of it.

''Fire is dangerous and incredible at the same time,'' he says. ''It is very secret because few people can be in the middle of it. It's like a volcano - very exciting because of the smell, and the vibration hitting something at the back of the mind. The show we're presenting in Edinburgh is not very street theatre, it's more a performance that does something a little bit special around the idea of the light. Fire is the basis of any light. There's no light without fire.''

Berthonneau is wise to the commercial possibilities of his expertise. After 18 years in the firework business, he and his cohorts have a formidable specialist knowledge. This they will profit from - installing a flame system to Disney for its Parisian theme park, for example - in order to spend time furthering the artistic potential of their know-how. Fireworks aren't a thing you can do too much rehearsing for, not least because their colours and trajectories are affected by something as arbitrary as the weather.

''We've worked for a long time developing the tools, and the tools give the possibility of doing something new,'' he says. ''We want to do research, and at the same time we want to have a show working, producing emotion, giving satisfaction, raising questions.''

Fireworks are an expensive business and the company has to find work wherever it can. Many of its more commercial-sounding collaborations have been a legitimate extension of its artistic ideals. Providing pyrotechnical effects for selected dates on Bjork's 1996 world tour, for example, was a genuine meeting of minds. ''Working with Bjork was not commercial,'' says Berthonneau. ''She'd seen one of our shows and wanted it. I like all kinds of music done with quality, and I think we can say Bjork is doing very good music. What I hear by Bjork, I don't hear anywhere else. It's my idea to collaborate with people who are searching, and if they also have money, we can do something more.''

Berthonneau makes a subtle linguistic distinction to explain what he and Groupe F are up to. The company is to fire what a musician is to an instrument. It is not the servant of the flames, but the master of them: ''What we try to do is not to play with fire, but to play the fire.''

n A Little More Light, 7pm, December 30, and 6pm, January 1, East Princes Street Gardens, Edinburgh; The Birds of Fire, midnight, December 31, George Street, Edinburgh.