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Imagine if Steve Jobs' next trick of innovative brilliance was a whole new 3D-movie experience that was ten times better than the current offer, which didn't require you to wear faux-1960s specs and that had the aural sensation of a hundred-piece orchestra. I think we can agree such a notion is not particularly far-fetched.

What though, if there were just one small problem with his new, funky iCinema: if the state-of-the-art movie play-back hard-drive was prone to burst into flames that couldn't be put out with water, that emitted disgusting poisonous smoke and that might turn not only the film you were watching to ash but also the cinema and you? Would it be stretching believability to suggest that in our world of Health-and-Safety executives, the iCinema would be given the go-ahead on the basis that, barring this notable imperfection, it was otherwise terrific? Reckon so.

Go back a hundred years or so, though, when Health-and-Safety executives still worked as bank clerks, and you'll find that's exactly what happened. From 1895 to the early 1950s, all commercially available 35mm film, stills, negatives and even X-rays were made out of cellulose nitrate: a fragile, combustible, unstable, highly-flammable substance that was also used in explosives. And those are just some of its drawbacks. It can also give off a toxic vapour, turn into a brown sticky glue and disintegrate into a pile of dust as it has done on countless occasions, thereby obliterating swathes of film history.

Not that that deterred directors. Quite the opposite: it brought out the mad professor in them. Nitrate film has had at least three starring roles. The first was in Michael Powell's (1934), where a young scientist tries to discover a method for making nitrate fireproof. Then in Giuseppe Tornatore's poetic Cinema Paradiso (1988), the cinema is razed to the ground due to a projection room fire. And in Quentin Tarantino's movie (2009), the projectionist stands in front of a huge heap of nitrate film smoking a cigarette - cool / stupid - before flicking the butt onto the pile, starting a fire that destroys the Nazi high command. Any idea why this movie didn't win the Best Picture Oscar?

But there's more to nitrate film than a fiery nature and odour issues: it has a sensitive, artistic side. According to , cellulose nitrate film is the most vivid film stock ever created. In a short summer season this July, the BFI at London's Southbank is running a programme called in which five films will be shown including the Oscar-winning (1933) directed by Alexander Korda and starring Charles Laughton, and the John Boulting-directed (1947), which stars a young Richard Attenborough. The phrase is always "a young Richard Attenborough"; the older version is called "Dickie", a luvvies' gag on the mercilessness of the ageing process.

All of the movies will be all shown on their original nitrate film stock from a specially designed projector room replete with metal shutters, fire extinguishers and projectionist with a keen interest in dangerous sports. It is the first time in a decade that films have been shown in the UK on their original nitrate stock and the BFI is now the only venue in the country licensed to do so.

I asked Robin Baker, Head Curator at the BFI National Archive, whether the friction of the film going through the projector's gate could cause one of the movies to ignite. "Oh yes, absolutely," he said with the kind of alacrity normally associated with gung-ho 19th-Century explorers who consider a limb-to-limb mauling by a lion as jolly good fun.

And as Spinal Tap memorably demonstrated and as Four Lions is now mimicking, the idea of something spontaneously combusting has a certain frisson.

Robin is captivatingly passionate about nitrate film and says that the real allure of this film stock is its aesthetic attributes; that it exhibits a quality never matched by modern safety film stocks. The luminosity of the blacks caused by the stock's high silver content means that black-and-white movies have an extraordinary lustre and richness that can create a contrast between light and shade similar to that seen in the paintings of the renaissance artists using their .

Nitrate film consisted of nine strips of colour film recording simultaneously, resulting in the "truest, purest colour you will see" and the BFI says the vibrant colour of an original dye transfer Technicolor nitrate print is unforgettable. For Robin, this season is about learning to look, to gain an appreciation of the difference between film stocks which he says is a marked as the difference between oil and acrylic paint. It's about the medium as much as the message.

The season is also about conservation. It marks 75 years of , which boasts over 180,000 cans of nitrate film, making it one of the world's largest holdings. But don't let any of this deter you from a trip to the Southbank: all the films are kept out of harm's way in bunkers - due to their explosive nature and also because of the BFI's determination to preserve them for future generations. The plan is to create a special microclimate to radically slow down their deterioration process. Ideally they would be stored at -5C and 35% relative humidity. Me: "What's that?" Robin: "Very dry."

Conservators tend to be the unsung heroes of the arts. Few will think of or thank them when they sit down and watch an original nitrate film and amaze at its quality or when they buy a new copy of the recently restored Powell / Pressburger classic The Red Shoes (1948) - . But they don't do the job for the plaudits: they do it because they love film - even when it's temperamental, noxious and potentially fatal. In fact, it wouldn't surprise me if the BFI's conservators spent their weekends lighting cigarettes with fireworks. Just for fun.