CITIES of zeppelins and pods on giant stalks have been the stuff of futurology since the 1920s.

Always part of a future that seemed just around the corner, they were the off-the-peg indicators of limitless technology, symbols of dizzying change, while buildings in the real world remained stubbornly old-fashioned and earthbound.

Now, a material that can give shape to these fantasies is available.

ETFE (ethylene tetro flouoro ethylene) is a fluorine-based transparent plastic that works as a sort of puffer jacket for buildings, and is a lightweight alternative to glass. It allows architects to escape the weight of steel, glass, stone and concrete.

Its first major public outings are spectacular. Like Sunday supplement spreads of science's latest discoveries, the Leicester National Space Centre and the Eden Project, both scheduled to open mid-year, and the Air Pavilion at the Magna Science Adventure Centre in Rotherham, which opened this month all have the cellular structure of biological closeups, blood cells and flies' eyes and tortoise shells.

These are all improbable and romantic buildings, but ultimately ETFE will be seen in ordinary developments.

As a cheap alternative to glass for covered streets, office building atriums, shopping centres and leisure parks, it could spread like an umbrella in rainy climates.

ETFE is put together in sections of transparent inflated pillows. Its weight is 1% that of glass, it transmits 15% more light, has the thermal properties of triple glazing and costs a quarter to half less to install than glass.

It has been available since the early 1980s, but architects have not until now had the confidence that it would prove durable. Installed in Centreparcs leisure centres in the UK, its life expectancy originally estimated at 10 years is now put at 50 years. Double glazing, which is only as durable as its silicone seals, gives out in less than 20 years.

A researcher at DuPont originally discovered Teflon, from which ETFE was developed, by accident in 1938. While researching refrigerants, he found that he was unable to dissolve or burn this new substance. It was immediately taken up in the war effort, coating wires and lining tanks against chemical corrosion.

Twenty years later, Teflon was used as the sacrificial shield on the space programme's reentry capsules as it was extremely slippery and resistant to heat before evaporating.

A 'foil' version, ETFE, was developed by the mid-1980s to provide the mechanical strength Teflon lacks, and was triplelayered into pillows for building projects.

When used in a roof, the bulbousness of each pillow is not noticeable, nor does it matter that the curvature distorts the view of the clouds.

At the Magna Science Adventure Centre, Marc Barron of Wilkinson Eyre Architects was afraid that the Air Pavilion would look like an overweight grub suspended in the void if the sections puffed out between the ribs.

The idea of the centre, housed in what was Europe's largest foundry, 'was to leave the plant of the foundry untouched, as rusty relics of a bygone age, as if being explored by the miniaturised products of our own', says Barron.

The material had to be cut to lie flat. The sleek torpedo shape, lit from within, looks magical in the dark ruins of the foundry. The asymmetrical pressure inside the sections of the Air Pavilion reduces the strength of the surface, but it will never suffer wind or the weight of snow.

At the National Space Centre, set to open in June, ETFE wraps the entire rocket tower. It puffs out between the bands of horizontal ribs like a restricted beer belly. It is a Michelin man of a building. Apart from the cost, the architects, Nicholas Grimshaw & Partners, who also designed the Eurostar Terminal at Waterloo, had ample reason to be wary of glass. Small imperfections in the glazing at the station have meant that the whole complicated, snaking roof has had to be covered in tarpaulins. ETFE would have been perfect.

No doubt in time, the puffy effect will seem quite familiar. Eventually, the space centre will seem a suitable sort of place to have braved a new look. In the meantime, the new wonder material may be limited to rooftops and futuristic public projects. Financial Times.