Ectoplasm in a choice of colours

It's almost alive, and heading for your living room: Serena Mackesy on the thing that is the lava lamp

Try this test on your friends: Astro, Jet and Telstar are increasingly discussed on the coolest living-room floors. Who or what are they? Pirate television stations? Gladiators? Entrants in this year's Derby? No. They are all models of lava lamp. And they are coming soon to a household near you.

Lava lamps - those glass cylinders in which viscous globules wander in an underlit watery world - are the quintessential emblem of both the space age and the psychedelic era. They light up the eyes of Prisoner bores. They are associated inexorably with those dystopic Seventies film futures with James Caan in them. In Coogan's Bluff, Clint Eastwood and his cowboy boots find themselves in a world of shell curtains, clubs called Pigeon Toed Orange Peel, psychotic hippie chicks and lava lamps. People who wore headbands had them.

This icon of interior decorstarted life as a novelty eggtimer amid the utilitarian dreariness of wartime Britain: when the wax melted and rose to the top of the container, your egg was ready. In 1963, a crazed genius called Edward Craven-Walker adapted them and launchedCrestworth Trading to sell the original model, Astro (£49.95), whose inverted waist and chrome tips are still the biggest seller in the range today.

The world went wild: they sold in their millions throughout the greater part of the Sixties and Seventies; you had to have at least one to illuminate your Warhol posters. Then came the great design slump of the Eighties and sales dried up almost overnight: swirly, semi-animate objects sit uncomfortably with matt black and bare floorboards.

Twelve years ago, one of the most common objects in skips was an Astro or a Jet (the plain cylinder model, launched in the early Seventies, £39.95), its liquid irretrievably clouded (after roughly 1,000 hours' playing time, the wax and water in the bottle form an emulsion) the plug stripped off and pressed into service on a halogen spot.

By 1990, when entrepreneurs David Mulley and Cressida Granger came across Cresworth, they were shifting roughly 10 lamps a year and had been running as a tax-loss concern for some time.

They saw the potential immediately; a bit of smart marketing to the burgeoning band of New Agers and the cash would follow. They changed the company name to Mathmos (sci-fi buffs will recognise this name from kitsch- fest Barbarella), introduced new models - the latest is a wall of Astro lamps whose interconnectable modules are 2 metres high and almost a metre wide - and have watched sales double each year since.

They now sell 10,000 units a month. Their biggest market is Germany, where hippiedom never really died out, but business is also growing apace here. The company can provide replacement liquid bottles for all the models ever made, so if you have a superannuated Jet in your attic, or fancy a change of colourway from, say blue with white bubbles to pink with orange, all you have to do is call.

I have a Telstar (£59.95), the smaller of the two rocket-shaped models (Lunar, 80cm high, retails for £295). It is shaped like the rocket in the Tintin book Destination Moon, with three elegant chrome legs and a chrome tip.

Bubbles of red wax meander through a sea of violet water. The process of watching its lazy progress is pure meditation: you can lie for hours on your stomach going "ohh, maaan". It is better than Prozac and cheaper, too.

Mathmos Direct, Sterte Avenue, Poole, Dorset BH1 2BD (0202 666 776)