Sky admits its science show faked explosions

To viewers of the science programme Brainiac, the exploding bath seemed spectacular proof of the potency of what the presenter described as "the two dog's nuts of the periodic table".

In fact the blast was not the result of a meeting between water and rubidium and caesium, but the triggering of a bomb, Sky television confirmed yesterday.

The artifice was spotted by Dr Ben Goldacre, who runs the Bad Science website dedicated to exposing pseudo-science.

The programme promises viewers that the experiments on the show - ranging from blowing up caravans with different gases to seeing if a mobile phone ignites petrol vapours - arebased on proved science.

But in a 2004 episode, the producers compromised. Explaining what happened when the metals were put in the bath, a crew member said: "Absolutely bloody nothing. The density of caesium ensured it hit the bottom of the bath like a lead weight. The volume of water then drowned out the thermal shock. They could not go home empty-handed. So they rigged a bomb in the bottom of the bath."

Sky said its viewers would be aware when the effects of any experiment had been exaggerated. Those responsible were longer part of the production team.