Scientists at Tempra Technology claim to have invented the holy grail of lager drinkers - the self-cooling beer can - which is said to cool beer to the perfect temperature of 3 degrees centigrade within three minutes. The Instant Cool Can works by using water evaporation. The top half is surrounded by a layer of watery gel. The base contains a water-absorbing material in a vacuum, and a special heat-absorbing chamber, which is activated by as twist of the can. Trials showed that the temperature of the liquid in each can fell by an average of 16 degrees centrigrade when the system was activated, and drinks stayed cool for up to an hour. Two unnamed British brewers are already testing the cans, with as view to putting them on the market before the end of the summer. According to Barney Guarino, the chief executive of Tempra Technology, said that higher priced beers and cocktails are likely to be the first be packaged in the cooling cans, as consumers are already used to paying higher prices for them. "All the market research we have seen shows consumers don't mind paying premium prices for this," he claimed. "There simply aren't the economies of scale to make it cheap. But that will happen over time, and we hope these cans will become commonplace." Scottish Courage said it would be unlikely to use the system at the present time. "The price premium is a problem, but this is an area we are looking at for the future," he said.