Three litres of water are brought to the boil in a standard 200-liter-barrel. This takes about ten minutes. After that the barrel is closed, the gas is switched off and cold water is poured over the barrel. After 10-30 seconds the barrel implodes.
How does it work?
Before the barrel is closed, there is no air in it any more, only water vapour. When the vapour is cooled, it goes back to being water and the pressure inside the barrel sinks enormously. This results in the air pressure outside being strong enough to squash the barrel together.
Safety reference:
The barrel is heated with a large propane gas camping stove (10 kW), that has been approved by the German Association of Gas and Water (DVGW).
