Firefighters have shared their frustration after they were called to rescue a Youtube prankster who cemented his head inside a microwave.West Midlands Fire Service said it took an hour for five firefighters to free the man after they were called to a house in Wolverhampton on Wednesday. In a tweet after the incident, the service said had been left "seriously unimpressed" by the dangerous prank which required valuable emergency service resources.The 22-year-old and his friends mixed seven bags of Polyfilla before they poured it around his head, which was protected by a plastic bag, the fire service explained. The intention was to use the microwave as a mould."He and a group of friends had mixed seven bags of Polyfilla which they then poured around his head, which was protected by a plastic bag inside the microwave," said Watch Commander Shaun Dakin."The oven was being used as a mould and wasn't plugged in. The mixture quickly set hard and, by the time we were called, they'd already been trying to free him for an hour and a half."Dakin added that members of the technical rescue team were called to take the microwave apart. It took an hour and half for the man to come unstuck."He was very relieved when we removed a large chunk of the Polyfilla with a screwdriver, allowing him to breathe more easily. But we had to be extremely careful with the screwdriver, working so closely to his head," he said."All of the group involved were very apologetic, but this was clearly a call-out which might have prevented us from helping someone else in genuine, accidental need."