Olympic ice is a special, uniform surface made for international winter sports like hockey, skating, and curling. Skilled technicians known as 'ice masters' make and maintain this ice so athletes perform their best. For Milan-Cortina’s Winter Olympics, the ice hockey arena was built new, despite delays and last-minute work. The ice-making starts with five centimetres of insulation on the concrete floor. A vapour barrier goes on top. Then, mats filled with glycol are laid to keep the ice cold. Boards and glass walls surround the rink next. Next, about two inches of water are added over the mats to form ice sheets. The surface is painted white and sealed with hockey markings and logos. Finally, they add three to four extra centimetres of water for the playing surface. Ice temperatures stay between -5 and -4°C. Zambonis, the ice resurfacing machines, regularly shave the surface to keep it smooth. Ice master Mark Messer said the toughest part is "working with a new system for such a high profile event, with little time for preparation." This Winter Games is the first time long track speed skating uses a temporary outdoor venue. Different sports need different ice. Curling ice is pebbled by spraying droplets of water. Hockey ice is hard for quick stops. Speed skating ice is thin, hard, and coldest of all. At Milan-Cortina, figure skating and short track speed skating share a venue. Technicians spend hours switching the ice — figure skating needs softer, warmer ice for safe landings, while short track skaters want hard, cold ice. Water purity is crucial. Ice masters check pH and remove minerals to avoid cloudy or crumbly ice. External things like temperature, humidity, lights, and crowd noise can also affect the ice. Messer said, "Air temperature, air movement, humidity, spectator sound, heat from lighting, water composition and others all affect the final product. As well, the ice resurfacer operator can change ice conditions tremendously."