High-Tech Ice-Making Speed-skating events will be held in the M-Wave, which is one of the largest wooden buildings in the world. The M-shaped exterior of the structure, with its two peaks, symbolizes the mountainous landscape of Nagano. The best temperatures for ice in skating rinks are around minus 7 degrees Celsius (19 Fahrenheit) for ice hockey, and up to minus 5 C (23 F) for speed skating. The fast skating in these events requires a hard, solid surface that lets competitors apply more power directly. For figure skating, the temperature is raised to about minus 4 C (25 F). This makes the ice softer, to cushion the blow when skaters land after jumps. Water quality is very important. If the water contains impurities, these enter the gaps between the ice crystals, causing the ice to become brittle. Air bubbles have the same effect. The special water used in ice rinks is filtered until it is 20 times as clean as tap water. The ice is formed slowly and gradually. Hot water at a temperature of around 50 C (122 F) is sprayed onto the rink like mist. After an interval to allow air bubbles to escape, another layer of mist is applied. Each layer is around 0.6 millimeters thick--about 1/50 inch--so only a few millimeters can be put down each day. It takes at least a week to prepare a rink 3-4 centimeters (1-2 inches) thick. The final step is to scrape and polish the surface to create a mirror-like finish. Computers are used to control the ice temperature and keep the rink in top condition for the competitors. Infrared heat sensors in the ceiling monitor the temperature of the ice surface. The system automatically adjusts the amount of coolant flowing through pipes under the rink.

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