Creating an ice surface is one thing, but to make and maintain a top-quality indoor rink is quite another. Today's ice-making technology and techniques are the product of decades of trial and error. Around the world, the art of making and marking ice for hockey purposes has become a trade employing thousands of arena workers. Despite what many may think, it's a job requiring a great amount of skill and knowledge. Keeping things under control, no matter what the out- side temperature might be, demands nonstop care from ice-keepers and machines. As one might suspect, modern arenas are equipped with advanced refrigeration systems to keep the ice slab chilled. Huge compressors refrigerate and pump the cooling fluid under the rink. But even in the twenty-first century, the cooling fluid is far from high-tech-it's saltwater. Brine, as it's also called, freezes well below O°C
and, since it is still mostly water, has a large heat capacity that makes it quite efficient at freezing the ice.
The game plan is simple: to cool the rink down you transfer its heat to the brine. The saltwater is cooled to subzero temperatures and car-ried through an extended network of crisscrossing pipes underneath the ice surface, inside a thick slab of concrete. Upon contact, the brine heats up and the slab cools down. This is what engineers call a heat exchanger, and it is the same principle used in cooling your car engine. Coolant circulates around the engine block, taking heat away from the engine and sending it to the radiator and then to the outside world.
Once the concrete slab is cold enough, the first few layers of water are spread on it and ice-making begins. The first layers of ice are sealed
with a layer of white paint to increase the color contrast between the puck, the lines, and the ice. Without the paint, the ice would look
grayish, which it did in the old days. More layers of ice are then added, and, once it has reached a thickness of about one-eighth of an inch, lines, dots, circles, logos, and advertisements are applied using water-based paint that dries quickly. Nowadays, a special kind of durable, paperlike tissue is often used to make straight lines. The paint is then covered with another eight to ten thin layers of ice. This process ensures that the marks are well inside the ice and do not disappear after the first resurfacing. With time, though, skates dig deep enough to remove and damage lines bit by bit until they become dim and need repainting. Making a standard-size rink from scratch is a matter of one or two full days of work.
So many layers of ice may sound like a lot, and, indeed, as much as 40,000 liters goes in to icing a standard rink. But, unlike the ice on lakes and rivers, the final thickness of the ice is less than one inch; typically it is only three-quarters of an inch to one inch. While you wouldn't want to play on such thin ice on a lake without wearing a life jacket, indoor ice is entirely supported by the concrete slab, so there is no reason for it to be thicker.
Depending on the sport being played, the ice temperature may be adjusted from about -5°C to -10°C. The icemakers at the San Jose Arena, home of the San Jose Sharks, keep the ice at -5.5°C for figure skating and -9°C for hockey. Other rink managers prefer slightly warmer ice, but cooler ice is harder, which makes it better for fast skating. Figure skaters prefer a softer ice surface for smoother landings, whereas hockey players like it hard and fast. Maintaining the appropriate ice temperature throughout a game in a place like the America West Arena in Phoenix, with 16,000 cheering fans, is a challenge. Humans burn, on average (accounting for different body sizes and children), about 1,000 calories a day. A good part of this energy is transformed into heat and released into the environment through breathing and through the skin. During a two-hour hockey game, we can expect the Coyotes fans to burn roughly 1.4 million calories, or nearly 6 billion joules (probably more if the game is tight and they're getting excited). That's plenty of energy to heat up the place. 2 The humidity coming from the outside environment adds to the problem. Since humidity is water, it is very effective at warming things up, and a rise of a single degree in temperature will make the ice more susceptible to chipping and damage.
With so many people packed in an arena, keeping the ice cool becomes a real challenge, especially in southern regions where heat is a year-long problem. Every time deliveries of beer, pretzels, or hot dogs arrive for the concession stands, the doors are opened and heat and humidity come in. Though this is hardly a concern in places like Ottawa and Edmonton in the middle of winter, many arenas in the South have dehumidifiers working at full capacity during the game.
All things considered, it is quite amazing that the Florida Panthers, in Miami, can play at home in June! Without modern ice-making technology, the NHL would never have been able to expand south and the regular season would not be 82 games long, even in Canada. In all NHL arenas the ice is kept at least from September until May, and sometimes all year round, even though other events take place. For example, the newly built Air Canada Center in Toronto is home to the Maple Leafs as well as the Toronto Raptors, an NBA franchise. When the Raptors are in town, a couple of hours is all the crew needs to install a basketball court on top of the ice and arrange the seats around it.
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