| The Ice! |
| Why is the ice slippery? |
| One of the most unique aspects of hockey is the surface on which the game is played: the ice itself. The players talk about the quality of the ice; they've helped coin the terms "fast ice" and "slow ice." Scientists, on the other hand, are still studying the chemistry of the ice. In just the last few years, there have been major discoveries. |
| Anyone who has watched a hockey game on television has heard the announcers use the the terms "fast ice" and "slow ice," or even "good ice" and "bad ice." What's the difference? Fast ice is harder and colder with a smoother surface, while slow ice is warm and soft and may have a rough surface. For the players, the difference seems to be that "fast ice" is less "chippy" and there is less "snow." Passing and skating are easier when the ice is "fast." The quality of the ice differs during the course of the game and it even changes how teams play the game. Sharks defensemen Doug Bodger told us, "At the end of periods when the ice tends to get 'snowier', and the puck tends to bounce a little bit, you might not try to 'stick-handle' as much-you might just try to get the puck out the zone." In other words, players tend to make a safe play rather than a finesse play when "slow ice" or "bad ice" conditions exist. |
| Certain arenas seem to have better ice than others. Bodger thinks the difference is the hardness of the ice. Rinks in Canada are well known for the quality of their ice. Edmonton in particular was mentioned by Bodger as having fast ice. Why is the ice so much better in Canada? One of the differences may be climate. Bruce Tharaldson, the ice maker at the San Jose Arena, cited deliveries to the arena as a concern. Opening the delivery doors of the arena and letting in heat and humidity is a problem in San Jose, California. This is not as much of a concern for a rink in Edmonton, Alberta, especially in the middle of winter. Apparently, the freezing and refreezing of the ice brings impurities to the surface. |
| Keeping the ice cold is one of the keys to maintaining fast ice. You should keep the temperature of the ice at sixteen degrees Fahrenheit (-9 centigrade) for hockey and twenty-two degrees (-5.5 centigrade) for figure skating. Apparently, the figure skaters prefer softer ice for their landings and the six-degree temperature difference provides that. |
| Slippery All the Time |
| Why is the ice slippery in the first place? Is it more slippery when it's "fast ice" or is something else going on? How would a chemist explain the difference between "fast ice" and "slow ice"? I looked up to see what Professor Gabor Somorjai of the Lawrence Berkeley National Laboratory had to say to about these questions. |
| Somorjai's recent discoveries have explained why skaters and pucks slide on the ice. These new findings challenge long-held theories about why ice is slippery. In the past, scientists believed that either pressure or friction melted the ice, creating a water lubricant that allows skates and pucks to slide. Berkeley chemist Michel van Hove, a colleague of Somorjai's, has done calculations which show that skates and pucks do not generate enough pressure to instantly liquefy ice. Somorjai has discovered that ice has a "quasi-fluid layer" that coats the surface of ice and makes it slippery. Even ice that is 200 degrees below zero Fahrenheit (-129 Celcius) or more still has this layer. |
| External Forces |
| External forces, such as pressure and friction, can melt the ice. But Professor Somorjai's findings indicate that ice itself is slippery. You don't need to melt the ice to skate on it, or need a layer of water as a lubricant to help slide along the ice. |
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