by Peter Hendsbee

Created on: April 15, 2009

If you have ever played road hockey or floor hockey with a tennis ball, you may understand better than most, that a hockey puck is frozen to significantly reduce its ability to bounce. A shot or pass is easily missed when the puck is bouncing and it is much harder to control.

Hockey pucks are made from vulcanized rubber. The vulcanization of rubber is a process of chemically altering the natural characteristics of the rubber through the addition of other materials, typically sulfur, and the application of heat over time.

Natural, uncured rubber has a low level of elasticity, meaning that it deforms easily when warmed and is brittle when it gets cold. This prevents it from being used to make items that are subject to variations in temperature and that are subject to physical forces that may cause it to break apart. However, the curing process of vulcanization changes the properties of the rubber so that it becomes stronger, requiring much higher temperatures to melt it and requiring much lower temperatures before it will break apart. This process also increases the elasticity of the rubber so that when forces are applied the rubber can bend without breaking and then return to its normal shape once the force is removed.

Considering the game of hockey, it is easy to see why the use of vulcanized rubber is required. Having the puck shatter every time a player took a shot or every time the puck hit the boards would be unacceptable. But a puck manufactured with vulcanized rubber is strong enough to withstand the forces applied to it during a hockey game and retain its shape. Similarly, the vulcanized rubber puck can easily withstand the lower temperatures of a sport that is played on ice.

However, there is one consequence of this process that is not beneficial to the game of hockey. The increased elasticity of the rubber, which provides so many other benefits, causes the puck to bounce. The bouncing effect is not be as great as that of a tennis ball in road hockey but it would still be sufficient enough to disrupt a game of hockey and reduce the amount of control a player may have over the puck.

The simple solution to this problem has been to freeze the hockey pucks. The vulcanization process has increased the ability of the rubber to withstand much colder temperatures and the freezing process reduces just enough of the elasticity of the puck to significantly reduce the bouncing effect. It is a balancing act that produces the desired qualities of a hockey puck.

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