An ice rink, or ice skating rink, is a large oval of flat, smooth ice intended to be used for ice skating or curling. Ice hockey, figure skating, and speed skating are skating sports which require an ice rink, and when games are not being played the rink is sometimes available for lessons or recreational skating, and non-skating ice sports such as broomball. Outdoor ice rinks can be natural (ponds or lakes which have frozen over) or artificial (flooded depressions in the ground or snow) and are only available in freezing weather. Indoor ice rinks are artificially cooled and are available year-round. How Stuff Works reports the first indoor ice rink was opened in 1876 in London.

Dimensions

An official NHL rink measures 200 feet (61 m) in length and 85 feet (26 m) in width, with corners rounded to a 28-foot (8.5-meter) radius. This is therefore the dimensions of a typical ice rink. When used for ice hockey, two nets will be placed on opposite ends of the rink for scoring. When used for speed skating, cones or markers will be put around the perimeter to designate the track area, and pads are put along the walls in case of high-speed falls. When used for figure skating the rink is cleared of obstructions so the skater can use all the available space.

Freezing the Ice

Indoor rinks are not simply flooded and then frozen. Since ice expands as it freezes, this would result in a very uneven surface and poor quality ice. Instead, the ice is built up in layers. Underneath the ice are layers of concrete, piping, insulation, and sand. From bottom to top:

  1. Sand and Gravel Base: This is the bottom layer which everything else sits on. It has a groundwater drain buried in it.

  2. Heated Concrete Pad: This is a concrete layer which is heated to keep the ground from freezing underneath the ice.

  3. Insulation: This layer thermally separates the cold layers above from the heated concrete pad below.

  4. Chilled Concrete Slab: This layer of concrete has the cooling pipes embedded in it. The cold slab is what freezes the water above it and keeps it cold.

  5. Ice: The ice itself is made of several layers. The water used must be filtered and de-ionized to make the resulting ice as clear as possible.

    1. Layer 1: This is a very thin, 1/32" (1 mm) layer of ice sprayed on as a mist which freezes almost instantly. This layer bonds to and protects the chilled concrete pad.

    2. Layer 2: This is a second 1/32" (1 mm) layer of ice. This layer is painted white. In ice hockey, this provides a strong contrast with the black puck.

    3. Layer 3: This is a slightly thicker, 1/16" (2 mm) layer of ice. This layer is painted with logos, decorations, hockey lines, or whatever else is appropriate. For figure skating or speed skating, it may not be painted at all.

    4. Additional Layers: The ice is then built up to a total thickness of 1 inch (25.4 mm) in a series of layers about 1/8" thick (4 mm). The more layers which are used, the better quality the ice will be because thin layers suffer less from expansion problems while freezing.

All told, it takes about 12,000 gallons (45,000 Liters) of water to make enough ice for a regulation NHL hockey rink.

All the cooling for the ice is done with the chilled concrete layer. The concrete is chilled by pumping cold liquid through the pipes embedded in it. This liquid will be something with a lower freezing point than water, such as brine, so it remains liquid while freezing the water. The liquid is cooled with large compressors such as those found on a refrigerator or air conditioner, and the temperature is controlled to give the correct surface type for the ice's purpose. Hockey games require colder, harder ice, and figure skating requires warmer, softer ice to get the right amount of control from the skates. In warm weather, dehumidifiers may be necessary to prevent the creation of fog inside the arena as the warmer, moist air from outside meets the cold, dry air over the ice.

Walls

The edge of the ice rink will be surrounded with short, wooden, removable walls with gates built in to them. These walls help keep the cold air in and warm air out, keeping the ice insulated, but their primary purpose is to provide borders for the ice skating sports. Sliding across the ice isn't always the most controlled process, and the walls provide something to keep the skaters from running into the audience. For hockey games, the short wall will be extended with Plexiglas or tempered glass, which allows the fans to see into the rink but prevent the puck from flying into the stands. It also provides players something to body check each other into.

Surface Damage

Ice skating is the process of sliding sharpened steel blades over a smooth ice surface, which provides a very low-friction glide. Hockey and speed skating use three basic motions to move the skater forward. Forward motion is obtained by pushing the sharpened edge of the skate against the ice at an angle, which cuts into the ice and provides a surface to push off of. The glide happens as the sharpened edge of the skate slides along the ice in the direction of momentum. The action of the thin skate melts a bit of the ice into water, which lubricates the surface under the skate. The crossover is a technique of crossing one foot in front of the other in order to turn a corner as a series of small angles. Figure skaters additionally use the toe pick, a series of short spikes on the upward curve of the leading edge of the skate, to bite into the ice and make sudden changes in motion for jumps and spins. The "hockey stop" is a quick way to stop on the ice, which involves scraping the blade of the skate across the top of the ice using the skater's momentum. This shaves a thin layer of ice off the surface (which looks like, and is called, snow, although it isn't really), creating enough friction to stop the skater in a short distance.

All of these techniques damage the surface of the ice in some way. After a period of time, especially in a hockey game with several players making quick turns and hockey stops while chasing after the puck, the surface of the ice gets very rough. Skates don't traverse rough ice as well as smooth ice, so at regular intervals the ice needs to be resurfaced.

An ice resufacer, often called by the trade name Zamboni, is used to make the surface smooth again. The resurfacer performs several functions as it drives slowly across the ice rink. First it scrapes a thin layer of ice off the top to eliminate the rough spots by shaving them into "snow". Second it collects the snow so it doesn't litter the rink. Third, it applies a thin layer of hot water to the ice, which bonds with the ice to create a new, smooth surface. Finally, it squeegees and vacuums up excess water. The end result is a new, smooth skating surface left behind the machine.

When Not In Use

When not being used for skating, the ice can be covered so the arena can be used for other events such as conventions or basketball games. The cooling system remains in operation during these times so the ice remains frozen, it's just covered with plywood and insulating pads. For some events, or if the rink isn't going to be used in a while, it may be necessary to remove the ice entirely. Simply letting it melt would create a huge mess and take a very long time, so a different technique is used.

To remove the ice from the rink, first the operation of the compressor is reversed so it pumps hot liquid instead of cold liquid into the concrete pad under the ice. This softens and loosens up the ice, and breaks its seal with the concrete pad. The ice is then broken up and removed with front-end loaders or other heavy equipment. When the ice rink is ready to be used again, the ice has to be built up again layer by layer, and repainted.

Some information taken from http://www.howstuffworks.com, mostly the rink dimensions and supporting layers underneath the ice. The rest is from my experiences as a speed skater.

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