What is Curling?
Curling is a sport played on a sheet of ice, called a curling rink, using granite stones. Two competing teams take turns delivering stones from one end of the sheet towards a target at the far end, called the house. The goal is to have one or more of your team's stones closer to the center of the house than those of your opponent.
The game is divided into eight or ten ends, or innings. In each end, each team delivers eight stones. After all sixteen stones have been delivered, the team with stones closer to the center of the house scores points; only one team can score in any given end.
A variety of shots can be used for strategic and tactical advantage. In some cases, teams will deliver a stone so that it comes to rest in a strategically advantageous position; this kind of shot is called a draw. In other cases, teams will attempt to remove the other team's stones by hitting them; this is called a takeout.
Curling stones are delivered with a slight spin, causing the stone's trajectory to curl (curve) as it travels along the ice. This is the origin of the name "curling".
The Curling Rink
The playing surface of a curling rink is ice, specially prepared to have a bumpy pebbled surface by spraying the ice with drops of water. The pebbling allows the stones to travel much farther than on a smooth ice surface.
A curling rink may have one or more sheets, the playing area on which a game is played. A regulation curling sheet is 138 feet long and approximately 14 feet wide.
The main features of a curling sheet include:
- the house at each end of the sheet, a 12-foot-wide circle that indicates the scoring zone (stones must be within the house at the conclusion of each end to be eligible for scoring)
- the hack at each end of the sheet, a step that is frozen into or on top of the ice; players push off the hack when delivering a stone
- the tee line, a line that crosses the sheet laterally through the center of each house
- the hog line, a line that crosses the sheet laterally 21 feet from the tee line
When delivering a stone from one end of the sheet, the player must fully release the stone before crossing the near hog line; in addition, the stone must come to rest between the far hog line and the back of the house in order to remain in play. The stone may not contact the sides of the sheet.
The house is divided into concentric rings, 4, 8, and 12 feet in diameter. The various rings are simply indicators to help determine which stones are closer to the center of the house; the rings themselves do not determine scoring.
A small one-foot-wide ring at the very center of each house is called the button.
The Curling Stone
The curling stone originated in Scotland from large chunks of rock, bowled across the ice, none having any particular size or shape. They evolved into what are now matched sets of uniformly-made stones. They are all made of pure granite, and they are amazingly hard. The best stones come from a single granite mine on an island off the coast of Scotland. Shipping is quite expensive due to weight (16 stones in a set, at 42 pounds apiece, not including packaging), and manufacturing is expensive because the tough granite must be ground with diamonds. Hence, sets of curling stones are usually owned by curling clubs and not by individuals.
The stone is concave on both the upper and lower surfaces. On some stones, the degree of concavity is different on each side, to allow for reversing the stone for "faster" or "slower" ice. A handle, usually affixed to a circular plastic disc, is bolted onto the stone through a channel in the middle of the stone, as shown in the red highlighted region in the cross-sectional diagram.
In the figure above, diagram A shows the bottom of a curling stone. The red circle indicates the actual running surface of the stone. Since the surface area that actually comes into contact with the ice is small, the stone can travel farther than would be possible with a flat surface.
There is a lighter-colored band in a ribbon around the curling stone. This is the "striking surface". In manufacturing, the entire stone is very highly polished. The striking surface is dulled down for the purpose of improving the effect of collisions with other stones; not only will there be a larger contact patch in the collision, but also, the stones will be less likely to chip.
Delivery of the Stone
A curling stone is delivered in what might be described as a cross between a bowling motion and a forward dive. It is a motion that is unique to the sport of curling, requiring both balance and touch; as such, it takes a little bit of practice to master.
Delivery of the stone starts by getting positioned in the hack, a block frozen into or onto the ice. Then, while leaving the stone on the ice, the curler draws the stone backwards slightly, shifting their weight into a partial standing position.
The player gives the stone momentum by pushing strongly with one leg (the right leg for a right-handed delivery) out of the hack. That leg ends up trailing behind the player; the front leg is bent and carries most of the player's weight. The player holds a broom under one arm (the left arm for a right-handed delivery) to help maintain balance.
Good curlers will slide along with the stone for several seconds, adjusting aim and calculating the correct release speed along the way. Note, however, that the longer the stone is held, the more speed is lost due to drag from the player's body. The player assumes a low, stretched pose that not only improves balance, but also helps get a better look at the stone's trajectory relative to the aiming point.
Upon release, the player puts a gentle spin on the stone, causing it to curl as it travels down the ice. The player must fully release the stone before reaching the nearest hog line (see "The Curling Rink", above). Once the stone is released, the player may not touch it again.
A curling team consists of four players. The four players each deliver two stones, in a set order.
- The lead is the player who delivers stones first on the team.
- The second is the player who delivers stones second on the team.
- The vice-skip, or third, helps determine team strategy, and delivers stones third on the team.
- The skip is essentially the team captain, usually the most experienced and skilled person on the team. The skip is responsible for calling shots and dictating the team's strategy. When other players are delivering their stones, the skip stands at the far end of the ice near the house, and holds a broom to indicate the aiming point. The skip is last to deliver stones.
When the lead, second, or vice-skip are delivering their stones, the skip calls the shot and holds the broom as an aiming point for the stone's release. The two other players sweep the ice to control its trajectory and speed (see "Sweeping", below), with direction from the skip. When the skip is delivering stones, the vice-skip is responsible for holding the broom and directing the sweepers, acting temporarily as the skip.
The reason that the skip throws last is because the later stones are more critical for scoring, and often require making more difficult shots.
Shots and Strategy
Curling is a highly strategic game. Although it superficially resembles bocce or shuffleboard, the complexity of the strategy makes some call it "chess on ice".
Each team attempts to deliver its own stones to the house, closer to the button than any of its opponents stones, and maintain that advantage while the opposing team does the same. However, this is not a simple matter of aiming for the center of the house with every shot. Teams will frequently play guards, which are stones delivered in front of the house, in order to protect stones that may score points. Opposing teams will counter guards by either curling around them, or by hitting them to take them out. In some cases, guards are placed so that future stones may be placed behind them. The fact that the stones curl as the travel is what enables teams to play to areas behind guards.
Here are a few of the most common types of curling shots.
The draw shot is the most-frequently employed shot in curling. It involves delivering the stone down the sheet, at the right trajectory and speed, such that it comes to rest in the desired location. The stone does not contact any other stones along the way. The team can help influence the stone's location by sweeping the ice (see "Sweeping", below).
In this diagram, the green stone is taken out by the yellow stone. The yellow continues on, maintaining most of its momentum (takeouts are thrown harder than draws), while also knocking the green stone out of play. It is possible, and sometimes desirable, to keep the delivered stone (the yellow stone) in play; typically, though, the primary object is to remove the other team's stone.
A guard is a type of draw show. As its name implies, is a stone that is placed in front of another, to prevent a takeout. Its primary purpose is not to score points, but to provide tactical advantage. In this diagram, two green stones and three yellow stones have already been played. To protect stone A, the yellow team has put up a guard, stone B, immediately in front of A. This helps prevent a takeout by stone C.
There are a variety of other, more difficult, specialty shots:
- A raise involves multiple collisions between stones. In some cases, teams attempt to counter a guard by hitting it directly backwards onto the stone it is guarding; this is known as a "raise takeout".
- A freeze involves playing a draw such that the delivered stone comes to rest immediately in front of a stone already in play. A "frozen" stone is difficult to remove, because attempts to take it out would more likely result in the stone behind it being taken out instead, while the frozen stone remains stationary.
- A wick involves playing a shot such that it barely contacts another stone, enough to change the delivered stone's trajectory towards the desired target. (This rarely happens on purpose!)
Sweeping is a critical part of curling. Newcomers to the game are generally aware of (and amused by) the frantic sweeping that goes on during a match, but aren't exactly sure of the purpose.
Sweeping is used to make a stone travel farther and straighter that it ordinarily would. Sweeping the ice in front of the stone has three effects:
- it smooths and polishes the pebble of the ice
- it removes frost and debris from the ice (especially in outdoor curling)
- it momentarily warms the ice, allowing the pressure of the stone against the ice to generate a thin film of water; the water acts as a lubricant
All these effects combine to reduce friction between the stone and the ice. This not only makes the stone travel farther down the ice, but it also reduces the curling effect caused by the stone's spin.
Good sweepers can have a large impact on the stone's final position, changing the distance traveled by ten feet or more, and changing the trajectory by several inches.
The skip directs the sweepers by voice, calling "sweep!" or "yes!" when sweeping is needed, or "up!" or "whoa!" if sweeping is not desired. There are many variations of these voice signals, including "hurry" or "hurry hard" when more intense sweeping is required, or "clean" if the only concern is to remove debris that might interfere with the shot.
Sweeping is the most vigorous activity in curling. Sweeping works arm and shoulder muscles, as well as muscles of the upper and inner thighs.
Game Play and Scoring
Each player delivers two stones in each end, alternately with their counterpart on the opposing team. In total, sixteen stones are played in each end.
Once all sixteen stones have been played, the two teams' vice-skips must agree on how the end is to be scored. Only one team can score points in an end; to score, a team must have stones within the house and closer to the button than any of its opponent's stones. Each stone that meets these criteria is worth one point. In theory, it is possible to score up to eight points in an end; in practice, an "eight-ender" is rarer than a hole-in-one in golf.
If there are no stones in the house, then neither team scores; this is called a blank end.
If a team scores a point in one end, then that team throws first in the succeeding end. The other team has last rock (also known as the hammer); this is strategically advantageous. If the end is blanked, then the same team retains last rock in the succeeding end.
A full game consists of ten ends (in standard tournament play). Casual games may be eight ends or less, or may be dictated by time constraints. Each end requires about fifteen minutes to play, so a typical game lasts from 2 to 2.5 hours.
The team with the most points at the end of the game is the winner!