Editing Curling (section)

=== Sweeping ===
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[[File:Olympic Curling, Vancouver 2010 crop sweeping.jpg|thumb|The skip of Team Sweden joins the front end in sweeping a stone into the house at the [[2010 Winter Olympics]] in Vancouver]]

After the stone is delivered, its trajectory is influenced by the two sweepers under instruction from the skip. Sweeping is done for several reasons: to make the stone travel further, to decrease the amount of curl, and to clean debris from the stone's path.<ref>{{cite web |url=http://www.businessinsider.com/why-curlers-sweep-the-ice-2014-2 |title=Why Curlers Sweep the Ice |website=[[Business Insider]] |date=14 February 2014 |access-date=20 August 2017 |url-status=live |archive-url=https://web.archive.org/web/20170820010904/http://www.businessinsider.com/why-curlers-sweep-the-ice-2014-2 |archive-date=20 August 2017}}</ref> Sweeping is able to make the stone travel further and straighter by slightly melting the ice under the brooms, thus decreasing the friction as the stone travels across that part of the ice. The stones curl more as they slow down, so sweeping early in travel tends to increase distance as well as straighten the path, and sweeping after sideways motion is established can increase the sideways distance.

One of the basic technical aspects of curling is knowing when to sweep. When the ice in front of the stone is swept, a stone will usually travel both further and straighter, and in some situations one of those is not desirable. For example, a stone may be traveling too fast (said to have too much weight), but require sweeping to prevent curling into another stone. The team must decide which is better: getting by the other stone, but traveling too far, or hitting the stone.

Much of the yelling that goes on during a curling game is the skip and sweepers exchanging information about the stone's ''line'' and ''weight'' and deciding whether to sweep. The skip evaluates the path of the stone and calls to the sweepers to sweep as necessary to maintain the intended track. The sweepers themselves are responsible for judging the weight of the stone, ensuring that the length of travel is correct and communicating the weight of the stone back to the skip. Many teams use a ''[[Glossary of curling##s|number system]]'' to communicate in which of 10 zones the sweepers estimate the stone will stop. Some sweepers use stopwatches to time the stone from the back line or tee line to the nearest hog line to aid in estimating how far the stone will travel.

Usually, the two sweepers will be on opposite sides of the stone's path, although depending on which side the sweepers' strengths lie this may not always be the case. Speed and pressure are vital to sweeping. In gripping the broom, one hand should be one third of the way from the top (non-brush end) of the handle while the other hand should be one third of the way from the head of the broom. The angle of the broom to the ice should be such that the most force possible can be exerted on the ice.<ref>{{Cite journal|date=2009|title=The Sports Science of Curling: A Practical Review|journal=Medicine & Science in Sports & Exercise|volume=41|pages=3|doi=10.1249/01.mss.0000352606.48792.77|issn=0195-9131}}</ref> The precise amount of pressure may vary from relatively light brushing ("just cleaning" - to ensure debris will not alter the stone's path) to maximum-pressure scrubbing.

Sweeping is allowed anywhere on the ice up to the ''tee line''; once the leading edge of a stone crosses the tee line only one player may sweep it. Additionally, if a stone is behind the tee line one player from the opposing team is allowed to sweep it. This is the only case that a stone may be swept by an opposing team member. In international rules, this player must be the skip, but if the skip is throwing, then the sweeping player must be the third.