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Curling sheet

The playing surface or curling sheet is defined by the World Curling Federation Rules of Curling.  The sheet is an area of ice, carefully prepared to be as flat and level as possible, 146 to 150 feet (45 to 46 m) in length by 14.5 to 16.5 feet (4.4 to 5.0 m) in width.  Because of the elongated shape, several sheets may be laid out side by side in the same arena, allowing multiple games to be played simultaneously.

A target, the house, is marked at each end of the sheet.  The house consists of three concentric rings formed by painting or laying coloured vinyl sheet under the ice and are usually distinguished by colour.  These rings are defined by their diameters as the four-foot, eight-foot and 12-foot rings.  The rings are merely a visual aid for aiming and judging which stone is closer to the centre;  they do not affect scoring but a stone must at least touch the outer ring or it does not score.

Each house is centred on the intersection of the centre line, drawn lengthwise down the centre of the sheet and one of the tee lines, drawn 16 feet (4.9 m) from, and parallel to, each backboard.  These lines divide the houses into quarters.

The centre of each house, at the intersection of the centre line and the tee line, is known as the button.  Two hog lines, are drawn 37 feet (11 m) from, and parallel to, each backboard.

The hacks are fixed 12 feet behind each button; a hack gives the thrower something to push against when making the throw.  On indoor rinks, there are usually two fixed hacks, rubber-lined holes, one on each side of the centre line, with the inside edge no more than 3 inches (76 mm) from the centre line and the front edge on the hack line.  A single moveable hack may also be used.

A curling sheet, with dimensions – CL: Centreline • HOL: Hogline • TL: Teeline • BL: Backline • HA: Hackline with Hacks • FGZ: Free Guard Zone

The ice may be natural but is usually frozen by a refrigeration plant pumping a brine solution through numerous pipes fixed lengthwise at the bottom of a shallow pan of water.  Most curling clubs have an ice maker whose main job is to care for the ice.  At the major curling championships, ice maintenance is extremely important.  Large events, such as the Brier or other national/international championships, are typically held in an arena that presents a challenge to the ice maker, who must constantly monitor and adjust the ice and air temperatures as well as air humidity levels to ensure a consistent playing surface.  It is common for each sheet of ice to have multiple sensors embedded in order to monitor surface temperature, as well as probes set up in the seating area (to monitor humidity) and in the compressor room (to monitor brine supply and return temperatures).  The surface of the ice is maintained at a temperature of around 23°F (−5°C).

A key part of the preparation of the playing surface is the spraying of water droplets onto the ice, which form pebble on freezing.  The pebbled ice surface resembles an orange peel, and the stone moves on top of the pebbled ice.  As the stone moves over the pebble, any rotation of the stone causes it to curl to the inside or outside; the amount of curl (commonly referred to as the feet of curl) can change during a game as the pebble wears.  Due to this, the ice maker must also be aware of the pebble wear, and the ice will typically be scraped and re-pebbled prior to each game.

[edit]Curling Stone

The curling stone or rock is made of granite
An old-style curling stone

The curling stone (also sometimes rock, North America), as defined by the World Curling Federation is a thick stone disc weighing between 38 and 44 pounds (17 and 20 kg) with a handle attached to the top.  The maximum allowable circumference is 36 inches (910 mm).  The minimum height is 4.5 inches (110 mm).  The handle is attached by a bolt running vertically through a hole in the centre of the stone.  The handle allows the stone to be gripped and rotated upon release; on properly prepared ice, the stone's path will bend (curl) in the direction the front edge of the stone is turning, especially as the stone slows.  The handles are colored to identify the stones by team.  Two popular colors in major tournaments are red and yellow.  The only part of the stone in contact with the ice is the running surface, a narrow, flat annulus or ring, 0.25 to 0.50 inch (6.3 to 13 mm) wide and about 5 inches (130 mm) in diameter; the sides of the stone bulge convex down to the ring and the inside of the ring is hollowed concave to clear the ice.

Traditionally, curling stones were made from two specific types of granite called "Blue Hone" and "Ailsa Craig Common Green", found on Ailsa Craig, an island off the Ayrshire coast in Scotland.  Blue Hone has very low water absorption, which prevents the action of freezing and melting water from eroding the stone.  Ailsa Craig Common Green granite is a lesser quality granite than Blue Hone . In the past, most curling stones were made from Blue Hone; however, the island is now a wildlife reserve and the quarry has closed.  The second location where granite comes from to manufacture curling stones from is in Northern Wales.  This granite is called "Trefor" and comes in shades of blue/gray and red/brown.  The quarry in Wales that supplies the granite to its exclusive curling stone manufacturing company in Canada, Canada Curling Stone Co., is a full and active quarry and it is not anticipated to ever run out of this granite for making curling stones.  Canada Curling Stone Co. has been manufacturing curling stones since 1992.  The cost of new Trefor granite curling stones is about Canadian $600 a stone.

Kays of Scotland has been making curling stones since 1851 and has the exclusive rights to Ailsa Craig granite, granted by the Marquess of Ailsa, whose family has owned the island since 1560.  The last "harvest" of Ailsa Craig granite by Kays took place in 2001.  Kays have said that they harvested 1,500 tons, sufficient to fill anticipated orders through at least 2020.  Kays has been the exclusive manufacturer of curling stones for all three Olympics where curling has been a medal sport.

In competition, an electronic handle known as the eye on the hog may be fitted to detect hog line violations, the game's most frequent cause of controversy.  This electronically detects whether the thrower's hand is in contact with the handle as it passes the hog line and indicates a violation by lights at the base of the handle.  The eye on the hog eliminates human error and the need for hog line officials.  It is mandatory in high-level national and international competition but its cost, around US $650 each, currently puts it beyond the reach of most social curling.

Curling broom

[edit]Curling broom

The curling broom, or brush, is used to sweep the ice surface in the path of the stone and is also often used as a balancing aid during delivery of the stone.

In earlier days, brooms were made of corn strands and were similar to household brooms.  Brushes were used primarily by elderly curlers as a substitute for corn brooms.  Today, brushes have replaced traditional corn brooms at every level of curling but are universally referred to as brooms.  Curling brushes may have fabric, hog hair, or horsehair heads.  Modern curling broomsticks are usually hollow tubes made of fiberglass or carbon fiber instead of a solid length of wooden dowel.  These hollow tube handles are lighter and stronger than wooden handles, allowing faster sweeping and also enabling more downward force to be applied to the broom head with reduced shaft flex.


Curling shoes, showing a slider sole

Curling shoes are similar to ordinary athletic shoes except that they have dissimilar soles; the slider shoe is designed for the off foot (or sliding foot) and the non-sliding shoe for the hack foot.

The slider shoe is designed to slide and typically has a Teflon sole.  It is worn by the thrower during delivery from the hack and by sweepers or the skip to glide down the ice when sweeping or otherwise traveling down the sheet quickly.  Stainless steel was once common for slider soles, and "red brick" sliders with lateral blocks of PVC on the sole are also available.  Most shoes have a full-sole sliding surface, but some shoes have a sliding surface covering only the outline of the shoe and other enhancements with the full-sole slider.  Some shoes have small disc sliders covering the front and heel portions or only the front portion of the foot, which allow more flexibility in the sliding foot for curlers playing with tuck deliveries.  When a player is not throwing, the player's slider shoe can be temporarily rendered non-slippery by using a slip-on gripper.  Ordinary athletic shoes may be converted to sliders by using a step-on or slip-on Teflon slider or by applying electrical or gaffer tape directly to the sole or over a piece of cardboard.  This arrangement often suits casual or beginning players.

The non-sliding shoe, or hack foot shoe, is worn by the thrower on the hack foot during delivery and is designed to grip.  It may have a normal athletic shoe sole or a special layer of rubbery material applied to the sole of a thickness to match the sliding shoe.  The toe of the hack foot shoe may also have a rubberized coating on the top surface or a flap that hangs over the toe to reduce wear on the top of the shoe as it drags on the ice behind the thrower.

[edit]Other equipment

Other types of equipment include:

  • Curling pants, made to be stretchy to accommodate the curling delivery.
  • A stopwatch to time the stones while sweeping to get a feel of the speed of the stone.  Stopwatches can be attached either to clothing or the broom itself.
  • Curling gloves and mittens, to keep the hands warm and improve grip on the broom.
Information provided by: Wikipedia