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97-468: Playoffs Playoffs Playoffs This curling -related article is a stub . You can help Misplaced Pages by expanding it . Curling Curling is a sport in which players slide stones on a sheet of ice toward a target area that is segmented into four concentric circles. It is related to bowls , boules , and shuffleboard . Two teams, each with four players, take turns sliding heavy, polished granite stones, also called rocks , across

194-444: A ball's motion throughout its skid, hook and roll phases. The particular way in which energy is imparted to a ball—with varying proportions of that energy divided among ball speed, axis control and rev rate—determines the ball's motion. The following discussion considers delivery characteristics separately, with the understanding that ball motion is determined by a complex interaction of a variety of factors. Greater ball speeds give

291-502: A bowling ball core is symmetrical or asymmetrical. Analytically, ID is defined by the USBC as the "difference in radius of gyration between the Y (high RG) and Z (intermediate RG) axes". In practice, a higher ID indicates greater asymmetry, which causes more area to be created at the break point to cause the ball to respond more quickly to friction than symmetrical balls. Informally, a low-differential ball has been likened to one whose core

388-472: A bowling ball's core, include radius of gyration (RG), differential of RG (commonly abbreviated differential ), and intermediate differential (also called mass bias ). Analytically, the United States Bowling Congress defines RG as "the distance from the axis of rotation at which the total mass of a body might be concentrated without changing its moment of inertia ". In practice,

485-444: A curved path, described as curl , by causing the stone to slowly rotate as it slides. The path of the rock may be further influenced by two sweepers with brooms or brushes, who accompany it as it slides down the sheet and sweep the ice in front of the stone. "Sweeping a rock" decreases the friction, which makes the stone travel a straighter path (with less curl) and a longer distance. A great deal of strategy and teamwork go into choosing

582-435: A fingertip grip. Finger inserts enhance the torque provided by the fingers after the thumb exits the ball. A complex interaction of a variety of factors influences ball motion and its effect on scoring results. The factors may be categorized as the bowler's delivery, the bowling ball's design, and the condition of the lane. Bowling ball motion is commonly broken down into sequential skid, hook, and roll phases. As

679-423: A foreign object is called a pick-up or pick . The thrower starts from the hack . The thrower's gripper shoe (with the non-slippery sole) is positioned against one of the hacks; for a right-handed curler the right foot is placed against the left hack and vice versa for a left-hander. The thrower, now in the hack , lines the body up with shoulders square to the skip's broom at the far end for line . The stone

776-485: A higher RG indicates that a ball's mass is distributed more toward its cover—making it "cover heavy"—which tends to make the ball enter the roll phase later (further down the lane). Conversely, a lower RG indicates the ball's mass is distributed more towards its center—making it "center heavy"—which tends to make it enter the roll phase sooner. Differential of RG is the difference between maximum and minimum RGs measured with respect to different axes. Differential indicates

873-433: A list, said to be updated weekly, of about 100 bowling ball manufacturers and their approved bowling balls. Duckpin bowling balls are regulated to be from 4.75–5.00 inches (12.1–12.7 cm) in diameter and to weigh between 3 pounds 6 ounces (1.5 kg) and 3 pounds 12 ounces (1.7 kg). They lack finger holes. Though duckpin balls are slightly larger than candlepin balls, they have less than 60%

970-568: A member of the Duddingston Curling Club, who wrote An Account of the Game of Curling in 1811, which speculates on its origin and explains the method of play. In the early history of curling, the playing stones were simply flat-bottomed stones from rivers or fields, which lacked a handle and were of inconsistent size, shape, and smoothness. Some early stones had holes for a finger and the thumb, akin to ten-pin bowling balls . Unlike today,

1067-621: A minimal threshold of flare exists to present a "dry" surface for successive ball revolutions. Similarly, though manufacturer literature often describes specific core shapes, differently-shaped cores can make exactly the same contribution to ball motion if they have the same overall RG characteristics. "Weak" layouts ("pin down": pin between finger and thumb holes) hook sooner but have milder backend reaction, while "strong" layouts ("pin up": pin further from thumb hole than finger holes) enable greater skid lengths and more angular backend reaction. Manufacturers commonly cite specifications relating to

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1164-411: 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 gripper is worn by the thrower on

1261-431: A sharper hook. Another source states that strictly behind-the-ball release (0° axis rotation) causes an end-over-end rotation, with early hooking, while a release with large side rotation causes greater length before hooking. Greater degrees of initial (at-the-foul-line) axis tilt cause the ball to rotate on smaller-circumference "tracks" (rings on the ball at which it contacts the lane on each revolution), thus reducing

1358-401: A violation by lights at the base of the handle (see delivery below). 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 curling clubs. The curling broom , or brush , is used to sweep the ice surface in the path of

1455-434: Is a rectangular 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. The shorter borders of the sheet are called the backboards. A target, the house , is centred on the intersection of the centre line , drawn lengthwise down the centre of the sheet and the tee line , drawn 16 feet (4.9 m) from, and parallel to,

1552-820: Is a spherical object (whose height and width are the same); a high-differential ball has been likened to a tall drinking glass (whose height and width are different); and a high-mass-bias ball has been likened to a tall drinking mug with a handle on the side (which has different widths in different directions). Higher-friction surfaces (lower grit numbers) cause balls to hook earlier, and lower-friction surfaces (higher grit numbers) cause balls to skid longer before reacting (hooking). Reactive cover stocks finishes include matte (aggressive reaction), shiny (longer skid distance than matte finish), pearl (greatest skid distance among reactive cover stocks), and hybrid (combination of skid distance and back end reaction). The phenomenon of lane transition occurs when balls remove oil from

1649-533: Is chemical friction—controlled by the manufacturer's proprietary coverstock formulation governing its "stickiness"—that primarily determines ball motion. Further, surface finish—modifiable by sandpaper, polish and the like—is also a material factor. Though manufacturer literature often specifies track flare —exhibited by successive tracks of oil in a "bowtie" pattern and caused by RG differential—the USBC ball motion study showed flare's influence to be small, assuming that

1746-416: Is closer to the button. Two hog lines are drawn 37 feet (11 m) from, and parallel to, the backboard. The hacks , which give the thrower something to push against when making the throw, are fixed 12 feet (3.7 m) behind each button. 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

1843-423: Is commonly used to enforce this rule. The sensor is in the handle of the stone and will indicate whether the stone was released before the near hog line. The lights on the stone handle will either light up green, indicating that the stone has been legally thrown, or red, in which case the illegally thrown stone will be immediately pulled from play instead of waiting for the stone to come to rest. The stone must clear

1940-439: Is designed for the sliding foot and the "gripper shoe" (usually known as a gripper ) for the foot that kicks off from the hack. The slider 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 and "red brick" sliders with lateral blocks of PVC on

2037-435: Is extremely important. Large events, such as 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

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2134-645: Is home to the international governing body for curling, the World Curling Federation in Perth , which originated as a committee of the Royal Caledonian Curling Club, the mother club of curling. In the 19th century, several private railway stations in the United Kingdom were built to serve curlers attending bonspiels , such as those at Aboyne , Carsbreck , and Drummuir . Today, the sport

2231-923: Is influenced by the oil absorption characteristics and rev rates of the balls that were previously rolled, and carry down is mitigated by modern balls having substantial track flare. Lane materials with softer surfaces such as wood engage the ball with more friction and thus provide more hook potential, while harder surfaces like synthetic compositions provide less friction and thus provide less hook potential. Higher- viscosity lane oils (those with thicker consistency) engage balls with more friction and thus cause slower speeds and shorter length but provide more hook potential and reduced lane transition; conversely, lane oils of lower viscosity (thinner consistency) are more slippery and thus support greater speeds and length but offer less hook potential and allow faster lane transition. Various factors influence an oil's native viscosity, including temperature (with higher temperatures causing

2328-403: Is maximized; however, this optimum axis rotation also causes minimal length. Specifically, Freeman & Hatfield (2018) report optimal axis rotation to be arcsin   (ωr/v) where ω is rev rate (radians/sec), r is ball radius (m), and v is ball speed (m/s). Below and above optimal axis rotation, more length and less hook are encountered, with greater-than-optimal axis rotation causing

2425-571: Is most firmly established in Canada , having been taken there by Scottish emigrants . The Royal Montreal Curling Club , the oldest established sports club still active in North America , was established in 1807. The first curling club in the United States was established in 1830, and the sport was introduced to Switzerland and Sweden before the end of the 19th century, also by Scots. Today, curling

2522-407: Is placed in front of the foot now in the hack. Rising slightly from the hack, the thrower pulls the stone back (some older curlers may actually raise the stone in this backward movement) then lunges smoothly out from the hack pushing the stone ahead while the slider foot is moved in front of the gripper foot, which trails behind. The thrust from this lunge determines the weight , and hence the distance

2619-560: Is played all over Europe and has spread to Brazil, Japan, Australia, New Zealand, China, and Korea. The first world championship for curling was limited to men and was known as the Scotch Cup , held in Falkirk and Edinburgh , Scotland , in 1959. The first world title was won by the Canadian team from Regina, Saskatchewan , skipped by Ernie Richardson . (The skip is the team member who calls

2716-407: Is rare now to see a curler using a corn broom on a regular basis. Curling brushes may have fabric, hog hair, or horsehair heads. Modern curling brush handles are usually hollow tubes made of fibreglass or carbon fibre instead of a solid length of wooden dowel . These hollow tube handles are lighter and stronger than wooden handles, allowing faster sweeping and more downward force to be applied to

2813-511: The Low Countries had strong trading and cultural links during this period, which is also evident in the history of golf . The word curling first appears in print in 1620 in Perth, Scotland , in the preface and the verses of a poem by Henry Adamson . The sport was (and still is, in Scotland and Scottish-settled regions like southern New Zealand) also known as "the roaring game" because of

2910-570: The Rink Rat , also became common later during this time period. Prior to the late sixties, Scottish curling brushes were used primarily by some of the Scots , as well as by recreational and elderly curlers, as a substitute for corn brooms, since the technique was easier to learn. In the late sixties, competitive curlers from Calgary , Alberta, such as John Mayer, Bruce Stewart, and, later, the world junior championship teams skipped by Paul Gowsell , proved that

3007-473: The first Olympic medals in curling , which at the time was played outdoors, were retroactively awarded for the 1924 Winter Games, with the gold medal won by Great Britain, two silver medals by Sweden, and the bronze by France. A demonstration tournament was also held during the 1932 Winter Olympic Games between four teams from Canada and four from the United States, with Canada winning 12 games to 4. Since

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3104-496: The lead ) throws, the players not delivering (the second and third ) sweep (see Sweeping , below). When the skip throws, the vice-skip takes their role. The skip , or the captain of the team, determines the desired stone placement and the required weight , turn , and line that will allow the stone to stop there. The placement will be influenced by the tactics at this point in the game, which may involve taking out, blocking, or tapping another stone. The skip may communicate

3201-418: The weight , turn , line, and other tactics by calling or tapping a broom on the ice. In the case of a takeout, guard, or a tap, the skip will indicate the stones involved. Before delivery, the running surface of the stone is wiped clean and the path across the ice swept with the broom if necessary, since any dirt on the bottom of a stone or in its path can alter the trajectory and ruin the shot. Intrusion by

3298-402: The "particle-enhanced" balls developed in the late 1990s, microscopic particles embedded in reactive coverstocks reach through oil lane coatings to provide even greater traction. Ball manufacturers developed closely guarded proprietary blends including ground-up material such as glass, ceramic or rubber, to enhance friction. Within the reactive category are solid reactive coverstocks (having

3395-469: The "thinking time" system, in which the delivering team's game timer stops as soon as the shooter's rock crosses the t-line during the delivery, is becoming more popular, especially in Canada. This system allows each team 38 minutes per 10 ends, or 30 minutes per 8 ends, to make strategic and tactical decisions, with 4 minutes and 30 seconds an end for extra ends. The "thinking time" system was implemented after it

3492-499: The 2 lb 8 oz (1.1 kg) candlepins themselves. American nine-pin bowling uses the same ball (and pins) as in ten-pin bowling. European nine-pin bowling balls (such as those used in German kegel ) are smaller, sized between ten-pin and duckpin balls, and have no holes. The ball is 16 cm (6.3 in) in diameter and weighs approximately 2.85 kg (6.3 lb). There are also special balls for novice players, which

3589-611: The August 1, 2020 rule change. Bowling balls were made of lignum vitae (hardwood) until the 1905 introduction of rubber balls. Polyester ("plastic") balls were introduced in 1959 and, despite developing less hook-generating lane friction than rubber balls, by the 1970s plastic dominated over rubber balls. Briefly, "soaker" ball technology—involving softening coverstocks to achieve greater hook—were used, until rules for minimum hardness were implemented. The early-1980s development of polyurethane ("urethane") balls developed more friction with

3686-471: The Canada Curling Stone Company, which has been producing stones since 1992 and supplied the stones for the 2002 Winter Olympics . A 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 rotation will bend ( curl ) the path of the stone in the direction in which

3783-727: The Winter Olympics since Chamonix in 1924 and has been the exclusive manufacturer of curling stones for the Olympics since the 2006 Winter Olympics . Trefor granite comes from the Yr Eifl or Trefor Granite Quarry in the village of Trefor on the north coast of the Llŷn Peninsula in Gwynedd , Wales and has produced granite since 1850. Trefor granite comes in shades of pink, blue, and grey. The quarry supplies curling stone granite exclusively to

3880-467: The action of repeatedly freezing water from eroding the stone. Ailsa Craig Common Green is a lesser quality granite than Blue Hone . In the past, most curling stones were made from Blue Hone , but the island is now a wildlife reserve, and the quarry is restricted by environmental conditions that exclude blasting. Kays of Scotland has been making curling stones in Mauchline, Ayrshire, since 1851 and has

3977-436: The amount of frictional contact to provide greater length and less hook; conversely, smaller degrees of axis tilt involve larger-circumference tracks with more frictional contact per revolution, thus providing less length and more hook. Loft—the distance past the foul line at which the ball first contacts the lane—determines the effective length of the lane as experienced by the ball: greater loft distances effectively shorten

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4074-478: The angle of axis rotation until it exactly matches the direction of the ball's forward motion, and rev rate (rotational speed) increases until it exactly matches the ball's forward speed: full traction is achieved and the ball enters the roll phase in which forward speed continues to decrease. Release ratio denotes the ratio of the ball's forward (translational) speed to its rev rate (rotational speed) at time of release. This ratio continually decreases throughout

4171-444: The backboard. These lines divide the house into quarters. The house consists of a centre circle (the button ) and three concentric rings, of diameters 4, 8, and 12 feet, formed by painting or laying a coloured vinyl sheet under the ice and are usually distinguished by colour. A stone must at least touch the outer ring in order to score (see Scoring below); otherwise, the rings are merely a visual aid for aiming and judging which stone

4268-403: The ball less time to hook, thus reducing observed hook though imparting more kinetic energy to the pins; conversely, slower speeds allow more time for greater hook though reducing kinetic energy. Greater rev rates cause the ball to experience more frictional lane contact per revolution and thus (assuming non-zero axis rotation) greater and earlier hook (less "length"— which is the distance from

4365-506: The ball design factors that most contributed to ball motion were the microscopic "spikes" and pores on the ball's surface (considered part of chemical frictional characteristics), the respective coefficients of friction between ball and lane in the oiled and dry parts of the lane, and the ball's oil absorption rate, followed in dominance by certain characteristics of the ball's core (mainly radius of gyration, and total differential). Freeman and Hatfield (2018) explain that in most circumstances it

4462-440: The ball to enter the roll phase before reaching the pins, sacrificing power to friction that would ideally be delivered to the pins to enhance pin scatter . Ball speed and rev rate are said to be matched if the ball enters the roll phase immediately before impacting the pins, maximizing power imparted to the pins yet helping to provide an entry angle that minimizes ball deflection. Various characteristics of ball delivery affect

4559-486: The ball travels down the lane in the skid and hook phases, frictional contact with the lane causes the ball's forward ( translational ) speed to continually decrease, but to continually increase its rev rate ( rotational speed). Especially as the ball encounters greater friction in the last ≈20 feet (approximate) of the lane, the ball's axis rotation (side rotation) causes the ball to hook away from its original direction. Concurrently, lane friction continually decreases

4656-399: The ball's internal structure—especially the density, shape (symmetric vs. asymmetric), and orientation of its core (also called "weight block") relative to the ball's axis of rotation—substantially affect ball motion. A "dull" (rough) ball surface, having spikes and pores, provides greater friction in the oil-covered front end of the lane but reduced frictional contact in the dry back end of

4753-415: The ball's track flare potential, and contributes to how sharply a ball can hook . A higher differential indicates greater track flare potential—more angular motion from the break point to the pocket—and a lower differential indicates lower flare potential and a smoother arc to the hook. The lesser-used intermediate differential rating (sometimes termed mass bias rating) quantifies the degree to which

4850-426: The ball's travel until it reaches exactly 1.0 when full traction is achieved upon entering the roll phase. A too- high release ratio, also known as a speed-dominant release, causes the ball to reach the pins while still in the hook phase, resulting in a shallow angle of entry that permits ball deflection and resultant leaves of the 10-pin, while a too- low release ratio, also called a rev-dominant release, causes

4947-427: The balls have no finger holes. Candlepin bowling balls have a weight of between 2 lb 4 oz (1.0 kg) and 2 lb 7 oz (1.1 kg), and a diameter of 4.5 in (11 cm)—much smaller than the 8.5 in (22 cm) balls in ten-pin bowling, and even smaller than the 5.0 in (13 cm) balls in duckpin bowling . Candlepin balls deflect significantly upon impact, being even lighter than

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5044-408: 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

5141-421: The broom head with reduced shaft flex. In 2014, new "directional fabric" brooms were introduced, which could influence the path of a curling stone better than the existing brooms. Concerns arose that these brooms would alter the fundamentals of the sport by reducing the level of skill required and giving players an unfair advantage; at least thirty-four elite teams signed a statement pledging not to use them. This

5238-402: The centre line and the front edge on the hack line. A single moveable hack may also be used. 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

5335-453: The curling brush could be just as (or more) effective without all the blisters common to corn broom use. During that time period, there was much debate in competitive curling circles as to which sweeping device was more effective: brush or broom. Eventually, the brush won out with the majority of curlers making the switch to the less costly and more efficient brush. Today, brushes have replaced traditional corn brooms at every level of curling; it

5432-435: The diameter of ten-pin balls, to match the smaller size of duckpins. Duckpin balls are sometimes used for scaled-down ten-pin bowling lanes installed in arcades and other amusement facilities . The basic specifications of five-pin balls are the same a duckpin balls: diameters from 4.75 to 5.0 in (12.1 to 12.7 cm), weights from 3 pounds 6 ounces (1.5 kg) to 3 pounds 12 ounces (1.7 kg);

5529-585: The exclusive rights to the Ailsa Craig granite, granted by the Marquess of Ailsa , whose family has owned the island since 1560. According to the 1881 Census , Andrew Kay employed 30 people in his curling stone factory in Mauchline. The last harvest of Ailsa Craig granite by Kays took place in 2013, after a hiatus of 11 years; 2,000 tons were harvested, sufficient to fill anticipated orders through at least 2020. Kays have been involved in providing curling stones for

5626-440: The far hog line or else be removed from play ( hogged ); an exception is made if a stone fails to come to rest beyond the far hog line after rebounding from a stone in play just past the hog line. 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

5723-413: The foot that kicks off from the hack during delivery and is designed to grip the ice. 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 rubberised 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

5820-424: The foul line to the breakpoint at which hooking is maximum); conversely, smaller rev rates cause less frictional engagement and allow the ball to hook less and later (more "length"). Analysis of the influence of axis rotation (sometimes called side rotation ) is more complex: There is a degree of axis rotation—generally 25° to 35° and varying with ball speed and rev rate—that may be considered optimal in that hook

5917-505: The front edge of the stone is turning, especially as the stone slows. Handles are coloured to identify each team, two popular colours in major tournaments being red and yellow. In competition, an electronic handle known as the Eye on the Hog may be fitted to detect hog line violations. This electronically detects whether the thrower's hand is in contact with the handle as it passes the hog line and indicates

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6014-442: The games only eight ends. Most tournaments on that tour are eight ends, as are the vast majority of recreational games. In international competition, each side is given 73 minutes to complete all of its throws. Each team is also allowed two minute-long timeouts per 10-end game. If extra ends are required, each team is allowed 10 minutes of playing time to complete its throws and one added 60-second timeout for each extra end. However,

6111-551: The greatest amount of microscopic pores), pearl reactive coverstocks (including mica additives that enhance reaction on dry lane surfaces), hybrid reactive coverstocks (combining the mid-lane reaction of solid coverstocks and the back-end reaction of pearl coverstocks), and particle coverstocks (including microscopic silica particles, favored for use on heavy oil volumes). Hook potential has increased so much that dry lane conditions or certain spare shots sometimes cause bowlers to use plastic or urethane balls, to purposely avoid

6208-451: The heavy stone weights from the looms' warp beams , fitted with a detachable handle for the purpose. Central Canadian curlers often used 'irons' rather than stones until the early 1900s; Canada is the only country known to have done so, while others experimented with wood or ice-filled tins. Outdoor curling was very popular in Scotland between the 16th and 19th centuries because the climate provided good ice conditions every winter. Scotland

6305-447: The ice curling sheet toward the house , a circular target marked on the ice. Each team has eight stones, with each player throwing two. The purpose is to accumulate the highest score for a game ; points are scored for the stones resting closest to the centre of the house at the conclusion of each end , which is completed when both teams have thrown all of their stones once. A game usually consists of eight or ten ends. Players induce

6402-479: The ideal path and placement of a stone for each situation, and the skills of the curlers determine the degree to which the stone will achieve the desired result. Evidence that curling existed in Scotland in the early 16th century includes a curling stone inscribed with the date 1511 found (along with another bearing the date 1551) when an old pond was drained at Dunblane, Scotland . The world's oldest curling stone and

6499-466: The lane and provide greater length, while smaller loft distances engage the lane earlier and cause an earlier hook. Various characteristics of ball core structure and coverstock composition affect a ball's motion throughout its skid, hook and roll phases. Such motion is largely (about 75%) governed by the lane's frictional interaction with the ball, which exhibits both chemical friction characteristics and physical friction characteristics. Also,

6596-663: The lane as they pass, and deposit some of that oil on originally dry parts of the lane. The process of oil removal, commonly called breakdown, forms dry paths that subsequently cause balls to experience increased friction and to hook sooner. Conversely, the process of oil deposition, commonly called carry down, occurs when balls form oil tracks in formerly dry areas, tracks that subsequently cause balls to experience less friction and delayed hook. Balls tend to "roll out" (hook sooner but hook less) in response to breakdown, and, conversely, tend to skid longer (and hook later) in response to carry down—both resulting in light hits. Breakdown

6693-460: The lane, and thus enables an earlier hook. In contrast, a "gloss" (smooth) ball surface tends to glide atop oil on the front end but establishes greater frictional contact in the dry back end, thus promoting a sharper hook downlane, such as in the " skid/flip " ball path. Accordingly, because different lane conditions and bowler styles favor different hook profiles, there is no single "best" surface. A 2005-2008 USBC Ball Motion Study found that

6790-450: The larger hook provided by reactive technology. See also: § Effect of coverstock, core and layout on ball motion A ball's drilling layout refers to how and where holes are drilled, in relation to the ball's locator pin and mass bias (MB) marker. Layout is determined with reference to each bowler's positive axis point (PAP ‍ — the pocket end of the ball's initial axis of rotation). "Pin down" layouts place

6887-415: The newly developed polyurethane lane finishes of the day, sparking the evolution of coverstock technology to pursue ever-stronger hooks with correspondingly higher entry angles . The early 1990s brought development of reactive resin ("reactive") balls by introducing additives in urethane surface materials to create microscopic oil-absorbing pores that increase the "tackiness" that enhances traction. In

6984-494: The oil pattern—is popularly thought to influence entry angle , but Freeman & Hatfield (2018) discount its contribution to ball motion. Holes may be drilled for a conventional grip (fingers inserted to the second knuckle as with "house balls"), a fingertip grip (fingers inserted only to the first knuckle, enabling greater rev-generating torque), or less standard grips such as the Sarge Easter grip (ring finger inserted to

7081-433: The oil to be thinner) and humidity (variations of which can cause crowning and cupping of the lane surface). Also, high humidity increases friction that reduces skid distance so the ball tends to hook sooner. The lanes' physical topography—hills and valleys that diverge from an ideal planar surface—can substantially and unpredictably affect ball motion, even if the lane is within permissible tolerances. The USBC maintains

7178-468: The other stone, but traveling too far, or hitting the stone. Bowling ball A bowling ball is a hard spherical ball used to knock down bowling pins in the sport of bowling . Balls used in ten-pin bowling and American nine-pin bowling traditionally have holes for two fingers and the thumb. Balls used in five-pin bowling , candlepin bowling , duckpin bowling , and European nine-pin bowling have no holes, and are small enough to be held in

7275-947: The palm of the hand. The USBC and World Bowling promulgate bowling ball specifications. USBC specifications include physical requirements for weight (≤16 pounds (7.3 kg)), diameter (8.500 inches (21.59 cm)—8.595 inches (21.83 cm)), surface hardness, surface roughness, hole drilling limitations (example: a single balance hole including the thumb hole for "two-handed" bowlers ), balance, plug limitations, and exterior markings (structural and commercial), as well as requirements for dynamic performance characteristics such as radius of gyration (RG; 2.46—2.80), RG differential (≤0.06), and coefficient of friction (≤0.32). The USBC banned weight holes (balance holes) in competition, effective August 1, 2020, to prevent their changing ball dynamics. The USBC permits three ounces (85 grams) of static side weight and three ounces (85 grams) of top weight. These figures are up from one ounce (28 grams) following

7372-462: The pebbled ice. The pebble, along with the concave bottom of the stone, decreases the friction between the stone and the ice, allowing the stone to travel further. As the stone moves over the pebble, any rotation of the stone causes it to curl , or travel along a curved path. The amount of curl (commonly referred to as the feet of curl ) can change during a game as the pebble wears; the ice maker must monitor this and be prepared to scrape and re-pebble

7469-448: The pin between the finger holes and the thumb hole, while "pin up" layouts place the pin further from the thumb hole than the finger holes (see photos). Bowling ball motion is influenced by how far the pin and the mass bias (MB) are from the PAP, the distances determining track flare . Track flare—the sequence of oil rings showing migration of the ball's axis on successive revolutions through

7566-422: 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

7663-401: The second knuckle but middle finger inserted only to the first knuckle). Many bowlers using the so-called "two-handed delivery" (which is still a one -handed release ) do not insert their thumbs, thus allowing their fingers to impart even more torque than the fingertip grip. Finger inserts and thumb slugs are custom-fit urethane tubes inserted into the drilled holes, generally for balls with

7760-717: The shots; see below.) Curling has been a medal sport in the Winter Olympic Games since the 1998 Winter Olympics . It currently includes men's, women's, and mixed doubles tournaments (the mixed doubles event was held for the first time in 2018 ). In February 2002, the International Olympic Committee retroactively decided that the curling competition from the 1924 Winter Olympics (originally called Semaine des Sports d'Hiver , or International Winter Sports Week) would be considered official Olympic events and no longer be considered demonstration events. Thus,

7857-433: The sole are also available as alternatives to Teflon. 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

7954-438: The sound the stones make while traveling over the pebble (droplets of water applied to the playing surface). The verbal noun curling is formed from the Scots (and English) verb curl , which describes the motion of the stone. Kilsyth Curling Club claims to be the first club in the world, having been formally constituted in 1716; it is still in existence today. Kilsyth also claims the oldest purpose-built curling pond in

8051-502: The sport's official addition in the 1998 Olympics, Canada has dominated the sport with their men's teams winning gold in 2006 , 2010 , and 2014 , and silver in 1998 and 2002 . The women's team won gold in 1998 and 2014 , a silver in 2010 , and a bronze in 2002 and 2006. The mixed doubles team won gold in 2018 . The playing surface or curling sheet is defined by the World Curling Federation Rules of Curling. It

8148-499: The stone (see sweeping ) and is also often used as a balancing aid during delivery of the stone. Prior to the 1950s, most curling brooms were made of corn strands and were similar to household brooms of the day. In 1958, Fern Marchessault of Montreal inverted the corn straw in the centre of the broom. This style of corn broom was referred to as the Blackjack . Artificial brooms made from human-made fabrics rather than corn, such as

8245-443: The stone in contact with the ice is the running surface , a narrow, flat annulus or ring, 6.4 to 12.7 millimetres ( 1 ⁄ 4 to 1 ⁄ 2  in) wide and about 130 millimetres (5 in) in diameter; the sides of the stone bulge convex down to the ring, with the inside of the ring hollowed concave to clear the ice. This concave bottom was first proposed by J. S. Russell of Toronto, Ontario, Canada sometime after 1870, and

8342-457: The stone will travel. Balance may be assisted by a broom held in the free hand with the back of the broom down so that it slides. One older writer suggests the player keep "a basilisk glance" at the mark. There are two common types of delivery currently, the typical flat-foot delivery and the Manitoba tuck delivery where the curler slides on the front ball of their foot. When the player releases

8439-430: The stone's path. 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

8536-413: The stone, a rotation (called the turn) is imparted by a slight clockwise or counter-clockwise twist of the handle from around the two or ten o'clock position to the twelve o'clock on release. A typical rate of turn is about 2 + 1 ⁄ 2 rotations before coming to a rest. The stone must be released before its front edge crosses the near hog line. In major tournaments, the " Eye on the Hog " sensor

8633-522: The surface prior to each game. The curling stone (also sometimes called a rock in North America) is made of granite and is specified by the World Curling Federation, which requires a weight between 19.96 and 17.24 kilograms (44 and 38 lb), a maximum circumference of 914 millimetres (36 in), and a minimum height of 114 millimetres ( 4 + 1 ⁄ 2  in). The only part of

8730-551: The thrower had little control over the 'curl' or velocity and relied more on luck than on precision, skill, and strategy. The sport was often played on frozen rivers although purpose-built ponds were later created in many Scottish towns. For example, the Scottish poet David Gray describes whisky-drinking curlers on the Luggie Water at Kirkintilloch . In Darvel , East Ayrshire , the weavers relaxed by playing curling matches using

8827-456: The thrower. Other types of equipment include: The purpose of a game is to score points by getting stones closer to the house centre, or the "button", than the other team's stones. Players from either team alternate in taking shots from the far side of the sheet. An end is complete when all eight rocks from each team have been delivered, a total of sixteen stones. If the teams are tied at the end of regulation, often extra ends are played to break

8924-539: The tie. The winner is the team with the highest score after all ends have been completed (see Scoring below). A game may be conceded if winning the game is infeasible. International competitive games are generally ten ends, so most of the national championships that send a representative to the World Championships or Olympics also play ten ends. However, there is a movement on the World Curling Tour to make

9021-562: The world at Colzium , in the form of a low dam creating a shallow pool some 100 by 250 metres (330 by 820 ft) in size. The International Olympic Committee recognises the Royal Caledonian Curling Club (founded as the Grand Caledonian Curling Club in 1838) as developing the first official rules for the sport. However, although not written as a "rule book", this is preceded by Rev James Ramsay of Gladsmuir ,

9118-732: The world's oldest football are now kept in the same museum (the Stirling Smith Art Gallery and Museum ) in Stirling . The first written reference to a contest using stones on ice coming from the records of Paisley Abbey , Renfrewshire , in February 1541. Two paintings, " Winter Landscape with a Bird Trap " and " The Hunters in the Snow " (both dated 1565) by Pieter Bruegel the Elder , depict Flemish peasants curling, albeit without brooms; Scotland and

9215-406: Was dubbed the broomgate controversy . The new brooms were temporarily banned by the World Curling Federation and Curling Canada for the 2015–2016 season. Since 2016, only one standardized brush head is approved by the World Curling Federation for competitive play. Curling shoes are similar to ordinary athletic shoes except for special soles; the slider shoe (usually known as a "slider")

9312-414: Was recognized that using shots which take more time for the stones to come to rest was being penalized in terms of the time the teams had available compared to teams which primarily use hits which require far less time per shot. The process of sliding a stone down the sheet is known as the delivery or throw . Players, with the exception of the skip, take turns throwing and sweeping; when one player (e.g.,

9409-633: Was subsequently adopted by Scottish stone manufacturer Andrew Kay. The granite for the stones comes from two sources: Ailsa Craig , an island off the Ayrshire coast of Scotland, and the Trefor Granite Quarry, North of the Llŷn Peninsula , Gwynedd in Wales . These locations provide four variations in colour known as Ailsa Craig Common Green , Ailsa Craig Blue Hone , Blue Trefor and Red Trefor . Blue Hone has very low water absorption, which prevents

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