Curling Explained

The object of the game is to score more points (rocks) than your opponent after a designated amount of "ends". An end is like an inning in baseball. Each team throws eight rocks each (two per player, alternating with your opponent) toward the twelve-foot diameter target called the "house".  After the sixteen rocks have been thrown, the score for that end is determined. Teams score one point for each rock closest to the center of the house without an opponent's rock closer. In each end, only one team can score. The team that throws last in each end would have a big advantage. Having last rock in the end is called having the "hammer".  Once you score in the end, you relinquish the hammer to your opponent, and so on.  The hammer in the first end is determined by coin toss in most cases.  In championship play, the hammer in the first end is determined by a "closest to the button" shot conducted by each team. 

Houses are usually fixed into the ice just below the surface at both ends of the sheet (like a lane in bowling), allowing the game to be played back and forth, usually for eight or ten times. Each end takes about fifteen minutes so an eight-end game would take about two hours. Rocks traveling down the ice will curl (curve) anywhere from six inches to six feet, depending on ice and rock conditions. As the rocks are thrown, they are intentionally rotated clockwise or counterclockwise (depending on the shot called). This rotation causes the rocks to curl in a predictable way.

A unique part of curling is the concept of sweeping. Players vigorously sweep, or brush, the ice in front of the rock as it travels. The friction of the brooms momentarily changes the ice surface by warming and polishing a thin layer of the ice in front of the rock. This thin layer lubricates the bottom of the rock allowing it to travel farther and straighter. In recent years, the sweeping motion has been known to scratch the ice slightly helping to steer the rock. Good sweepers can manipulate the distance, and possibly the curl, resulting in rock placement.

Traditional Fours

Most games are played four against four, each player throwing two rocks per end. The number of ends varies depending on the level of play, generally eight or ten ends. There are many different categories based on gender and age.  The following is a list fo some format categories.

• Men's and Women's

• Under 18 (men's and women's)

• Under 21 (men's and women's)

• Senior Men's & Women's (over 50) 

• Five-Year and under.

• Etc.

Mixed Doubles

The object of this format is the same as traditional fours, but it is played two against two. One male, one female. Only five rocks are thrown per team in each end. One payer throws the first and last rocks while the other throws the middle three. The order can switch every end if so desired. Two rocks are prepositioned before play begins, one in the house and one in the Free Guard Zone. Refer to the World Curling rules for more detail.

Wheelchair Curling

The objective of wheelchair curling is the same as traditional fours. There are some rule differences, such as no sweeping.  Rocks are thrown using a throwing device acting as an extension of the arm. Wheelchair curling is also mixed gender - a female player must be on the ice at all times. Refer to the World Curling rules for more detail.

Teams are made up of four players. The positions are traditionally called Skip, Vice Skip, Second, and Lead. The traditional name for a curling team is a "rink". For example, "The Smith Rink" would describe the team skipped by John Smith. This term is fading and most teams today are just called teams.

Each player throws two rocks. Traditionally, the first position is known as the Lead and throws the first two rocks for the team. The second position is known as the Second and throws the second two rocks. The third position is known as the Vice Skip and throws the third two rocks and controls the house while the skip throws. The fourth position is known as the Skip (calls the shots and is the team captain) and in most cases throws the last two rocks. All players, excluding the skip, throw AND sweep.

Quick Note: The role of the players determines the position names. The person calling the shots, managing the game, and standing in the house is the Skip. The person that takes over the skip's responsibilities while the Skip is throwing is the Vice Skip or Acting Skip. Throwing order has no bearing on position names.

The skip controls the game by determining the game strategy and calling all of the shots. Since the rocks curl as they travel down the ice, the throwers must aim at a point other than the intended resting point or target rock. The Skip is responsible for providing that aiming point. They place their broom upright, directly over the desired aiming point. The Skip is also responsible for determining whether sweeping is necessary on some shots and communicating this to the sweepers*.

The use of a team coach is becoming more popular, particularly at the more competitive level. Curling coaches are required to passively coach the team. Rules state that the coach only has limited interaction with the team during play. Even with the existence of a team coach, the Skip must call all of the shots. Coaches generally communicate before, after, during a break half-way through the game, or between ends. Time-outs are another opportunity for coaches to provide assistance or intervene.  See the Coach's Corner section.

* On more skilled teams, the skip is not responsible for determining sweeping on draw shots. The sweepers judge the distance and sweep when necessary.

Essentially, there are two types of curling shots:

1. The Draw

2. The Take-out

There are many variations of these two shots. Draws are only thrown hard enough only to reach the field of play at the other end. Take-outs are thrown to remove rocks from play.

Draw shots:

• Open Draw: a rock thrown into an empty house.

• Center (front) Guard: a rock thrown to the center of the sheet, short of the house to be used as protection.

• Corner (side) Guard: a rock short of the house and off to the side.

• Come around: any draw shot that curls around and behind another rock.

• Raise: Tapping-up an existing shot.

• Tap back: a heavier weight draw designed to push another rock back but not out of the house.

• Freeze: a draw that comes to rest touching another rock without moving it.

• Corner-freeze: a draw that comes to rest on the edge of another rock.

Takeout shots:

• Normal Takeout: a takeout thrown with enough weight to firmly remove another rock (a normal takeout undisturbed should hit the back wall and bounce back about a few feet).

• Control Takeout: Enough weight to clearly remove a rock. Less weight allows more curl and sweeping control.

• Hack Weight: a takeout thrown with enough weight to gently remove another rock (a hack weight takeout undisturbed should come to rest at the hack).

• Peel: a takeout thrown very hard to remove rocks from play (undisturbed peel weight shots should hit the back wall and bounce back several feet).

• Hit & Roll: a takeout that, after making contact with another rock, rolls to a designated place.

• Runback: a takeout thrown to hit a rock straight back into another.

Players intentionally rotate the rocks as they throw them. These rotations are called turns. A clockwise rotation (for a right handed person) is called an In-turn while a counter-clockwise rotation is called an Out-turn. The names originally come from the direction your elbow took as you were throwing (the elbow pointed out as you rotated the out-turn and vice versa). This is no longer appropriate because the elbow shouldn't move in a proper delivery. The names remain.

As mentioned earlier, games consist of either eight or ten ends depending on the level of competition. League and bonspiel (tournament) games are generally eight ends while championship games are ten ends. Each end takes approximately fifteen minutes, so an eight end game would generally take two hours to play.

Each game, the teams are assigned a sheet of ice at the curling club. Curling clubs have anywhere from two sheets to ten sheets of ice.

Pre-Game Routine

The game begins with a handshake. It is customary for each player to shake hands with each opposing player AND each teammate. Shake hands with your opponent first. Players commonly exchange the term "good curling".

Practice Slides

In most league games, it is customary to NOT practice before a game. But, most curlers take a few practice slides before throwing the first rock. This is done by sliding out of the hack with no rock. Do not throw rocks prior to any game unless it is specifically mentioned in the league or competition rules.

In championship games, a short pre-game practice is allowed, generally six to ten minutes per team.

The Coin Toss

We've already mentioned that the last rock in any end is a huge advantage.  In most league-level games, the vice skips toss a coin to determine who has the last rock advantage (also called the hammer) in the first end. In most cases the winner of the coin toss chooses to throw the last rock in the first end, the loser of the toss chooses the rock color. Choosing rock color may seem arbitrary, but not all rocks behave the same. Home teams who are familiar with the rocks at their club have an advantage.

In championship games the hammer is not determined by chance. Before each game, it is determined by the Last Shot Draw (draw to see who has last rock). Both teams throw a closest-to-the-button (center) shot. The winner of the draw contest chooses hammer or rock color.

Beginning of the Game

At this point, the skips move to the opposite end of the ice and the team not delivering moves between the hog lines. The skip calls the shot, the first rock is thrown, and the game is on.

Note: In many clubs, the rocks are numbered from one to eight. Unless told otherwise, the Lead should throw rocks number one and two, the Second throws three and four, and so on.

Each player will throw two stones per end, alternating with the opponent. Your team throws one; the opposing team throws one, and so on. As the Lead is throwing, the Second and Vice are designated sweepers, with the Skip calling the shots. When the Second is throwing, the Lead and Vice are the sweepers. When the Vice is throwing, the Lead and Seconds are sweeping. When it comes time for the Skips to throw, the Vice Skip takes over responsibility of the house and calls all sweeping for direction. The Lead and Second remain as the sweepers for the Skip's shots. The Lead and Second sweep more than the Vice, and the Skip doesn't sweep at all.

Position of Players

Understanding where to position yourself on the ice is critical to team performance as well as playing by the rules. The Leads and Seconds must position themselves between the hog lines (sometimes the courtesy lines) unless they are about to sweep or about to deliver a rock.

If you are about to deliver a rock, position yourself behind the hack and to the side. Remain quiet and still as your opponent delivers. As soon as the opponent delivers the rock, choose your rock and move into the hack area. While the opponent's rock is still in motion, begin the setup process in the hack.

If you are about to sweep, position yourself on the back line, approximately two feet from the sideline. Confirm the shot and weight with the thrower. As your teammate begins to deliver, start moving forward and to the center trying to meet the rock near the hog line. At this point you may begin sweeping the rock if necessary. Most teams will "clean" the area in front of the rock as it travels.

When you have stopped sweeping, return to the other end of the ice. Be sure not to walk down the center of the sheet, preventing the opponent from viewing. As you are walking back, try not to distract the opponent in the hack. If time permits, stop and remain still while the opponent is delivering.

Defensive Sweeping

Curling rules of play allow you to sweep your OPPONENT'S rock once it touches the tee line. This may not be consistent with the "Spirit of Curling" since you help your opponent miss a shot by sweeping it out of the house. But, it is an acceptable and commonly used practice.

Completing the End

Once all sixteen rocks have come to rest, the vice skips from each team agree on how many rocks are counting and to which team they belong. Only one team can score in an end and the most any team can score is eight. Occasionally, when the counting rock or rocks can't be determined by eye, a special measuring device is used. Normal scoring in an end may be zero, one, two, three or even four rocks. Scoring more than four is less common. Scoring all eight rocks is as rare as a hole-in-one in golf and many players never see one.

Having last rock in any end is a clear advantage. The scoring team gives up the hammer in the next end. If no team scores in an end (called a blank), either deliberately or accidentally, the hammer is retained.

The Curling Scoreboard

After agreeing on the score, the Vice Skip of the scoring team is responsible for posting the score after each end. On the curling scoreboard, numbers 1 through 16 (possibly 17, 18, 19 etc.) are painted horizontally from left to right. These numbers represent the rocks scored. At one end of the scoreboard, there is a stack of individual numbers from 1 to 10. These represent the ends and are hung either over or under the painted numbers. Since teams throw different colored rocks, the ends are hung above or below the painted numbers depending on color. In curling, the rocks scored are posted cumulatively, meaning two rocks scored in the second end are added to whatever was scored in the first end (if any).

Finishing the Game

At the completion of the game, it is customary to again shake hands with your opponents and then your teammates. Players often exchange the phrase "good game". It is now time for Broomstacking. Most curling clubs have some sort of gathering area for Broomstacking teams. There will usually be table set up behind each sheet of ice designated for this.

Winners buy first the the loser reciprocates.

Conceding the Game

Curling is one of only a few sports that allows a team to concede before the end of the game. It is customary to concede the game if you think the lead is insurmountable, even if it is mathematically possible to still win or tie. Of course, if it is mathematically impossible to tie or win, the game is over and the losing team should immediately shake hands.

Rule of Thumb - If you don't think you can win the game, concede. It is never appropriate to keep playing just to "practice".

Game Speed

Most people find that fifteen minutes per end is a comfortable pace for the game. In fact, most league schedules and game times rely on this. Slow play not only delays the following games, it allows players to get bored and/or cold. It is important to be ready to throw when it is your turn. Skips must also be aware of the time. Over-analyzing and chatting will delay the game.

Like golf, slow play is never appropriate. Fifteen minutes per end!!!

Timed Games

At all championship level games and in some bonspiels, time clocks are used to control the speed of the games and to prevent exceedingly long games. The clock is similar to a chess clock and each team has 38 minutes to complete a ten end game. The clock only runs during your thinking time and not while your rock is in motion. Thinking time does not penalize a team for throwing mostly slower, draw shots.

The clock begins when the opponent's rock comes to rest and the skip is allowed to take control of the sheet. The clock will continue to run until the next rock is thrown.

It is necessary for the Lead and Second to be ready to play when the opponent's rock comes to rest. "Ready Play" makes a noticeable difference in the pace of the game. The pace at the beginning of end is usually faster than the pace at the end due to the Vice Skips and Skips discussing the shots. The faster the Leads and Seconds are, the more time the back-end (skip and vice skip) has to discuss the strategy.

If time runs out - the offending team loses the game.

In many league games a "Game Clock" is used to control the speed of play.  This clock is used for all games being played.  For example, the game clock starts at 1 hour and 40 minutes and counts down.  When the clock strikes zero, teams finish the end they're in and play only one more.  An end is considered finished when the teams agree on the score (once the score is agreed upon in the sixth, you are in the seventh).  Since this clock type does not time teams separately, one team can effect the whole game by playing slow.

Since all players are directly involved with every shot in curling, team communication is vital to success and game enjoyment.  In many cases, the curling arena is loud, making regular voice communication very difficult. There are two main categories of communication.  This applies to all levels of play.

1. Between-shot communication.

2. During-shot communication.

Between Shots

More than half of your team communication will happen between shots. Calling and confirming the shot, types of weights, ice conditions, and ice speed make up most the between-shot communication.

Let's start with the skips shot calling signals, All shots called by the skip have an associated hand or arm signal. Hand signals were developed due to the length of the sheet of ice (the option is to scream to players at the other end). Also, many curling clubs are loud, making talking difficult.

Skip signals can vary dramatically. Listed below are the most common non-verbal signals used:

Signals to determine the draw shots:

• Tap the intended area of the house with your broom.

• Indicate weigh if other than draw weight.

Signals to determine takeout shots:

• Tap the rock with the broom (intended takeout target).
  Touching the arm at the wrist, elbow or shoulder to indicate takeout weight.

or

• Touching the upper body at the waist, chest and neck.

With all shots, there are two signals, one to call the shot and another to indicate turn or rotation.

During the Shot

Once the shot has been called and confirmed, the rock is thrown. After the rock is released, the shot is in the hands of the skip and sweepers, who are in constant communication, mostly about line and weight.  Understanding the roles and responsibilities here will make this process easy.  Later on the Sweeping page  we talk about the specific tasks of each sweeper.  The sweepers are responsible for judging the weigh of the rock.  The skip is responsible for line.  The more these are clearly separated, the better. 

Draws

The sweepers may use stopwatches to help judge draw weight (see The Timing Rocks page).  If they think the shot needs sweeping for weight at any time during the shot, they should start sweeping and communicate any weight problems to the skip.

Take-Outs

Immediately after release, the skip will assess the the shot based on "line".  If the shot starts wide of the target, no sweeping is necessary and the skip indicates by saying "No" or "Whoa".  Usually anything with an "O" sound means no sweeping.  If at any time the skip wants the sweeper to sweep, they will say any number of things such "Sweep", "Yep", "Hurray".  Your team will have it's set of words that you will agree on. 

In most cases, teams have an associated non-verbal signal to sweep or not to sweep.  The skip's hand up or to the side indicates no sweeping.  A waving hand indicates sweep.

Pro Tip:  Skip's want the sweepers to judge weight and not line.  Sweepers want the skip to call line and not weight.

Equipment for Curlers

Curling equipment comes in a range of complexity and cost. The only essential items are a slider and a broom, both available at the club. A slider is a piece of Teflon®, plastic, or steel that is slipped onto one foot in order to slide during the delivery. Today's game of curling is designed around the ability to slide with no effort. The other foot usually has a rubber-soled shoe used to grip the ice. To throw the rock, one foot pushes while the other slides.  Right-handed curlers push with their right foot and slide on their left.

The broom or brush is used to sweep the ice (polish it, actually) and most curling clubs have brooms available for use. More advanced curlers may choose to purchase special curling shoes with a built-in slider, covered by a gripper when not throwing.

There are many manufacturers of curling equipment in the United States and Canada. Most veteran curlers choose to have their own curling equipment; shoes, brooms, special curling gloves, pants, jackets, etc. The list of equipment types and styles is endless. 

Pro Tip: The stability of the high-end shoes is worth the money.  Ask around the club for recommendations.

Equipment for the Curling Club

Curling facilities own a variety of equipment.

• Refrigeration System: The most expensive and complex equipment in the club is the refrigeration system used to make artificial ice. Heating, dehumidification, and water purification systems are also complex and expensive.

• Rocks: The next most critical piece of equipment is the set of rocks. They are made from solid chunks of special, high-density granite found in Wales and Scotland. Earlier rocks came from an island in Scotland called Ailsa Craig. The island's best granite is called blue hone. Blue hone granite is very dense and lasts long as a running surface. Unfortunately, they have a tendency to break or chip near the striking band. A better striking rock is a Trefor (pronounced Trevor) quarried in Wales but its running surface wears quicker and can pit causing irregular movement. The best rocks today are Trefor granite with blue hone inserted as the running surface. The cost of a rock is between $400.00 and $600.00! With proper care, they can last many decades. See the Ice and Rocks section for more detail on rocks.

Photo courtesy of www.worldcurling.org

From a distance, curling ice appears perfectly smooth. After a closer look, you'll notice that the ice appears bumpy. The rocks ride on these small frozen bumps called pebble. The pebble is put on before each game with a machine that works like a flower sprinkler. Without the pebble, there would be too much friction between the ice and the rocks, making it too difficult to throw the rocks the full distance. Pebble is what makes curling a finesse game.

The ice is maintained between games by sweeping off debris and re-pebbling. The build-up of pebble is generally scraped off the surface two or three times a week, or as much as possible. A special scraping machine is manufactured just for curling ice. The resurfacing machine removes the build-up of pebble and any frost that has settled before new pebble is applied.

Occasionally, due to the uneven freezing of the surface, the entire area is flooded and allowed to freeze slowly. This levels the ice and is done about every six weeks or so.

It is very difficult to prepare a perfectly level ice surface. Even though most imperfections can't be seen, the way the rocks behave while in motion may indicate the presence of ridges and troughs. This is part of the game. Skips must determine what the sheets are like as early as possible, similar to reading the green in golf.

The ice surface temperature is maintained somewhere in the 22-25 degree F range. In some cases, sophisticated equipment is used to measure and maintain these temperatures.

New Era Curling Ice: Up until the mid-1980's, the ice surface was relatively crude. Ice was made with mineral-laden tap water. Pebble was added every game and built up over time. Corn brooms littered the ice with corn chaff and debris. The ice was relatively slow and straight (rocks didn't curl much) and games were played with mostly takeouts.  A draw game was played by seniors.

Two major contributions or breakthroughs in the 1980's changed the game.

1. The use of purified water.

2. The invention of the curling ice-scraping machine.

Purified ice and regular scraping completely changed the ice surface and therefore change the game. The ice was faster with more curl. Teams immediately took advantage by shifting from a takeout game to a draw game and the new era of curling began.

The Air: The air temperature in most clubs is controlled. The ideal air temperature at chest level is around 40-45 F. Not only is it comfortable for the curlers, the heat keeps the relative humidity lower so frost won't build up on the ice surface. Some clubs have dehumidification systems. This further decreases the relative humidity and dew point. Lower latitude clubs with no heating capabilities usually have frost problems. Higher latitude clubs with no heat are very cold and dry. In extremely cold and dry cases, the ice may sublimate. Sublimation is the process of ice changing to vapor without passing through the liquid stage.

The following text is taken directly from the World Curling Federation website:

"Curling is a game of skill and of tradition. A shot well executed is a delight to see and it is also a fine thing to observe the time-honoured traditions of curling being applied in the true spirit of the game. Curlers play to win, but never to humble their opponents. A true curler never attempts to distract opponents, nor to prevent them from playing their best, and would prefer to lose rather than to win unfairly.

Curlers never knowingly break a rule of the game, nor disrespect any of its traditions. Should they become aware that this has been done inadvertently, they will be the first to divulge the breach.

While the main object of the game of curling is to determine the relative skill of the players, The Spirit of Curling demands good sportsmanship, kindly feeling and honourable conduct.

This spirit should influence both the interpretation and the application of the rules of the game and also the conduct of all participants on and off the ice."

Curling is one of the few sports in the world that emphasizes etiquette. All games, regardless of level, start and finish with handshakes. In most league play, there are no referees or judges. Adhering to the rules is based on the honor system and good shots are admired by all. Missed shots are never cheered. Now that you are familiar with the time-honored spirit of curling, let's apply it to a real game:

• There's no trash talking in curling.

• Shake hands before and after the game (firm, with eye contact).

• Stay still while your opponent throws.

• Stand between the hog lines (or courtesy lines).

• Never cheer a missed shot. Even if the missed shot allows you to win a game. In this case, calmly shake hands with your opponent and enjoy your victory graciously.

• Acknowledge great shots. It's ok to acknowledge your opponents called and made great shots.

• Never, ever cheat. There are subtle ways to skirt the rules. Don't do it. Hog line, sweeping your opponent's rock before the tee, not disclosing a burned or displaced rock, blocking out your opponent at the tee. Fake sweeping at the tee. Intentionally tricking the opponent into more rocks than you deserve.

• Always disclose burned or displaced rocks.

• Never intentionally intimidate your opponent.

• Broomstack.

Broomstacking

Broomstacking is a curling tradition - a social get-together between opponents after each game. Originally, curlers, after completing half of a game on the pond, would stack their brooms in front of the fire and enjoy beverages with the opponent. In most cases they would resume the game, if able. This tradition is alive today, although teams now wait until after the game. It is expected that you partake in Broomstacking after every game. The original pond curlers most likely enjoyed their social time with the consumption of spirits. Today's game is very similar but people are more conscious of and knowledgeable about alcohol consumption.

The true origins of curling is still an open discussion.  Several Northern European countries have claimed the origin.  We do know that it was invented centuries ago on the frozen lakes of Europe.  Most curlers acknowledge Scotland as the  original "curling country".  It wasn't until the turn of the 20th century that the game was played on artificial ice.

Conditions certainly improved when the game moved indoors.  No more wind, snow and debris issues.  Most curlers were happy to be directly out of the elements.  Even so, the indoor conditions were weather dependent.  If it was cold out side, it was cold inside.  Early 20th century photos show curlers in wool coats, scarfs and hats.  Heating the ice area was un-heard of.  It wasn't until the 1950's that clubs began to heat the ice area for player comfort. It still seems odd that we try to keep the ice frozen and at the same time heat the building.

In the early days of curling, when games were played outdoors on the lochs, snow and other debris was cleared from the path of the moving rocks. Bunches of sticks were used as debris clearing devices. However, as the sport evolved, it became clear that, in addition to clearing debris, vigorous sweeping affected the moving rock's distance and curl.

Throwing the Rock - The Evolution 

Before we get into the detail about delivery mechanics, let's consider some history. The methods for throwing a curling rock (the delivery) have evolved over hundreds of years. In the early days it was as simple as gaining a foothold on the ice and hurling an object forward. In the 20th century, equipment such as rubber hacks and polished rocks were introduced. It wasn't until the 1940's that the slide was incorporated into the delivery, thanks to Canadian curling great, Ken Watson. By adding a slippery surface to the non-hack foot, the curler could slide out of the hack and control the rock's weight and direction with greater ease. It was at that time that the delivery began its accelerated evolution. Almost immediately after Watson showed curlers his slide technique, they began to modify it. The ice was rough, dirty and slow, and the first modification was the toe-tuck delivery where the sliding foot was tucked under the hip by rolling onto the sliding toe. Lifting the heel off the ice added less friction and allowed the player to slide farther. In some cases, a lot farther. Because of this modification, a significant rule change was needed.

The near hog line became a dual-purpose demarcation as the players were not allowed to slide past it (no part of the body could cross the line). Although a flat-footed slide was introduced by Watson, the tuck delivery became popular for two reasons. It reduced friction on the slow surface and allowed the curler's body to get closer to the ice. Since the slower conditions were conducive to a takeout game instead of draw game, this delivery allowed them to better sight the rock toward the skip's broom on the takeout. Again, a rule change was need. Since many players were sliding, the hog line rule was changed so the body could cross the line as long as the rock had been released. This type of long slide, toe-tuck game continued through the 1970's but some leading-edge players preferred the stability of the full-foot slide. In the early 80s, ice conditions improved dramatically due to the introduction of purified water/ice and the use of the ice scraper as regular maintenance tools. These two things improved the speed of the ice and curling began a rapid evolution to an aggressive, draw-type game and the need for the tuck delivery was no longer. In 1990, the Free Guard Zone rule further propelled the game to finesse shots and draws.

Timing Rocks - See the Timing Rocks Section for detail.

Using a stopwatch to time rocks began in the 1980's as a way to measure the speed of the ice. This helped teams play at different clubs where the conditions could be different. It also helped measure different paths on the ice. Keep in mind that the ice conditions up to this point were fairly crude compared to today's standards. The original timing method was the long time, from the hog line to the tee line. Conditions were slow at 20-23 seconds, hog to tee (about 12.0 to 12.5 HTH) but consistent. As ice conditions improved through better water quality and the invention of the ice scraper, the need to monitor conditions increased. With faster and cleaner ice, other factors were introduced that could effect conditions. In the early days of timing, the "split time" did not exist.  The split time, back line to near hog line became popular in the 1990's, allowed sweepers to immediately judge draw shots.

The Free Guard Zone rule made long times more difficult since there were more rocks in play. The five-rock rule essentially made long times obsolete, and the new ice measurement timing standard is Hog-to-Hog. This eliminates the issues of too many rocks in play when timing the rocks to their stopping point.

Innovation Timeline

The sport of curling has been played for hundreds of years. It has only been in the last fifty or so years that curling has seen any significant innovation. The following is a list of curling innovations:

• 1500's Sweeping debris from the ice surface makes rocks go farther.

• 1800's Polished rocks make shots more consistent.

• 1900 Artificial ice allows curling indoors and in lower latitudes.

• 1900's Sweeping is accepted as more (farther and a little straighter) than just removing snow and debris. 

• 1940 Ken Watson invents the slide delivery. Thrower cannot slide past near hog line.

• 1972 Players can slide past the nearer hog line as long as they release prior.

• 1985 Ice resurfacing machine (scraper) was invented.

• 1987 Timing rocks begins.

• 1988 Purified water is used to make curling ice.

• 1990 Canada experiments with a "no take-out rule".

• 1991 Free Guard Zone rule (three rock) was implemented by the WCF.

• 1991 Synthetic brush heads increase in popularity.

• 1992 Corner sweeping is widely used.

• 2010 We finally figured out why rocks curl (frictional melting).

• 2015 Wait!! Swedish scientists suggest another reason why rocks curl (scratching/grooving).

• 2015 Directional scratch-sweeping begins. Broomgate begins.

• 2017 Scratching brushes are banned from competition.

• 2024 The "No Tick" rule is adopted by the WCF.

• 2025 Foamgate begins as manufacturers experiment with firmer foam. Certain foam pads are banned from competition.