What Are The Green Lights On A Curling Stone? (Remarkable Red and Glorious Green)

When the ball goes out of play in a soccer game, it’s up to the referee to call out the violation. However, in a competitive curling match, the red and green lights on top of the stones make them somehow self-policing. 

Why does every curler hope it’s a green light? Please keep reading to discover more!

Key Points

  • Curling is an exciting sport whose popularity is growing every day. The curling stone has two lights: a green light and a red light.
  • A green light means the curler has not violated hog line rules, while a red light means the player has violated hog line rules. 
  • There are two hog lines in curling: The near hog line and the far hog lines, each of which plays a significant role in the game. 

In this post, you’ll discover more about the green lights on a curling stone. For instance, you’ll learn what the lights mean, when the curling stones got the lights and the basic curling rules. 

What do the lights mean on curling stones?

Some people may find curling a complicated sport because of the lights on the stones and the term “hammer.” The lights act as a tracking system that ensures the curlers release the stone before the first hog line. 

The game requires teams to release the stone before they pass the red line. There is a heat sensor embedded into the ice. This sensor is triggered if your hand continues to clutch onto the handle. 

  • Green light: The lights remain green, and play continues as long as the curler lets go of the stone before the front crosses the first red line (also known as the “hog line“). This is why curlers cannot wear gloves on their delivery hand, as it hinders the touch sensor. 
  • Red light: If you notice the red lights turned on, the curler committed a hog line violation by keeping their hand on the handle for an excessive amount of time. The shot is declared invalid, and the stone is swiftly removed from the curling sheet so it won’t obstruct any other stones.

You have to release your hand from the stone before the Hog Line. The little lights are somehow rigged to turn green if you do that; red if you don’t. If the light is red, you messed up, and the rock is removed from play. It’s very rare on the world stage, but it happens.

– said Brock Pan-Yellow, a sports player and fan for life. 

What are the green lights on the curling rocks?

Have you watched curling before? If yes, you’ve probably seen two green lights shining near the edge of the stone during its release. These lights are connected to a sensor that detects when a curler releases the stone. 

In addition, the green light is a part of the electronic hog line device. The function of this light is to ensure that the curler does not commit a hog line violation. However, the high caliber of curlers in significant events like the Olympics means there are barely any hog line violations. 

When did curling stones get lights?

The stone lights are a detection system called “Eye on the Hog.” Eric Salt, an engineering professor at the University of Saskatchewan, encouraged his advanced electrical engineering students to invent a detection system as part of their class project. 

He helped them do it, and Startco, a Canadian engineering company, modified the design and brought it to the market. Soon after, The Canadian Curling Association adopted it for official use, and it continued to spread. 

What is a curling stone made of?

The curling stone is made from a singular granite, shaped and polished. Most of the granite used to manufacture curling stones is exclusively sourced from two quarries in the world: the Trefor Granite Quarry in Wales and the Scottish island of Ailsa Craig

The World Curling Federation uses curling stones manufactured with granite from the Aisla Craig quarry. Because granite is very rare, they could run out of granite to make new curling stones in the future. 

How heavy is a curling stone?

According to the official USA Curling rulebook, each curling stone cannot weigh more than 44 pounds (19.96 kilograms). On the flip side, it should not weigh less than 38 pounds (17.24 kilograms). 

The handle is included in the weight considerations. In addition, the stone’s circumference should not exceed 36 inches (91.4 centimeters), and its height should not exceed 4.5 inches (11.43 centimeters). 

What is the hog line in curling?

A hog line is placed about ten meters in front of every hack. The sheet has two hog lines with two essential uses for every throw. Why hog line?

The Scottish farmers commonly used the term hogged to refer to a weak lamb that was not likely to survive with the rest of the herd. In essence, the term is used to draw a parallel between a weak lamb and a stone that does not cross the hog line. 

This is why you’ll hear some stones referred to as hogged stones because the curler delivered them so weakly that they did not cross the line. 

The near hog line

This is the line on the sides where the competing teams are throwing. Its role is to show the throwers the point at which they must release the stone. 

Suppose any part of the stone crosses this line before the curler releases the stone; a hog line violation is called. After that, the stone will be removed before it reaches the house. 

The far hog line

This line is located furthest from the throwing side. It also plays a crucial role in a curling game. If the stone does not wholly cross the far hog line when it comes to a stop, it has to be removed from play. 

What does sweeping do in curling?

In curling, sweeping involves lightly warming the surface of the ice where the stone will slither across. You’ll have to sweep the ice with downward force to achieve this.    

Sweeping can help make the stone’s path longer. In this regard, good sweeping allows the stone to go farther by up to three meters. In addition, it can also reduce the curl making the stone’s trajectory straighter.  

Curling rules

While curling is regarded as a gentleman’s game that starts and ends with a handshake, it still needs rules to ensure everything runs smoothly. Here are some notable curling rules: 

  • Any part of the sweeper’s broom, body, or other team members cannot touch a moving stone. Suppose that happens; the playing team must remove the stone from the ice. 
  • A team scores a point for each stone nearer the button than any of their opponent’s stones. Any curling stone touching the outer circle is eligible. In addition, the vice-skips will settle any uncertain shots. There’ll be no measuring until the end is over.
  • Any stone that goes beyond the back line is automatically out of play. 
  • For a stone to remain in play, it must pass the hog line unless it hits another stone first. 
  • All curlers are required to start their delivery from the hack. If any part of the body goes beyond the hog line during delivery, the stone has to be removed from play. 

Final thoughts

Curling is not as complicated as it sounds, right?

Its gameplay is pretty straightforward, especially with the red and green lights on the curling stones. That incredible invention prevents the curlers from violating the hog line rules. 

With these details, you can comfortably look for a Curling Club near you and start curling. And hey, don’t allow the red lights to discourage you! You’ll be enjoying the green light to curl in due time!  

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