A curling stone is what is thrown by a curler during a game. Curling stones weigh about 42 pounds and are made of granite. Each team throws eight stones during an end for a total of 16 total stones thrown. After the stone is thrown, two other curlers will sweep it as it travels down the ice, making it travel both straighter and farther.
The underside of a curling stone is concave in, meaning that there is an air pocket under the stone as it travels down the ice. Since curling ice is textured, there are miniature air pockets on the surface of the ice. The presence of these air pockets on the stone and ice is what allows a curling stone to travel 150 feet down the ice. Additionally, only a small part of the curling stone makes contact with the ice - this part of the stone is known as the running band or running surface.
Ailsa Craig is an island off the coast of Scotland and is one of the few places in which the granite used to make curling stones is mined. Some people believe that the island also looks like a curling stone.
Three types of granite are harvested from Ailsa Craig: blue hone, red hone, and green granite. The granite harvested from Ailsa Craig is different from the granite that is used in countertops because it is significantly more impact resistant. Therefore, a curling stone will never crack or rupture when being used in a game.
The official dimensions of a curling stone are regulated by the World Curling Federation, the global governing body of the sport of curling. Based on their regulations, a curling stone must have a circumference no larger than 36 inches and cannot be shorter than 4.5 inches. Additionally, there are weight standardizations between 38 and 44 pounds. Note that this weight includes the handle and the bolt that attaches the handle to the stone.
Curling stones are usually sold in sets of eight or 16. They can be sold either new (directly from the manufacturer) or used (from one curling club to another). The only difference is that the new stones have not been used for curling yet.
From a price perspective, the used stones are less expensive. For a curling club with limited funds, it may be easier to purchase a used set of curling stones and paper them before use to save money.
Curling stone handles are made of plastic and come in a variety of colors. The two most common colors are red and yellow, as seen in most curling clubs and international competitions.
On the handle of each stone, there is either an engraving or a sticker with a letter in front of the handle and a number to each side of the handle. This is to distinguish one curling stone from another. Although curling stones look the same to the average person, each one behaves a little bit differently from the others.
As previously mentioned, most curling stones are made of Blue Hone granite, which comes from Ailsa Craig in Scotland. Additionally, the curling stone handle is made of plastic, and gets attached to the curling stone via a screw that runs through the middle of the curling stone (from top to bottom).
Typically, curling stones are sold in a set of 16: enough for one sheet. For this quantity of stones, the expected sale price is anywhere between $8,000 to $12,000. Average curling stones will be worth $500 to $750 each.
Some curling stone manufacturers do not sell their stones with handles. Therefore, you may be required to purchase stone handles separately, which usually run about $30 to $40 per stone handle.
Since curling has become a rather standardized sport, there is only one type of curling stone used for play at most curling clubs and international competitions. However, there are some differences between curling stones at a 'regular' curling club and for high-level competition.
At high-level competitions, each stone is installed with an electronic hog line sensor. This device illuminates green if the stone is released before reaching the hog line and red if not (meaning that a Hog Line Violation was committed).
For young children, there are curling stones that weigh 21 pounds as opposed to 42 pounds. These lighter stones allow for children to curl that may not be able to physically push a full-sized stone.
Generally speaking, curling stones weigh approximately 42 pounds. Due to manufacturing processes, there is slight variation in the weight of a curling stone. Therefore, it is said that curling stones weigh between 40 and 44 pounds.
In addition to regular sized curling stones, there are also stones that weigh 21 pounds for children to throw. Many young curlers from ages under 12 will throw these smaller stones, commonly known as "Little Rocks." This allows young people to enjoy the game of curling just as much as a teenager or adult, but have an easier time delivering the stones.
Trefor granite is one of the types of granite that curling stones are made from. The main manufacturing company to use trefor granite is the Canada Curling Stone company, which uses both blue/black and red/brown trefor granite. This type of granite is known for being impact resistant, which means that the curling stones will not fracture or crack when they collide with one another on the ice.
The other type of granite used is Blue Hone or Red Hone Granite, which comes from the island of Ailsa Craig.
A curling stone is the piece of equipment that curlers will throw during a game of curling. Each stone weighs approximately 42 pounds and are made of granite from Ailsa Craig, an island off the coast of Scotland. A plastic handle is attached to each curling stone for players to grip when they are delivering the stone. During an end of curling, each team will throw eight stones, for a total of 16 stones.
At some arena curling clubs, the curling stones are also used to smooth out the pebble before curling begins. This is done to cut the top of the pebble for a flat, but textured playing surface. If the ice isn't completely level, a blade may further dish the ice, but curling stones will not do that.
Curling stones can be purchased from a few manufacturers in the world. The most common two are Kays of Scotland and the Canada Curling Stone Company. Each of these manufacturers uses a different type of granite, but the resulting curling stone still weighs in at 42 pounds. Additionally, note that curling stones may or may not come with handles attached to them. If the handles aren't attached, you must purchase them separately.
First, granite for curling stones is harvested from a granite mine. These large slabs of granite are broken down into a smaller size such that curling stone 'templates' can be cut. After the 'templates' are cut, stones are individually sanded and ground down to represent the shape of a curling stone. Next, the circumference of the stones are pitted with glass beads to better distribute the impact forces when the stones collide with one another. Lastly, a plastic handle is attached to the stone via a screw.
An average set of 16 curling stones will cost roughly $8,000 to $12,000. This means that each curling stone costs about $500 to $750. However, the prices are significantly lower for the 21 pound stones for children to throw. These stones cost about $4,500 per set: about $280 to $300 per stone.
Note that some curling stones are sold without handles, so you may need to purchase them separately.
Curling stones, if taken care of properly, can last for more than ten years. One of the most common problems with curling stones is that they have trouble 'gripping the ice' as they age. To remedy this, curling clubs will "paper the stones." This means that curling clubs use sandpaper to texture the running surface of the curling stone so that the stones can have a better grip on the ice and travel down the ice as one would expect them to.
According to the World Curling Federation, a curling stone must have a circumference no larger than 36 inches and must be taller than 4.5 inches. This guideline is given because the manufacturing of curling stones isn't an exact science; each stone will turn out a little differently than every other stone. This imprecision in manufacturing also explains why each curling stone behaves differently from all of the others.
There are a few companies that sell curling stones. Some of the top companies are the Canada Curling Stone Company and Kays of Scotland, both of which have produced curling stones for the Winter Olympics. Another common curling stone manufacturer is Thompson Rink Equipment. Note that when you purchase curling stones, they may come in sets of eight or 16, depending on the manufacturer.
In general, the physics of curling hasn't been studied well but we do know that there is some friction between the curling stone and the ice. This friction acts as a source of heat, which melts a small layer of the pebble. Since the front of the curling stone 'sees' the pebble first, it encounters a higher frictional force than the back of the curling stone. The additional friction at the front of the curling stones allows the back part to move faster. This frictional force differential creates a velocity differential, thus allowing the stone to move laterally.
Since 2006, curling stones used in the Olympics have been manufactured by Kays of Scotland, which come straight from the island of Ailsa Craig. This means that no curler has used the curling stones before the Olympics begins. Having new curling stones for the Olympics helps ensure that the stones play as consistently as possible since they have not been used yet. Before 2006, the curling stones were produced by the Canada Curling Stone Company.
Curling stones come in one color, gray, because that is the color of the granite that is used to produce all curling stones. The curling stone handles, however, come in a variety of colors. While the most common colors are red and yellow, other colors such as blue and green can also be seen on a curling stone handle. On the curling stone handles, there may also be an engraving, which is painted a different color from the main color on the handle.