Narrator: Using rare granite
from just one island in the world,
experienced stonemasons turn these giant boulders
into hundreds of uniform curling stones.
But these aren't just any curling stones.
They're the only ones allowed in the Olympic Games.
A single stone certified for the Olympics costs over $600.
That makes a full set of 16 stones worth $9,600.
So, how are Olympic curling stones made?
And why are they so expensive?
Since 2006, every curling stone
used in the Olympic Winter Games has come from here.
It's produced stones since 1851.
But today, there are just 10 people
in the world who make them.
Mark: They love what they do.
They're very passionate about it
because they know that this particular
block of granite they're working on
that becomes a curling stone
could be the stone that's thrown
for the gold medal at the Olympic Games.
It could be the stone that decides a world championship.
Narrator: Every stone comes from one tiny island
off the coast of Scotland.
For over a century, masons have ventured
to Ailsa Craig island to harvest granite for curling stones.
Until its lease expires in 2050,
Kays is the only company in the world
with permission to harvest granite here.
And for curling, Ailsa Craig's granite structure
is the gold standard.
But getting granite to the mainland is far from simple.
Well, the harvesting process
is a logistical work of art, I think.
There is nothing on the island, as you say.
It's uninhabited. There's no water supply
other than some running water
from the rivers and streams on the island.
There's no electricity supply.
So we have to take absolutely everything with us.
Narrator: Kays uses two types of granite
from the island to produce curling stones.
First, there's blue hone granite,
which makes up the layer that runs along the ice.
Then common green is used for the part
that strikes other stones.
This is Ailsa Craig common green granite.
So this makes up the full body of the stone.
You can also see this slightly lighter,
grayer-color granite inside,
and this is Ailsa Craig blue hone.
Narrator: The rock is densely constructed,
thanks to how well its fine-grained crystals
and the feldspar interlock.
This makes the stone resilient.
While other rocks might crack or splinter,
Ailsa Craig granite stays intact
amid cold temperatures and collisions.
Most other rocks will have imperfections,
like veins that cut through the stone.
And while it's not free from weaknesses,
there aren't many throughout Ailsa Craig rock.
Weaknesses make it more likely
a stone will fracture upon hard impact,
something that would upend a curling game.
Before Kays can begin making stones,
each rock is cut into slabs.
But not all the granite the company harvests
is suitable for a curling stone.
Sometimes areas of a slab have small imperfections
that could cause it to erode or impact the game.
Mark: It's generally because there's a flaw
or a fissure or a crack or something in it.
Narrator: This is where the eye of the masons comes in.
Throughout the process, they assess the granite
and confirm it satisfies Olympic requirements.
Mark: The slab thickness, we are looking for
145 millimeters, you know, 14.5 centimeters, thick.
Then that gives us the ideal depth for coring,
which then allows us to shape the stone
while retaining the weight.
Narrator: From the slab, Kays marks
only the best parts worth coring,
which are the areas it'll eventually shape into stones.
Mark: We've gone to a lot of time and effort
to bring this resource from an island
over to the mainland that we want to make
the most effective use out of it.
We can get boulders off the island
that can be in the region of 5 to 7 tonnes.
They will yield way more than five or six cheeses per tonne.
But if we average it out across a whole harvest,
then if we get around six cheeses per tonne,
we're doing pretty well.
Narrator: They call them cheeses,
for no clear reason other than:
Mark: I suppose in one respect, they maybe look
like a Babybel cheese or something like that.
I've never really thought about it too deeply, to be honest.
Narrator: While the process today
largely depends on machines,
it needs experienced craftspeople to see each stage through.
Mark: The cutting process or the coring process
is a skill and an art in itself.
So while it's semiautomatic in terms of feeding itself in,
the speed is manually controlled,
and that's where the skill of the operator comes in.
Narrator: After each cheese has been cored,
masons chip away the excess stone around the corners
and prepare it for shaping.
The International Olympic Committee
determines the size, shape,
and weight of each stone for the games.
Before the stone reaches its final shape,
masons fit the blue hone granite
into the common green body.
The stone itself weighs 40 pounds,
plus another pound for the handle.
After it reaches its final form,
it's time to polish it.
Each stone needs to be uniform in weight,
size, and running surface.
The running surface on the bottom
determines how much the stone curls.
To curl, there needs to be friction
between the ice and the stone.
That roughness is achieved
by the experienced hand of a mason.
Kays stores granite over time,
returning to Ailsa Craig about once a decade.
Other producers harvest granite
from the Trefor Quarry in Wales.
Kays once sourced granite from Trefor, too.
But Mark says quality-control issues turned it away.
And it didn't hurt that the World Curling Federation
preferred Ailsa Craig stones.
Mark: They found that the Kays stones with the insert,
the blue hone insert, were the best,
because they also discovered that having a curling stone
that's not got a blue hone insert will pit.
It has a certain porosity, it will pull in water,
and water and ice will then freeze.
When water freezes, it expands;
leads to the detriment or the damage to the stone.
Narrator: While curling has recently
skyrocketed in popularity, demand for stones
has fluctuated since the game began.
Curling is believed to have started in Scotland,
but today, Canada is the most successful team
in the history of curling.
Curling here goes back to the late 19th century ...
Clip: A curling stone gets some last-minute polishing.
Narrator: When many of the Scots who immigrated to Canada
brought the game with them.
By the '50s, Canada was building
hundreds of curling rinks.
Now retired, Jimmy Wyllie worked at Kays during this period
and saw the company thrive before demand dropped again.
Jimmy: When all of these new ice rinks in Canada
were satisfied, the demand fell off dramatically.
So we went from 25, 30 people
down to about between five and 10 people.
Narrator: A major component that's kept the game —
and Kays — alive today: the Winter Olympics.
Mark: When curling was put back into the Olympics,
it was great.
It was a really — it was a momentous moment
in terms of a curling-stone manufacturer,
because it suddenly opened curling up to the world.
During 1990, there was only 25 countries in the world
that were in any way involved in curling.
And now, 20 years later, that's almost tripled.
Narrator: As of 2022, 67 countries compete in curling.
Naturally, that's created an uptick in demand for stones,
which has carried over into their price.
Mark: We have increased our sales,
which is really, really good news.
And having said that, we've also increased our cost,
because we have to go back for granite more frequently
to satisfy the demand.
Narrator: In 2000, Kays harvested
about 1,500 metric tons of common green
and about 300 metric tons of blue hone.
13 years later, it took 2,500 metric tons of common green
and 500 metric tons of blue hone.
Fortunately for the growing interest in the sport,
and for the only supplier of Olympic curling stones,
supply isn't a problem.
Mark: The last harvest, in November 2020,
we took less than 0.01% of the island.
So we're scratching the surface.
The whole island is made of granite.
We're not making that big a dent in it.