A Tech Controversy is Hitting the World of Curling

You know technology is a pervasive force in sports if the seemingly-tranquil game of curling is getting involved. Yes, it seems as if the roaring game is mired in its own back and forth over technological advances. No, no one has installed remote controls in the rocks, but — at least according to some people — recent changes in the sport mean that comparison isn’t too far off.

To explain the scientific changes going on in the sport, one must first understand the science behind curling itself. If you are a veteran of the sport, please forgive my high-level overview.

I won’t go into the intricacies of scoring in curling, but suffice it to say that the point of it is for the person delivering the stone to get it to stop exactly where they want on the other side of the ice. That ice is covered in tinier bumps of ice called pebble. Essentially, a watering can of sorts sprays droplets on a flat surface of ice. Those droplets freeze to the surface and create a bumpy texture. It’s this bumpy texture that allows the curling stone to move as far as it does. The stone glides along those bumps, rather than on a flat sheet of ice. If curling were played on hockey ice, the stone would barely move as the concave bottom of the stone would create a suction. The pebble is also how the sweeping comes into play, and that’s what everyone is up in arms about.

If you’ve ever seen a picture or video of curling, you may have noticed two people flanking the rock while holding weird looking brooms. The person throwing the rock has the most influence on what happens, but the sweepers are there for the fine tuning. Sweeping the pebble momentarily melts it. This allows the stone to move farther down the ice while also decreasing its rate of curl. Sweeping makes stones go farther and straighter.

Way back when, the sweeping was done with good old-fashioned corn brooms — you know, the kinds witches ride around on. But in the last quarter of the 20th century, broom technology began to see upgrades. The handles went from wood to fiberglass to carbonfiber. The broom heads went from corn to horse hair to synthetic fabric stretched over a type of cushion. Brooms got lighter and more effective, meaning sweepers could influence the stone more and more. But for the most part, the changes were incremental. Things got better over a long period of time. Now, it’s an arms race.

Old horse hair curling brooms. Taken by the author at the Chicago Curling Club.
Old horse hair curling brooms. Photo taken by the author at the Chicago Curling Club.


Examples of the newer, synthetic style of brooms. Photo taken by the author at the Chicago Curling Club.
Examples of the newer, synthetic style of brooms. Photo taken by the author at the Chicago Curling Club.

Teams these days — and I’m talking about the tops teams that play for cash prizes and sponsorships in Canada — put a very strong emphasis on sweeping. While teams certainly still work on strategy and delivery, sweeping is now a big part of the game. The reigning men’s Olympic champion and 2015 Canadian National runner-up squad from Northern Ontario knows this. That’s why their front two players (those that sweep the most) look like this:

The Harnden Brothers (EJ and Ryan) of team Jacobs (Northern Ontario). Image via WikiMedia
The Harnden Brothers (EJ and Ryan) of team Jacobs (Northern Ontario). Image via WikiMedia

Technique and physical fitness are now part of a sweeper’s training regimen. Teams with great sweepers have an advantage. But fitness and technique can only take one so far. Eventually, the tool has to be upgraded.

The synthetic brooms from even a few years ago were all pretty similar. They all had lightweight handles, and the pads were made of a sort of nylon material — not dissimilar from a boat canvas. It was durable and swept quickly and smoothly. Different companies made variations of course, but they were all fairly similar.

Then, about five years ago or so, a company called Hardline came out with a new kind of pad. They call it the icePad. It’s a little smaller, much thinner, and the material that covers it is much different than previous broom. Hardline broom material is more like something found used to make a tent or winter coat. It’s much thinner and the weave is much tighter. The broom as a whole is very light and easy to sweep.

In the past couple years, the use of Hardline brooms among top competitive teams has grown quite a bit. They can be seen in almost every major event. Hardline sponsors many teams in hopes that exposure will convince recreational curlers to buy their product. They are fine brooms that make sweeping easier and are competitively priced. And some people want them banned.

The controversy revolves around what’s now being called “directional fabric.” There’s a lot of bickering and conjecture involved, but here’s the gist. Hardline started making a serious dent in the curling industry. This, theoretically, cut into the profits of other equipment manufacturers like BalancePlus. This year, BalancePlus released their own version of a “directional” broom that can do some really amazing things to a curling stone. In case you’re interested, here are two videos put out by BalancePlus.

The first shows a BalancePlus broom essentially changing the curl direction of the stone:

The second shows a stone being held incredibly straight down the line:

Basically, BalancePlus took Hardline’s broom concept and cranked it to 11. Now, people are calling foul saying that these new brooms make the game too easy, that simple sweeping techniques and new brooms are taking the art of shotmaking out of the game all together. They debuted these brooms earlier this year, and some teams and fans got pretty peeved.

Now, some teams have agreed to a pact where they will not use any of the “directional” brooms in competition, including both the BalancePlus and Hardline brooms.

Hardline believes that BalancePlus is playing the part of a bully — making an absurd product to garner vitriol over all makes of these brooms in an attempt to get them banned. As of this writing, these brooms are legal. But if that were to change, teams would have to go back to using more traditional brooms. One of the biggest makers of traditional brooms? BalancePlus.

Hardline doesn’t make traditional brooms. They are a smaller company (they were even featured on the Canadian version of Shark Tank) with limited resources. These types of brooms are their bread and butter. They can’t go back to making other kinds without incurring significant costs. Even further, they claim their heads don’t even perform in a directional way — that their brooms aren’t even capable of the things the BalancePlus offerings are.

At some point, a committee will have to be set up to sort all this out. Some independent testing will have to be done and some rules will have to be put in place. But until then, what’s being dubbed as BroomGate (cue audible eye roll) will remain the talk of curling clubs all across the world — after the requisite drinking stories and dirty jokes, that is.

(Header image via RyAwesome)

David G. Temple is the Managing Editor of TechGraphs and a contributor to FanGraphs, NotGraphs and The Hardball Times. He hosts the award-eligible podcast Stealing Home. Dayn Perry once called him a "Bible Made of Lasers." Follow him on Twitter @davidgtemple.

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6 years ago

I’m a medium fan of curling and quite enjoy the strategy and shot making. I’ve always been annoyed at the concept of sweeping. From what I understand, sweeping used to be necessary since in the early days of the sport, ice conditions weren’t what they are today. I would love to see curling where we eliminate sweeping entirely, or limited to sweeping before a shot (to clear any debris in the path).

Love seeing a curling article! Thanks.

6 years ago


6 years ago

nice article. as a competitive curler for a number of years i can say that you more or less nailed the gist of the whole debacle. my view? the BalancePlus fabric should obviously be banned. it takes all of the skill out of throwing the rock. you could miss the target by 30 feet of distance and 6 feet of line and still make a perfect shot because of the sweeping. that’s not in the spirit of the game at all. the Hardline product i am less sure of. i have seen them and used them in competition countless times and have never noticed any of the ridiculous action seen in those videos. there is all kinds of weird politics going on here though, cause certain teams are sponsored by certain companies that either stand to gain or lose depending on where the World Curling Federation draws the line on what is fair and what isn’t. for example the team featured in the above videos is Team Glenn Howard, an excellent team from Ontario that has been maybe the most outspoken against the use of “directional” fabric of any team. who are they sponsored by? BalancePlus, who would love for broom technology to go back to how it was 3 years ago. so defending the integrity of the game, or sticking up for a sponsor?

Jetsy Extrano
6 years ago

Fascinating. Paging Dr. Alan Nathan to the curling rink to explain these directional broom effects, please.

The front and rear of the stove have different angles of motion across the ice, so maybe these brooms create an anisotropic surface that has different friction between the stove that travels aligned with the pattern axis, and the stone that travels misaligned?

Say what now?
6 years ago

So the little bumps on the ice exist to make the rock go farther, but sweeping the bumps to melt them also makes the rocks go farther? Does that make sense to someone somehow?

6 years ago
Reply to  Say what now?

Sure, the sweeping only slightly melts the bumps (so they’re still there over a smooth surface, just ever so slightly and temporarily melted) but it does reduce the friction on the spinning rock, and reduced friction is more speed and less curl.