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From Behind the Hack: Reading the Ice

Reading the Ice – It’s All in Your Head (Kind of)

By Mark Olson

In Arena curling, any given game often turns into a bit of a race: whichever skip figures out what the rocks will do on the ice that night stands the best chance of prevailing.

In other words, with all other things being equal:

Who reads the ice best, first, wins.

Some inspiration

“Show me a [team] of readers, and I will show you the people who move the world.”  ~  Napoleon Bonaparte

“Not all readers are leaders, but all leaders are readers.”  ~  Harry S Truman

“The more that you read, the more things you will know. The more that you learn, the more places you’ll go.”  ~  Theodore Geisel


While all that is really at play here is gravity and a bit of physics (no biggie, right – how complicated can THAT be?), reading arena ice can rapidly become more of an art than a science.  This is true both for all of us, from the scientifically-minded engineer that’s trying to work the numbers, to the more experienced curlers that will be all-too-happy to tell you that they’ve seen it all, and have the faded pictures to prove it.  In fact, I have seen a number of very experienced skips have the hardest time trying to figure out arena ice…. Why, you ask?  We’ll get into that.  Read on.

Reading arena ice can be a challenge because, as we’ll see, every game is a new and different set of conditions to interpret.  Even with a generalized plan, the results from week to week are often very different.  But you still want to have that plan, and we’ll spend time plenty of time discussing that, too.  Never fear.

Why is the ice the way that it is?

Let’s talk about the ice first.  In particular, ask yourself, “What is being done to an arena’s ice surface when our roaring game isn’t being exhibited in all its glory and splendor?”  Really only two things are going on outside of curling – skating and resurfacing.  That’s it.  Of these, the skating is actually the lesser concern.  Yes, there are gouges, scrapes, picks, pits, runs, and all that.  True enough.  But those, for the greatest extent, at least try to get taken care of through the other part of the conversation – the resurfacing.  Yes, the dreaded Zamboni.  That, dear readers and true believers, is the primary source of all the issues we face.

Zamboni is a brand name, like Frigidaire, Band-Aid, or Kool-Aid.  It’s also become a collective term, like those others as well, so while not all ice resurfacers are Zambonis, that’s the term we’ll use here.

You don’t believe me when I say that the Zamboni is the heart of our ice surface problems?  There’s a reason why dedicated ice clubs don’t use Zambonis to resurface and maintain the base ice surface, even if they’re open enough to do it.  You’ll see – it’s like lighting your backyard grill with a flamethrower.  Sure, it’ll work, but what else is going to happen….

To start with, Zamboni-based resurfacing has a tendency, over time, to build up the ice surface, especially near the boards.  That makes the entire hockey rink like a bit of a bowl, over time.  Take a look at the ice surface right next to the Zamboni doors at your rink at the start of the season, and then again at midseason, and once more shortly before the season ends.  It’s not uncommon to see inches of buildup in the ice surface in a relatively short period of time.  And remember – they’re not going out and flooding in the meantime – it’s all the Zamboni that’s doing that, a cut at a time, several cuts per day in most arena environments.

That’s just the beginning.  Zamboni resurfacing runs, to ensure complete coverage of the ice surface, have to overlap.  The driver is too far away from the actual blade surface to make really fine path adjustments, and the actual cutting blade is covered anyway – so the driver can’t even see it.  So just like when you’re mowing your lawn, the driver needs to overlap the passes a little bit.  That leaves areas where extra ice is removed over the length of the travel path, resulting in runs.  Now add in the water being put down onto the freshly scraped surface during a “wet cut”.  The water is being applied to the ice surface through a fabric pad (to ensure even coverage across the entire pass width), but in order to have complete saturation of the pad, the flow rate of the water into the pad is such that some water comes off the side of the pad, creating an excess of water being applied just outside the travel path of the vehicle.  Excess water = ridges, once that water freezes.  Small ridges, often not even visible to the naked eye, but they’re there.  Combine those with the runs that we just talked about (also too small to see), and you actually get an invisible wave effect running parallel to the travel path of the vehicle.  Since that travel is generally in the same direction as the curling sheet, you get…. you get the idea.

Factor in the mechanical fact that most of the blades on a Zamboni aren’t 100% level to the ice surface (higher or lower on one side than the other), variations from side to side on water flow rates, and other mechanical issues that can’t be helped, along with all the rest, and you get a real mess, from the perspective of a curling stone.

OK, I have to stop here – We love our Zamboni drivers, and we appreciate everything that you do to try help us, from dry cuts, to alternate cut patterns, and all that.  I’m not taking anything away from what you do, and the effort that you make to keep us happy.  We know it, we appreciate it, and we thank you for it.  The things I’m talking about aren’t your fault; they’re simply the fact of the matter.  We get that….. Peace, Okay?

Yes, there are laser levels that can be mounted to Zambonis for help in preparing curling ice.  You’ve probably seen the ads in Curling News.  If anyone in the Club is willing to donate several thousand dollars to get one for the Arena, let me know, and I’ll get you in touch with the right people to make that happen.

“But hockey is played in lanes, which get worn down more than other parts of the sheet.”

True enough.  Not to mention that the primary lane is down the middle of center ice, and then splits into two lanes inside the offensive zones inside the blue lines (ever so near our hog lines, you may have noticed – very convenient).  Add that to the resurfacing issues, and it gets a little bit more crazy.

The last piece of the puzzle, at least for here and now…. None of these features (blade overlap, freeze ridges, hockey attack lanes, figure skater toe pick holes, speed skating paths. etc.) are the width of, or isolated to the boundaries of, our curling sheets.

Very simply, to make a long story short – you can expect to see any ice effect anywhere on your ice sheet at any given time, and it’ll change from week to week, depending on the ice usage between your last league draw and your current game.

What should perfect curling ice be like?

  1.  ABSOLUTELY level everywhere, as compared to everywhere else on the sheet.
  2.  ABSOLUTELY flat everywhere, as compared to everywhere else on the sheet.
  3.  A button draw should take about 23 seconds to travel from tee line to tee line.
  4.  That same button draw should curl about 4 feet from the line of delivery, for either turn, no matter where on the sheet you hold the broom.

OK, so now that we know what Heaven is supposed to look like, let’s look at what you’ll really see.  Having an idea of what you should expect is great, but NEVER let what you expect overshadow what you SEE.

That is the most common pitfall that dedicated ice curlers tend to make when encountering arena ice – they tend to assume that the ice will do what it’s supposed to, and even when they understand that it won’t, they often expect it to be consistent from arena visit to arena visit.  Both of these assumptions are pitfalls, and should be avoided.  The ice is fickle, and you need to believe what you see, here and now.

What can I expect to see on the ice?

There are some general “forms” that the ice can take.  We’ll look at them individually, even though you can expect to see combinations and superpositions of them anywhere, at any time.


Falls can be defined as ice that is sloped to cause the rock to move consistently in one direction, regardless of turn, regardless of location of the ice.  An out-turn that moves like an in-turn, and an in-turn that falls to the sideline like it’s late to a party – you’ve got a fall.


Ridges appear as lines in the ice – if the rock is one side of the line, it falls one way.  If it’s on the other side of the line, it falls the other way.  A rock that is released on one side of the ridge with a curl that takes it over the top will often look to be a slow curl that breaks a LOT as the rock crosses over the ridgeline.  If a rock is released on one side of the ridge to curl on that same side, it may look like a fall.


A trough is defined as two falls that fall toward each other.  The width of the area between the falls can vary from a line, to a trough like a river bed along the sheet.  These can often be read by noting the rock as it tries to climb out of the trough and seeing it fall back in, only to repeat the same action on the other side.  Getting out of a trough is possible, but will often need a lot of weight.  Then, you have that to deal with afterwards.  So, be careful.


Plateaus are similar to ridges, except there is a flat area in between the two directional falls. If the rock is released in between the falls, then the rock may look fine until it reaches the edge of the fall, and then it goes.  This can be hard to read sometimes, because the effect can look like a hard curl in one direction only, depending on where you are.  Cases like this are why it’s so important to try get a read on the WHOLE ice as you’re building your mental map.

Negative ice

Negative is not an ice feature unto itself, but is an effect of playing on a fall…. When you want the rock to move one way and it simply refuses, and goes the other.  This can be predicted to some extent over the course of a single game, but no other assumptions should be made about it beyond that.  Watch and learn from what you SEE.

Pits and chunks

You know – holes from figure skater’s toe picks, the hard pivots and cuts from the hockey players that don’t get completely filled in by the Zamboni, maybe a chunk of ice here or there that gets missed during the sweeping while we set up the ice.  Some things we can address and take care of, some things we have to live with.  Fortunately, most of these things are very small and isolated to singular locations that hopefully we can correct or avoid.  If you see one, note it and try to avoid it, if it’s an issue.  It might not be.


Oh, no, you won’t just see these features in isolated cases.  You will usually see them in various combinations, so be ready to put pieces one on top of another on top of a third…. It’s never as easy as you’d like it to be.  Sorry.   Take a look at the pictures shown above and think about how you would expect to see the rock move in each of these cases?

How do I figure out what the ice is doing tonight?

As I mentioned before, knowing what conventional “perfect” ice should do is a start, but that has got to be superseded by what you actually see.  So you need a plan to figure out the ice quickly.  To start the conversation, let’s look at this one:

In quick succession:

  • Lead: In-turn guard
  • Second: In-turn draw, front-of-house, under guard
  • Third: In-turn hit
  • Skip: In-turn button draw
  • Repeat with the Out-turn.
  • Repeat (both turns) for the other colored stones as time permits.

Sounds great for a practice session, or an 8-or-9-minute warmup without a Draw Shot Challenge, but we don’t always get that luxury.  OK, so this plan is kind of a pipe dream for League curlers.

The nice thing with that plan, though – both for reading ice, and for warming up, is that it’s based around a few key ideas:

  1.  Everyone shoots shots that are reasonable to expect for their position
  2.  Both turns are thrown by everyone
  3.  You see varying weights, in both directions
  4.  All rocks (of at least one color) are thrown at least once.
  5.  Did you notice – no sweepers?  That gives a truer evaluation of what the ice is actually doing.

So what if you don’t get to do this nice, pristine, antiseptic warm-up?  You have to read the ice as you go, during the game, using your actual shots – and your opponent’s as well.

Look back at the keys ideas behind the plan.  Some items have been starred – those are the key points that are geared more toward reading the ice, so they are things you want to keep in mind as you read the ice in the game:

  • Use reasonable, predictable shots to evaluate the ice.
  • Read shots of both turns
  • Read shots of different weights
  • Try to evaluate shots independently of sweeping

Using your shots to read

Every shot you throw tells you something about the ice, if you choose to listen to it.  It may only tell you what you already know, but that is also telling you that things aren’t changing – yet.

While the shot comes into the house, pay attention to where it ends up.  Add to that consideration of whether or not the shooter hit the broom, and the weight, and you have the read for that shot.

Skips, you have the best sense to judge whether or not the shooter hit the broom.  So you now need to keep two things in mind for every shot – what you wanted and what you got.

Reading the ice is one of the reasons you’ll see skips picking a lot of different weights and turns in the early ends.  They’re building up a mental map of the ice sheet that they use when judging what ice to call for other, later shots.

Using opponent’s shots to read

You should also watch every shot your opponent makes.  Yes, this means everybody, not just the Skip.  

Sweepers: Once the shooter passes you in their slide and delivery, quietly slide in behind them and watch the shot – are they on the broom?  What’s the weight?  Based on your knowledge of the ice, should they sweep?  Did they?  Is the ice behaving differently for then than it did for your teams’s last shot?

Skips: Stand behind the calling skip, even as they make the call.  Remember to stay behind the back line.  Where is the skip holding the broom?  Watch the slide and delivery – did the shooter hit the broom?  How does the line look for the called shot?  Is the shot on weight?  Does the shot break where your team’s rocks break?  Is the break point moving?  Is the pebble changing?

File all of this away.  You will use it later.

Don’t be surprised if things do change over the course of the game…. they’re going to.  Expect it.  More on that in a bit.

The Mental Map

What any skip is actually trying to do – or should be trying to do – as they’re reading the ice, is to build up a map of the sheet in their head.  The amount of information on this map will grow with experience.

If you have experience in building these maps and you have a method that works for you, don’t stop what you’re doing, unless you feel it isn’t working.

If you are new to building these kinds of mental maps, or if you are looking for a new way to approach it, I would suggest building up answers to the following questions, by about the middle of the second end:

  1.  Do the rocks curl normally or not?
  2.  Does the behavior of the rock differ on the right side of the sheet versus the left?
  3.  Does the behavior of the rock differ in the center of the sheet versus the outside, near the sidelines?
  4.  From the delivery side hog line to half ice:
    1.  Does the rock run true to the line of delivery, or does it start to move early?
    2.  If it moves, what direction does it move on each side of the sheet, and for each turn?
    3.  Which of the ice features does this match?
  5.  From half ice to the house-side hog line:
    1. Where’s the break point?
    2. Does the fundamental behavior of the rock change (for whatever part of the sheet the rocks is on) from the earlier part of the shot – that is, are the ice features changing over the length of the sheet?
    3. What effect does (regular, non-directional) sweeping have? Does the rock run straight?  Is motion after the break amplified or dampened with sweeping?  What direction?
  6. From the house-side hog line to the end of the shot:
    1. How is the rock travelling after the break? Does it vary with different weights?
    2. How does the rock finish? That is, what effect does sweeping have on the rock in the slowest part of the rock’s travel, especially at the very end of the shot?
  7.  How do all of these change with different weights?  Start with draw weights.  Always build your map based on draw weights.  Hits often travel too fast to get really accurate reads, but they also have information to give, so don’t discount them out of hand – especially the amount of curl to call on hits.
  8.  Repeat all of this playing in the other direction.  Your results WILL be different.  It’s not unusual to play downhill (fast) one way and uphill (slow) the other.  Keep track of which effect is playing in which direction, reading a map that’s upside down is no fun.

Lots of questions – and you want answers by the middle of the second end?  Sure – use that same plan from the warmup, but use the actual shots you are playing to get the information you need.  That’s why you’ll often see skips trying opposite turns for the same intended result in the early ends.  It’s not that you can’t make the shot.  In fact, they’re counting on you to make the shot, and want your shot tell then things they don’t know.

Yes, some of these questions and some of these areas of the sheet that you’re looking at, overlap; that’s OK.  The results you get will be different playing away as compared to playing home.  At the end of the day you have an idea of how each turn will react on each part of the sheet, at least at draw weight.  That’s your base map.  That’s the one you want to builds as fast as you can, because while it’s your baseline, you need to learn its lessons quickly – because it’s going to change a bit as the game progresses.

How does the ice change over the course of the game?

The main effect you’ll see changing over the course of the game is the breakdown of the pebble.  What does this mean?  The big thing you’ll see is that somewhere around the third end or so, the rocks will start to run straighter and a bit keener, so the ice will become faster, and guard weight from the beginning of the game will all of a sudden become draw weight around the middle of the game.  It’s going to happen, without exception.  The thing to also be ready for, though, is that the behavior of the rocks outside of the weight may also change, because changes in the pebbles, as well as changes in the effective weight of the shot, can expose features in the ice surface as compared to the surface that was in play at the beginning of the game.  The magnitude of these changes is generally greater between the start of the game to the middle of the game, as compared to the differences seen between the middle of the game and the later ends.

Over the course of the game, you can expect shots to run straighter and keener, starting in about the third end or so.  After that, it tends to kind of level out.  You may discover some refinements of your mental map of the overall ice surface when this happens, so be ready for it.

How the ____ do I deal with all this?

Good question.

There are two ways to approach this – as a sweeper, and as a Skip.  Yes, those of you who play Third, here’s yet one more part of the game where you are being asked to be able to do everything.

Sweepers: When you know that a particular feature of the ice surface is coming into play – SPEAK UP!  It’s not like you’re giving away state secrets here – the other team is in the process of building their map, and probably knows what you’re thinking anyway.  It’s much more important that your team knows what’s happening with the shot than to worry about telling the opposition something you don’t want them to know – chances are they know it already.

When you’re sweeping a rock that’s under the effect of an “ice feature”, ask yourself one singular question –

Does my sweeping keep the shot on track or does it make the shot worse?

Sweeping a rock that’s falling (or a regular shot after the break) will result in the sideways movement of the rock being amplified.  I know that we say a swept rock travels farther and straighter – that’s actually a bit of a big-picture generalization.  In reality, a swept rock keeps going on the direction it’s already traveling.  If there is a significant sideways component to the motion, it will continue.  If the motion is straight, that will continue as well.

Do you want to sweep a falling rock and try to bring it back?  Once the rock starts to veer off, probably not.  You may be able to employ some directional sweeping to help, but that’s now a fight of friction effects against the momentum of the rock…. Last time I checked my old, worn, college physics book, the rock’s momentum and inertia are much greater effects than the friction change that even furious sweeping will give.  At the same time, if the Skip says sweep, then sweep.  Argue about whether that call was right after the game.

Directional sweeping?  Tell me more!!!!

Ease up.  Let’s stick with the ice for now.  Directional Sweeping is a discussion for another article, assuming that sweeping rules don’t change in the near future….

In summary:

If sweeping helps the shot, sweep.  If not, don’t.  Talk to the skip about what you see as you move with the rock.  It’s better to start sweeping early than late, and always listen to the person in the House.

Skips and Thirds: The fact that a swept rock continues on its current path is why the person in the house is the one who should be watching and calling line – they have the best view of the overall motion of the rock with respect to its target.  That’s you.

Use the map that you have, but always be willing to modify it.  Talk to your sweepers.  They see the small picture where the rock is at the moment, you see the bigger picture of the shot.  You need both parts to know the whole story.

There is nothing wrong with calling sweepers on and off like you’re schizophrenic.  It might drive them crazy, but deep down they do realize that trying to keep all of this straight can be confusing, and sometimes you’re trying to make the best of a really odd situation.   But listen to them, too – if they tell you that all the crazy work they’re doing isn’t helping, they just might be right.  Trust what you see – not what you think you should see.  Talk to each other.  Talk to each other.  Talk to each other.

If that one shot got read just plain wrong, don’t sweat it.  There are plenty more to make.  Get ready – here comes the other team’s next shot – what’s the call, and what is the rock doing?

The only thing constant about the ice is the change

Of course, none of the features of the ice surface that you see on Week 4 of League will necessarily be the same as the features you see on Week 5, Week 6, or Week 7…. you get the idea.  All this really means to you is that the map you built last week, while maybe a part of the answer, is not and never will be the full and final answer.  You need to build a new map every week.

The Wrap-Up

Have a plan – and execute it

Use ALL the shots to build your map

Trust what you SEE, not what you expect

Remember that the Map is going to change

Sweeping keeps the rock on its current path – is it the one you want?

This has been a lot, I know.  Don’t get yourself wrapped around the axle, and take one step at a time.   Just keep on making better and better maps over the long term, with improvement measured over the course of an entire season, or from year to year, and you’ll get to where you want to be.

Slide straight and shoot true,