Ice and Rocks

Before we get into the details of making club ice, consider the the big three priorities.  Many clubs have the same problem.  Under-scraping and over-pebbling.

Club Ice - The Big Three

1. Keep your ice surface at 24-25 degrees.

2. Deep scrape before every draw.

3. Use a game appropriate pebble (in many cases a single pebble is good enough).

A discussion of modern day curling and the success of your club, events, team, programs, etc. would not be complete without talking about the quality of your ice. Today's curlers expect the ice conditions to be fast and true. However, the ice is constantly changing and will change from club to club, event to event and even during the game. Local ice technicians study the control factors, listen to playability feedback and make adjustments to always improve the ice conditions.

In addition to your good delivery, sweeping mechanics and strategy, the ability to assess and monitor the ice (and rocks), will determine you team's success.

Ice playability has evolved rapidly in the last twenty years to thirty years. The invention of the curling ice scraper and the use purified water has changed the game. The ice of the past; slow, straight and dirty, is no longer acceptable. 

As the ice conditions improved, the ice technician gained more and more influence on the game itself.  The ice tech has the ability to change conditions by adjusting several factors.  The need to ice playing standards arose.

Overriding Ice Maintenance Principles

Your club's leadership is responsible for setting the club's ice standards.  Speed, curl, durability and air temperature (for player comfort) standards must come from the top down.  Whatever management structure you have, Board of Directors, Company President, etc., they must drive the ice condition standards.  It is quite common for club leadership to accept "what the Ice Tech gives you".  This is a great example of the tail wagging the dog.

Whether you have a paid Ice Tech or a group of volunteers, they should expect to work toward you standards.

Modern Ice Performance Standards

What do we expect when it comes to the ice? In some countries rigid field of play standards have been developed for championship play. To date, the World Curling Federation has not developed a set of printed standards. In the United States, for example, club and championship field of play conditions must meet the following standards:

Standard Acceptable Deviation

Curl 4.5 feet both ways   1/2 foot either way

Speed 14.0 - 14.8 seconds hog to hog   .5 seconds either way

3.80 - 4.00 seconds back to hog .25 seconds either way

Durability Pebble durability through 11 ends   None

The above standards were developed through a partnership between athletes and US governing body. They represent a good balance between ice that plays well for the athletes and ice that is suitable for an aggressive game, where lots of rocks are in play. Television audiences prefer the action of a house cluttered with rocks.

Ice Maintenance

Curling ice maintenance is an art.  The information below will give you a working knowledge of the main principles of ice maintenance.  We encourage ice makers to attend as many clinics, certifications, etc. as possible.

To achieve the above standard, the ice must be maintained using some basic maintenance techniques. Ice should be scraped daily to remove the pebble from earlier games. A proper scrape completely removes the old pebble so new pebble can be applied. In many clubs, the ice is either not scraped daily or under-scraped. It may also be over-pebbled. This means the pebble will build up over time, creating a course surface which be slower and straighter and keep dirt from being scraped away. The ice will also slowly increase in thickness as the pebble builds-up.

In championships conditions, the ice is leveled during the pre-event preparation and is scraped flat after each game. This completely removes the old pebble before the new pebble can be applied.

The information below is a guideline for ice making. Every facility is different and ice standards may be different. Work with your facility to make the best ice possible.

Club Ice Maintenance Recommendation

• Maintain your ice surface temperature in the 23-25 degree range.

• Keep your air temperature 40-43 degrees at chest level for player comfort.

• Humidity - Dew Point should be 2-5 degrees above surface temperature.

• Deep-scrape daily with a freshly honed blade.

• Use a minimum of three scraping sets adjusting the blade angle after each set.

• Scrape as close to the draw time as possible (4-6 for a 6:15 draw)

• Light-use social league play - Single, fine or medium pebble, 120-degree water, 60 seconds, 100 swings.

• Heavy use competitive league - Use a double pebble, 35 seconds each, 80-100 swings.

• Nip (preferred) before the game.

To re-pebble the ice during back-to-back games, adjust you're your time and coverage. A 35 second, 80 swing pebble could work. Be sure to nip again.

Ice Performance

Several factors come into play when trying to achieve the ice playability standard. We break them down into three categories: Facility, Ice Technician, and Athlete.

1. Facility

• Ice sub floor
  Sand based vs. concrete base and the amount of insulation under the base. Concrete is preferred due its durability, levelness and even distribution of heat pull. Sand bases can cause pipe runs due the uneven cooling of the feed and return cooling pipes.

• Overhead lighting
  Light creates heat. Certain lighting systems create more radiant heat than others. Fluorescent and LED lights create almost no radiant heat.

• Ice paint
  In some cases, dark painted ice can absorb heat more than lighter colors.

• Radiant energy from the sun
  Radiant heat from the sun can penetrate the roof and ceiling. A barrier (Low E curtain) can be created to reduce the radiant heat.

• Compressor Cycling
  The capacity of the compressor(s) will dictate how fast the heat can be "pulled" from the ice bed. Surface temperature sensors and control set points will determine the temperature range of the surface. Large capacity compressors combined with tight set points (a tenth of a degree) will allow the ice technician to maintain a constant surface temperature. During a championship, the compressors may cycle more often with a tighter temperature range. For example, the system could be set to maintain a surface temperature between 23.0 and 24.0 degrees.

• Heat and Humidity control
  Heat will make your members comfortable and at the same time suspend moisture. A dehumidification system will remove moisture. A combination of the two is preferred. Heat will also create a load that the compressor will have to pull out. The humidity in the rink should be controlled to provide a proper amount of humidity. High humidity will result in frost settling on the ice due to the temperature change between air and ice. A low humidity (dew point lower than the ice temperature) environment may result in "sublimation" which means the ice is changing from solid to vapor without passing through the liquid stage.

Finding the right heat and moisture combination depends on your needs, budget and equipment capabilities. Remember, the more heat you add to your ice shed, the more heat needs to be pulled out with the compressor. Burning fossil fuels to heat a large ice shed can be extremely inefficient without a heat recovery system. A "closed system" is always preferred but not always practical. In a closed system, fossil fuels are burned to heat the shed.  The warmer air in the shed reaches the ice and causes the compressor to pull it out. Then the heat and is dissipated through the condenser and back into the atmosphere. The closed part of the system is a heat recovery process that takes the heat from the condenser and uses it again, back into the ice shed. It's not 100% efficient but a lot better than losing the heat to the atmosphere.

• Ceiling Fans

Most ice technicians will agree that moving air is a problem. However, clubs try to maintain a comfortable air temperature for player comfort. Depending on the height of your ceiling, creating a 42 degree temperature at chest level can be a problem. Clubs are heated by burning fossil fuels.  As the heat rises, the warm air fills the top portion of the shed. In order to heat the lower areas, more heat is needed. Moving the warm air down with ceiling fans will greatly save on energy costs. It is important that the moving air does not touch the surface. 

2. Ice technician

• Scraping

Scraping frequency and number of scraping sets will directly effect playability.  Ice should be scraped daily using the guidelines above.

• Amount of Pebble
  The ice tech can control the amount of pebble applied. They will consider the type of play and length of game. Generally, after a clean scrape (scraping the ice back to flat with no pebble build-up) the ice tech will apply either a single or a double pebble with either a medium or small pebble head. Club play at eight ends (and many league games end after six) and no practice will require only a single pebble.

• Pebble Size and Shape
  The size and shape of pebble will depend on the temperature of the ice surface (freezing base) and the temperature of the pebble water. Warmer water is desirable because it melts into the surface and freezes in a rounder, flatter form. Cold pebble freezes on the surface with a tall shape. Experiment with different pebble heads and listen to your curlers.

• Pebble Water Quality
  Pebble water should always be a good quality de-ionized or RO water. Pebble water will adhere best if there is no gas or impurities in the water. The ice tech can de-gas the pebble water by letting it stand open for several minutes after heating.

• Pebble Temperature
  As mentioned above, warmer water (120 f) is best for pebble.  Experiment with different temperatures.

• Ice Surface temperature
  The ice temperature is critical to achieving your performance standards. Surface temps must be kept between 23.0 and 24.0 degrees. This allows the proper frictional melting needed for speed and curl. All clubs are different, but there is a "crash" point with your surface. In the 24-degree range, the ice has good frictional contact with the rock (rock-ice interface). As the surface warms, the ice gets faster. At some point (something like 27-28 degrees) the ice loses its playability and gets too soft. It is also difficult for players to grip a surface that is too warm.

• Heat
  The ice tech can control the amount of heat in the rink area. Heat suspends moisture and will not allow it to condense on the ice. Players also like warmer conditions. Air temp should be kept in the 40-42 degree range.

• Humidity and Dew Point
  Humidity can also be controlled. The perfect humidity or dew point in your shed won't allow frost to condense OR the ice to sublimate. Try to keep the dew point in the shed just above the ice surface temp.

• Rock Running Surface
  All rocks (running surface) polish over time. The friction of the ice will slowly polish the running surface creating a straighter curl profile. Adjusting ice conditions may help keep your desired curl. However, it is necessary from time to time to "scratch" or texture the running surface to make a more aggressive curl profile. It is recommended the club rocks be scratched on a controlled schedule. See the section on scratching rocks.

3. Athlete

• Weight of the Athletes
  Heavier athletes create more friction on the pebble with their shoes. A large-frame person draw will break down pebble faster than a smaller-frame draw.

• Types of Shoes
  Hi-grip shoes will also cause more friction. Players wearing a slider when sweeping will create less friction.

• WCF Tournament Compliant Broom Heads
  The new WCF compliant brush heads create less friction to prevent "scratching" the ice. A side benefit to the use of these heads is longer lasting pebble, particularly down the heavy-use center path.

Ice Technician Control Points

A good ice technician will assess the facility and the rocks to develop a plan of action. There are four main areas that an ice tech must control:

1. Ice levelness

2. Ice surface temperature

3. Ice surface moisture

4. Pebble durability

Moisture is an ice technician's biggest problem. It causes condensation on the surface which leads to frost. Moisture lubricates the running surface, causing straighter ice.

Curling rocks are made of solid granite quarried in only two places in Europe. Rocks come in different types, mainly distinguished by the types or types of granite used.

Types of Granite 

Blue Hone
Blue Hone (from Ailsa Craig, Scotland) granite is light gray in color and has a smooth, tight grain. These rocks have superior running surfaces and are usually well matched. Blue hone rocks chip easily and are usually chipped at the striking band due to their poor striking characteristics.

Trefor (pronounced Trevor)
Trefors are quarried in Wales and come in different colors, red, brown and gray. The striking bands are usually in good condition due to the great striking characteristics. However, depending on the age and care of the rocks, the running surfaces are probably in poor condition due to pitting. These rocks must be checked carefully for a proper match.

Common Green
These rocks have a distinctive, green, speckled color. They are particularly good rocks but should be checked carefully like the Trefors.

Types of Rocks 

With the three main granite types, rock types are either solid trefor, blue hone or common green or a combination of the granite types.

Inserted Rocks
A common practice today is to insert Trefors and Common Greens with blue hone insert to act as the running surface. This is done by coring-out the running surface of a rock and gluing in a blue hone insert. As far as matching these rocks, they will behave like a solid blue hone with better striking characteristics. These have the best of the best as far as overall playing characteristics.

Scratching the Rocks* 

There is a method to gain aggressiveness in your rocks.  Scratching or texturing the rocks will roughen the running surface and gain aggressiveness. This method is very popular in the competitive world as the world class curlers demand more and more rock performance. It is not uncommon to scratch the rocks mid-way through a world or provincial championship. This method does not actually sharpen the running surface. It roughens it.

Rock manufacturers will agree that texturing the rocks should be the last step in the overall ice/rock performance plan for your club. There are several ice maintenance tricks that will give you more curl without touching the rock's running surface.

Every time a rock is played, practiced with, and/or used for dragging it is slightly polished by the ice friction. The more the rock is used, the more polished it gets. This gradually changes the rock/ice interface.

If you decide to texture your rocks, use a texturing jig to roughen the running surface. The jig allows you to consistently sandpaper the running surface. Several methods can be used based on how aggressive you need them.

Considerations:
Adjust your texturing schedule after considering the following:

• Is your ice normally frosty?
  More friction

• Cold surface?
  More friction

• Do you run rocks before games?
  More friction

On the other hand, warmer, freshly scraped ice has less friction. Nipping instead of running rocks will lengthen the interval.

*Note: Contact rock manufacturer for more information and any possible warranty issues.

Determine how many rocks throws occur at your club.

Scratch Frequency 

Use the following as a guide to rock texturing frequency.

Determine if your rocks are high, medium or low use by counting the number of times each rock is thrown per week. Count your regularly scheduled draws, practice sessions and the number of times the rocks are used to drag. Multiply that number by the number of weeks in your season.

High Use Club 3000 annual or more throws each

Medium 1500 - 3000 annual throws

Low Below 1500 annual throws

If you keep your ice warm (23-25 degrees) which is recommended, texture your rocks every 2000 throws.

If your ice is cold and/or frosty (20-22 degrees) texture every 1500 - 1800 throws.

Type of Scratch 

Start by prepping each rock by cleaning the running surface with camp fuel or other suitable solvent.  Using the texture jig and aluminum oxide paper. One piece per rock.

Type Grit Process

Full 80 Push, pull, 90 degrees turn, push, pull again

Maintenance 100 Push, pull, 90 degrees turn, push, pull again

Light 150 Push, pull, 90 degrees turn, push, pull again

Wipe clean with camp fuel.

The CurlTech "Deep Clean"

The deep clean is a less aggressive scratch.  Using a flat surface (2X4) wrapped with 150 grit sandpaper, use a light circular motion to deep clean the running surface.  After a few rotations, you will see the running surface change color due to the collection of stone dust.  Continue the rotations until the running surface is uniform.  Try to apply the same amount of pressure for each rotation and each rock.

Let's understand what is happening underneath the rock as it travels down the ice. Curling rocks are approximately 12 inches in diameter; however, there is a smaller, ringed portion that the rock rides on. This narrow ring is about 5 inches in diameter and is called the running surface.

As you know, rocks are intentionally rotated either clockwise or counterclockwise when thrown. Intentional rotation provides the necessary degree of predictability as the rock travels down the ice. Most rocks, if thrown without a rotation, will assume a rotation at some unpredictable point. As the rock is rotating, one side of the running surface will always be moving faster than the other as it travels over the ice surface.

• Clockwise rotation curls from left to right.

• Counter clockwise rotation curls from right to left.

Interestingly, a water glass slid on the kitchen table curls in the opposite direction. 

Example: If a rock traveling down the ice has a clockwise rotation, the left side of the rock is traveling faster over the ice than the right side.

For most of curling history, no one was clear about why rocks curl. A breakthrough study by a University of Northern British Columbia physics professor, Mark Shegelski identified the physics under the rock (described below). In 2015, a Swedish study by Harald Nyborg of Uppsala University in Sweden provided a different insight into the physics. This brings up the two main theories of why rocks curl.

• Theory #1: Differential frictional melting (Canadian study)

• Theory #2: Ice grooving/scratching (Swedish study)

Why Rocks Curl

Dominant Theory #1: Differential Frictional Melting

Differences in pressure between the right and left sides of the running surface create frictional melting that cause a rock to pivot (or drag) over the slower side. This right/left asymmetry is influenced by ice temperature, running surface thickness, pebble, etc.

How Sweeping Affects Differential Friction
First of all, let's discuss what is happening under the rock as it travels over the ice. The rock travels over the pebble. The pebble provides a low friction interface with the running surface (the rock rides up on the pebble).The limited contact area created by the pebble allows a low friction environment to exist. Simply put, the heavy rock creates friction and causes frictional melting on the faster moving side. The melted ice is more slippery. This naturally occurring frictional melting helps explain why rocks seem to "glide" down the ice.

Now add sweeping. The sweeping motion briefly polishes the ice (pebble) just before the rock travels over it. The sweeping action melts a molecular layer of ice for a very brief moment, resulting in a molecular layer of moisture. This creates an even lower friction environment that helps the naturally occurring frictional melting. This combination allows the rock to decelerate slower. This results in the rock traveling farther. The overall reduction in friction has another effect. Since the rock is dragging less on both sides, the rock will travel straighter.

Sweeping cannot make a rock move faster, only farther!

Theory #2 - Grooving/Scratching

Swedish researchers argue that the running surface, which is much rougher than the rest of the polished granite, creates scratches in the ice that the rock tracks through. The leading, front edge of the rock is scratching in the direction of rotation. The rock would then track along the scratch lines, which are about 20 degrees to the right of an in-turn (depending on speed and rotation).

Which is Correct?
The scratching theory has some unanswered questions. Consider the following:

• Why do rocks curl "more" with less rotation?

• Does the amount of rotation affect scratch angles?

• What are the angles of scratch based on speed and rotation?

• What are the best sweep scratch angles compared to actual?

• Are rock speed deceleration and rotation deceleration different?

• Can sweeping add scratches to the ice surface?

See the new 2024 sweeping science of more on scratching.

Good teams have a plan to assess the field of play before each game. Below is a sample plan for assessing the conditions.

Assessing the Ice

Assessing the field of play conditions is not the same as reading the ice. Good teams understand ice and the variables that affect performance. There are four key ice variables a player should know.

• Ice surface temperature

• Pebble size and amount

• Climate control (heat and humidity)

Scraping Methods 

The type and frequency of the ice scraping will have huge impact on the ice speed and curl .Understand how often the ice is scraped and if the pebble is completely scraped off before it is pebbled and nipped again.

Surface Temperature 

Teams should know the ice surface temperature at the beginning of the game. They should also know when the compressor "pulls". Surface temperatures in the 21-22 degree range will produce a slower, straighter condition. Temperatures in the 23-24 range will produce faster and swingier ice. Know the factors that affect the surface temperature during a game. There is no such thing as a constant surface temperature. At night, when the lights are off and the ice is not in use, the refrigeration system will maintain a surface temperature in the set range with very little margin of error. Large heat loads (lights, players. heaters, etc.) are difficult to remove quickly resulting in a spike of surface temperature. For example, a surface that will remain at or near 23 degrees when the ice is not in use may increase or spike to 25 or 26 degrees when the players start the game. The capacity of the plant and the set points dictate how high the spike will be.

Example
A curling club maintains a 23-degree surface when not in use and the lights and heaters on. When all of the players enter the ice area and begin to play, an enormous heat load is added to the static condition. Each player represents a certain BTU (British Thermal Units) heat load. This heat will be transferred to the ice surface and the compressor will have to pull it out. There is a lag between the addition of the heat load and the compressor sensor. In some cases, the compressor is unable to pull the heat out fast enough and the surface temperature rises.When players leave the ice (removing a heat load) the surface will either remain constant or drop (if the compressor is pulling).

Begin your ice assessment by having a discussion with the ice technician. Prior to the competition, ask to see the refrigeration plant and ask what the compressor cycles on;

Sensing Area    Result

Brine temp Long lag time, large temp range

Bed temp Medium lag time, med temp range

Surface temp Short/No lag time, small temp range

Surface temperature is the preferred sensing area.

Ask the ice tech what the ice surface temperature will be at the beginning, middle and end of the game. Ice with surface temperatures in the low 20's may be straighter and slower.As the temperatures rise, the rocks curl more and it becomes faster. This is the case until about 27 degrees. Temperatures higher than that create soft, unplayable ice and there's probably something wrong with refrigeration system. The pebble will last longer in lower temperatures and will break down faster in higher temperatures.

The key to managing the surface temperature is knowing when it changes.Everyone has experienced a change in speed and curl after the all the other sheets have left the ice.With four to six sheets of people on the ice, the refrigeration system is working to remove the heat load (BTU's).If the heat load leaves quickly, the compressor lags behind and continues to operate.The surface temperature can drop a full degree by the time the system shuts off on temperature. In addition, the heat source offered by the players is no longer available, resulting in the air losing its moisture-suspension qualities.

Pebble Size and Amount 

Ask the ice technician what size pebble he or she plans to use. A medium pebble will last longer while a fine pebble will break down earlier.

Heat and Humidity Control   

Ask the ice tech if the club or arena has heat and/or dehumidification. Dry air has less moisture than humid air. With no moisture in the air (dehumidification) there will be no condensation on the surface. This means no visible moisture (frost).Early condensation looks like a dull film across the ice. You will notice that the sweeper's shoes will displace the moisture and cause a smooth spot. The moisture taken up by the shoes may even leave a spot on the ice where the shoe stops. Dry ice conditions promote speed and curl. Moist conditions lubricate the running surface and prevent curl.

Assessing the Rocks 

At the higher levels, your ability to assess rocks is critical. Games have been decided on a team's inability to spot a bad rock and deal with it. The following is a guide to rocks and how to assess them.

Ask the Ice Tech when and how the rocks were last scratched.

There are many different types of rocks in play across the world. Wear and tear on these rocks differ with the type of granite used and the amount of playing time they get. As mentioned earlier, some granite is susceptible to wear and pitting causing them to behave differently. Mismatched rocks are a growing concern. With the good ice conditions we have today, particularly the speed, mismatched rocks can play an important role in the outcome of the game. As rocks age, the running surfaces change shape. They either wear (get flatter) or they "pit" which means small pieces of granite break lose due to constant freezing and thawing (expansion and contraction). This aging process is important to advanced curlers because it rarely happens evenly across a given set of rocks, causing the speed and curl of some rocks in the same set to differ. Most players use the rock numbers to throw rocks in sequence but there is no guarantee that these rocks travel over the ice at the same speed or in the same manner.

Know the Granite
Your first step in rock assessment is knowing what granite you're playing with. Most rocks today are Trefor granite with blue hone inserts. This is the best rock type. The running surface is made of blue hone which is a durable running surface. Visually inspect the running surface and determine if the rock is aggressive or conservative. An aggressive running surface will feel rough to the touch. The aggressive running surface will curl more with less speed.

Matching Rocks
Mismatched rocks (one slower or faster than the other) can greatly affect your ability to calibrate draw weight. A rock that is ten feet slower than the other will cause you to over compensate on each throw.

The best way to determine if two rocks are running at the same speed is to throw many, many draw shots on a good quality ice surface. The larger the sample size, the more accurate the data. Record the results and use the information in the future.

Steps for assessing rocks during a competition:

1. 1. 1. Ask the locals for rock information

      2. Visually inspect the running surfaces

      3. Throw the rocks in practice and look for patterns

      4. Run the rocks together

      5. Track game patterns

      6. Watch other teams throw them

Throw the Rocks
In practice throw the rocks that you will be throwing in a game. Start by playing the rocks straight up the numbers. If you suspect a mismatch move to step 2.  Your team may have a rock-matching system that can be performed before the games begin.

Run the Rocks
If you suspect a bad rock, run the two rocks one in front of another for about fifteen to twenty feet. If the rocks are matched, they will run together in both directions. If one is faster, it will pull away from the other. This is not an exact science. Use this process only to determine really bad rocks.

Look for Patterns
Since most players do not have the luxury of running rocks (particularly at other clubs), the next best thing is to watch each rock closely for signs of unusual behavior. Designate a player to watch the rocks and the tracks on the ice. Bad rocks usually create a pattern (always light but with a good split, for example).Always confirm split times with the team timer if you suspect a bad rock.

If time is not a concern (rocks at your own club) a good way to match rocks is to time them. If you have an opportunity to throw practice rocks, or you want to match rocks at your club, throw as many rocks to tee line as you can. Time them from hog to tee. This will give you the rock's speed in seconds. When complete, match the similar times. Teams using "split" or "interval" timing can match rock speed quickly by monitoring the splits. Consistent rocks will have consistent times in either case.

Understanding the Geometry of the Sheet 

At first glance, the sheet of ice, excluding the houses, has many parallel lines and other lines that intersect at 90-degree angles. In particular, the center line and the four-foot lines, if in use, represent reference lines for throwers and sweepers. However, only a few shots in a game will run parallel to these lines. Since all shots are thrown from the hacks that are fixed a few inches away from the center line, most shots will initially travel at an angle to the center line. Compounding the issue is the draw back point of the individual player. Some will draw back on the center line while others will draw back to the hack toe. This represents four inches or so at the front end of the line of delivery (imaginary line between the skip's broom and the starting point).

The Outturn Issue
Outturn shots, particularly the ones farther outside, are visually complex since the LOD in most cases, crosses the centerline first, then the four-foot line. These shots will, for most of the path, be travelling away from these lines. Since they are actually moving away from the parallel lines, the rock "appears" to be "falling" to the outside. If the center line and four-foot lines were not there, there would be no apparent fall. In addition to the visual, sideways delivery and release energy may straighten the rocks' curl profile contributing to the wide and/or fall problem. See the Wide Trifecta.

Arena Ice Considerations

With the popularity of curling growing every year, new clubs are forming without dedicated curling facilities. By acquiring rocks and basic equipment, new clubs can form using ice at the local skating rink. This is a great way to enjoy curling at a low cost. Curling on arena ice does present some challenges. Most arenas share ice with hockey and figure skating. Preparing the ice temperature and surface for each group looks different. Hockey players want a cold, flat surface at about 20 degrees. Figure skaters want a warmer, flat surface at about 25 degrees. Both hockey and figure skating don't necessarily need a level surface. Curlers want a level, pebbled surface at about 23 - 25 degrees.

All preparations for daily use involve the Zamboni. The Zamboni is an efficient machine for prepping hockey and skating ice. For curling however, it can be a problem. The machine scrapes the surface and lays water down to fill holes and create a seemingly flat surface. It does not create a level surface. Even the curling scraper can't level the surface properly.

A surface that's not level may produce a "negative ice" situation. Negative ice happens when the surface is not level. The physics under the rock that make it curl no longer exist (see Why Rocks Curl).In this case gravity may make the rock curl, even against the turn. Our staff has arena experience and they report situations where rock curl twelve feet with the turn and back up eight feet against the turn.

Your game strategy and shot calling may have to be adjusted to make shots on the non-level surface.

Tips for Playing on Arena Ice
Throw shots down the middle of the sheet. Typically, the center of the sheet is the most level. Because of this, shots down the center can be more predictable and very effective. Playing the outside sheet is dangerous and is where the fall (negative ice) exist.

Throw more draws than take-outs. Chasing your opponent's shots with take-outs is a mistake. Even on a non-level surface, draw weights can be normal. A team that can fill the house with draw shots has an advantage since the takeout is less predictable. We've seen teams throws eight take-outs in a row and miss all of them.

Is the ice is running negative, gravity is making the ice curl and not differential frictional melting. If gravity is making the rock curl, sweeping makes it curl more. Of course this is the opposite result from normal curling.

Occasionally, two or more rocks are too close to measure by eye. Whether it is to the tee, in the house, on the center line or around the perimeter. Measurements come in four categories:

1. Closest to the Tee - Rocks in the house

2. In the house - Free Guard Zone Rule.

3. Perimeter - Rocks in Play

4. On the center line - No Tick Rule.

Measuring the rocks by device will help. There are four types of measuring devices available at most clubs.

1. Mechanical Measure

2. Laser Measure

3. The Six-Foot Measure

4. T-Square

The Mechanical Measure 

The first and most often used device is simply called the "measure". It is used to determine the counting rock or rocks in the house. There two types of mechanical measures, the spring gauge and the manual touch no touch device. Since the spring gauge is a mechanical device with moving parts (springs, levers, etc.), there may be some inaccuracy on very close measures. The TNT device eliminates the mechanism and the determination is made based on where the device touches or not. This is far more accurate.The spring gauge device can also be used as a TNT.

A note on both devices:
Any downward pressure on the device may cause a bad reading. In addition, many of these devices have significant "play" when trying to move the device from a point near the center. On very close measures, have a teammate moving the device from the end, near the twelve-foot. This will eliminate the play.

Laser Measure 

The Laser is an electronic device that reads distance via laser and provides a reading in 100's.  This is NOT the most accurate way to measure.  The naked eye can judge closer with a mechanical device using the touch/no touch method.

The Six-Foot Measure 

The six-foot is used to determine whether or not a rock is in the house. It is also used as a perimeter measure at the back of the house at the intersection of the center and backlines. Unlike the above device, it may be used during the end before all eight rocks have come to rest. There are only two reasons to use the six-foot measure during an end:

1. In Play at the Back of the House
   To determine if a rock, at the intersection of the back line and centerline, is in play. The back line overlaps the back of the house and if the lines were installed properly, a rock that is not within six feet of the center, it is not only out of the house, it is out of play.

2. Free Guard Zone Measure
   To determine if a rock is in the house. If the free guard zone rule is being played, it can be used during the first four rocks (fifth rock can be removed either way).

The T-Square 

The third measuring device is called the "90 degree" measure, or T-Square. It is an L shaped piece of metal use to determine if a rock is in play around the perimeter of the playing area.  The T is also used to determine if a rocks is touching the center line area when dealing with the No Tick Rule.

Measuring Procedures 

Measurements are needed when the teams can't agree by eye. A quick note about measuring rocks. The object of the game, of course, is to get closest to the tee, which is an exact spot where the center line intersects the tee line. Measurement by device actually measure s closest to the center of the hole that is drilled over the tee. In some cases, where the hole is drilled improperly, erroneous results could occur. In addition, the standard measure has a cone shaped tip that fits into any size hole. The Laser measure may have a smaller tip and may not fit slush into the hole. Always push the laser toward the rocks being measured.

If officials are not present, the vice skips are responsible for measuring rocks if necessary. The following is the correct procedure for measuring. Rocks are measured clockwise from the back of the house. This is the standard.

Too Close to Call?
If it cannot be determined by device or by eye, the end is considered blanked. Mechanical devices do not give an exact measure. Some interpretation of the dial value is necessary. It is also difficult to determine tie using mechanical device because it is not exact. Since the Laser measure, more ties are recorded since the numeric readout could be the exact same.

Touch/No Touch Method

Some mechanical devices have no gauges.  A screw-type adjustment allows the device to touch the rock with no gauge deflection.  This is the most accurate way to measure rocks that are very close.

Measuring Two Rocks (standard championship procedure)

1. After retrieving the measuring device, enter the house from the back with the measuring point (the part that goes in the center hole) in your right hand.

2. You will measure rocks in a forward, clockwise direction to avoid "backing" into a rock. Place the center point in the center hole and put the measuring device on the ice 90 - 180 degrees from the first rock to be measured. This allows you to place the device on the ice away from the rocks to be measured.

3. As you approach the first rock, determine if any adjustments are needed at the end of device and make them. Adjustments can be made at the far end of the device to accommodate rocks in the twelve-foot. Adjust the mechanical sensor to provide an accurate reading.

4. Measure the front of the first rock (never measure the back of the rock as rocks have different diameters), leave it in place and remember the reading on the device. The opposing vice skip should be looking as well.

5. Slowly move the device clockwise to the next rock, putting no downward pressure on the device.

6. Measure the second rock and make a decision as to which one is closer. Point to the closer rock and move the second rock either in or out depending on the result and point to the closer rock for spectators.

Measuring Three Rocks

1. 1. 1. After retrieving the measuring device, enter the house from the back with the measuring point in your right hand.

      2. You will measure rocks in a clockwise direction. Place the center point in the center hole and put the measuring device to the left of the odd-colored rock.  You must measure the odd-colored rock first.

      3. As you approach the odd-colored rock, determine if any adjustments are needed in the device and make them.

      4. Measure the odd colored rock first, take a reading and leave it in place.

      5. Swing the device clockwise to the next rock and measure it.

      6. After making the decision on the second rock as compared to the odd colored rock, move it either in or out depending on the decision. Indicate with your hand the closer rock.

      7. Move to the third rock and measure it. Again, move it in or out based on your decision. The first rock (odd-colored) will be your reference rock and should not be moved.

In both situations it is acceptable to swing the device back to the first rock for a closer look. If rocks cannot be determined by device, a blank end will result. This is very rare. If the measure is very close, consider moving the mechanical sensor "away" from the rocks. This reduces friction between the sensor arm and the rough rock running surface. If the sensor arm cannot provide a reading, visually determine.

If two or more rocks are so close to the button that the device cannot be used, a decision must be made visually. Find an impartial person to do this for you.

Using the Laser Measure

1. Locate the laser on turn it on.

2. Insert the bottom extender into the hole at the Tee.

3. Put a slight amount of pressure toward each rock for a fair reading. Slowly point the laser at the first rock and note the lowest number. A back and forth motion may be needed.

4. Point the laser at the other rock(s) and note the lower number.

5. Make the determination and signal to the fans.

Using the Six-Foot Measure

1. Enter the house from the rear with the pointer in your right hand.

2. Place the six-foot pointer in the center hole and rest the device on the ice at 90-180 degrees from the first rock.

3. Slowly swing the device clockwise until it either contacts the rock or swings past it. Never throw the device at the rock as it may come out of the hole and displace the rock.

If, during a free guard zone measure, another rock is in the six-foot path, a decision must be made visually.

Using the T-Square
The T-Square helps determine perimeter rocks and can determine rocks in play. Since the rocks have an "overhang", the 90-degree angle helps sight the perimeter line by extending the sight downward.

Procedure:

1. Locate the T-Square device.

2. Place the vertical flat side against the rock.

3. Visually check the bottom of the device compared to the line.

LSD and The Formula 

In championship play, where the Last Stone Draw (LSD) is used to determine hammer in most games, rocks are measured from the center of the rock. A tape measure or laser is used for the initial reading from the closest edge of the rock. Then, the radius of the rock is added to complete the distance measure. It may be necessary to measure two rocks that both cover the tee. At the highest level, it is common to cover the tee on more than one shot. The official in charge would take measurements from two spots, one on the tee line at the intersection of the four foot circle and the other on the center line at the intersection of the four foot. With these two numbers a mathematical formula can determine which rock's distance from the tee.  Download the Curl Distance App. to assist.

Championship rock performance and ice conditions go hand in hand. The performance of the rocks is generally related to the aggressiveness and consistency of the running surface. As stated earlier, differential pressure from a rotating rock creates uneven friction and frictional melting. It also creates deeper grooves in the ice. The term "aggressive" refers to the running surface that creates good overall friction. The rougher the running surface, the more friction is created. Rock-makers create a balance between a rough surface that will curl and a surface that will still run at speeds within the standard. A more difficult task for the rock-maker is creating perfectly matched running surfaces. All rocks on a given sheet must perform the same.

Running surfaces (running edges) don't last forever. The manufacturer shapes the edge on the lathe with a cutting tool. When the rock is placed into service at the cub, it begins a slow polishing and deterioration process. The edge can either wear away or "pit". Pitting occurs slowly as the rocks expand and contract.A pitted edge is very inconsistent in how it plays.

Aggressive edges smooth-out as they age and must be retouched occasionally.Some ice techs believe rocks should be "worked" before every large event."Working" the rocks or "scratching" the rocks is achieved by sanding the running edges with sandpaper or emery. Different techniques exist but they all involve turning or dragging the rock on a piece of sandpaper.This roughens the edge and makes the rock more aggressive.It also helps gain consistency in the rock sets.

Sweeping/Mopping (best with two people)

1.  Person 1 - Sweep out the hack areas by sweeping debris toward the house.

2.  Person 2 - With the sheepskin broom, start sweeping from behind the hack.

4.  Sweep up one side, gather house debris, sweep down the other side.

5.  On the ice surface, lift sheepskin vertically and sweep snow/debris from top to bottom onto the ice.

6.  Pickup debris with hand brush and pan. Discard.

3-Pass Nip        Careful – The blades are very sharp.

Sheet widths vary from club to club.  They can be as narrow as 13.0 feet or as wide as 15.5 feet.  The Nipper is 64 inches wide with a blade width (cutting width) of 58 inches. It is important to cover the entire middle of the sheet with a three-pass method.

1.  Carefully remove Nipper from the skids using the wooden handle. Lift with your legs.

2.  Attach the Nipper sheepskin.

3.  Position the blade guard down.

4.  Start at the back line. Push the Nipper at a medium walking pace.

5.  Place side runner on the sideline.  Turn slowly at the back of the house and move to the other side line.  Finish up the center.

6.  Remove sheepskin and clean.

7.  Lift the blade guard. With the blades still on the ice, clean them with a broom.

8.  Clean up debris/snow with hand brush.

9.  Replace Nipper on skids.

To move the Nipper around the ice without cutting, turn the machine 90 degrees to maneuver.  This will allow you to move the machine across sheets without cutting.

Pebbling (See Pebble Video below)

1. Cover the hacks.

2. Fill pebble can with hot (120) water. Enough for two sheets.

3. Hold pebble head above the water line during transport.

4. Standing directly in front of the hack, lower the pebble head and start swinging.  Head should be just below parallel (to the ice).

5. Pebble the area behind the hack with a short stroke.

6. Start moving down the sheet swinging hard enough to cover the entire width.

7. Target 35 seconds from back line to back line.

8. Target 80 -100 swings (across and back is one swing).

9. Finish with an up-stroke to stop the water flow. 

DO NOT DRAG ROCKS

Your game-based pebble and properly adjusted Nipper should be enough to achieve game standard speed and curl.  Running the rocks will increase the need for "scratching" as the running surface is polished with each run.

Providing good ice at the club level can be challenging.  Clubs have a variety of structures when it comes to ice techs.  Some have full-time, paid ice techs, but the majority of local clubs make and prepare ice with member volunteers.

Although they use the same assessment metrics (splits and hog-hog times), club ice standards are slightly different than championship ice.  Championship ice is 5 feet of curl with 14.8 seconds in speed.  However, many club members would struggle with those conditions so the ice at the club should be more like 3-4 feet of curl at 14.0 seconds.  It is very difficult to please your super-competitors AND the general membership at the same time.

Create the Standard

Have your club define the standard.  It is much easier to work toward a known standard than to create your own.

If you are not achieving the standard, start with this.

• If your ice is slow and straight - the ice surface is the problem.

• If you ice is fast and straight - the rocks are the problem.

This may help you move in the right direction when it comes to making changes.

In many cases at the club level, the ice is generally over-pebbled and under-scraped.  Make adjustments in these areas.  Other areas of concern:

• Ice surface temperature should be in the 23-15 degree range.

• Air temperature should be 40-43 degrees at chest level.

• Dew point should hover just over surface temperature.

• See the ice prep section for proper daily maintenance.

• See the scratching rocks section.

Sublimation (solid evaporation ) 

High latitude clubs may have dew points lower than the surface temperature.  Lower latitude clubs may still experience this but in shorter periods.  If your ice is sublimating, it is a huge problem.  As the ice changes state from solid to vapor, it leaves the surface dry and uneven.  This will directly effect the speed and curl.