The Ice

Science of Ice

For 40 years, the NCC has been maintaining what is now known as the world’s largest naturally frozen ice rink.

The Rideau Canal was first open for skating in 1971, after a team of NCC employees armed with brooms and shovels cleared a small section of ice near the National Arts Centre. Over time, as the length of the Rideau Canal Skateway grew, so did the NCC’s knowledge of the science of ice. Partnerships with experts were developed, and the NCC is now at the leading edge of ice maintenance. This expertise makes for better and safer ice conditions.

Did You Know?

The average skating season is 50 days long, but the record (set during the 1971–72 season) is 95 days.

Consulting the Ice Experts

To create the world’s largest skating rink, the NCC has developed numerous partnerships with leading ice experts.

Ice is such a complex material that scientists have spent decades studying it. The NCC has relied on the knowledge of experts to improve skating conditions and ensure the safety of Skateway visitors.

The survey team monitors the vertical movement of the ice. If the ice sinks, it means there is too much weight on its surface. Once the weight is dispersed, the ice will float back to its normal position.

Did You Know?

Although he has never learned to skate, Dr. Nirmal Sinha, a scientist with the National Research Council Canada, is a world leader in the science of ice. The NCC has relied on his advice to establish ice safety guidelines.

From Liquid to Solid

Understanding the process of ice formation helps the NCC to create and maintain the ideal surface for skating.

When the cold weather first arrives, the NCC allows nature to do its job. As the water of the canal begins to cool, it contracts and sinks. However, once the temperature of the water drops to an even 4 degrees Celcius from top to bottom, the water begins to crystallize and expand. Because ice crystals are less dense than water, they rise to the surface and eventually form a frozen cap on the water’s surface. Once the frozen cap is thick enough, we can skate on it.

All Kinds of Ice

Depending on the weather, different kinds of ice form on the Rideau Canal Skateway. There are two main types of ice: clear ice and white ice.

When fallen snow becomes soaked with water and freezes, it forms white ice or “snow ice.” White ice is opaque and milky, and contains many air bubbles. Ice experts suggest that white ice is not as strong as clear ice.

Clear ice is colourless, though it may look blue, green or even black from above. It is formed by a long, hard freeze at the surface of calm water. This is the preferred type of ice for Skateway operations.

Measuring the Ice

The NCC takes regular samples of the ice, not only to measure the total thickness, but also to analyze the combination of clear and white ice.

It is not only the thickness of the ice, but also how it is formed that determines its strength. An ice core is a sample of the ice from the surface to the water line. At the surface, there is likely to be a section of white ice that formed when the snow was falling. Typically, the lower part of the core shows clear ice.

As shown in this ice sample, the ice composition varies at different depths. Before the NCC hoists the green flags to announce that the Rideau Canal Skateway is open, ice samples must show that there is a sufficient thickness of good quality ice for safe public skating.

Did You Know?

Cracks in the ice are normal. They occur because temperature changes cause the ice to expand or contract.

A Weighty Issue

The NCC not only monitors the thickness and composition of the ice, but also makes sure that there’s not too much weight on the ice surface, particularly in any one spot.

The weight of crowds, snow and snow removal equipment must be dispersed so as not to make the ice unsafe. Ice has an amazing capacity to depress gradually when weight is applied, and then to gently rebound as the weight is removed. Did you know that there’s water underneath the surface you’re skating on? The ice surface floats, sinking slowly into the water as weight is applied.

Did You Know?

Water expands as it freezes, making ice less dense than water. That’s why ice floats. Look closely at the ice cubes in your next cold drink, and you’ll see that only about 10% of their volume floats above the liquid.

The Enemy of Ice

Snow is the enemy of ice.

It forms an insulating blanket over the ice surface and causes melting. The weight of snow also depresses the surface of the ice. That is why the maintenance crew loses no time after a snowfall and rapidly clears away the snow with snow blowers and scrapers, not only to improve skating conditions, but also to protect the ice.

Making the Skateway

Turning the Rideau Canal into the world’s largest skating rink requires much more than just removing the snow.

Work on the Skateway starts well before the skating season. After the water level of the Rideau Canal is lowered in the fall, chalets and other structures used on the Skateway are installed.

The drilling team uses an ice auger to draw out core samples of the ice in order to measure its thickness and check its quality.

Once sweepers clear the ice surface, the pumping team floods the ice to smooth out the cracks. As temperatures fall during the night, the water freezes. The result is a smooth, clean skating surface, ready for early morning skaters.

Safe and Sound

When daily testing shows that the ice is sufficiently hard and thick, the green flags go up, and 35 entrances to the Skateway open up. When the flags are red, stay off the ice!

A team of 50 skate patrollers dressed in neon yellow jackets patrol the Skateway, ensuring that all visitors have a safe skate.

World Famous

In 2005, the Rideau Canal Skateway made it into the Guinness Book of World Records.

It is the largest naturally frozen ice rink in the world. In 2007, the Rideau Canal was designated a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). You are skating on the world’s most famous rink!

The Rideau Canal Skateway receives over a million skater visits every year.

Did You Know?

The Rideau Canal Skateway is the size of 90 Olympic-sized rinks (165,621 square metres), and extends 7.8 kilometres (about 5 miles).