The Science Of Hockey Ice

Hockey is a game played by linebacker-sized men moving at vehicular speed on razor-sharp blades. Skaters will travel almost 320km in a single game, slicing, shredding and shaving a surface just 60m long, 26m wide and one-inch thick.

The abuse the New Jersey Devils and Los Angeles Kings will heap upon their rinks during the Stanley Cup finals would pulverise a frozen lake, let alone the ice in your freezer. Yet the ice here at the Prudential Center will remain so smooth that a puck will slide over it with nary an untoward bounce.

Creating a rink suitable for the rigours of professional hockey is a feat of engineering, a lesson in chemistry and a work of art.

"It's a living, breathing apparatus," Nick Kryshak, the Devils' official ice technician, said of the flawless polycrystal plane he's created. "It's not too hard, it's not too chippy, it's not too soft. Every little thing matters. You want that perfect consistency."

Achieving that perfect consistency is an arduous task. Building a sheet from scratch takes four days, with veneer-thin layers of water successively frozen and leveled in a carefully controlled climate.

Outside the Prudential Center in downtown Newark, less than 24 hours before Game 1, heat shimmered over the footpaths and humidity draped like a wet towel. Inside, the arena was a nippy 10C and the mirror-clear ice a frigid -6C. Its clarity reflected its purity. The water used to create it passes through a truck-sized, eight-filter reverse osmosis system to remove excess oxygen and trace minerals, two enemies of ideal consistency.

Oxygen is what gives an ice cube its cloudy core. Too much of it softens ice, making skate blades sink and founder. It's the same story with minerals — total displaced solids, in technician argot. Too much softens the ice, but too little hardens it, making traction difficult. Kryshak will sometimes add baking soda until the balance is right.

When the water is purified and primed, it's sprayed onto a concrete slab that rests on a labyrinth of pipes 14km long. Chilled salt water, which has a lower freezing point than fresh water, flows through the pipes, lowering the slab's temperature to -8C. That's cold enough to flash-freeze a layer of water precisely measured at 1/32 of an inch (0.8mm) thick. Speed is essential.

"The more time you allow water to sit and freeze, the dirtier it gets," Kryshak said.

Much like plywood, layers of ice create strength and density. The first layer is called a bond, and it is painted bright white. Lines and logos are all placed in the first eighth of an inch (3mm).

Kryshak isn't yet using the Zamboni, hockey's iconic icemaking vehicle, but walks back and forth with a spray wand and water tank for eight hours. Only when the ice is a half-inch thick do the Zambonis come out, depositing more 1/32-inch (0.8mm) layers and scraping uneven patches level.

All told, Kryshak and his crew will spend four days laying down a sheet one-inch thick, using sonar depth guns to ensure consistency across its surface. During the playoffs, when overtime can keep players on the ice into the wee hours and grind a standard sheet down to the concrete, Kryshak's team builds the ice to a depth of 1.5 inches.

The full bottom-to-top process will occur only a few times in a season — during basketball games and concerts the ice is simply covered, though a March circus visit and the threat of animal droppings necessitated a full rebuild — but maintenance is constant.

After every game and practice, Kryshak's crew will spend two hours working on the ice, fixing damage or flaws they hadn't noticed. Each morning, even if the ice hasn't been touched, they shave off the top layer and add a new one: over the previous night, the arena's dry air — kept at 35 to 40 per cent humidity — will have drawn impurity-laden moisture to the surface.

Come game time, Kryshak's team concerns itself with on-the-fly care. They measure temperature, relative humidity and dewpoint at ice level, instructing ventilation engineers to pull air into the rink or blow it out as needed. The ice surface is kept at steady -6C to -7C, while the arena stays between 10C and 15C. Humidity is allowed to rise gradually, perhaps to 50 per cent by a game's end.

"When you run the dehumidifiers too much, you dehydrate the sheet," said Kryshak. "You cause it to be brittle."

Zambonis provide finishing touches, scraping away shavings cut by players' skates, removing the deeply scored top layer and resurfacing the rink with a fresh sheet of water 1/32-inch (0.8mm) thick. Even this seemingly simple task requires near-perfect coordination.

Most community rinks use a single Zamboni, but the pros use two. That cuts the flooding time in half, buying a few more minutes for fresh ice to settle, but the machines must be identically calibrated. Any variation between them creates minute ridges that might cause a puck to bounce or a skate to slip. For want of a mere millimetre of ice, a game could be lost, a series changed.

"The process is long. It's tedious. It takes a lot of patience," Kryshak said. "But it's all worth it in the end when you get to this stage of the game. You're in the Stanley Cup final."

Image: Vaclav Volrab/Shutterstock

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