An ice surface is manufactured rather than frozen in a single pour. Its condition during a game depends on a continuous fight against heat entering the building.
Building the sheet
The floor beneath the ice contains piping through which chilled brine circulates, cooling a concrete slab to below freezing across its entire area.
Water is then applied in very thin layers, each allowed to freeze before the next is added, because a deep pour would freeze unevenly and trap air.
Markings and advertising are painted onto an early white layer and then sealed under further ice, which is why they appear to sit beneath the surface.
Why it is kept thin
A finished sheet is only a few centimetres deep, since ice insulates and a thicker layer would separate the surface from the refrigeration beneath it.
Thin ice responds quickly to the cooling system, which allows operators to adjust hardness between periods rather than hours in advance.
The trade-off is fragility, because deep gouges can reach close to the concrete and require patching rather than simple resurfacing. Crews carry slush and cold water to fill such damage during stoppages.
What softens it during a game
Every spectator radiates heat, and a full arena raises the air temperature well above what the same building holds when empty.
Lighting and broadcast equipment add more, and humidity from the crowd condenses on the cold surface, leaving a wet film that slows the puck.
Skate blades themselves generate heat and cut into the surface, so the ice degrades fastest exactly where play is most concentrated.
Resurfacing between periods
The resurfacing machine shaves a thin layer from the top, collects the snow and lays down a film of heated water behind it.
Hot water is used because it contains less dissolved gas and bonds more cleanly to the existing surface, producing a smoother finish than cold water would.
The new layer needs several minutes to set properly, which is one reason intermissions are as long as they are.
Why hardness is a matter of preference
Colder, harder ice is faster and holds an edge better, favouring skating teams, while softer ice slows the puck and rewards physical play.
Operators work within a narrow band, and the temperature is a building decision rather than something either team controls during a match.
Visiting players routinely notice the difference between venues, and complaints about ice quality are usually about consistency across the sheet rather than about speed.
