This article is from last year, but gives you a good flavor of the time and energy it takes to create these outdoor masterpieces. The bottom of the post is where you can find Culligan's role.
From the Ottawa Citizen
For the past half dozen years or so, the National Capital Commission has stocked Winterlude with blocks of ice from a company called Iceculture, based in Hensall, Ont., just southeast of Goderich on the southeastern shore of Lake Huron.
Iceculture claims to be possibly the world's largest supplier of crystal-clear ice, and certainly North America's biggest. Each year, the company makes 25,000 blocks of ice for clients around the world. Apart from Winterlude, for example, the company recently hauled 90,000 kilograms of ice -- roughly enough to fill a school bus, and also the amount of water a fin whale draws in a single gulp -- to Dubai and then spent two weeks building an ice lounge, called Chill Out, inside a shopping mall. Next month, they'll head to Thailand to construct a similar one there.
This year, Iceculture will ship 1,800 blocks of ice to Winterlude, each weighing about 140 kilograms (300 pounds) and measuring 100 centimetres by 50 centimetres by 25 centimetres. That's enough ice to cover an NHL rink to a thickness of 15 centimetres. Its total weight of about 245 metric tonnes is roughly equivalent to four times the weight of all the players currently on NHL rosters.
But what makes the ice blocks clear?
According to Iceculture general manager Heidi Bayley, the secret is in the freezing process, which is designed to remove the trapped bubbles of air that typically make the ice cubes in your freezer so cloudy.
"It's very simple, but it's really sensitive," she says. "We have tanks that freeze the blocks from one side through to the other -- the cooling elements are on the bottom of the machine. At the same time, we circulate the water so that, as it freezes from one side, the circulation actually pushes any air out.
"The second thing we do," adds Bayley, "is we run it through an RO (reverse osmosis) system, a really giant Culligan water system that removes any impurities and minerals, such as calcium, which can add white spots to the blocks."