How Ice Rinks are Made

Rob Cockerham happened upon a crew setting up an outdoor ice skating rink and took the opportunity to find out how it's done. It turns out the whole thing rests on a series of tubes.

The ice was to be kept frozen with very cold liquid flowing inside the tubes. There was 40,000 ft of tubing in the rink, filled with 1,620 gallons of water mixed with propylene glycol to a 35% solution. These were the numbers off of the top of his head, but 5 ounces per foot of tube sounds about right to me.

Propylene glycol is antifreeze, so in essence the water can circulate at a temperature much lower than the freezing point of water, which sucks the heat from the water outside the tubes, turning it to ice. Read the rest, with plenty of pictures, at Cockeyed Science Club. Link