Amazing!
Since salty water has a lower freezing point than pure water, you could circulate below-32-degrees salty water under the rink to freeze pure water in the rink.
Brine... also used in making Ice Cream
Trump gave two examples of botched, unbelievably behind schedule and outrageously over$pent projects that he took over, turned around and completed beautiifully in a short time and on le$$ money than expected. I thought he explained so well and so clearly how he got everyone together and working as a team. And that when he needed information on something, like the right refrigerant for the ice rink, he talked to the top people, got the best information, and finished the job.
Those two stories surely impressed a bunch of people; including Ms. Clift. They impressed me!