During every break in the action, a guy comes out with an infrared thermometer and measures the ice temperature around that area (picture taken 1/28/13). IIRC the process of 'painting' the ice is non-trivial. On a concrete pad they first freeze several thin layers of water. Then using a special sprayer they spray a special white paint, which is quite expensive and I think is formally called "NHL White". Then they apply more layers of water. Then they paint the lines and graphics. And then they apply a much more generous coating of ice layers on top of that. It's difficult to make a repair job come out perfectly like the original.
