There were some pretty incredible sculptures around the fair, with very detailed use of white accents and clear ice. Some were using rough ice block for white, polished ice for clear (using tools to rough the white spots out), but they must be using something to enhance the white.
In terms of how long they last, they usually break them up shortly after the fair. Not ideal to have a melting ice sculpture with a corporate sponsor's name on the dissolving art
Here is the other one that Louis Black had done