Casting ice brings the problem of expansion, as a volume of water increases approximately 10% when frozen.  Different ways of casting the ice were explored during the construction of ‘The Snow Show’: as solid sheets, as a hollow volume, and as a large mass in layers.  One thing is true to all processes: the thickness of the ice increases rapidly at first but the growth is slowed down as the ice gets thicker die to the outer ice acting as an isolator to the inside water.  Weather plays a vital role in deciding whether the water in the moulds will freeze with the appropriate clarity or structural integrity or even whether it will freeze at all.  The optimal freezing temperature for cast-ice constructions is -10°C.

When casting the ice sheets for the Lawrence Weiner and Enrique Norten project, the freezing process had to be inversed.  Water naturally freezes from the top downwards but here the water had to rise up instead of being captured under the ice, thus relieving the moulds of a significant amount of pressure.  For this reason, the “ice walls” were frozen in moulds laid horizontally on the ground and only then were the moulds removed and the sheets delicately rotated vertically 90 degrees to their final position.

The two teams Robert Barry and Hollmén-Reuter-Sandman and Ernesto Neto and Ocean North employed a method of freezing inspired by the Finnish tradition of making ice lanterns.  Cylindrical volumes were completely filled with water, which was left to freeze for several weeks.  Once frozen to the desired thickness on the top and sides, the water trapped in the center of the ice was emptied out to create an interior space carved by nature.

 With the massive ice walls of the Top Changtrakul and LOT-EK edifice, the technique was to freeze the ice in layers of 10cm to 15cm in height.  This enabled the walls (20m x 3m) to freeze as solid structures rather than having to be assembled with ice blocks.  The method also allowed the ice to release its pressure inwards incrementally to prevent it from expanding beyond the mould; had the moulds been filled at one pouring, the pressure when freezing would have caused them to explode.