What’s so special about "carving ice"?
Carving ice is made by a special process that freezes water from the bottom up in a Clinebell machine. This process allows the impurities to rise to the top and be trimmed off, resulting in a crystal clear block of ice. Each block of ice is 1M (40″) X .5M (20″) X .25M (10″) and weighs 135 KG (297 LBS).

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https://www.iceonwhyte.ca/festival/international-ice-carving-competition/