Why Man-Made Snow is Extremely Abrasive?
You noticed for sure that the so called man-made snow is much more abrasive than the natural types of snow. Man-made snow is used in alpine resorts (on ski slopes) more often than in nordic areas (XC tracks) but currently it is the most common snow type especially in lower regions.
Especially if the temperature is deep under zero, the man-made snow is so hard and so abrasive that you can have the feeling “it is cutting into the ski base”... And your feeling is almost literally correct.
Man-made snow consists of ice grains which are small, rounded and extremely hard. Thanks to small size or diamter of individual ice grains the man-made snow is also extremely compact and dense - it contains small share of air compared to natural types of snow. Shortly after production man-made snow is moist to wet even if it is freezing.
What’s the reason why man-made snow is so abrasive?
The correct answer is hidden in the hardness. We mentioned that individual ice grains of man-made snow are small, rounded and extremly hard. Especially the extreme hardness of the snow grains connected with the very compact surface of the snow pack are the main reasons why man-made snow is much more abrasive than natural types of snow.
Why are the ice grains of man-made snow so hard?
The extreme hardness of ice grains of man-made snow is caused by freezing direction which is opposite to natural snow types.
Natural snow types freeze from the center to the edges. Air humidity condenses on a snow flake nucleus (most often a dust or dirt particle) and starts to develop from the center to the edges in various forms and shapes.
In case of man-made snow a small water droplet is flying out of the snow cannon and meets the cold air, at the moment as the water droplet gets in touch with the cold air, a thin ice shell develops on the outside perimeter of the water droplet, while the middle remains filled with water. Ice grains of man-made snow freeze from the outside to the center gradually. Liquid centre is locked in a ice shell.
If water changes from liquid to solid state its volume increases slightly. Water locked in a ice shell cannot increase the volume resulting in the increase of density. Increased density means increased hardness.
Increased density = increased hardness of ice grains of man-made snow is the main reason why man-made snow is so extremely abrasive.
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