De-Icing Salts for Slippery Walks

January 18, 2011; 9:54 AM ET
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When the Christmas goose is finally all eaten, icy paths are not far behind. It helps to know all the alternatives to prevent slipping, sliding, and accidents.

There are two main ways. One is to melt ice down to bare surfaces. The other is to cover the ice with something gritty or not slippery. When ice builds up thicker and thicker, it takes a lot of time until it melts all the way down, so ideally one should try to keep it under control.

Melting is done with soluble salts which lower the freezing point of water. If it can't freeze, it stays liquid and non-slippery, then evaporates when the air is clear.The common salts are Sodium Chloride which is table salt, and Calcium Chloride because both of these have freezing points well below that of water. Plain water freezes at +32° F., while sodium chloride's minimal freezing temperature is minus -21° and calcium chloride's is minus -55°. The more salt, the lower the freezing temperature will be.

Calcium Chloride is less damaging to plants but costs considerably more than table salt. Cost may be an important factor if one is doing a huge area, but it doesn't add up to much more for home use. Calcium Chloride is better at lower temperatures, while Sodium Chloride is generally used when it isn't so cold. During storage, both absorb water from the air and can cake, especially the calcium. Occasionally potassium chloride is also used, too.


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