SALT IS THIS SEASON'S SEASONING
You’ve heard “salt lowers the freezing point of water,” but what does that mean? It’s called freezing point depression, and it means that salt makes it harder for water molecules to bond into solid ice. When table salt (or sodium chloride, NaCl) dissolves in water, it separates into sodium and chloride ions, and those ions interfere with the formation of ice. Calcium chloride (CaCl ) breaks down into three ions—one calcium and two chloride—providing even more ions to block the bonding.
Enough science; what does this mean for your icy sidewalk? Instead of freezing at 32 degrees F, water will stay liquid until about 15 degrees F after salt is applied, or maybe even 0 degrees F, depending on the type of salt you use. Here are the most common types. They are sold under different brand names, so check ingredients lists.
ROCK SALT OR HALITE
In states where roads can freeze, DOT crews for years have spread basic rock salt on public roadways. Rock salt is table salt (sodium chloride) that hasn’t been purified for human consumption. Its impurities include aluminum, lead, iron and phosphorus, which are bad for the environment. Rock salt can damage trees, plants along your sidewalk or driveway, and any waterways it will eventually wash into. Plus, it’s mostly ineffective when the temp drops below 15 degrees F. But it’s readily available and a 50-lb. bag costs about $10.
CALCIUM CHLORIDE
Calcium chloride is a much more effective ice melter than rock salt; it can melt ice at temps below zero. It’s less corrosive to ferrous metals, which helps protect cars and any metal in the infrastructure, and it is less toxic to aquatic plants. The downside? CaCl is more expensive than NaCl. Calcium chloride is often blended with magnesium chloride, which is also an effective ice melt chemical. However, magnesium chloride is less effective than CaCl and is more corrosive to both metals and concrete. All the chlorides can be hard on pet paws.
UREA
Used in several deicer products labeled as “pet safe,” urea is a nitrogen-rich organic compound. (Urea is not urine; it’s formed in the liver to help humans and animals excrete urine—fun fact.) With its high nitrogen content, urea is produced widely as an agricultural fertilizer. It's not as corrosive as chloridebased deicers, so it’s kinder to metal, concrete and pet paws, but urea is much less effective as a melting agent. And its high nitrogen content can make it harmful to nearby bodies of water. Pet owners, read labels carefully.
DIY SOLUTIONS
If you have leftover lawn fertilizer, spread a few handfuls of it on your icy walkway. It’s abrasive and will melt ice, and it will nicely settle into your lawn in the spring. However, if you can prevent ice from forming on your sidewalk and driveway, you won’t have to worry about ice melt chemicals. Fix leaks in gutters— check corners and transitions—so they don’t drip meltwater that will refreeze and form treacherous spots. Clear snow quickly before it gets packed and hardens into ice. An ice chipper or heavy shovel can help you remove ice as it forms and before it gets too thick.
BEET JUICE MIX
Better than salt and safer for pets and the environment, beet juice lowers the freezing point of water to as low as 20 degrees below zero. First used commercially on roadways in northern Minnesota (beet farming is big business there), a combination beet juice-brine solution is a highly effective ice melter and is now used in states across the north. Beet juice deicer is also easier on vehicles, pavement and the environment. Make your own beet-brine solution (25% beet juice and 75% salt water) and keep it in a spray bottle near the front door. Use white or golden beets to avoid stains.