Salt brine: A primer on what makes icy roads safer

Let us now praise road salt brine.

Public works people study this salty subject assiduously.

Glazed and black ice, the sort we’re expected to get Saturday, makes driving dangerous, not to mention annoying.

Using salt brine “requires careful thinking about temperature, timing, and that sweet spot when the pavement temperature is still warmer than freezing when it’s freezing outside,” said Zachary Oswald, a spokesman for the Kansas Department of Transportation. “There’s a scientific method to using salt brine – and an art form in the application.”

In Wichita, public works crews have laid down salt brine on city streets since Monday. They’ll work around the clock on alternating 12-hour shifts, using all or most of the city’s 60 trucks, said Van Williams, a city spokesman.

Crews are focusing on arterial roads, bridges and overpasses, Williams said. Similar work has been done by crews on state roads as well, Oswald said.

Bear in mind that public officials also are cautioning us that salt brine, as well as it works, is no safety substitute for staying off icy bridges and roads unless you have an emergency.

Oswald offered a small but useful primer, prepared by the American Public Works Association, on how salt brine works.

▪ Brine is a solution of salt and water. There’s more than one kind of salt; road crews typically use sodium chloride. Some crews also mix in calcium chloride and/or magnesium chloride. The science of salt brine is such that brine is a little like coffee, in that there are different kinds for different consumer desires. Mixers can make the best brine cocktail recipe for whatever type or severity of ice storm they face.

▪  Salt washes off. To make it stick longer on roadways, some brine makers mix in “organics.” By-products from cheese whey are one example. Sugar beet processing by-products are another. All interesting, but please resist the urge to taste it. Unless you’re a dog.

▪ Yes, salt brine can corrode metal on your car — not right away, and not so much if your car was treated with a sealant in anticipation of brine. What to do? Rinse afterward.

▪ For those of you fond of mathematics and proportions: Most brine applied to roadways is 23.3 percent sodium chloride and 76.7 percent water. Brine has a lower freezing temperature than water, so that’s why it works.

▪ Anti-icing is what those work crews have done since Monday: They’ve laid down layers of brine on road surfaces, days before the bad weather was forecast to arrive. The brine slows and even prevents icy rainwater from freezing to the road, depending on how severe the precipitation is. Road crews on average use 50 gallons of salt brine per mile.

▪ Anti-ice brine is good in part because it requires one-fourth to one-fifth less salt than our next bullet item:

▪ De-icing uses a lot more salt, in this case pre-wetted rock salt. But the idea is the same: Apply the salt; the salt turns the ice into brine; the brine dissolves even more of the ice on the roadway. De-icing is done after the ice has arrived.

What’s the best way to not slide off the road? As good as brine is, it’s not as effective as doing one other thing.

“We rely on the media to get the word out,” Oswald said.

What they often tell the media when they get the word out is: Stay off the roads.

This story was originally published January 13, 2017 at 5:07 PM with the headline "Salt brine: A primer on what makes icy roads safer."