(WXYZ) — We saw everything on Wednesday morning when it came to rain and snow. It started with rain in the morning for some areas, then turned over to wet snow, and then temperatures dropped later at night, freezing much of what was on the ground.
Road crews have been treating roads across metro Detroit ahead of the Thursday morning commute, but with bitterly cold temperatures expected over the next couple of days, we wanted to see how salt would work in the temps. Temperatures will hover around the 20s on Thursday.
Temps close to 20° all day, which is still warm enough for the salt to be effective. The next couple of nights will be in the single digits, so hopefully most of your roads get cleared today. pic.twitter.com/XdmXpQVnm7— Kevin Jeanes WXYZ (@KevinJeanes) February 3, 2022
According to Cargill, the "practical working temperature" of salt is usually above 15° or even 20° but will work down to -6°.
Cargill said there are two main reasons that the practical working temperatures are around 15-20.
The first is that the amount of ice that can be melted per pound of salt decreases with temperature. Below is a list of the temperatures and what one pound of salt can melt, according to Cargill.
- 30° – 1 pound of salt melts about 46 pounds of ice
- 20° – 1 pound of salt melts about 9 pounds of ice
- 1° – 1 pound of salt melts about 4 pounds of ice.
Also, in colder temperatures, Cargill said the ice melting speed of rock salt gets slower, so when it's imperative to clear it quickly like on highways, it doesn't always work well.
"The ice melting speed of rock salt can be improved by blending it with a chloride salt brine to make a pre-wetted deicer, and this will provide some increase in effectiveness at temperatures below 20°," they wrote.