Spreading Road Salt

The Magic Behind Road Salt — How it Really Works

Posted December 11, 2013 by 7 Comments

Big bad four-wheel drive! It won’t help you on a sheet of ice.

For some, the only confidence booster they need is to see the flashing lights of a salt truck passing down the road.

Some states do it better than others, but once that salt hits the ground, the magic begins.

Like a Seventh Grade Science Project

Who has made homemade ice cream?

The combination of table salt and ice, in order to freeze milk, cream, and sugar will blow the minds of most 7th graders stuck in Chemistry class.

So what’s the trick?

Yes, when salt contacts the ice, it will begin to melt. But, the salt also lowers the freezing point of the ice, so the colder temperature can freeze the surrounding milk and cream below 32°F.

A lower freezing point! That’s the key to salting roads.

How Road Salt Really Works

Rock Salt on Road Surface

Road salt melting ice on a parking lot.

When salt hits the road it will begin to melt any ice and snow, leaving a salty mixture layer on the road’s surface.

Since the salt lowers the freezing point, ice will not form at the typical freezing temperature (32°F, 0°C).

Instead, the new freezing point of this salty road mixture will be around 15° – 20°F.

One flaw: If the road temperature is below that 15° – 20°F level, the salt can’t do its job. Then it basically just provides some traction.

How Road Salt Is Made

Here’s a quick look at how road salt (rock salt) is made from the hit Discovery Channel show “How It’s Made.”

The Salt vs. Sand Controversy

Other than making slippery roads safer, road salt is a corrosive compound. Its corrosive effects on vehicles, road surfaces, and bridges are most often seen in the Northeast where more snow means more salt. Salt can also drain into nearby water supplies.

The alternative, sand, provides helpful traction in slick spots, but doesn’t always get the job done in harsher weather conditions. So those salt stock piles probably aren’t disappearing anytime soon.

Either way, the road crews are kept busy every year spreading over 15 million tons and
$2 billion (EPA, 2010) of salt to keep all four of your wheels on the pavement.


  1. George Zwilling
    on December 12, 2013 at 4:19 pm

    The salt might leave all four tires on the ground, but over time, the body of your car will also be on the ground..in the form of rust. Also, where a lot of salt is used the environment is adversely impacted, contaminating water ways and killing road side vegetation.

    Reply to this Comment

  2. Marilyn Kilmer
    on December 12, 2013 at 7:24 pm

    I ejoyed watching it. My whole life I lived across from the Retsof Salt Mine, in Retsof, NY. I have had the oppuratunity of going down in the old one. We had a cavein and flooding and had to be shut down. Now about 5miles away in Geneseo,NY The New Salt Mine is up and running. It is a big business in our area. It helps the railroad I have hundres of semis going by my house so many trucking jobs.
    We need it in Our area between Rochester, NY and Buffalo, NY.

    Reply to this Comment

  3. Dwight Slocum
    on December 13, 2013 at 10:52 am

    Auto-body shops “Love It”!!!!!!!!!

    Reply to this Comment

  4. Holy Cross
    on February 15, 2016 at 11:30 am

    I hear so much about #1 road salt for tailgate spreaders but no one seems to know where to buy it. If you ask the stores if they carry it, they give the deer in the headlight stare.

    Reply to this Comment

  5. Alan
    on February 15, 2016 at 2:13 pm

    It is the combination of road salt with liquid calcium the dissolves a car or truck

    Reply to this Comment

  6. Kim Hagins
    on February 15, 2016 at 3:10 pm

    I spend the fall months getting my 4×4 pickup ready for another winter body work from rust out ,brake lines fuel lines ,on and on every year wish there was a better way to treat the ice and snow!

    Reply to this Comment

  7. Ken
    on February 15, 2016 at 3:48 pm

    In Maine the salt washes to the side of the road and you can often find the Moose down on their knees licking it. Good for the moose watchers.

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