Home / Editor's Pick /

What does salt do? The science of gritting

06:00
20 January 2023

What does salt do?
The science of gritting

gritter

With frost frequenting our roads amidst the cold weather, we thought it was time to take a look at what exactly gritting the roads does.

Although we often refer to it as gritting, there is usually little grit involved, and instead mined rock salt is used. Salting the roads is primarily a preventative technique, and works most effectively via three main methods:

  • Salt lowers the freezing point of water. Water freezes at 0C but the presence of the salt prevents water from freezing until -6C to -8C.
  • It stops snow bonding as ice to the road, so can be ploughed away more easily.
  • Can also be added post-snow to small depths of lying snow (up to around 4cm) to help dissolve and melt it away.

Salt is most commonly used because it is what we call hygroscopic. It acts like a magnet by drawing in and absorbing moisture from the air and the road surface, to the granules.

If the air is too dry, or it hasn't rained recently, salt can be pre-wetted. It also needs a flow of traffic to be worked into the road properly. And if there is no moisture present, the salt won't be absorbed and thus won't do its job.

Salt can also be ineffective at particularly low temperatures, so if you live somewhere like the Scottish Highlands, then it's likely that a mix of salt and grit will be used.

Other alternatives aside from salt include molasses, although depending on where you live, can often get licked up by sheep, which is a road hazard in itself!

Each year new names are unveiled for council's gritter lorries, with this year featuring David Plowie, Salt Disney, Sled Zeppelin and Sleetwood Mac.

Weather & Radar editorial team
More on the topic
Tuesday 1 July 2025

Not just the UK

Heatwave grips continental Europe
Sunday 6 July 2025

Your weather - Your shots

Shining summer clouds light the night
Flood water and weather radar showing heavy rain and thunderstorms over the southern US.
Thursday 10 July 2025

Downpours & flash floods

More severe weather in the USA
All weather news
This might also interest you
Friday 4 July 2025

Breakfast brief

Gusty and wet end to the week
Two weather radars side-by-side, one showing sunny conditions over the UK and the other a temperature map showing widespread warmth.
Thursday 10 July 2025

Breakfast brief

Turning sunnier and warmer
Wednesday 9 July 2025

Breakfast brief

Overcast start, warmer afternoon
All articles
Weather & Radar

www.weatherandradar.ie

facebooktwitteryouTubeContact uslinkList
Privacy Policy | Legal info | Accessibility statement