Home
Weather London
WeatherRadar
RainfallRadar
TemperatureRadar
WindRadar
LightningRadar
Weather News
Editor's Pick
Discover the app
Weather widget
Contact us
Apps
Career
    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
Drought for North Wales and Upper Severn. 2% of average rainfall. . . Thursday, 23 July 2026
Split image showing a July rainfall anomaly map of Europe on the left with below-average rainfall across the UK, Ireland, and much of western and central Europe, and an active moorland wildfire on the right producing flames and thick smoke near homes.
Thursday, 23 July 2026

2% of average rainfall

Drought for North Wales and Upper Severn
Drought across large parts of Europe. High fire risk. . . Monday, 20 July 2026
Split image showing a Europe rainfall anomaly map on the left with widespread dry conditions across much of the continent, and a cracked, parched field on the right alongside a wildfire warning symbol highlighting elevated fire risk.
Monday, 20 July 2026

High fire risk

Drought across large parts of Europe
Rain returns to end dry spell in places. Jet stream delivery. . . Thursday, 23 July 2026
Split weather graphic showing widespread showers across the UK and Ireland on the left, and a wind forecast map on the right with a windsock icon and gusts of 25 to 35 mph, highlighting breezy conditions across the two countries.
Thursday, 23 July 2026

Jet stream delivery

Rain returns to end dry spell in places
All weather news
This might also interest you
Turbulent weather in the Canary Islands. Storm and rain. . . Friday, 12 December 2025
Weather graphic showing rain and wind fields over the Canary Islands and a central warning symbol.
Friday, 12 December 2025

Storm and rain

Turbulent weather in the Canary Islands
New records for England and Wales. Broken again tomorrow?. . . Thursday, 25 June 2026
Temperature map of southwest Britain on 25.06 showing extreme heat across southern Wales and southwest England, with Bute Park in Cardiff highlighted at 34.2°C and Yeovilton at 36.4°C amid widespread deep red heat zones.
Thursday, 25 June 2026

Broken again tomorrow?

New records for England and Wales
Super Typhoon Bavi threatens Taiwan. Up to 1,000 mm of rain. . . Wednesday, 8 July 2026
The image shows an intense tropical cyclone over the western Pacific, east of Taiwan and the Philippines. The centre of the system is depicted as a light purple and white vortex with a clearly visible eye, surrounded by a ring of red and orange areas indicating the strongest wind speeds. A white arrow marks the typhoon’s predicted track towards the north-west, in the direction of Taiwan. To the west of the storm lie the Philippines, with the cities of Manila and Cebu; to the north of these lies Taiwan, with Taipei. Further west, the Chinese coast, including Hong Kong, and parts of Vietnam can be seen. The coloured wind map shows predominantly green areas outside the storm’s core, indicating significantly weaker winds. White streamlines illustrate the typhoon’s anti-clockwise circulation in the Northern Hemisphere. The highest wind speeds are concentrated around the eye of the cyclone.
Wednesday, 8 July 2026

Up to 1,000 mm of rain

Super Typhoon Bavi threatens Taiwan
All articles
Weather & Radar

Weather & Radar is also available on

Google Play StoreApp Store

Company

Contact us Privacy Policy Legal info Accessibility statement

Services

Uploader

Socials

facebooktwittertikToklinkList