Does table salt melt ice? Will it work on ice - how to deice and defrost driveways, paths and windscreens
As winter blankets landscapes with a layer of ice and snow, the challenge of keeping driveways and paths clear becomes a priority for homeowners.
One commonly explored solution is the use of common table salt, or sodium chloride (NaCl), a familiar substance found in kitchens around the world, for melting ice.
This practice has been widely adopted, but how effective is salt, and what alternative methods exist for efficiently defrosting driveways and paths? Here is everything you need to know.
Will table salt melt ice?
When salt is applied to ice, it forms a solution with the surrounding water. This solution has a lower freezing point than pure water, causing the ice to melt and preventing further freezing at temperatures below the normal freezing point of water.
The exact freezing point of saltwater depends on how much salt is dissolved into the solution, and the higher the salt content, the lower the freezing point. Saltwater that's as saturated as it can possibly get (meaning there's no way to dissolve any more salt in it), won’t freeze until it reaches -21.1 degrees Celsius.
Table salt's ability to lower the freezing point of water makes it a popular choice for melting ice, but while salt is indeed effective, its efficiency decreases as temperatures drop. At extremely low temperatures, other deicing methods may be more suitable.
To use salt effectively, it is recommended to apply it before ice forms. This proactive approach prevents the formation of a solid layer and eases the removal of any existing ice. Spread the salt evenly across the icy surface to ensure consistent coverage. This helps in breaking the bond between the ice and the pavement.
Applying salt to already formed ice will only have a noticeable effect once the affected areas have seen some traffic – either boots or tyres treading the salt into the ice – so the first few across it will be subject to icy conditions regardless.
Never use ‘normal’ water on surfaces like pavements, as it may refreeze and make the problem worse.
Table salt will also help remove ice from surfaces like windscreens, but just sprinkling it straight on is not the best way to fix your problem. Instead, you’re better off mixing one tablespoon of salt with two cups of water; apply this solution to your windscreen and the salt will melt the ice.
You can then use an ice scraper to remove the ice as it begins to thaw. Note that a plastic scraper should only be used to remove chunks of ice that are already thawed and should not be pressed against the windscreen as it can scratch the glass if enough force is used.
What else can be used to melt ice?
Calcium chloride is another deicing option, which works at lower temperatures than sodium chloride and is particularly effective in extremely cold conditions. It's hygroscopic, meaning it absorbs moisture from the air, generating heat that aids in melting ice. However, it can be more expensive than common table salt.
Potassium chloride is an alternative to sodium chloride, and it is less damaging to vegetation and concrete. It is effective at higher temperatures but may be less potent in extremely cold conditions.
While not a melting agent, sand is often used in conjunction with deicers - it's what gives "grit" its rather unappealing brown colouring. The addition of sand can improve traction on icy surfaces by providing a textured surface, reducing slipperiness and enhancing safety.
For particularly thick or stubborn ice layers, mechanical removal methods such as scraping or chipping can be employed. It is essential to use tools specifically designed for this purpose to avoid damaging the pavement.
And did you know - salt used for de-icing by councils and other authorities in the UK predominantly comes from a single mine in Cheshire, and is formulated to work as efficiently as possible, with anti-caking agents and other additives to prevent clumping.