Ice melt is great for clearing ice-covered driveways, paths and road to make them safe to walk and drive on. But how long does it take ice melt to starting working and how long until your driveways or paths are safe to be on?
Ice melt starts working as soon as you spread it over your ice and will take about 15–20 minutes for a significant amount of ice to melt. While some ice melt products can completely melt a thin layer of ice within 20 minutes, other products may take at least 45 minutes to obtain the same result.
The speed at which it will melt ice and make your driveway or paths safe will depend on a variety of factors including the outside temperature, type of ice melt used, quantity of ice melt used and the thickness of the ice you're trying to melt.
For example, calcium chloride ice melt usually takes about 30 minutes to melt ice completely following application.
Similar is true about magnesium chloride (35 minutes after application), potassium chloride (25–30 minutes), and sodium chloride or table salt (at least 15 minutes).
Though sometimes ice melt works faster and your driveway or path will be safe to walk on in 5 minutes and other times it'll take longer or you may still need to scrape ice away with a shovel after 20-30 minutes and then apply more ice melt.
Factors That Affect How Quickly Ice Melt Works
There are many factors that affect how long it takes ice melt to start working and ways to know when your ice melt product has done its job. It’s important to know these things so you know when your driveway is safe to be used again.
When determining how long your ice melt will take to melt ice in your driveway, there are factors to consider, including:
- Air temperature – Warmer temperatures means the ice you're trying to melt will melt a lot faster. One colder days you may have to wait longer for ice melt to do its job.
- Amount of salt applied – The more salt you use to do the job, the faster and more effective it works. However, too much can be costly and also damage concrete or surrounding plants.
- Type of salt applied – Ice melts come in different variants that display different levels of performance. Some dissolve quicker and work faster but at higher temperatures, while others work great at lower temperatures but might take longer to work.
- The volume of ice to melt – The more ice you will melt, the longer will be the melting job to complete. A thin layer of ice will melt a lot quicker than ice that is 1-2 inches thick.
How does ice melt work?
Technically, ice melt products work by lowering the freezing point of water.
The compounds (usually some form of salt molecule) mixes with a thin layer of water on top of the ice and dissolves into it.
These molecules then get in the way of the water molecules bonding together to form ice, thus causing it to stay in liquid form and turning the remaining ice into liquid form.
I go into detail in the science behind this in my article on how exactly salt melts ice.
This process is called “freezing point depression” because the ice melt lowers (or depresses) the temperature the ice needs to be at in order to stay in it's solid form.
For example if the temperature outside is -2ºC/28ºF then regular water will freeze into ice. However salt water freezes as low as -9ºC/16ºF. Because the outside temperature is above this salt will melt ice, or salt water won't turn into ice in the first place.
Typically, table salt will melt ice at temperatures as low as -9ºC/16ºF, whereas calcium chloride ice melt works at lower temperatures down to -31ºC/-25ºF. So for extremely cold areas you might not be able to use table salt.
The closer the outside temperature is to the freezing temperature of the ice melt you are using the slower it will work.
For regular salt if the outside temperature is -8ºC/18ºF it'll still work, but only just. It'll take a lot longer to work than if temperatures were closer to 0ºC/32ºF.
How Long Does It Take Magnesium Chloride To Melt Ice?
For magnesium chloride with a freezing point of -15ºC/5ºF, it takes about 35 minutes to start melting ice. Before applying the de-icer, you should shovel as much snow as possible so all that is left is the layer of ice.
Magnesium chloride is more expensive than common salt, but it's a good alternative to regular salt for melting ice in colder climates.
Magnesium chloride is a hygroscopic salt (which has the ability to absorb moisture from the air) to lower water’s freezing point, making magnesium chloride perfect for reducing ice build-up during multiple winter storms.
How Long Does It Take Calcium Chloride To Melt Ice?
Calcium chloride beats traditional de-icing solutions to achieve safer and bare pavement faster.
It works faster than salt or abrasives alone, as it can melt up to eight times more ice than salt alone, and it can start melting ice very quickly. 30 minutes following application you should notice most ice is melted.
Of all the four common choices for ice melts, calcium chloride has the lowest freezing point, which is -31ºC/-25ºF. Plus, calcium chloride is known to be safe for plants if not used in excessive amounts.
Nearing -9ºC/16ºF, calcium chloride melts about twice the amount of snow that rock salt can melt at the same temperature. The difference is even more dramatic at much colder temperatures where regular table salt stops working as a de-icer.
How Long Does It Take Potassium Chloride To Melt Ice?
The endothermic properties of potassium chloride and its low effective temperature of -4oC limit its use as an ice-melting chemical. However, like other chloride materials, there are moderate environmental impacts.
Urea is another product with the same properties and effective temperature as potassium chloride. Potassium chloride also starts to melt ice 25–30 minutes after application.
Vinegar is another substance that melts ice however it doesn't work nearly as well as ice melt salts.
Is It Effective To Use Ice Melt Before It Snows?
You can apply ice melt over your paths or driveways to stop ice from freezing in the first place. Making these areas safe to use straight away the next day.
It can reduce damage to concrete caused by water absorption or excess refreeze cycles. Just make sure to use an ice melt that is safe on concrete as regular table salt can be horrible for concrete.
It also helps to use quality sealant to prevent moisture from entering cracks in concrete that are frequently in contact with ice melts. Do not apply ice melt to newly installed concrete, as it can damage uncured concrete.
So, how long will it take you to melt ice in your pathway using an ice melt product? It depends on the following:
- The volume of snow to be melted
- The surrounding temperature
- The amount of ice melt used
- The type of ice melt used
Calcium chloride is the best ice melt to use if you want to maintain the lowest freezing point so that the mix remains in the liquid form longer. For any options above, expect melting to start 15 minutes after application or 35 minutes at the latest.