What’s the Best Snow and Ice Melt? Here’s Why Using Rock Salt Shouldn’t Be Your Default Option.

5 min readIf the winter weather in recent years hasn’t already been causing some chaos, this year’s Super El Niño isn’t helping. Preparation is key. Setting down a layer of snow and ice melt (i.e., deicers) on your driveway and walkways before a snowstorm hits can save you a lot of time shoveling or snow blowing. But when you walk into the home improvement store, there might be more options than you were prepared for. Don’t worry, with just a little bit of information under your belt, you can choose the best ice melt for the job.Not all ice melt is created equal. Some melts don’t work as well as others in subzero temperatures and won’t be effective against bonded ice. And some ice melt negatively affects nearby lawns and plants, or causes irritation and health issues for pets. Knowing the difference between the ingredients that power your snow and ice melts is important when choosing the right one for you.Exothermic vs. EndothermicHunter YoungThere are two basic types of ice melt, and they work differently.Deicers work by exhibiting one of two thermal reactions: exothermic or endothermic. Exothermic materials, such as sodium chloride and magnesium chloride, release heat when they come into contact with ice or snow. Endothermic materials, such as rock salt and calcium magnesium acetate, absorb heat from their surroundings (such as the sun) and use that heat to melt ice.Because of this difference, exothermic ice melts perform better in subzero temperatures, and endothermic melts become less effective below 20 degrees Fahrenheit or so, especially at night. However, though exothermic reactions are stronger, they can also be more corrosive and less friendly to plants and animals. Blended melts may offer a good balance, which can help the melt work better in lower temperatures, but also be less corrosive and harmful to pets and plants.Types of Ice and Snow MeltSometimes referred to as a deicer and often simply called “salt,” ice and snow melts can be made of different chemical compounds or blended to take advantage of their different attributes. This can make some less damaging to pavements or nearby plants. We put together a list of the most typical compounds that you’ll see sold by themselves or in a list of ingredients in blended options, which are the most common types you’ll see at stores.Typical Types of Snow and Ice MeltThese are some of the most common types of compounds used for melting ice and snow. Some are sold in their pure form or may be an ingredient in a blended formula.❄️ Rock Salt (Sodium Chloride)Thermal Type: EndothermicMinimum Operating Temperature: 15 degrees FahrenheitPros: Inexpensive; Can be more effective in liquid (brine) formCons: Corrosive; Less effective below 15 F; Not pet- and plant-friendly in high dosesShop Rock Salt❄️ BlendsThermal Type: VariesMinimum Operating Temperature: VariesPros: Often affordable and commonly available; Many are pet- and plant-friendly; Many are low-corrosionCons: May contain ingredients that are harmful to plants and pets (always read the ingredients).Shop Various Blends❄️ Urea-BasedThermal Type: EndothermicMinimum Operating Temperature: 25 degrees FahrenheitPros: Pet- and environmentally friendly; Non-corrosiveCons: Less effective below 25 F; Mostly used in fertilizer, so it’s hard to find on its ownShop Urea-Based Blends❄️ Calcium Magnesium AcetateThermal Type: Mostly endothermicMinimum Operating Temperature: 20 degrees FahrenheitPros: Mostly pet- and environmentally friendly; Long-lasting; Low corrosionCons: Not readily available in pure form; Less effective below 20 FShop Calcium Magnesium Acetate❄️ Sodium Acetate Thermal Type: ExothermicMinimum Operating Temperature: 0 degrees FahrenheitPros: Mostly pet-friendly; Long-lasting; Low corrosionCons: Not readily available in pure form; Less effective in subzero temperaturesShop Sodium Acetate❄️ Magnesium ChlorideThermal Type: ExothermicMinimum Operating Temperature: Minus 13 degrees FahrenheitPros: Works in subzero temperatures; Fast-acting; Gentler on surfacesCons: Bad for plants in high concentrations; Corrosive; Slippery when the temperature goes above freezing.Shop Magnesium Chloride❄️ Calcium ChlorideThermal Type: ExothermicMinimum Operating Temperature: Minus 25 degrees FahrenheitPros: Mostly pet-friendly; Works in subzero temperaturesCons: May harm pets and plants; No residual effect; CorrosiveShop Calcium ChlorideThings to Consider When Buying Ice Melt➥ TemperatureExothermic ice melt compounds, such as calcium chloride and magnesium chloride, work better in subzero temperatures because they release heat. If you live in an area where winter temperatures regularly drop below zero, consider one of these types or a blend that contains them.If your winters are milder and average temperatures tend to hover in the twenties, an endothermic ice melt like rock salt or a urea blend can get the job done. Blended ice melts will often combine exothermic and endothermic compounds to help them perform better in lower temperatures and keep the cost more reasonable. Companies that make these blends will often label the bag with the lowest effective temperature to help you know for sure.➥ Pet-friendlinessTraditional salts can irritate dog and cat paws, and some of the stronger exothermic compounds that include chlorides can also be irritating or harmful if ingested. The American Society for the Prevention of Cruelty to Animals (ASPCA) says ingestion can lead to ice melt toxicosis, which can cause vomiting or neurological issues. However, ice melt toxicosis is unlikely to happen from just a few licks; the most serious cause is when a bag of melt is left unattended and ingested by your pet in large amounts.To help combat this, many brands offer “pet safe” varieties of ice melt, but no blend is truly perfect. These animal-friendly blends tend to eliminate sodium or chloride from the mix, but not all do. The ASPCA recommends using urea-based ice melts, as urea (a compound made of carbon, hydrogen, nitrogen, and oxygen) is the least likely ingredient to cause stomach irritation. Another simple idea, especially in cities and suburbs where there is little control over what ice melt the neighbors use, is to adorn your dog in paw booties before taking a walk.➥ Plant- and Eco-friendlinessIce melts that have high concentrations of salts or chlorides can be problematic for vegetation and the environment in general. According to a study by Penn State Extension, when used in large amounts, simple rock salt (sodium chloride) can injure or kill plants near the treated pavement as it washes away, and further pollute waterways, harming fish and other marine life. Instead, the study notes, a compound like calcium magnesium acetate (CMA), which forgoes the use of chlorides or salts, is a safer option for environmentally sensitive areas. Urea-based ice melts are also a good choice.Like the pet-friendly varieties of deicers, brands can be very loose with how they market their eco-friendly products, especially with the blends; there’s no guarantee that the one you buy won’t partially contain a compound that is harmful in large quantities. If you want to be as eco-friendly as possible, avoid blends that include chlorides and salts.If that can’t be avoided, just follow the golden rule of “everything in moderation.” After all, overtreating an area is more likely to damage nearby vegetation—even if you use the more environmentally friendly varieties. If you’re still finding noticeable piles of deicer after the snow and ice are gone, you might be using too much.➥ Corrosion Corrosion is a considerable problem caused by deicers. Salt-based melts or brines can penetrate porous stone, freeze, and cause the surface to expand. Meanwhile, chlorides can accelerate the rate of corrosion in metal. The Minnesota Pollution Control Agency noted that acetate-based deicers that don’t use chlorides or salts caused low to moderate levels of corrosion, but again, using any ice melt in moderation will help lower the chance of corrosion to your sidewalks, driveways, and nearby railings.Editor-Recommended Snow ShovelsDavid is a Reviews Editor for Hearst’s Enthusiast Group, contributing to Popular Mechanics, Runner’s World, Bicycling, Best Products, and Biography. He has over 25 years of experience writing about and reviewing consumer electronics, kitchen appliances, DIY products, outdoor gear, and more. He also spent years covering the ever-changing world of online retail. To relax, he loves experimenting with new recipes, tweaking his smart home setup, and spending time outdoors on his bike or camping.