Ice Melters: Part 1
January 16, 2017 - Scott's Exterior Maintenance
I have wanted to do an informational post on ice melters, aka "salt", for a while, but I'm just now getting around to it. The funny thing is this week is pretty warm for the middle of January, so snow and ice are nowhere to be found! Regardless of the current warming trend, we’ve already been through some icy stretches and will most likely see more this season, so I hope this will help explain how it works.
We have all seen ice melters being spread on roads, sidewalks, driveways, parking lots, etc. We do it, cities do it, state highway departments do it, and you may very well have done it yourself. Living in northern climates it's simply part of our life in the winter. But what exactly is everyone spreading, what exactly is it doing, and what’s the best one?? My goal here is to tackle a very big topic and try to explain it.
Part 1: Basic Chemistry of Ice "Salt"
Let’s look at some basics first. Why are we using this stuff? To melt ice. Right? How exactly? I'll explain, but first, remember basic chemistry? Turns out it's pretty helpful after all so hopefully you were paying attention in class…..
So, we aren't exactly "melting" ice directly, which would imply adding a heat source, which we are not. In fact we are doing something called "freezing point depression". This is the same principle that keeps our antifreeze from freezing and cracking the engine block in our cars, the same as adding alcohol to water, and sugar to water. In our case we are adding salt to water. All the same principle with the outcome being the freezing point, which is also the melting point, of water in our case, is lowered from the typical 32F to a lower temperature. In other words, instead of ice melting at 32F as it normally would, it might melt at 25F, for example, with the addition of salt.
One of the big problems with ice melters is the fact that they can only lower the melting point a certain amount below 32F before they reach a limit. If you’ve ever heard someone say “it’s too cold for salt to work”, this is part of the reason why. If we are able to lower the melting point to 25F, but it’s only 15F outside, the ice still isn’t going to melt because it simply isn’t warm enough to reach our melting point. Our goal is to lower the melting point sufficiently below the ground/ice/air temperature using the right product and have the melting process take place naturally. The resulting water can then either run off or evaporate and leave us with a dry surface. We are simply providing the catalyst for this to happen.
So that’s a short explanation of our goal in the ice melting process without getting too deep into the chemistry of it all. Next time I will talk about the different ingredients in ice melters. Stay tuned.