Big ice cubes

I’m not sure when the current fetish for huge ice cubes started, but I’ve been noticing it for a few years now. And when I say I’ve “noticed” it, I mean I’ve seen people touting huge ice cubes on the internet—in real life, the ice cubes I come across are the same size they’ve always been. Perhaps my circle of friends is hopelessly old fashioned.

At any rate, the articles promoting big ice cubes always say they’re superior because they have a low surface area per unit mass. Since melting occurs at the surface of the cube, the low surface area is said to reduce melting and prevent your drink from getting as watered-down as it would if you used the same mass of smaller cubes. The writers of these articles seldom invoke the square-cube law explicitly, but that’s what they’re talking about. In some cases, they go beyond just saying that big cubes melt slower and also claim that they do so while cooling your drink just as much. These claims should be looked upon with a gimlet eye, because the cubes’ melting is what does the cooling.

No question, some of the cooling comes from raising the temperature of the ice from below freezing up to the melting point. But that’s small beer. The specific heat of ice (0.50 cal/g-K) is only about half that of water (and about equal to that of ethanol), so raising the temperature of ice does little to lower the temperature of your drink. The significant cooling comes from ice’s heat of fusion, which is a whopping 80 cal/g. This is what pulls heat out of your drink and lowers its temperature.

As I started to read this recommendation for the best ice cube tray from the new Sweethome site, I got a sour feeling in my stomach. Not only did it make the usual “less surface area is better” claim, it had this bizarre pull quote:

You can control the rate of dilution, it gets just as cold, and you have less surface area.

If you needed proof that you shouldn’t take physics advice from a bartender (excuse me, mixologist), this would be it. No, you can’t control the rate of dilution with big cubes any more than you can with small cubes. Thermodynamics is in the driver’s seat in both cases—you’re just in a sidecar, along for the ride.

Despite highlighting this quote, Sweethome deserves credit for coming through with the most complete explanation of the difference between big and small cubes I’ve ever seen in an article of this type. Yes, big cubes melt (and therefore dilute your drink) more slowly, but at the cost of cooling your drink more slowly. How much more slowly?

[The recommended big cubes] cooled a glass of room temp water by 26.8 degrees in 10 minutes, diluting it by 26 grams.

… Using the same 100 grams of ice but in two cubes instead of one giant one, the small ice cubes cooled the drink the most (28.5°) and also diluted the drink the most (28 grams).

So the differences are about degree Fahrenheit1 and one-fifteenth of an ounce. Hardly worth the effort to sling around big cubes. No wonder none of my friends bother with them.

  1. Sweethome doesn’t say whether their temperatures are in Fahrenheit or Celsius, but it has to be Fahrenheit. Room temperature water wouldn’t up around 30° C, would it?