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Cocktail Science: 5 Myths About Ice, Debunked

Editor's Note: Please welcome Kevin Liu of Science Fare to SE: Drinks. We're pumped to have him here to share a bit of cocktail science.


[Photographs: Kevin Liu]

The difference between a perfectly balanced cocktail and a so-so one often comes down to ice. How does ice affect temperature? Dilution? Since as much as half the volume of a cocktail can be melted ice, why not pay a little more attention to what you put in your glass?

If you spend time at fancy cocktail bars, it's quite possible that you've heard a few things about ice that that aren't quite true when you put them to the scientific test. Today, we're debunking those myths and clearing up a little of the science behind the chilly stuff.

Myth #1: Impurities in water lead to cloudy ice.

False. Impurities in water, such as dissolved minerals or gases, are part of the what makes ice cloudy, but there are ways to freeze perfectly clear ice without using boiled or distilled water.

4 factors can make ice cloudy and any technique for making clear ice has to control for each of them. Here are the culprits, in order of importance.

If distilled water doesn't work, what does? For all the reasons listed above, the clearest ice is ice that freezes slowly and without supercooling—that is, ice that forms right at 0°C. So how do you do that?

Method 1: Use a cooler. The best known method is Camper English's directional freezing method. Camper freezes ice in an open igloo cooler in his freezer so that the ice freezes from top down, layer by layer. The top of the ice stays clear while only a bit at the bottom ends up cloudy.

Method 2: Use a temperature controller. I've written about my personal favorite method. I hook up a sous-vide temperature controller to a mini fridge so I can guarantee my ice freezes at just below 0°C. The temperature controller turns the fridge on and off based on an algorithm that takes into account factors like insulation and air flow to maintain a more constant temperature than the fridge would be able to maintain on its own. I've found that by tweaking the right parameters, I can keep the temperature within a + or - 1°C window. This technique works best if you don't have to open the door to the fridge much throughout the day.

Method 3: Start with hot water. While I was working on my cocktail science book, I spoke with former NASA cryogenic engineer Doug Shuntich, who pointed out that depending on your freezer conditions, simply starting with hot water can help. When hot water freezes, it moves around more due to convection, which can actually help to prevent supercooling and "encourage" the water to freeze closer to 0°C.

Any technique you can use to get your ice to freeze at 0°C should work. For example, since impurities in ice actually help prevent supercooling through a process called nucleation, it's possible that an intentional impurity, like a mint leaf, could actually make your ice more clear by forcing it to start forming crystals in a localized spot; the area right around the leaf will be imperfect, but the rest of the cube should form more clearly.

*Watch this video to see ice grow after it's already frozen.

Myth #2: You should never add ice to Scotch

More false than I thought. The basic argument for not adding ice to Scotch is this: ice waters down the Scotch and chills it. When you chill Scotch, fewer aromatic compounds from the spirit get released into the air, which means you experience much less of the Scotch's potential. All of this is true.

So why might adding ice to Scotch be ok?

First off, even the most prestigious Scotch makers acknowledge that some Scotches benefit from a little water. Water changes the solubility of some aromatic molecules, which means a few drops can help highlight particular flavors or mask others.

Scotch is pretty strong stuff (in the academic literature, Scotch has been used as a particularly intense spirit in alcohol taste tests.) Cooling down and diluting the Scotch reduces the burn that some people, especially supertasters, might experience. And that might make the Scotch more palatable for them. If anything, the popularity of whisky stones proves that there is a market for chilled Scotch.

What about all that lost aroma due to chilling?

The concerns over lost aroma deal primarily with orthonasal olfaction, or the sensations derived from aromatic compounds that enter the nose through the nostrils. But the tastes we derive from food (or Scotch) also depend on aromatic compounds that enter the nose through the back of the mouth. See pretty picture, below.


This image was first published in my book.

So the point I'm making is this: although chilled Scotch won't be shooting aromatic molecules all over the place while it's still in the glass, as soon as it gets warmed by body heat in the mouth, those molecules will become volatile and travel up the back of the mouth into the nose via retronasal olfaction.

Myth #3: Larger ice cubes melt more slowly

Depends. You've probably heard that large blocks of ice are better for drinks because larger ice melts more slowly. The argument usually goes something like "more surface area = faster melting = more dilution." It turns out that surface area does matter, but perhaps not the way you think it would. But, let me come back to that in moment.

First things first.

Whenever we talk about ice and chilling, it's important to remember that there is no chilling without dilution. The vast majority of the chilling power of ice comes from the heat of fusion—that is, the heat ice sucks up from its surroundings when it turns into water. And since it takes 80 times as much energy to melt a gram of ice as it does to raise a gram of solid ice one degree in temperature, any significant change in the temperature of a drink correlates directly with the amount of ice melted.

What happens when you add equal masses of small rectangular vs. big spherical ice to a room-temperature glass of Scotch?

In the glass with small ice, the extra surface area of the ice would lead to very fast chilling and dilution. The drink would quickly drop down to around 0°C or just below** and stay in that rough temperature range until you finished your drink.

In the glass with a big sphere of ice, chilling and dilution would occur more slowly because spheres have the smallest ratio of surface area to mass. The Scotch surrounding the sphere would eventually chill to 0°C, but the ice would also melt a bit and probably float, which means the bottom of the drink would probably be closer to 4°C* because water is densest at that temperature and the sphere would not be able to chill fast enough to generate the convection necessary to circulate the Scotch. Of course, simply stirring the drink a little would chill it more.

Now that we know the conditions under which big ice does melt more slowly, let's look at a situation where the opposite is true.

What happens when you add equal masses of small rectangular vs. big spherical ice to an Old-Fashioned that has been chilled down to 0°C?

In both cases, when you add the ice, the temperature gradient between ice and surrounding pre-chilled cocktail would essentially be zero, so relatively little initial melting would take place. As you drank the two cocktails, the ice in each would melt as heat would be lost to the surrounding environment. Whether or not the large ice melted more slowly would depend on insulation, air temperature, and volume of cocktail to ice, but in most situations, the sphere would likely be able to keep up with heat loss, so the two cocktails would chill and dilute at almost the same rate.

Why might smaller ice be preferable to large in some cases?

If, as you drink your cocktail, the large ice gets exposed to the air. Then what happens is that the big ice starts cooling the atmosphere instead of your drink and you get additional dilution with no added chilling. It can be easier for small ice to rearrange and stay submerged in a drink as you sip it. So in the case of a chilled Old-Fashioned, all that really matters is you use ice that stays submerged for as long as you intend to drink the cocktail.

Does that mean we should use crushed ice for every drink?

No—you also have to consider water that is on the surface of the ice before you add it to your drink. Small ice has tons of surface area. As a result, it accumulates surface water—liquid water that builds up on the outside of the ice through melting and through condensation. When you add small ice to a drink, that surface water immediately dilutes the drink without adding any chilling benefit.

Of course, this is really much more of an issue if you are in a bar situation where ice is stored at room temperature. If you use lots of small ice directly from the freezer, surface liquid should be insignificant.

So, what ice do I use? When I'm drinking cocktails home, I'm perfectly happy using lots of small cold ice cubes straight from the freezer. But that doesn't mean I don't like big cubes—they may not make a difference in chilling, but they're still pretty [ahem] cool.

*Although water is densest at 4°C, the temperature at which mixtures of alcohol and water will be densest will vary based on ABV.
**A mixture of water and ethanol has a lower freezing point than water by itself, so the incredible cooling power of melting ice *can* take a drink below 0°C. But, in the case of a big ice ball and room-temperature Scotch, the effect probably won't be significant. See myth #5, below, for more.

Myth #4: Egg-based drinks always benefit from a "dry shake"

False. It turns out that drinks that contain only egg whites do benefit from a dry shake (that is, shaking without ice), but drinks that contain whole eggs do not.

What does this "myth" have to do with ice? Dry shaking isn't so much about dry vs. wet as it is about temperature. As any baker knows, an egg white foams form much more easily at room temperature than when chilled, which is why a dry shake will create a foamier egg-white-based drink.

Whole-egg foams are different because they contain fat from the egg yolk and so are not as much affected by temperature.

But all that doesn't change the fact that two separate shaking processes is a huge pain in the butt for bartenders, so here are some tips for making great egg drinks without worrying about a dry shake.

For egg-white-only drinks

For whole-egg drinks

You can read more about using eggs in cocktails here and here.

Myth #5: Shaking a Martini "Bruises" the Gin

TRUE! Well, sorta.

The fact of the matter is that a shaken drink rapidly reaches an equilibrium temperature well below the freezing point of water. For a stirred drink to reach the same temperature, a bartender would have to stir for nearly 2 minutes.

Because of physics and stuff, a colder drink translates into a more diluted drink, as ice does not chill unless it also melts. In a test done by Gizmodo, a shaken cocktail ended up at 48 proof while its stirred twin finished at a much higher 65 proof.

What if you stir long enough that you do manage to get a stirred drink as cold as a shaken one?

The two drinks would probably still taste different because the violent action of shaking a drink aerates it. Although the tiny bubbles that affect texture dissipate relatively quickly, at the molecular level atmospheric oxygen and carbon dioxide will stay dissolved. Whether this makes a noticeable effect on taste is questionable, but it's certainly possible.

A short public service announcement

These little tidbits about ice are really just the tip of the proverbial... well, you know. I think it's always worth knowing the science behind your drink; but, as with all science, you shouldn't just take my word for it. Keep in mind that real-world factors like glassware, room temperature, even humidity, will affect your results.

Have you played around with cocktail science at all? Any questions out there about ice in drinks? Feel free to share your experiences or tell me how totally wrong you think I am in the comments.

About the author: Kevin Liu likes to drink science and study cocktails. Wait, that's backward. Ask him geeky food and booze questions on twitter @kevinkliu. While you're at it, check out his book about cocktail science and his blog about food and science

Special thanks to Mike, Angus, Andrew, Doug, and Jimmy for helping with this article.

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